Access to this full-text is provided by Taylor & Francis.
Content available from Cogent Food & Agriculture
This content is subject to copyright. Terms and conditions apply.
FOOD SCIENCE & TECHNOLOGY | RESEARCH ARTICLE
Kale: Review on nutritional composition, bio-
active compounds, anti-nutritional factors,
health beneficial properties and value-added
products
Neela Satheesh
1
* and Solomon Workneh Fanta
1
Abstract: There has been an increasing trend in recent times for taking more of green
leafy vegetables (GLV) portion in the human diet. Among various GLVs available for
human consumption, some are confined to a specific region and few are available in
many parts of the world. Kale (Brassica oleracea L. var. acephala) is among the latter
group which belongs to Brassicaceae family. This review summarizes the nutritional
composition and anti-nutritional factors of kale available in different parts of the world.
Consideration was also given for summarization of the studies reported on health
benefits, pharmacological activities and different food products. It is noted from the
literature that kale is a good source of fiber and minerals like potassium with higher
calcium bioavailability than that of milk. Kale also contains prebiotic carbohydrates,
unsaturated fatty acids and different vitamins while the anti-nutritional factors such as
oxalates, tannins and phytate are present in higher concentrations. Research studies are
reported different health beneficial activities of the kale like protective role in coronary
artery disease, Anti-inflammatory activity, Antigenotoxic ability, gastro protective activ-
ity, inhibition of the carcinogenic compounds formation, positive to gut microbes, anti-
Neela Satheesh
ABOUT THE AUTHOR
Dr. Neela Satheesh is an Associate Professor in
Faculty of Chemical and Food Engineering,
Postharvest Technology Department, Institute of
Technology, Bahir Dar University, Ethiopia. He
obtained his PhD degree from JNTU (Jawaharlal
Nehru Technological University) Anatapur, India.
His research areas include Postharvest
Management, Technology, Food Product
Development and Food Quality and Safety,
Processing and Handling of Perishables and
Durables.
Dr. ir. Solomon Workneh Fanta is an Associate
Professor in faculty of Chemical and Food
Engineering, Postharvest Technology
Department, Institute of Technology, Bahir Dar
University, Ethiopia. He obtained his PhD degree
from KU Leuven, Belgium, working in the area of
Postharvest Technology, Development and mod-
eling of Thermal and non-thermal storage struc-
tures for perishables and durables,
Transportation phenomenon, Food Quality and
Safety.
PUBLIC INTEREST STATEMENT
Kale is widely consumed Green leafy vegetable in
worldwide; it is providing high bioavailability of
calcium, better than milk and good concentra-
tion of the Iron. In addition, kale reported better
concentrations of the probiotic carbohydrates,
organic acids, unsaturated fatty acids, carote-
noids, phenolic acids and different vitamins. The
in vitro and in vivo studies reported various
health benefits for the consumers like coronary
artery disease, anti-inflammatory activity, anti-
genotoxic ability, gastro protective activity etc.
However, value-added products from the kale
was reported in very limited areas and the most
common foods reported are bread incorporate
with kale, juice, puree. With all the reported
nutritional and health benefits, kale reported
good concentrations of the Anti nutritional
components.
Satheesh & Workneh Fanta, Cogent Food & Agriculture (2020), 6: 1811048
https://doi.org/10.1080/23311932.2020.1811048
© 2020 The Author(s). This open access article is distributed under a Creative Commons
Attribution (CC-BY) 4.0 license.
Received: 05 March 2020
Accepted: 13 August 2020
*Corresponding author: Neela
Satheesh, Faculty of Chemical and
Food Engineering, Bahir Dar Institute
of Technology, Bahir Dar University,
Bahir Dar, Ethiopia
E-mail: neela.micro2005@gmail.com
Reviewing editor:
Fatih Yildiz, Middle East Technical
University, Food Engineering and
Biotechnology, Ankara, Turkey
Additional information is available at
the end of the article
Page 1 of 31
microbial against specific microorganisms. However, in case of value-added products
kale was reported limited usage like, in baked products and beverages. Finally, concluded
that, kale has good potential to use in different food and nutritional applications.
Subjects: Food Chemistry; Food Analysis; Fruit & Vegetables
Keywords: Flavonoids; glucosinolates; kale; prebiotic carbohydrates; polyphenols
1. Introduction
Kale (Brassica oleracea L. var. acephala) is a green leafy vegetable in Brassicaceae family (Fahey,
2003). Initial evidence of kale is from the eastern Mediterranean and Asia Minor regions. Kale was
considered as the food crop since 2000 B.C, this is evidenced by the Theophrastus report in 350 B.C. on
curved and wrinkled kale. Leonard (2019) reported that, kale has spread over the centuries across the
world through immigrants, travelers and merchants. Kale plant is an annual crop and its size and
nutritional variation depends on the variety and growing conditions (Lefsrud et al., 2007). The growth
of this plant depends on the agricultural practices employed and geo-climatic conditions and gen-
erally, it will be ready after two months of sowing. Different varieties of kale are available they include,
green kale, dwarf kale, marrow-stem kale, tronchuda kale, curly leaf kale, scotch kale, tree kale and
bore kale. Kale leaves are generally consumed as fresh and unprocessed as salad or cooked and used
as garnish and they are usually sold in fresh, canned and frozen forms (Fahey, 2003).
The vegetables of Brassicaceae family have specially gained attention due to their sulfur containing
phyto-nutrients that promote health. In Africa, kale is regarded as nutritious and its consumption
provides good health (Emebu & Anyika, 2011). Popular articles have described about the health benefits,
its nutritional composition (Megan, 2020) and consumer acceptance (Bryan, 2020). The Brassicaceae
exhibit positive cardiovascular protective roles preventing gastrointestinal tract cancer (Raiola et al.,
2018). Glucosinolates, flavonoids (glycosylated flavanols) and phenolic (kaempferol, quercetin and
isorhamnetin) compounds are responsible for antioxidant and free radical scavenging properties
(Cartea et al., 2011; Lin & Harnly, 2009). The United States Center for Disease Control has assessed the
vegetables for their nutritional quality with ≥10% Recommended Daily Allowance (RDA) of 17 essential
nutrients especially those are strongly associated with reducing risk of heart disease and other non-
communicable diseases. Among those, kale has been ranked as the 15
th
(Di Noia, 2014).
Although kale has been widely studied for its nutritional highlights, reviews on the consolidation of the
research findings are hardly find. Hence, the objective of the present paper is to review the nutritional
composition, bio-active compounds, anti-nutritional factors present in kale and health beneficial proper-
ties and value-added products of kale reported from different researchers around the world.
2. Proximate composition of kale
As indicated in Table 1, protein% in kale on fresh weight basis is 3.28%−11.67% (Emebu & Anyika,
2011; Manchali et al., 2012; Sikora & Bodziarczyk, 2012; Thavarajah et al., 2019) and 30.83%-36.8%
on dry weight basis (Acikgoz, 2011; Kahlon, Chiu and Chapman, 2008). The variation in protein
concentration is higher in fresh weight basis compared to that of dry, however, kale is reported to
have much higher protein than other brassica family vegetables (Cleary, 2003) and other GLVs like
spinach (2.9% in fresh weigh basis). The concentration of the protein is also much higher compared
to other GLVs (Ayaz et al., 2006; Gupta & Rana, 2003; Roy & Chakrabarti, 2003).
The energy levels of kale vary from 58.46–66 kcal per 100 g on fresh weight basis (Emebu & Anyika,
2011; Thavarajah et al., 2019) which is higher compared to other salad crops (Gupta & Rana, 2003) and
vegetables of brassica family (Fahey, 2003) as well as other temperate vegetables cultivated in
different parts of the world (mean 23.18 kcal per 100 g on fresh weigh basis) (Roy & Chakrabarti,
2003). For low energy requirements, the nutrition experts always suggest to consume more amount of
GLVs as they are rich source of moisture with low amount of the carbohydrates and fats (Pandey et al.,
Satheesh & Workneh Fanta, Cogent Food & Agriculture (2020), 6: 1811048
https://doi.org/10.1080/23311932.2020.1811048
Page 2 of 31
Table 1. Proximate composition of the kale leaf reported by different authors
Nutrient Talwinder,
et al., (2008)
1
(DW)
Acikgoz (2011)
2
(DW)
Thavarajah et al
(2010)
3
(FW)
Emebu and Anyika
(2011)
4
(FW)
Sikora and
Bodziarczyk (2012)
5
(FW)
Manchali et al.
(2012)
6
(FW)
Protein (%) 36.8 30.83 4.2 11.67 4.16 3.28
Energy (kcal/100 g) NR NR 66 58.46 NR NR
Ash (%) 15.8 NR ND 1.33 2.11 NR
Fat (%) 11.8 NR ND 0.26 0.67 0.74
Carbohydrates (%) 38.6 NR ND 2.36 10.14 10.0
Dietary fiber (%) 36.8 NR ND 3.00 8.39 1.94
Moisture (%) NR NR 85 81.38 82.92 NR
Where: FW = Fresh Weight; DW = Dry Weight; NR = Not Reported.
1
Samples collected from local grocery from California, USA
2
Kales cv. Karadere 077 grown in Turkey
3
Kale genotypes grown in South Carolina, USA
4
Samples collected from local market of Asba, Delta state, Nigeria.
5
Kale from Krakow, Poland.
6
The values are consolidated by the author reported from different studies
Satheesh & Workneh Fanta, Cogent Food & Agriculture (2020), 6: 1811048
https://doi.org/10.1080/23311932.2020.1811048
Page 3 of 31
2006; Sheetal et al., 2005). Kahlon Chiu and Chapman, (2008) reported higher ash content of 15.8% in
dry weight base and 1.33–2.11% in fresh samples by Emebu and Anyika (2011) and Sikora and
Bodziarczyk (2012). This deviation can be attributed to the variations in the agro-geological conditions
of the growth and variation in the moisture contents of the studied kale samples.
The dry samples have high fat 11.8% (Talwinder, et al., 2008) than in fresh samples reported as
0.26–0.74% (Emebu & Anyika, 2011; Manchali et al., 2012; Sikora & Bodziarczyk, 2012). The low
percentage of fat in fresh kale is similar to that of fruits (pomes) and vegetables (salad and
temperate) (Fahey, 2003).
The percentage of carbohydrates is high in dry kale which is equal to 38.6% (Kahlon , Chiu and
Chapman, 2008) whereas in fresh kale, the percentage varies between 2.36%-10.14% (Emebu &
Anyika, 2011; Manchali et al., 2012; Sikora & Bodziarczyk, 2012) as shown in Table 1. These values
are higher compared to other salad vegetables (Gupta & Rana, 2003) as well as vegetables of
brassica family (Fahey, 2003) and GLVs of temperate climate (Roy & Chakrabarti, 2003).
A high moisture percentage of 81.38%-82.92% (Sikora & Bodziarczyk, 2012; Thavarajah et al.,
2019) is found in kale which is more than other crucifer vegetables. However, it is less than spinach
which is 94.2% (Kawatra et al., 2001). This percentage of moisture in kale matches with other salad
crops like asparagus, artichoke, beet greens, mustard, rhubarb and it is less compared to that of
broccoli, brussels sprouts, cabbage, pakchol, cauliflower etc. (Fahey, 2003). This higher moisture
content, low energy (Pandey et al., 2006) and low dry matter will help in enhancing the metabolic
functions of human body (Sheetal et al., 2005).
3. Sugar alcohols, carbohydrates and organic acids in kale
It can be noted from Table 2 that the sugar alcohols are 24.5 mg/100 g and sorbitol as 17.9 mg/
100 g reported in kale (Thavarajah et al., 2016). Sorbitols are the sweeteners; they provide only half
Table 2. Sugar alcohols, Carbohydrates, prebiotic carbohydrates and selective organic acids
(mg/100 g) in kale leaf reported by different authors
Component Ayaz et al.
(2006)
1
(DW)
Thavarajah et
al. (2016)
2
(FW)
Wang (1998)
3
(FW)
Hagen et al.
(2009)
4
(FW)
Sugar alcohol NR 24.5 NR NR
Sorbitol NR 17.9 NR NR
Glucose 1056 993 3040 5800
Fructose 2011 545 5950 7200
Sucrose 894 39.3 300 3400
Arabinose NR 73.5 NR NR
Mannose NR 241 NR NR
Xylose NR 59.9 NR NR
Total identified prebiotic
carbohydrates
NR 1900 NR NR
Other prebiotic
carbohydrates
NR 5500 NR NR
Citric acid 2231 NR 386 NR
Malic acid 151 NR 124 NR
Where: FW = Fresh Weight; DW = Dry Weight; NR = Not Reported
1
Kale (B. oleraceae L. var. acephala Dc.) from six different fields of Trabzon, Turkey.
2
Mean of 25 genotypes of kale grown in South Carolina, USA
3
Local farms Beltsville, Maryland, USA
4
Curly Kale (B. oleracea L. var. acephale, cv. Reflex) from Norwegian University Life Sciences, Norway
Satheesh & Workneh Fanta, Cogent Food & Agriculture (2020), 6: 1811048
https://doi.org/10.1080/23311932.2020.1811048
Page 4 of 31
of the energy compared to other carbohydrates due to the inability of small intestine to absorb
sugar alcohols properly (Grembecka, 2015; Mäkinen, 2016). These are widely used in food products
for people with diabetes (Manisha et al., 2012). The sorbitals are non-carcinogenic (Hayes, 2001)
and prevents the formation of the teeth cavities (Anonymous, 2011). Very few common fruits and
vegetables are reported with sorbitols (Lee, 2015). Kale has other common sugars like, glucose and
fructose and sucrose, arabinose (73.5 mg/100 g), mannose (241 mg/100 g) and xylose (59.9 mg/
100 g) (Thavarajah et al., 2016). Xylose is generally found in smaller concentrations in many fruits
and vegetables like berries, oats and mushrooms (Hassan et al., 2011).
Glucose, fructose and sucrose are the major soluble sugars found in kale. The glucose ranges
from 993 to 5800 mg/100 g, fructose 545–7200 mg/100 g and sucrose 39.3–3400 mg/100 g (Ayaz
et al., 2006; Hagen et al., 2009; Thavarajah et al., 2016; Wang, 1998). This broad range in
carbohydrates may be attributed to the difference in species, agricultural practices and other
agro-climatic conditions. It is reported that kale grown at temperatures above 25° C is bitter in
taste compared to the one grown at temperatures between 7–21 °C (Thavarajah et al., 2016;
Wang, 1998). The kale grown under cooler temperatures is reported to contain higher concentra-
tion of the water-soluble prebiotic and have sweeter taste and superior nutritional quality.
The non-digestible carbohydrates and lignins are known as the dietary fiber (Cleary, 2003; El
Khoury et al., 2012) which stimulates immunity and enhances mineral absorption (Lee &
Mazmanian, 2010; Whisner & Castillo, 2018) and reduces the risk of colon cancer (Pool-Zobel,
2005) and risks due to the obesity (Cerdó et al., 2019; Ejtahed et al., 2019). It is reported that
prebiotic carbohydrates can reduce excess circulation of glucose in blood (Davani-Davari et al.,
2019), reduce cholesterol levels (Nakamura &Omaye, 2012) and improve insulin sensitivity. Table 1
indicates that the percentage of dietary fiber in dry kale is 36.8% (Kahlon , Chiu and Chapman,
2008) whereas in fresh kale, it is found to be 1.94–8.39% (Emebu & Anyika, 2011; Manchali et al.,
2012; Sikora & Bodziarczyk, 2012). This variation in fresh base may be attributed to maturity and
the proportion of the moisture removed in the dry samples (Barrett et al., 2010). Recommended
Dietary Allowance (RDA) for dietary fiber is 25 g/day for adults 18 years and above for normal
bowel function and human gut health (Anonymous, 2010; Phillips & Cui, 2011).
Thavarajah et al. (2016) have reported a total identified prebiotic carbohydrates of 1900 mg/
100 g and other pre-biotic carbohydrates of 5500 mg/100 g (Table 2) in kale. Dietary prebiotics are
considered as non-digestible fiber and can pass through the upper part of the intestine and
promotes the growth of beneficial microbes settled in large intestine by acting as substrate
(Scantlebury & Rgibson, 2004). The prebiotic carbohydrates are categorized from dietary fiber
lactulose (disaccharide), inulin (polysaccharide), fructo-oligosaccharides, gluco-oligosaccharides
(Lannitti & Palmieri, 2010).
Organic acids like citric, malic and oxalic acids are usually found in GLVs (Flores et al., 2012). Citric
acid in kale was reported to be 386–2231 mg/100 g and malic acid 124–151 mg/100 g (Ayaz et al.,
2006; Wang, 1998). In GLVs, the organic acid concentration depends on degree of maturity of the
plant with variations in different parts of the plant (Batista-Silva et al., 2018). Further, the content of
organic acid in GLVs also depends on the gene expression in the seeds due to the environment and
agronomic practices (Kader, 2008); Mu et al. (2018) have reported that the concentration of organic
acids govern the organoleptic properties especially the sourness in different fruits and vegetables.
Oxalic, malic and citric acids act as antioxidants due to their ability to chelate metals (Kayashima &
Katayama, 2002).
4. Minerals in kale
Mineral composition of kale is presented in Table 3. The highest concentration of potassium (Fahey,
2003) was found between 4.16–1350 mg/100 g, followed by Ca 2.6–1970 mg/100 g and Mg 0.36–
44 mg/100 g (Acikgoz, 2011; Ayaz et al., 2006; Emebu & Anyika, 2011; Manchali et al., 2012; Sikora
& Bodziarczyk, 2012; Thavarajah et al., 2016). Among all the vegetables grown in temperate
Satheesh & Workneh Fanta, Cogent Food & Agriculture (2020), 6: 1811048
https://doi.org/10.1080/23311932.2020.1811048
Page 5 of 31
Table 3. Mineral composition (mg/100 g) of kale leaf reported by various authors
Mineral Type Manchali et al.
(2012)
1
(DW)
Ayaz et al. (2006)
2
(DW)
Thavarajah et al.
(2016)
3
(FW)
Acikgoz (2011)
4
(FW) Emebu and Anyika
(2011)
5
(FW)
Sikora and
Bodziarczyk (2012)
6
(FW)
Potassium 446 1350 488 4.16 7.03 440.2
Calcium 13.5 1970 106 2.61 4.05 384.8
Magnesium 34 240 44 0.36 6.69 34.9
Iron 16 7.26 1.1 12.19 8.94 NR
Zinc 0.045 3.94 0.7 2.08 2.16 0.83
Manganese 0.75 5.35 0.8 14.77 NR 0.86
Copper 0.3 0.51 0.055 0.18 NR 0.05
Selenium 0.0009 NR 0.0023 ND NR NR
Phosphorus 56 573 NR 0.52 NR NR
Sodium 43 170 NR NR 4.69 38.5
Cobalt NR 0.02 NR NR NR NR
Aluminium NR 2.93 NR NR NR NR
Arsenic NR 0.07 NR NR NR NR
Barium NR 1.59 NR NR NR NR
Cadmium NR 0.01 NR NR NR NR
Chromium NR 0.26 NR NR NR NR
Lead NR 0.02 NR NR NR NR
Lithium NR 0.01 NR NR NR NR
Molybdenum NR 0.29 NR NR NR NR
Nickel NR 0.2 NR NR NR NR
(Continued)
Satheesh & Workneh Fanta, Cogent Food & Agriculture (2020), 6: 1811048
https://doi.org/10.1080/23311932.2020.1811048
Page 6 of 31
Table 3. (Continued)
Mineral Type Manchali et al.
(2012)
1
(DW)
Ayaz et al. (2006)
2
(DW)
Thavarajah et al.
(2016)
3
(FW)
Acikgoz (2011)
4
(FW) Emebu and Anyika
(2011)
5
(FW)
Sikora and
Bodziarczyk (2012)
6
(FW)
Strontium NR 25.2 NR NR NR NR
Tin NR 0.04 NR NR NR NR
Where: FW = Fresh Weight; DW = Dry Weight; NR = Not Reported
1
The values are consolidated by the author reported from different studies
2
Kale (B. oleraceae L. var. acephala Dc.) from fields of Trabzon, Turkey.
3
Mean of 25 genotypes of Kale grown in SC, USA
4
Kales cv. Karadere 077 (Istanbul Tohumculuk co.) from Turkey
5
Samples are collected from the local market of Asba, Delta state, Nigeria.
6
Kale varieties (Brassica oleracea L. var. acephala) was used for investigations from Krakow, Poland
Satheesh & Workneh Fanta, Cogent Food & Agriculture (2020), 6: 1811048
https://doi.org/10.1080/23311932.2020.1811048
Page 7 of 31
climate, kale is reported to have highest potassium concentration (Roy & Chakrabarti, 2003).
Dietary potassium effects on blood pressure (Bazzano et al., 2013), and reduces the blood pressure
(Binia et al., 2015) particularly in high-sodium diet (Susan Hedayati et al., 2012).
In case of Calcium, kale is appreciated for its high concentrations and excellent absorbability
compared to other salad crops (Gupta & Rana, 2003) and brassica vegetables (Fahey, 2003;
Heaney et al., 1993). Kale was reported to have 58.8% of absorption in calcium which is higher
than milk (32%). This fractional absorption percentage of kale is comparable to cauliflower
(58.6%), but lesser than Brussels sprouts (63.8%) (Connie & Aren, 1994). However, availability of
vegetables like Cauliflower and Brussels sprouts is difficult for poor people in under developed
countries, while kale is the best source for the calcium at low cost. Kale is also reported to have
high amount of magnesium compared to other vegetables of brassica family (Fahey, 2003). The
amount of potassium and magnesium in fruits and vegetables play a potential role in the manage-
ment of bone mineral density (Tucker et al., 1999).
The GLVs were reported to be a good choice for iron in vegan food habits. However, it depends
on the composition of ascorbic acid (promoter), dietary fiber, oxalates and tannins (inhibitors)
(Chiplonkar et al., 1999). Kale is found to have 5–10 mg/100 g of iron (Gopalan et al., 1989), which
is higher compared to spinach (2.71 mg/100 g) (Bhattacharjee et al., 1998) and other brassica
vegetables (Fahey, 2003). Hence, kale is the best source for fortification to enhance the iron
content. The iron content in kale ranges from 1.1 to 12.19 mg/100 g, Zn 0.045–394 mg/100 g
and 0.8–14.73 mg/100 g (Emebu & Anyika, 2011; Manchali et al., 2012; Sikora & Bodziarczyk, 2012).
Zinc content in kale is reported to be higher than in all other common brassica vegetables and
spinach (530 µg/100 g) (Bhattacharjee et al., 1998). The deficiency of zinc is considered as a
worldwide public health problem resulting in 1.4% deaths around the globe (Fischer Walker et al.,
2009). People in sub-Saharan Africa are identified with iron and zinc deficiencies due to the
consumption of cereal-based diets for energy and micronutrients (Joy et al., 2014) and GLVs
provide contribution of zinc in human diet. Cereals are composed of considerable amount of
anti-nutritional factors (phytate and tannins) which reduces the bioavailability of the iron and
zinc in the diet (Hunt, 2003; Gupta et al., 2013; Kruger et al., 2015). Kale has a higher quantity of
manganese compared to the vegetables of brassica family (Fahey, 2003) and spinach
(Bhattacharjee et al., 1998).
Kale is found to have good amount of the selenium ranging from 0.009 to 0.0023 mg/100 g
(Manchali et al., 2012; Thavarajah et al., 2016) compared to other brassica and green leafy vege-
tables (Fahey, 2003). According to the research of Navarro-Alarcon and Cabrera-Vique, (2000), this
good amount of the Selenium is important in several selenoproteins with essential biological
functions. Kale is reported as having good concentrations of phosphorus in rage of 0.52–513 mg/
100 g compared to other salad vegetable crops (Gupta & Rana, 2003) except for Cress among the
Brassica family vegetables (Fahey, 2003).
Sodium intake is necessary for humans and RDA may be vary from adequate intake and UL
(Anonymous, 1998). It is indicated in Table 3 that, 4.69–170 mg/100 g of sodium (Emebu & Anyika,
2011; Manchali et al., 2012; Sikora & Bodziarczyk, 2012) is found in kale which is higher compared
to other vegetables of brassica family (Fahey, 2003). Although, less than 500 mg/day Na is
sufficient for physiological requirements, usually, the average consumption of sodium is more
than recommendations (William et al., 2015).
Cobalt deficiency has not been reported generally and hence it is considered as a non-essential
mineral (Yamada, 2013). The RDA of Cobalt is very low (2.4 µg/day) compared to other minerals
(Bhattacharya et al., 2016). Cobalt is toxic to muscles with much exposure and higher concentra-
tions will increase in red blood cells number (polycythemia) (Squires et al., 1994). It is reported that
kale has 0.02 mg/100 g of Cobalt which is enough to achieve RDA (Ayaz et al., 2006).
Satheesh & Workneh Fanta, Cogent Food & Agriculture (2020), 6: 1811048
https://doi.org/10.1080/23311932.2020.1811048
Page 8 of 31
Uriu-Adams and Keen (2005) have reported the RDA of copper as 9 mg/day for an adult with a
tolerable upper intake level (UL) of 10 mg/day. Kale was reported to have optimum quantity of
copper in the range of 0.18–0.51 mg/100 g which is higher compared to other vegetables of
brassica family (Fahey, 2003).
The RDA of Lithium is 100 μg/day for adult human which helps in the stabilization of nerve
system activities (Schrauzer, 2002). An amount of 0.01 mg/100 g of lithium (Ayaz et al., 2006) is
found in kale which is higher than that is found in other brassica vegetables (Fahey, 2003). It is
reported that kale is found to have optimum concentration of Molybdenum as 0.29 mg/100 g
compared to the other brassica and leafy vegetables (Fahey, 2003).
Ayaz et al. (2006) have reported that kale contains the heavy metals like Arsenic (0.07 mg/
100 g), Barium (1.59 mg/100 g) Cadmium (0.01 mg/100 g), Chromium (0.26 mg/100 g), Lead
(0.02 mg/100 g), Titanium (0.04 mg/100 g), Strontium (25.2 mg/100 g) and Nickel (0.2 mg/
100 g). All these metals are toxic when they reach higher concentrations (Jaishankar et al.,
2014) but kale is reported to have very low concentrations within safety levels (Fahey, 2003).
Kale is usually consumed in fresh as salad or minimally cooked. Slow cooking has reported no
change in the kale’s mineral concentrations (Gupta & Rana, 2003). The broad range of minerals
and variation of the results among the authors reports are attributable to genetic (Phuke et al.,
2017), environmental and analytical differences (Howard et al., 1998). However, some authors are
reported the mineral information on dry weight basis, which created much difficulty for compar-
ison between different reports (Ayaz et al., 2006; Fadigas et al., 2010).
5. Amino acids in kale
Table 4 gives the composition of different amino acids in kale. Less amount of Cystine has been
found in kale compared to other GLVs grown in Africa (Ntuli, 2019). Cysteine content in kale is in
the range of 34.0–58 mg/100 g (Ayaz et al., 2006; Lisiewska et al., 2008). Large amount of cystine
is found in animal foods, lentils and seeds (Piste, 2013). Apart from kale, cruciferous vegetables
like, cabbages, broccoli and allium vegetables such as onions, leeks and garlic are the best source
of this amino acid (Doleman et al., 2017).
It is reported in Table 4 that the concentration of Glutamic acid in kale ranges from 33.20–
450 mg/100 g (Ayaz et al., 2006; Eppendorfer & Bille, 1996; Lisiewska et al., 2008), which is lower
than that is found in Hibiscus cannabinus and Haematostaphis barter (Kubmarawa et al., 2009),
Korean spinach (Yoon et al., 2016). But, the concentration of Glutamic acid in kale is higher than
that of the Nigerian spinach (A. hybridus), Bitter leaf (V. amygdalina), Pumpkin leaf (T. occidentalis)
and Water leaf (T. triangulare) (Arowora et al., 2017).
Serine is reported as having lower concentrations in kale ranging from10.49–163 mg/100 g (Ayaz
et al., 2006; Eppendorfer & Bille, 1996; Lisiewska et al., 2008) and it is less than that of Hibiscus
cannabinus and Haematostaphis barter (Kubmarawa et al., 2009). However, the serine concentra-
tion in kale is close to that exists in Veronica amygdaline, Gnetum africana, Gongronema latifolium
and Ocimum gratissimum (Chinyere & Obasi, 2011).
The Glycine content in kale ranges from 11.30–190 mg/100 g by Ayaz et al. (2006), Eppendorfer and
Bille (1996) and Lisiewska et al. (2008) whereas, it is less than those of spinach (A. hybridus), bitter leaf
(V. amygdalina), pumpkin leaf (T. occidentalis) and water leaf (T. triangulare) (Arowora et al., 2017). The
RDA of histidine is 10 mg/kg of body weight and kale contains 3.45–106 mg/100 g (Ayaz et al., 2006;
Eppendorfer & Bille, 1996; Lisiewska et al., 2008) which is relatively less than those of other GLVs
(Arowora et al., 2017; Ntuli, 2019). The amount of Arginine in kale is reported in the range of 14.02–
229 mg/100 g (Ayaz et al., 2006; Eppendorfer & Bille, 1996; Lisiewska et al., 2008) which is less than
that of spinach (Yoon et al., 2016). The vegetables like asparagus, onion, cabbage, brussels sprouts,
spinach are reported for the good source of threonine (Fahey, 2003). Threonine content in kale is in the
Satheesh & Workneh Fanta, Cogent Food & Agriculture (2020), 6: 1811048
https://doi.org/10.1080/23311932.2020.1811048
Page 9 of 31
Table 4. Amino acids (mg/100 g) and fatty acid (µg/g) compositions in kale leaf reported by different researchers
Amino acid type Ayaz et al. (2006)
1
(DW)
Eppendorfer and
Bille (1996)
2
(DW)
Lisiewska et al.
(2008)
3
(FW)
Fatty acid type Ayaz et al. (2006)
1
(FW)
Cys 34.0 NR 58 Myristic Acid (14:0) 0.70
Asp 27.60 20.03 349 Myristoleic Acid (14:1) 0.55
Glu 33.20 49.01 450 Pentadecylic Acid (15:0) 0.33
Ser 13.80 10.49 163 Palmitic Acid (16:0) 18.7
Gly 13.10 11.30 190 Palmitoleic Acid (16:1) 0.51
His 64.0 3.75 106 Hexadecatrienoic Acid (16:3) 15.7
Arg 20.60 14.02 229 Stearic Acid (18:0) 5.92
Thr 13.90 10.30 164 Oleic Acid (18: 1 n-9) 3.38
Ala 14.60 12.77 215 Vaccenic Acid (18:1 n-7) 1.10
Pro 17.50 19.24 434 Linoleic Acid (18:2 n-6) 18.6
Tyr 12.50 8.24 122 α- Linolenic Acid (18:3 n-3) 85.3
Val 17.10 12.04 207 Arachidic Acid (20:0) 0.72
Met 60.0 0 72 Gondoic Acid (20:1 n-9) 0.81
Ile 12.80 8.72 156 Eicosadienoic Acid (20:2 n-6) 0.34
Leu 20.30 16.32 299 Dihomo gamma-linolenic Acid (20:3 n-3) 0.50
Phe 14.60 10.94 186 Arachidonic Acid (20:4 n-3) ND
Trp 89.00 NR NR Eicosapentaenoic Acid (20::4 n-3) ND
Lys 15.00 12.91 221 Behenic Acid (22:0) 0.71
Erucic Acid (22:1 n-9) 1.50
Lignoceric Acid (24:0) 2.82
TS 30.0
TUS 129
Where: FW = Fresh Weight; DW = Dry Weight; ND = Not detected; NR = Not Reported; TS = Total saturated fat; TUS = Total unsaturated fats
1
Kale (B. oleraceae L. var. acephala Dc.) from Trabzon, Turkey
2
The samples were collected from Copenhagen, Denmark
3
The kale from Agricultural University of Krakow from Poland
Satheesh & Workneh Fanta, Cogent Food & Agriculture (2020), 6: 1811048
https://doi.org/10.1080/23311932.2020.1811048
Page 10 of 31
range of 10.30–164 mg/100 g (Ayaz et al., 2006; Eppendorfer & Bille, 1996; Lisiewska et al., 2008) which
is considered as a moderate source for threonine, whereas, meat products are reported to have high
concentration of the threonine (Coleman, 2015).
It is reported the concentration of Alanine is 12.77–215 mg/100 g of kale (Ayaz et al., 2006;
Eppendorfer & Bille, 1996; Lisiewska et al., 2008) which is similar to other GLVs (Arowora et al.,
2017; Yoon et al., 2016). Eggs, meet, fish, dairy products are the major sources of Alanine (Górska-
Warsewicz et al., 2018). Proline is reported to be in the range of 17.50–434 mg/100 g of kale (Ayaz
et al., 2006; Eppendorfer & Bille, 1996; Lisiewska et al., 2008), which is comparable with other GLVs
and vegetables of brassica family (Fahey, 2003). Tyrosine is in the range of 8.24–122 mg/100 g of
kale (Ayaz et al., 2006; Eppendorfer & Bille, 1996; Lisiewska et al., 2008). Usually, the plant based
foods are not the best source of the tyrosine (Yoon et al., 2016).
The valine concentration in kale is reported as 12.04–207 mg/100 g (Ayaz et al., 2006;
Eppendorfer & Bille, 1996; Lisiewska et al., 2008) which is similar to other GLVs (Ntuli, 2019).
Higher concentrations of valine is reported in kidney beans, leafy vegetables, poultry and milk
(Górska-Warsewicz et al., 2018). Methionine is reported in the range of 60.0–72.0 mg/100 g of kale
(Ayaz et al., 2006; Eppendorfer & Bille, 1996; Lisiewska et al., 2008) which is similar to other GLVs
(Arowora et al., 2017; Ntuli, 2019).
Isoleucine is reported in that kale has 8.72–156 mg/100 g (Ayaz et al., 2006; Eppendorfer & Bille,
1996; Lisiewska et al., 2008) which is comparable to other GLVs (Arowora et al., 2017; Ntuli, 2019). In
case of Lucien, it exists in the range of 16.32–299 mg/100 g of kale (Ayaz et al., 2006; Eppendorfer &
Bille, 1996; Lisiewska et al., 2008). The RDA of phenylalanine is 25 mg/kg of body weight (Traylor et al.,
2018). Kale is providing a good concentration of phenylalanine compared to other GLVs (Arowora et
al., 2017; Ntuli, 2019) and it is in the range of the 10.94–189 mg/100 g of kale (Ayaz et al., 2006;
Eppendorfer & Bille, 1996; Lisiewska et al., 2008). Tryptophan is reported as the 89 mg/100 g of kale
(Ayaz et al., 2006; Eppendorfer & Bille, 1996; Lisiewska et al., 2008; Ntuli, 2019) which is a moderate
amount compared to other GLVs. Tryptophan deficiency leads to pellagra, and severe alterations of
skin, gut and brain activity (Palego et al., 2016). Lysine is reported in the range of 12.9–221 mg/100 g of
kale (Ayaz et al., 2006; Eppendorfer & Bille, 1996; Lisiewska et al., 2008). Kale is considered as a
moderate source of the lysine in comparison with other GLVs (Arowora et al., 2017; Ntuli, 2019).
6. Vitamins and selected carotenoids in kale
Kale is reported to have high concentration of vitamin C than all other salad vegetables and
vegetables of Brassicaceae family (Fahey, 2003; Gupta & Rana, 2003). Edelman and Colt (2016)
have reported that the amount of vitamin C in kale is much higher than that of in Duck-weed and
also other GLVs of Africa (Uusiku et al., 2010). It is in the range of 62.27–969 mg/100 g and is
considered as the best source for vitamin C, satisfying the RDA for both males and females
(Acikgoz, 2011; Hagen et al., 2009; Murtaza et al., 2006; Sikora & Bodziarczyk, 2012). Vitamin C
RDA is 90 mg-120 mg/day (Aly et al., 2010). The deficiency of vitamin C leads to scurvy with
disturbances in collagen metabolism and a tendency to bleed (Mayland et al., 2005).
B-complex vitamins are water soluble and composed of vitamin B1 (Thiamine), vitamin B2 (Riboflavin),
vitamin B3 (Niacin), vitamin B5 (Pantothenate), vitamin B6 (Pyridoxal), vitamin B7 (Biotin), vitamin B9
(Folate) and kale has reported all the above vitamins except Vitamin B12 (Cyanocobalamin).
In case of Thiamine, it is reported to exist between 0.110–0.9 mg/100 g of kale as indicated in
Table 5 which is comparable with those of other salad vegetables as well as vegetables of
Brassicaceae family (Fahey, 2003; Gupta & Rana, 2003). Agte et al. (2000) reported that GLVs
are the best source of Vitamin B1.Gupta, Gowri, et al., (2013) has reported that kale has high
concentration of thiamine than Amaranthus gangeticus, Chenopodium album, Centella asiatica,
Amaranthus tricolor, Trigonella foenum-graecum.
Satheesh & Workneh Fanta, Cogent Food & Agriculture (2020), 6: 1811048
https://doi.org/10.1080/23311932.2020.1811048
Page 11 of 31
Table 5. Vitamin C, β-carotene, lutein, violaxanthin and neoxanthin compositions (mg/100 g) reported in kale (in fresh weight basis) by different authors
Component Type Acikgoz (2011)
1
Hagen et al.
(2009)
2
M. G. Lefsrud et
al. (2005)
3
De Azevedo and
Rodriguez-Amaya
(2005)
4
M. Lefsrud et al.
(2007)
5
Sikora and
Bodziarczyk
(2012)
6
Murtaza et al.
(2006)
7
Vitamin C 104.31 969 NR NR NR 62.27 151
β-carotene NR NR 10.97 3.887 8.92 6.40 44
Lutein NR NR 14.175 5.061 38.16 NR NR
Violaxanthin NR NR NR 3.316 NR NR NR
Neoxanthin NR NR NR 1.694 NR NR NR
Where: NR = Not Reported
1
Kale grown in South Carolina, USA.
2
Curly Kale (B. oleracea L. var. acephale, cv. Reflex) from Norwegian University Life Sciences, Norway
3
“Winterbore” kale from University of Tennessee, Knoxville, USA
4
Kale (Brassica oleracea) of the common cultivar “Manteiga” from S˜ao Paulo, Brazil
5
Brassica oleracea L. var. acephala DC cul. “Winterbor” were from USA.
6
Kale (Brassica oleracea L. var. acephala) from Krakow, Poland
7
Brassica Oleracea cv gongilodes kale from Kashmir, India
Satheesh & Workneh Fanta, Cogent Food & Agriculture (2020), 6: 1811048
https://doi.org/10.1080/23311932.2020.1811048
Page 12 of 31
The concentration of Riboflavin reported in kale is considered to be reasonably good which varies
between 0.13–0.9 mg/100 g (Fahey, 2003; Gupta & Rana, 2003) though it is lower than that of
spinach and Duck-weed (Edelman & Colt, 2016). A similar concentration of vitamin B2 is found in
vegetables of Brassicaceae family (Fahey, 2003). Agte et al. (2000) has analyzed 24 varieties of
GLVs for riboflavin concentrations and reported that kale is better among all. Uusiku et al. (2010)
has found that kale has the best concentration of vitamin B2 compared to several other GLVs from
Africa.
Catak and Yaman (2019) has analyzed the profiles of vitamin B3 in several fruits and vegetables
and kale showed a better concentration than in Broccoli, Brussels sprouts, Spinach and other
brassica vegetables (Fahey, 2003). Similarly, it is reported that kale has better concentration of
niacin than other common salad crops (Gupta & Rana, 2003). The concentration of niacin in kale
was reported as 1.00 mg/100 g.
Kale is considered as a good source of vitamin B5 and it ranges from 0.091 to 0.9 mg/100 g.
Hasan et al. (2013) have found no traces of Vitamin B5 in some of the indigenous GLVs of
Bangladesh and Indian spinach. It is found that pantothenic acid in kale is lower than that of
other brassica vegetables (Fahey, 2003)
Kale is considered as a good source of vitamin B6 among other GLVs and the amount of vitamin
B6 in kale is reported to be 0.27–2.5 mg/100 g (Fahey, 2003), which is better than other commonly
consuming Brassicaceae family vegetables. It is also reported that kale has better concentrations
of the pyridoxine compared to Indian spinach, red and green amaranth leaves and duck weed
(Edelman & Colt, 2016; Hasan et al., 2013).
Kale is reported to have higher concentrations of folic acid to the extent of 29 mg/100 g than
amaranth, mint, spinach and other common brassica vegetables (Agte et al., 2000). However, it
has smaller concentrations of vitamin B9 (Fahey, 2003). Takeiti et al. (2009) have reported that
kale has better folic acid concentration than P. aculeata (OPN leaves), Synanthera (chomte),
Oleracea (spinach), L. sativum (cress), I. batatas (sweet potato leaves), A. graveolens L. (dill),
Sagittifolium S. (Taioba). Uusiku et al. (2010) have reviewed the composition of vitamins in GLVs
in Africa and concluded that kale has the best concentration of the folate and a stated kale as a
good source of Vitamin B9.
It is reported that kale is a moderate source of vitamin A having 8900 IU with the retinal
equivalence (RE) as 890 µg/100 g (Fahey, 2003). The RE reported in GLVs from Africa is 99–1970 µg/
100 g (Uusiku et al., 2010) and also vitamin A in P. aculeata (OPN leaves) is 2333 IU/100 g (Takeiti
et al., 2009) which is lower than that in kale. Raju et al. (2007) have reported vitamin A (retinal
equivalent) as 641–19,101 µg/100 g in medicinal plants which is higher than in kale.
β -carotene (BC) is the precursor for retinol and vitamin A in kale which is reported to be 3.887–
44 mg/100 g as indicated in Table 5. Takeiti et al. (2009) have reported that 0.31–5.58 mg/100 g of
BC is available among the GLVs like P. aculeata (OPN leaves), L. synanthera (Chomte), S. oleracea
(Spinach), L. sativum (Cress), I. batatas (Sweet potato leaves), A. graveolens L. (Dill), X. sagittifolium
S. (Taioba). Raju et al. (2007) have reported 3.85–92.82 mg/100 g of BC in the medicinally
important GLVs from India. Gupta, Gowri, et al., (2013) have reported that Amaranthus gangeticus,
Chenopodium album, Centella asiatica, Amaranthus tricolor and Trigonella foenumgraecum con-
centration have 2.7–5.46 mg/100 g of BC. According to WHO the RDA of vitamin A is 700 and
900 µg/day for females and males, respectively (Trumbo et al., 2001). Consumption of 100 g of kale
will fulfill this requirement of vitamin A.
Vitamin E (α-tocopherol equivalent) is reported as 0.800 mg/100 g of kale (Fahey, 2003).
Achikanu et al., (2013) have reported that Ficus capensis, Solanum melongena, Mucuna prurient,
Solanum macrocarpon, Solanum nigrum, Moringa oleifera lam, Solanum aethiopicum, Cridoscolus
Satheesh & Workneh Fanta, Cogent Food & Agriculture (2020), 6: 1811048
https://doi.org/10.1080/23311932.2020.1811048
Page 13 of 31
acontifolius were have higher concentration of Vitamin E. Usually the best source of Vitamin E are
the oils and fats and the GLVs are considered as its poor source (Choo et al., 1996).
From the samples of kale grown in Boston and Montreal, vitamin K is reported as 573 µg/100 g
(Catani et al., 2005) and 6.21–16.57 µg/100 g (Booth Sarah et al., 1993), respectively. Compared to
other fruits and vegetables, kale is reported to have good concentration of the vitamin K. Novotny
et al. (2010) have reported that the bioavailability of phylloquinone from kale is 4 · 7%. However,
kale is reported as one of the best sources of vitamin K compared to other commonly consuming
vegetables (Booth Sarah et al., 1993).
Lutein, violaxanthin and neoxanthin are the major carotenoids and their concentrations in kale
are presented in Table 5. Lutein is in the range of 5.06–38.16 mg/100 g (De Azevedo & Rodriguez-
Amaya, 2005; M. G. Lefsrud et al., 2005; M. Lefsrud et al., 2007). Lutein cannot synthesize in
humans and should be obtained through food composed of vegetarian diet (fruits and vegetables)
(Calvo, 2005). Lutein, zeaxanthins are the stereo isomers which usually coexists in nature and GLVs
like kale and spinach are their best sources (Shegokar & Mitri, 2012). Holden et al. (1999) have
reported that 40 mg/100 g of lutein + zeaxanthin is available in kale. In contrast, only less than
1 mg is reported in 100 g of yellow-orange color food crops like carrots, peaches, corn, papaya and
oranges. Researchers have reported that lutein acts as an antioxidant and it is very important for
skin health (Shegokar & Mitri, 2012; Stahl & Sies, 2004). Finally, kale is reported as the best source
of lutein than other orange to yellow fruits and vegetables.
Perera and Yen (2007) have reported that violaxanthin and neoxanthin are abundant in green
parts of the plants like GLVs. They cannot be used by the humans but, their concentration can
influence the total carotenoid intake of an individual. Biehler et al. (2012) have reported that
yellow bell peppers were especially rich in violaxanthin (4.4 mg/100 g) followed by spinach (2.8 mg/
100 g) and creamed spinach (2.5 mg/100 g) and kale is also reported to have similar amounts of
the Violaxanthin (3.36 mg/100 g). De Azevedo and Rodriguez-Amaya (2005); Žnidarčič et al. (2011)
have reported 0.35–1.07 mg/100 g of neoxanthin in five leafy vegetable and found that neoxanthin
is lower than violaxanthin in all. Similar conclusions are reported by De Sá and Rodriguez-Amaya
(2003) and also stated that Violaxanthin in GLVs usually surpasses neoxanthin. The same trend of
the results was observed in the kale that 1.694 mg/100 g of neoxanthin is found (De Azevedo &
Rodriguez-Amaya, 2005) which is less than the violaxanthins.
7. Flavonoids, phenolic compounds, glucosinolates in kale
Flavonoids are group of polyphenolic compounds found widely in plants (Cao et al., 1997) and possess
strong antioxidant properties due to the phenolic hydroxyl groups (Subhasree et al., 2009). Different
types of flavonoids presented in the kale are presented in Table 6. The flavonoids content of kale is
reported as 661–892 of mg/100 g as shown in Table 6 (Olsen et al., 2009; Sidsel et al., 2009; Susanne et
al., 2010). It is reported that GLVs are the good source of flavonoids and other anti-oxidant vitamins
and compounds (Subhasree et al., 2009). Adefegha and Oboh (2011) have analyzed the Talinum
triangulare, Ocimum gratissimum, Amaranthus hybridus, Telfairia occidentalis, Ipomea batata,
Cnidoscolus aconitifolius, Baselia alba and Senecio biafrae leaves and reported the flavonoid content
is in the range of 8.2–42.1 mg/100 g. Marinova et al. (2005) have analyzed the total flavonoid content
of selected fruits and vegetables and reported it 20.2–190.3 mg/100 g. Bahorun et al. (2004) has
reported the total flavonoid content of the Mauritian vegetables as 94.4–4.5 mg/100 g with its highest
content in broccoli and the lowest in carrot. It can be concluded that kale is a good source of flavonoids
compared to other commonly consuming vegetables.
Quercetin is a flavonoid found in GLVs having special biological functions which improves mental
and physical performance, reduces the risk of infection, anti-carcinogenic, anti-inflammatory, anti-
viral, antioxidant and psychostimulant activities (Y. Li et al., 2016). Kale is reported to contain
Quercetin in the range of 44–319 mg/100 g (Olsen et al., 2009; Sidsel et al., 2009; Susanne et al.,
2010). Andarwulan et al. (2010) have reported 0.30–51.3 mg/100 g of Quercetin in vegetables from the
Satheesh & Workneh Fanta, Cogent Food & Agriculture (2020), 6: 1811048
https://doi.org/10.1080/23311932.2020.1811048
Page 14 of 31
Indonesia. On the contrary, Quercetin in Gnetum africanum (Afang), Lasianthera africana (Editan) and
Gongronema latifolium (Utazi) leaf extracts is reported as 429–546 mg/100 g (Nwanna et al., 2016).
Sultana and Anwar (2008), had evaluated selected fruits, vegetables and medicinal plants and
reported the content of Quercetin as 0.12–35.94 mg/100 g. Hence, kale is considered as having a
reasonably best concentration of Quercetin contributing to the antioxidant properties.
Kaempferol is a natural flavonol, an active compound reported for antioxidant, anti-inflamma-
tory, antimicrobial, anti-diabetic and anti-cancer activities (Calderón-Montaño et al., 2011).
Kaempferol is reported in the range of 58–537 mg/100 g of kale samples (Olsen et al., 2009;
Sidsel et al., 2009; Susanne et al., 2010). Bahorun et al. (2004) have reported that Kaempferol in
Chinese cabbage (9.6 mg/100 g), onion (4.5 mg/100 g), Mugwort (12.5 mg/100 g), Broccoli (4.6 mg/
100 g), Cauliflower (1.2 mg/100 g), Tomato (0.7 mg/100 g), Carrot (0.6 mg/100 g) and these
concentrations are reported as lower than that of kale. Lako et al. (2007) have analyzed the
Fijian fruits and vegetables and reported less than 1 to 34 mg/100 g of Kaempferol. In general,
kale has good concentration of the Kaempferol as compared to other vegetables.
Phenolic compounds are not nutrients but, the dietary intake provides health-protective effects
(Cheynier, 2012). They can be divided into phenolic acids, flavonoids, tannins, coumarins, lignans,
quinones, stilbens, and curcuminoids (Agati et al., 2012). Phenolic compounds are reported to have
health benefits including, antibacterial, anti-inflammatory and anti-mutagenic activities
(Chandrasekara & Josheph Kumar, 2016). Kale is reported for 201.67–1167 mg/100 g of total phenolic
content (Murtaza et al., 2006; Olsen et al., 2009; Sidsel et al., 2009; Sikora & Bodziarczyk, 2012; Susanne
et al., 2010). Johari and Khong (2019) have reported that the total phenolic content of Pereskia bleo as
252.0–408.2 mg/100 g. Aryal et al. (2019) have reported the total phenolic content of wild vegetables
from Western Nepal such as Alternanthera sessilis, Basella alba, Cassia tora, Digera muricata, Ipomoea
aquatica, Leucas cephalotes, Portulaca oleracea and Solanum nigrum to be 770.6–2926.5 mg/100 g.
Hossain et al. (2017) have reported that green amaranth, water spinach leaf and Indian spinach leaf
had a total phenolic content of 93.33, 92.14 and 91.95 mg GAE/100 g, respectively. Obeng et al. (2019)
have reported that, Solanum macrocaron (Gboma), Talinum fruticosum (Ademe), Corchorus olitorius
(Yevogboma) and Amaranthus spp. (Atormaa) have a total phenolic content of 0.014–0.982 mg/100 g
by the fresh weight. Research reports have clearly identified the quantitative and qualitative differ-
ences of polyphenols in fruits, vegetables and GLVs. These differences can be attributed to the method
of extraction, processing and growing conditions and varietal differences.
Table 6. Total flavonoid, quercetin, kamempferol, total phenol, hydroxycinnamic acids
reported in kale by different researchers
Constituent Sidsel et al.
(2009)
1
(DW)
Susanne et
al (2010)
2
S
(2012)
2
(DW)
Olsen et al.
(2009)
3
(FW)
Sikora and
Bodziarczyk
(2012)
4
(FW)
Murtaza et
al. (2006)
5
(FW)
Total flavonoids (mg/100 g) 661 892 646 NR NR
Quercetin (mg/100 g) 319 272 44 NR NR
Kaempferol (mg/100 g) 343 537 58 NR NR
Total phenols (mg of GAE/
100 g)
1167 NR 384 574.95 201.67
Hydroxycinnamic acids (mg
RE/100 g)
NR NR 204 NR NR
Where FW = Fresh Weight; DW = Dry Weight; NR = Not Reported
1
Curly kale (B. oleracea L. var. acephale, cv. Reflex) from Norwegian University, Norway.
2
Kales from the Germany
3
Kale from Norwegian University of Life Sciences, Norway.
4
Kale varieties (Brassica oleracea L. var. acephala) from Krakow, Poland.
5
Kale (Brassica Oleracea cv gongilodes) from Kashmir, India.
Satheesh & Workneh Fanta, Cogent Food & Agriculture (2020), 6: 1811048
https://doi.org/10.1080/23311932.2020.1811048
Page 15 of 31
Hydroxycinnamic acids are the natural phenyl propenoic acid compounds which are the metabolic
products of cinnamic acid with 3–6 carbon backbone (Johari & Khong, 2019). Hydroxycinnamic acids
are very important sources for antioxidants and possess the role in the stability of flavor, color and
nutritional bioavailability of foods (Wilson et al., 2017). Very little research is done on Hydroxycinnamic
acids concentration in the kale. Olsen et al. (2009) have reported that kale has 204 mg of
Hydroxycinnamic acids per 100 g kale. Dietary sources of Hydroxycinnamic acids include apples,
blueberries, cereals, cherries, cinnamon, coffee, ginger, grapes, lettuce, olives, oranges, pears, pine-
apples, plums, potatoes, prunes, spinach, strawberries, sunflower seeds, turmeric and herbs like basal,
marjoram, oregano, rosemary, sage and thyme (El-Seedi et al., 2012). Compared to fruits and vege-
tables, kale has less concentration of this phenolic acid. Some of the plant sources like tea showed
huge amount of the Hydroxycinnamic acids but kale has these acids similar to other GLVs like spinach.
Glucosinolates are the plant secondary metabolite characteristics of the Cruciferae family.
Glucosinolate containing plants include mustard, wasabi, cabbage, swede, rapeseed, kale, turnip
are the source for food and feed for humans and animals (Cartea et al., 2011). Kale is reported to
have 41 µmol/g by dry weight (Velasco et al., 2007) which is comparable with other brassica
vegetables. Recent studies have reported a positive nature of glucosinolates, which include reg-
ulation of inflammation, stress, antioxidant activities and antimicrobial properties (Melrose, 2019).
A comprehensive analysis of glucosinolates among broccoli, brussels sprouts, cabbage, cauliflower
and kale has reported that, Brassicaceae vegetables contained wider glucosinolates among the
other vegetables (Carlson et al., 1987). Broccoli contains glucoraphanin as the primary glucosino-
late whereas brussels sprouts, cabbage, cauliflower and kale have higher levels of sinigrin and
progoitrin with very little amounts of glucoraphanin (Jeffery & Stewart, 2004).
8. Fatty acids in kale
Ayaz et al. (2006) have reported different types of fatty acids in kale by dry weight basis and
presented in Table 4. Usually, the fat content in kale is reported as 11.8% on dry weight basis
(Kahlon, Chiu and Chapman, 2008) and 0.26–0.74% by fresh weight basis (Emebu & Anyika, 2011;
Manchali et al., 2012; Sikora & Bodziarczyk, 2012). Among the reported results, the unsaturated
fatty acids are higher than the saturated fatty acids. As reported by Ayaz et al. (2006), the total
saturated fats are 30.0 µg/g whereas, the total unsaturated fats are 129 µg/g of kale. Among the
saturated fatty acids kale is reported to have C14:0 (Myristic acid), C15:0 (Pentadecylic acid), C16:0
(Palmitic acid), C18:0 (Stearic acid), C20:0 (Arachidic acid), C22:0 (Behenic acid), C24:0 (Lignoceric
acid). Among all these saturated fatty acids, C16:0 is reported as 18.7 µg/g whereas other fatty
acids such as C14:0, C15:0, C18:0, C20:0, C22:0, C24:0 are reported to have 0.70, 0.33, 5.92, 0.72,
0.71 µg/g, respectively (Ayaz et al., 2006).
Saturated fatty acids are reported as the reason for elevated lipid levels in human blood and
considered as non-essential because they can synthesize in human body (Clifton & Keogh, 2017).
All saturated fatty acids from 8 to 16 carbon atoms are responsible to raise the serum LDL
cholesterol levels when they are consumed through human diet (Forouhi et al., 2018). However,
stearic acid does not raise the serum LDL cholesterol levels due to rapid conversion into oleic acid
in the body (Denke & Grundy, 1991). Kale is reported to have low composition of the saturated
fatty acids compared to some of the GLVs (Adeyeye et al., 2018).
Total unsaturated fatty acids reported in dry kale leafs as 129 µg/g (Ayaz et al., 2006). Among
the total unsaturated fatty acids, kale is reported to have 14:1 (Myristoleic acid), 16:1 (Sapienic
acid), 16:3 (Palmitolinolenic acid), 18:1 n-9 (Oleic Acid), 18:1 n-7 (Vaccenic Acid), 18:2 n-6 (linoleic
acid), 18:3 n-3 (α-linolenic Acid), 20:1 n-9 (Eicosenoic acid), 20:2 n-6 (Ecosadienoic acid), 20:3 n-3
(Eicosatienoic acid), 20:4 n-3 (Eicosatetaenoic acid), 20:5 n-3 (Heneicosapentaenoic acid), 22:1 n-9
(Erucic acid). Among all, 18:3 n-3 is reported to be 85.3 µg/g (Ayaz et al., 2006).
Kale is reported to have ω-3, 6, 7 and 9 fatty acids in good concentrations (Ayaz et al., 2006).
Unsaturated and poly unsaturated fatty acids (PUFA) are reported to have numerous benefits like
Satheesh & Workneh Fanta, Cogent Food & Agriculture (2020), 6: 1811048
https://doi.org/10.1080/23311932.2020.1811048
Page 16 of 31
preventing Coronary Heart Diseases (CHD) and deaths related to CHD (Mozaffarian et al., 2010).
Among different fatty acids, linoleic acid is reported for overall health benefits (Jandacek, 2017).
Researchers have reported that, ω-3, 6, fatty acids are very important to patients surviving from
myocardial, cardiovascular disease (Dunbar et al., 2014) and anti-inflammatory effects, positive
effect on obesity, improved endothelial function, reduced blood pressure, lowered triglycerides in
blood (Patterson et al., 2012), for alteration of chemotherapeutic drugs toxicity, protection from
skin and oral cancers (M. Johnson et al., 2019).
Calder (2015) has reported that, n-3 PUFA are very important in immunomodulatory and anti-
inflammatory properties. Consumption of fatty acids help in prevention of many inflammatory related
diseases like diabetes (Lee et al., 2014) and cardiovascular disease (Phang et al., 2013). Simopoulos
(2004) has reported that Purslane, Spinach, Butter crunch Lettuce, Red Leaf Lettuce, Mustard are good
source for omega fatty acids which contain more PUFA fatty acids compared to that of kale. M.
Johnson et al. (2013), (2018), 2019) had reported that the GLVs serve as a major dietary reservoir of
the essential PUFAs and the consumption of GLVs determines the liver fatty acid composition. Uddin et
al. (2014) have reported that, kale has low sources of omega-3 fatty acids which are similar to broccoli.
9. Anti-nutritional factors in kale
Oxalic acid and its salts are present in number of plant based foods that have an adverse effect on
mineral bioavailability of Calcium and other minerals (Bhandari & Kawabata, 2004). Tea, rhubarb, spinach
and beet are reported for high oxalate-containing foods (Noonan, 1999). Kale was reported as the rich
source of oxalates. Erdogan and Onar (2011) have reported that the oxalate content as 297 mg/100 g by
fresh weight and 2302 mg/100 g by dry weight of kale. These contents are less compared to the oxalates
in Chard and Spinach. The oxalate content (0.08 mg/100 g) reported by Emebu and Anyika (2011) is very
much lower than reported by Erdogan and Onar (2011). This difference can be attributed to variations in
the method of analysis, the species and agro-geological conditions. P Agbaire (2011) have reported that
Vernomia anydalira (Bitter leaf), Moni esculenta (cassava leaf), Teiferia occidentalis (Ugu leaf), Talinum
triangulare (water leaf), Amaranthus spinosus (Green vegetable) has 0.076–0.106 mg/100 g of oxalates
by dry weight base. Kale is a rich source of Calcium and oxalate content is very important consideration
for bio-availability of Calcium. Noonan (1999) has reported that processing methods like soaking and
heat processing of high oxalate food samples have reduced the oxalate content.
Nitrates in kale is reported to be 201.6 mg/100 g by fresh weight basis and 1563 mg/100 g by dry
weight basis of kale (Erdogan & Onar, 2011). It is noted that the nitrate content of kale is higher
than in spinach and lower than in chard. Nitrate in kale is 11.1 and 85.7 mg/100 g by fresh and dry
weight basis, respectively (Erdogan & Onar, 2011). Compared to spinach and chard kale is reported
to have more concentration of Nitrate. Dennis and Wilson (2003) have reported that, nitrate
content in the samples of kale from USA was reported as 178.0 mg/kg. Nitrate is a usual
component of plants which is found due to microbiological attack. Nitrate in the soil is utilized
by plant as nitrogen in protein synthesis. Photosynthesis is a key for protein synthesis in plant,
however, photosynthesis is decreased as the light levels fall and this situation leads to nitrate
accumulation in cell fluids (Keeton, 2011). The nitrate concentrations in vegetables grown under
subdued light are reported to be higher than that is grown under bright light. Overall, nitrate
content in plant is determined by genotype and growing conditions (Anjana & Iqbal, 2007).
Erdogan and Onar (2011) have reported that kale has phytate content as 0.12 mg/100 g and
tannin as 0.15 mg/100 g of the kale grown from the Nigeria. P Agbaire (2011) has reported that
Vernomia anydalira (Bitter leaf), Moni esculenta (Cassava leaf), Teiferia occidentalis (Ugu leaf),
Talinum triangulare (Water leaf), Amaranthus spinosus (Green vegetable) have 0.58–0.811 mg/
100 g of phytate, while kale is reported to have least concentration of the phytate than the above
leafy vegetables. P.O. Agbaire (2012) has analyzed the anti-nutritional factors in GLVs and reported
that the phytate is in the range of 0.412–1.3 mg/100 g which is higher than that of kale. The tannin
Satheesh & Workneh Fanta, Cogent Food & Agriculture (2020), 6: 1811048
https://doi.org/10.1080/23311932.2020.1811048
Page 17 of 31
content reported by P.O. Agbaire (2012) is 0.004–0.026 mg/100 g in different GLVs which is lower
than the phytate content in kale (Erdogan & Onar, 2011).
Phytate has anti-nutritional activities in human body by strong chelation of calcium, iron and
zinc to form insoluble complexes and contributes to the deficiency of iron and zinc (Lopez et al.,
2002). On the other hand, phytate has a positive nutritional role as an antioxidant and anti-cancer
agent (Kumar et al., 2010). Phytate is reported to be contributing 60 to 80% of total phosphorus in
cereals, legumes, nuts and oilseeds. The lower concentrations of phytate are found in roots, tubers,
fruits and berries (Reddy, 2001).
10. Studies reported on the health benefits of the kale
Consumers considering kale consumption provide better health, to confirm this, researchers reported
limited in vitro and in vivo studies, and they are summarized in Table 7. Only few researchers
established kales positive role in management of macular disease, bilirubin metabolism, protective
role in coronary artery disease, Anti-inflammatory activity, Antigenotoxic ability, Gastro intestinal
protective activity, inhibition of the carcinogenic compounds formation, positive to gut microbes,
anti-microbial nature against specific microorganisms. However, there are clear gaps and researchers
can work on different aspects related to the health and pharmacological activities of the kale.
11. Studies reported on the value-added products from the kale
Kale is widely consuming as part of the diet, but very limited studies were reported on the value-added
products and they are summarized in Table 8. The products reported from the kale are incorporation of
kale in bread, fresh kale juice sterilized with radiation, fermented kale juice by spontaneous and
induced fermentations (L. plantarum BFE 5092 and L. fermentum BFE 6620), beverages with addition
of apple juice, kale purée, dried kale leafs and kale leaves chlorophyll microcapsules. Even though kale
is a famous GLV, conversion of the kale to different value-added products are not studied well. Still
there is a huge scope for development of value-added products from kale.
12. Conclusions
Kale is one of the oldest GLVs in the world, known for its best source of fiber in dry conditions and
also for providing good concentration of prebiotic carbohydrates while it has been the poor source
of fat, energy and carbohydrates. Kale is a better source of potassium and calcium. The bioavail-
ability of the calcium in kale is very high which is better than milk. The amino acid composition of
kale is balanced and contains more unsaturated fatty acid than the saturated. Kale is also a good
source of vitamin A and β-carotenes and also for flavonoids like, Quercetin, kaempferol. In
addition, kale has good concentrations of the phenolic compounds hydroxycinnamic acids. With
better mineral compositions, kale contains high concentration of oxalates which is a major anti-
nutritional component. Kale also has glucosinolates along with tannins, phytates and nitrogen
compounds (Nitrates and Nitrites). In case of the health benefits, limited studies only reported in
vitro and in vivo studies and established that kales potential role in management of macular
disease, bilirubin metabolism, protective role in coronary artery disease, Anti-inflammatory activ-
ity, Antigenotoxic ability, gastro protective activity, inhibition of the carcinogenic compounds
formation, positive to gut microbes, anti-microbial against specific microorganisms. Kale is usually
consumed as a salad crop similar to other green leafy vegetable with minimal processing.
However, the value-added products and research on product developments from the kale leaf is
not reported well, except for its drying and preparation of juice. However, the role of kale in health
promotion also investigated in narrow. It can be concluded that kale is a potential leafy vegetable
for dietary recommendations for all age groups and it have very good potential for food and health
based products.
In future line of work researchers can intensively work on kale utilization in different foods and
kale based value-added food products for wider age groups consumers. Scholars can also carry
research on isolation of bio-active components from kale and their effective utilization in nutrition.
In addition, researchers can also work to determine kale role in nutrition, health and pharcological
Satheesh & Workneh Fanta, Cogent Food & Agriculture (2020), 6: 1811048
https://doi.org/10.1080/23311932.2020.1811048
Page 18 of 31
Table 7. Reported research studies on the health benefits of kale leaf, juice and extracts in humans by different authors
S. No Area of research Methodology employed Findings and conclusions References
1 Short-term
intervention with an
kale extract in
macular disease
A randomized, double-blind, placebo-controlled, parallel trial
conducted to determine the influence of a short-term
intervention of oleaginous extract of kale on plasma
xanthophyll concentrations and the optical density of the
macular pigment xanthophylls in 20 patients conducted for
10-weeks.
The concentrations of the xanthophylls in plasma and the
the macular pigment xanthophylls increased significantly by
the kale consumption within 4 weeks of intervention.
Arnold et al. (2013)
2 Kale consumption on
cytochrome activity
and bilirubin
metabolism
Randomized crossover study was conducted to determine the
effect of kale consumption on Cytochrome P4501A2 (CYP1A2,
CYP2A6, XO) and N-acetyltransferase (NAT2) activity was
determined by urinary caffeine metabolite ratios, UGT1A1
(Uridine di-phosphate glucuronosyl transferase1 A1) activity by
serum bilirubin concentrations and GSTA (Glutathione S-
transferase alpha) protein and GST (Glutathione S-transferase)
activity in blood by ELISA.
Authors concluded that, daily kale consumption increased
CYP1A2 activity as determined by caffeine metabolite ratios
by 16.4% and 15.2% after one and two weeks of feeding,
respectively. Also, daily kale consumption modified Bilirubin
metabolism such that serum conjugated Bilirubin decreased
from 19.4% of total Bilirubin on day 1 to 14.3% and 9.5% on
days 8 and 15, respectively.
Charron et al. (2020)
3In vitro binding of bile
acids by kale and
other vegetables
The in vitro binding of bile acids by kale in comparison with
other brassica vegetables was determined using a mixture of
bile acids secreted in human bile at a duodenal physiological
pH of 6.3.
The results of study revealed that, Bile acid binding for
spinach, kale and brussels sprouts was significantly higher
than for broccoli and mustard greens. These results point to
the health promoting potential of spinach = kale = brussels
sprouts > broccoli = mustard greens > cabbage = green bell
peppers = collards, as indicated by their bile acid binding on
dry matter basis.
Kahlon et al. (2007)
4 Phenolic acid contents
of kale extracts and
their antioxidant and
antibacterial activities
Nine phenolic acids were identified and quantified by HPLC–
MS in leaves and their antimicrobial properties are
determined against different micro organisms.
Concluded that, kale leaves rated as good dietary sources of
natural phenolic antioxidants and other compounds with
high or moderate antimicrobial activity. The plant extracts of
kale showed anti bacterial effect on Gram-positive (S. aureus,
E. faecalis, B. subtilis), Gram-negative (M. catarrhalis)
bacteria,and the two yeast-like fungi (C. tropicali and C.
albicans),
Ayaz, et al., (2008)
5 Kale Juice on
Coronary Artery
Disease risk factors in
Hypercholesterolemic
men
Evaluated the effect kale juice supplementation on coronary
artery disease risk factors among 32 hyper-cholesterolemic
men. The subjects consumed 150 mL of kale juice per day for
a 12-week intervention period.
Study concluded that, regular meals supplementation with
kale juice can favorably influence serum lipid profiles and
antioxidant systems, and hence contribute to reduce the
risks of coronary artery disease in male subjects with
Hyperlipidemia.
SooYeon S. Y. Kim et
al. (2008)
(Continued)
Satheesh & Workneh Fanta, Cogent Food & Agriculture (2020), 6: 1811048
https://doi.org/10.1080/23311932.2020.1811048
Page 19 of 31
Table 7. (Continued)
S. No Area of research Methodology employed Findings and conclusions References
6 Kale and papaya
supplementation in
colitis induced by Tri-
nitrobenzenesulfonic
(TNBS) acid in the rat
Researchers evaluated the effect of dried vegetables as a
prebiotic and intestinal anti-inflammatory in the rat colitis
model. Rats received, orally, 500 mg/kg of rat weight of three
treatments of dried vegetables: papaya, kale and the
mixture of both vegetables (60% of kale plus 40% of
papaya). After two weeks of feeding the evaluation was
done to determine anti-inflammatory activity.
Administration of the mixture was able to modulate the
bacterial flora in healthy rats, as well as in rats with colitis
induced by TNBS. In addition mixture of kale and papaya
showed intestinal anti-inflammatory effect in the colitic rats.
Lima et al. (2010)
7 Kale on Genotoxic and
Anti-genotoxic
potential in Different
Cells of Mice
The researchers were performed this study using the comet
assay, on leukocytes, liver, brain, bone marrow and testicular
cells,and using the micronucleus test (MN) in bone marrow
cells. In this study, eight groups of albino Swiss mice were
used, control (C), positive control (doxorubicin 80 mg/kg
(DXR)) and six experimental groups, which received 500,
1000 and 2000 mg/kg of kale extract alone while a further
three groups received the same doses plus DXR (80 mg/kg).
The results demonstrated that none of the tested doses of
kale extract showed genotoxic effects by the comet assay, or
clastogenic effects by the MN test. In addition, all cells
evaluated, the three tested doses of the kale extract
promoted inhibition of DNA damage induced by DXR. Finally,
concluded that, kale leaf extract showed no genotoxic or
clastogenic effects in different cells of mice. However, it
showed a significant decrease in DNA damage induced by
doxorubicin.
Gonçalves et al.
(2012)
8 Gastroprotective
activity of
hydroalcoholic extract
of kale leaves
Antiulcer assays were performed using the protocol of ulcer
induced by ethanol/HCl, and non-steroidal anti-inflammatory
drugs (NSAIDs). Parameters of gastric secretion were
determined by the pylorus ligation model and mucus in
gastric contents. In the study used Wistar rat’s female (250–
350 g) and Swiss mice male (25–35 g) were supplemented
with food and groups of six, in standard cages. The kale
extract administered by the oral route at 25, 50 and 100 mg/
kg.
Study showed a significant increase in gastric pH and mucus
production in the groups treated with kale when compared
with the control group. The results of the present study
showed that hydroalcoholic extract of kale displays antiulcer
activity, as demonstrated by the significant inhibition of ulcer
formation induced using different models.
Lemos et al. (2011)
9 Kale juice
supplementation up-
regulates HSP70 and
suppresses cognitive
decline in a mouse
model of accelerated
senescence
In this study researchers investigated the ability of kale juice
dietary supplementation to delay cognitive decline in the
senescence-accelerated mouse prone 8 (SAMP8) mouse.
SAMP8 mice were fed a diet containing 0.8% (W/W) of kale
for 16 weeks, and cognitive performance was examined
using the Morris water maze.
Kale juice administration improved spatial and leaning
memory as well as suppressed levels of serum 8-hydroxy-2′-
deoxyguanosine and brain malondialdehyde with respect to
the control group. This study concluded that dietary kale
supplementation can suppress cognitive decline and age-
related oxidative damage through the activation of HSP70 in
SAMP8 mice.
Kushimoto et al.
(2018)
(Continued)
Satheesh & Workneh Fanta, Cogent Food & Agriculture (2020), 6: 1811048
https://doi.org/10.1080/23311932.2020.1811048
Page 20 of 31
Table 7. (Continued)
S. No Area of research Methodology employed Findings and conclusions References
10 Inhibitory effect of
whole strawberries,
garlic juice or Kale
Juice on endogenous
formation of N-
nitrosodimethylamine
(NDMA) in Humans
In vitro and in vivo experiments were performed on inhibition
of nitrosation by strawberry, garlic and kale extracts. They
studied the formation of the carcinogen NDMA in humans
after administration of nitrate (400 mg/day) in combination
with an amine-rich diet and its possible inhibition by
administration of whole strawberries (300 g), garlic juice
(200 g: 75 g garlic juice in drinking water), or kale juice
(200 g) in 27 males and 13 females (ten healthy volunteers
in each group) of age 24±3 years.
Authors were reported that nitrate intake resulted in a
significant increase in mean salivary nitrate and nitrite
concentrations. Also, nitrate excretion in urine during the
experimental day was significantly increased compared with
the control days. When whole strawberries, garlic juice, or
kale juice was provided immediately after an amine-rich diet
with a nitrate, NDMA excretion was decreased by 70, 71 and
44%, respectively, compared with NDMA excretion after
ingestion of an amine-rich diet with a nitrate. These results
suggest that consumption of whole strawberries, garlic juice,
or kale juice can reduce endogenous NDMA formation.
Chung et al. (2002)
11 Functionality and
bioavailability of
kaempferol- glucoside
in kale by its
glucosidase activity by
gut microbes
Researchers studied the effects of the probiotic Lactobacillus
paracasei A221 on the functionality and bioavailability of
kaempferol-3-o-sophroside (KP3S), a kaempferol-glucoside
contained in kale, were investigated in vitro and in vivo.
Authors were reported that, using an intestinal barrier
model, treatment with Lactobacillus paracasei A221
significantly improved the effects of kale extract on the
barrier integrity in in vitro. Kaempferol (KP), but not KP3S,
clearly induced similar effects, suggesting that KP
contributes to the functional improvement of the kale
extract by Lactobacillus paracasei A221. Pharmacokinetics
analyses revealed that the co-administration of Lactobacillus
paracasei A221 and KP3S significantly enhanced the amount
of deconjugated KP in murine plasma samples at 3 h post-
administration. Finally, the oral administration of KP clearly
ameliorated various pathologies, including skin thinning,
fatty liver and anemia.
Shimojo et al. (2018)
Satheesh & Workneh Fanta, Cogent Food & Agriculture (2020), 6: 1811048
https://doi.org/10.1080/23311932.2020.1811048
Page 21 of 31
Table 8. Various food products from kale reported by different authors
# Product Objective/Method Findings of the Results References
1 Bread The impact of kale leaves on bread
making was assessed.
This study revealed that baking of non-processed kale in bread induced relatively low
losses of flavonoids, but high losses of glucosinolates break down products,
carotenoids and chlorophylls. Additionally, in kale an increase in hydroxycinnamic
acid derivatives was found after bread preparation. Hence, breads with added fresh
kale could enrich health-promoting secondary plant metabolites in baked goods.
Klopsch et al.
(2019)
2 Fermented
kale juice
Fermented kale juices was prepared
using four types of Lactobacilli
The study findings reported as after 48 h of fermentation time, viable cell counts of
all ferments reached an above 10
9
CFU/mL. The viability of the ferments after cold
storage in the refrigerator for 4 weeks showed 10
8
CFU/mL in all ferments. Among
four types of fermented kale juices, the ferment of Lactobacillus acidophilus IFO 3025
indicated a good nutritional composition, including neutral sugar (909. 76 µg/mL),
reducing sugar (564.00 µg/mL). Authors were concluded that probiotic kale juices
produced useful for the prevention of chronic diseases and are suggested as healthy
probiotic fermented beverages with high essential nutrients.
Seong Yeong Kim
(2017)
3 Fermentation of
African kale by L.
plantarum BFE 5092
and L. fermentum BFE
6620 starters
Lactobacillus plantarum BFE 5092 and
Lactobacillus fermentum BFE 6620
starter strains were investigated for
their application in fermentation of
African kale.
The strains utilized simple sugars in the kale to quickly reduce the pH from pH 6.0 to
pH 3.6 within 24 h. The strains continued to produce both D and L-lactic acid up to
144 h, reaching a maximum concentration of 4.0 g/L. Although vitamins C, B1 and B2
decreased during the fermentation, the final level of vitamin C in the product was an
appreciable concentration of 35 mg/100 g and shelf life also extended. Researchers
concluded that, controlled fermentation of kale offers a promising avenue to prevent
spoilage and improve the shelf life and safety.
Wafula et al.
(2015)
4 Kale Juice
spontaneous
fermentation by Lactic
acid bacteria
This study report on spontaneous
fermentation of curly kale and
characteristics of autochthonous
Lactic acid bacteria in kale juice
production.
Kale fermentation is the new possibility of the technological use of kale. Ten different
species of bacteria species were isolated from three phases of kale fermentation.
Among them, four species were identified as Lactobacillus spp. (L. plantarum 332, L.
paraplantarum G2114, L. brevis R413, L. curvatus 154), two as Weissella spp. (W.
hellenica 152, W. cibaria G44), two as Pediococcus spp. (P. pentosaceus 45AN, P.
acidilactici 2211), one as Leuconostoc mesenteroides 153 and one as Lactococcus
lactis 37BN.
Oguntoyinbo et al.
(2016)
5 Drying of kale in
convective hot air
dryer
Authors studied the effect of air
temperature and sample thickness (10,
20, 40 and 50 mm) on the drying
kinetics of kale using a convective air-
dryer at a fixed airflow rate of 1 m/s and
drying air temperatures of 30, 40, 50
and 60 °C.
The drying rate increased with drying air temperature but decreased with layer
thickness. The effective diffusivity for 10 mm thick layers was found to increase with
the drying air temperature and ranged between 14.9 and 55.9 × 10
−10
m
2
/s. The
effect of temperature on diffusivity could be expressed by an Arrhenius type
relationship with a high R
2
of 0.9989. The activation energy of kale was found to be
36.115 kJ/mol.
Mwithiga and
Olwal (2005)
(Continued)
Satheesh & Workneh Fanta, Cogent Food & Agriculture (2020), 6: 1811048
https://doi.org/10.1080/23311932.2020.1811048
Page 22 of 31
Table 8. (Continued)
# Product Objective/Method Findings of the Results References
6 Fresh kale juice
treated with gamma
irradiation
Researchers evaluated gamma
radiation treatment on shelf life of
natural kale juice. The total aerobic
bacteria in fresh kale juice, prepared by
a general kitchen process and the
bacteria survived in the juice in spite of
gamma irradiation treatment was
determined.
Two typical radiation-resistant bacteria, Bacillus megaterium and Exiguobacterium
acetylicum were isolated and identified from the 5 kGy-irradiated kale juices. The
growth of the surviving B. megaterium and E. acetylicum in the 3–5 kGy-irradiated
kale juice retarded and/or decreased significantly during a 3 day post-irradiation
storage period. This study suggested that 3–5 kGy of gamma irradiation may be
effective for prolonging the shelf-life of natural kale juice from a microbiological point
of view.
D. Kim et al. (2007)
7 Fresh Ashitaba and
kale juice treatment
with gamma
irradiation
In this study, examined the effects of
irradiation on the microbiological,
chemical and sensory properties of
ashitaba and kale juices for industrial
application and possible shelf-life
extension.
Irradiation of 5 kGy induced higher than 2 decimal reductions in the microbial level,
which was consistently maintained during storage for 7 days under refrigerated
conditions. Total content of ascorbic acid in vegetable juice decreased upon
irradiation in a dose-dependent manner, in contrast, flavonoids did not change,
whereas that of polyphenols increased upon irradiation. This study recommended
irradiation sterilizing fresh vegetable juice.
Jo et al. (2012)
8 Beverages based on
apple Juice with
addition of frozen and
freeze-dried kale
leaves
Authors were determined the
polyphenols, glucosinolates and
ascorbic acid content including
antioxidant activity of beverages on the
base of apple juice with addition of
frozen and freeze-dried kale leaves.
Upon enrichment with frozen (13%) and freeze-dried curly kale (3%), the naturally
cloudy apple juice showed an increase in phenolic compounds by 2.7 and 3.3-times,
accordingly. The antioxidant activity of beverages with the addition of curly kale
ranged from 6.6 to 9.4 μmol Trolox/mL. Prepared beverages were characterized
glucosinolates content at 117.6–167.6 mg/L and ascorbic acid content at 4.1–
31.9 mg/L. Sensory acceptability of prepared juice reported high acceptability.
Ró Ża et al. (2017)
9 Whey protein isolate-
kale leaves chlorophyll
(WPI-CH)
microcapsules
The authors were reported whey protein
isolate-kale leaves chlorophyll (WPI-CH)
microcapsules were prepared by spray
drying. Effect of inlet air drying
temperatures on the physicochemical
properties and antioxidant activity of
WPI-CH microcapsules were
investigated
The moisture content of WPI-CH (20% addition) microcapsule was decreased by
21.1% with the inlet air drying temperature increased from 120 to 180 °C. The
encapsulation efficiency and solubility of chlorophyll were enhanced by 3.78% and
7.79%, respectively. Furthermore, DPPH scavenging capacity of WPI-CH
microcapsules under different addition of chlorophyll were increased from 42.9% to
74.3%, 52.7%–82.7% and 71.8%–85.3%, respectively. This method concluded as
promising to preserve chlorophyll with WPI.
Zhang et al. (2019)
10 Kale purée: Thermal
processing impact on
process intensity and
storage on quality
The authors were focused on
investigating quality changes of
thermally processed kale purée. Low,
medium and high processing intensities
(carried out at 70, 90 and 128 °C) were
used.
The physicochemical properties, consumer acceptability of the puree is largely
dependent on the treatment intensity. The high intensity treatments resulted in the
least favorable quality characteristics (distinct brown color, chlorophyll and vitamin C
destruction as well as a phase separation after storage). Enzymes were inactivated
with increasing thermal load. Form this study concluded that, intermediate thermal
process intensity seems the best choice to create a high quality kale product that is
reasonably quality stable under refrigerated conditions.
Wibowo et al.
(2019)
Satheesh & Workneh Fanta, Cogent Food & Agriculture (2020), 6: 1811048
https://doi.org/10.1080/23311932.2020.1811048
Page 23 of 31
properties. Research should conduct on the loss of nutrient in kale by different preservation,
processing or cooking methods.
Acknowledgements
The authors are grateful to the Dean, Faculty of Chemical
and Food Engineering, at Bahir Dar Institute of
Technology, Bahir Dar University, Bahir Dar, Ethiopia for
constant encouragement in publishing this review article.
We are always kind to Professor Nageshwer Rao for help-
ing in proof reading and editing of this article.
Author details
Neela Satheesh
1
E-mail: neela.micro2005@gmail.com
ORCID ID: http://orcid.org/0000-0002-6474-2594
Solomon Workneh Fanta
1
ORCID ID: http://orcid.org/0000-0002-0244-1104
1
Bahir Dar University, Bahir Dar, Ethiopia.
Disclosure statement
The authors declare no conflict of interest.
Funding
The authors received no direct funding for this research.
Ethical statement
This article does not involve any human or animal testing
Citation information
Cite this article as: Kale: Review on nutritional composi-
tion, bio-active compounds, anti-nutritional factors,
health beneficial properties and value-added products,
Neela Satheesh & Solomon Workneh Fanta, Cogent Food
& Agriculture (2020), 6: 1811048.
References
Achikanu, C. E., Eze-Steven, P. E., U de, C. M., & Ugwuokolie,
O. C. (2013). Determination of the vitamin and mineral
composition of common leafy vegetables in south
eastern Nigeria. International Journal Current
Microbiology Applications Science, 2(11), 347–353.
https://www.ijcmas.com/vol-2-11/C.E.Achikanu,%20et
%20al.pdf
Acikgoz, F. E. (2011). Mineral, vitamin C and crude protein
contents in kale (Brassica oleraceae var. acephala) at
different harvesting stages. Africa Journal
Biotechnology, 10(7), 17170–17174. https://doi.org/
10.5897/AJB11.2830
Adefegha, S. A., & Oboh, G. (2011). Enhancement of total
phenolics and antioxidant properties of some tropical
green leafy vegetables by steam cooking. Journal of
Food Processing and Preservation, 35(5), 615–622.
https://doi.org/10.1111/j.1745-4549.2010.00509.x
Adeyeye, A., Ayodele, O. D., Akinnuoye, G. A., & Sulaiman,
W. (2018). Proximate composition and fatty acid
profiles of two edible leafy vegetables in nigeria.
America Journal Food Nutrition Health, 3(2), 51–55.
http://article.aascit.org/file/pdf/8290019.pdf
Agati, G., Azzarello, E., Pollastri, S., & Tattini, M. (2012).
Flavonoids as antioxidants in plants: Location and
functional significance. Plant Science, 196(1), 67–76.
https://doi.org/10.1016/j.plantsci.2012.07.014
Agbaire, P. (2011). Nutritional and anti-nutritional levels
of some local vegetables(Vernomia anydalira,
Manihot esculenta, Teiferia occidentalis, Talinum tri-
angulare, Amaranthus spinosus) from Delta State,
Nigeria. Journal Applications Science Environment
Management, 15(4), 625–628. https://www.ajol.info/
index.php/jasem/article/view/88615
Agbaire, P. O. (2012). Nutritional and antinutritional levels
of some local vegetables from Delta State, Nigeria.
African JournalFood, Sci.6(1), 8–11. https://doi.org/10.
5897/ajfs111.175
Agte, V. V., Tarwadi, K. V., Mengale, S., & Chiplonkar, S. A.
(2000). Potential of traditionally cooked green leafy
vegetables as natural sources for supplementation of
eight micronutrients in vegetarian diets. Journal of
Food Composition and Analysis, 13(6), 885–891.
https://doi.org/10.1006/jfca.2000.0942
Aly, N., El-Gendy, K., Mahmoud, F., & El-Sebae, A. K.
(2010). Protective effect of vitamin C against chlor-
pyrifos oxidative stress in male mice. Pesticide
Biochemistry and Physiology, 97(1), 7–12. https://doi.
org/10.1016/j.pestbp.2009.11.007
Andarwulan, N., Batari, R., Sandrasari, D. A., Bolling, B., &
Wijaya, H. (2010). Flavonoid content and antioxidant
activity of vegetables from Indonesia. Food
Chemistry, 121(4), 1231–1235. https://doi.org/10.
1016/j.foodchem.2010.01.033
Anjana, S. U., & Iqbal, M. (2007). Nitrate accumulation in
plants, factors affecting the process, and human
health implications-A review. Agronomy for
Sustainable Development, 27(1), 45–57. https://doi.
org/10.1051/agro
Anonymous. (1998). Dietary reference intakes: A risk
assessment model for establishing upper intake levels
for nutrients. Food and Nutritional Board, National
Academies Press.
Anonymous. (2010). Scientific opinion on dietary refer-
ence values for carbohydrates and dietary fibre.
EFSA. Journal, 8(3), 1462–1539. https://doi.org/10.
2903/j.efsa.2010.1462
Anonymous. (2011). Scientific opinion on the substantia-
tion of health claims related to the sugar replacers
xylitol, sorbitol, mannitol, maltitol, lactitol, isomalt,
erythritol, D-tagatose, isomaltulose, sucralose and
polydextrose and maintenance of tooth mineralisa-
tion, an. EFSA Journal, 9(4), 2076–2101. https://doi.
org/10.2903/j.efsa.2011.2076
Arnold, C., Jentsch, S., Dawczynski, J., & Böhm, V. (2013).
Age-related macular degeneration: Effects of a
short-term intervention with an oleaginous kale
extract-a pilot study. Nutrition, 29(11–12), 1412–
1417. https://doi.org/10.1016/j.nut.2013.05.012
Arowora, K. A., Ezeonu, C. S., Imo, C., & Nkaa, C. G. (2017).
Protein levels and amino acids composition in some
leaf vegetables sold at wukari in taraba state, Nigeria.
International Journal Biology Science Applications, 4(2),
19–24. https://pdfs.semanticscholar.org/5618/
6cf3cc4489d4997027a35b1f088f2ea807fe.pdf
Aryal, S., Baniya, M. K., Danekhu, K., Kunwar, P., Gurung,
R., & Koirala, N. (2019). Total phenolic content, fla-
vonoid content and antioxidant potential of wild
vegetables from western Nepal. Plants, 8(4), 96–107.
https://doi.org/10.3390/plants8040096
Ayaz, F. A., Glew, R. H., Millson, M., Huang, H. S., Chuang, L.
T., Sanz, C., & Haryirhoglu-Ayaz, S. (2006). Nutrient
contents of kale [brassica oleraceae l. var. acephala
dc.]. Food Chemistry, 96(4), 572–579. https://doi.org/
10.1016/j.foodchem.2005.03.011
Ayaz, F. A., Hayırlıoglu-Ayaz, S., Alpay-Karaoglu, S., Grúz, J.,
Valentová, K., Ulrichová, J., Strnad, M. (2008). Phenolic
acid contents of kale (Brassica oleraceae L. var. ace-
phala DC.) extracts and their antioxidant and anti-
bacterial activities. Food Chemistry, 109(1), 19-25.
https://doi.org/10.1016/j.Food Chemistry.2007 2007
107.07 1.003 doi:10.1016/j.foodchem.2007.07.003
Bahorun, T., Luximon-Ramma, A., Crozier, A., & Aruoma,
O. I. (2004). Total phenol, flavonoid,
Satheesh & Workneh Fanta, Cogent Food & Agriculture (2020), 6: 1811048
https://doi.org/10.1080/23311932.2020.1811048
Page 24 of 31
proanthocyanidin and vitamin C levels and antioxi-
dant activities of Mauritian vegetables. Journal of the
Science of Food and Agriculture, 84(12), 1553–1561.
https://doi.org/10.1002/jsfa.1820
Barrett, D. M., Beaulieu, J. C., & Shewfelt, R. (2010). Color, flavor,
texture, and nutritional quality of fresh-cut fruits and
vegetables: Desirable levels, instrumental and sensory
measurement, and the effects of processing. Critical
Reviews in Food Science and Nutrition, 50(5), 369–389.
https://doi.org/10.1080/10408391003626322
Batista-Silva, W., Nascimento, V. L., Medeiros, D. B.,
Nunes-Nesi, A., Ribeiro, D. M., Zsögön, A., & Araújo, W.
L. (2018). Modifications in organic acid profiles during
fruit development and ripening: Correlation or cau-
sation? Frontiers Plant Science, 9(1), 1–20. https://doi.
org/10.3389/fpls.2018.01689
Bazzano, L. A., Green, T., Harrison, T. N., & Reynolds, K.
(2013). Dietary approaches to prevent hypertension.
Current Hypertension Reports, 15(6), 694–702. https://
doi.org/10.1007/s11906-013-0390-z
Bhandari, M. R., & Kawabata, J. (2004). Assessment of
antinutritional factors and bioavailability of calcium
and zinc in wild yam (Dioscorea spp.) tubers of Nepal.
Food Chemistry, 85(2), 281–287. https://doi.org/10.
1016/j.foodchem.2003.07.006
Bhattacharjee, S., Dasgupta, P., Paul, A. R., Ghosal, S.,
Padhi, K. K., & Pandey, L. P. (1998). Mineral element
composition of spinach. Journal of the Science of
Food and Agriculture, 77(4), 456–458. https://doi.org/
10.1002/(SICI)1097-0010(199808)77:4<456::AID-
JSFA55>3.0.CO;2-M
Bhattacharya, P. T., Misra, S. R., & Hussain, M. (2016).
Nutritional aspects of essential trace elements in oral
health and disease: An extensive review. Scientifica,
2016, 1–12. Article ID5464373. https://doi.org/10.
1155/2016/5464373
Biehler, E., Alkerwi, A., Hoffmann, L., Krause, E., Guillaume,
M., Lair, M. L., & Bohn, T. (2012). Contribution of
violaxanthin, neoxanthin, phytoene and phytofluene
to total carotenoid intake: Assessment in
Luxembourg. Journal of Food Composition and
Analysis, 25(1), 56–65. https://doi.org/10.1016/j.jfca.
2011.07.005
Binia, A., Jaeger, J., Hu, Y., Singh, A., & Zimmermann, D.
(2015). Daily potassium intake and sodium-to-
potassium ratio in the reduction of blood pressure: A
meta-analysis of randomized controlled trials.
Journal of Hypertension, 33(8), 1509–1520. https://
doi.org/10.1097/HJH.0000000000000611
Booth Sarah, L., Guylaine, L. F., John, A. W., & Guylaine, L.
F. (1993). Vitamin K1 (Phylloquinone) content of
foods: A provisional table. Journal of Food
Composition and Analysis, 6(2), 109–120. https://doi.
org/10.1006/jfca.1993.1014
Bryan, L. 2020. How avocados and kale became so pop-
ular. BBC Work Life. 5 January. https://www.bbc.com/
worklife/article/20190304-how-avocados-and-kale-
became-so-popular.
Calder, P. C. (2015). Marine omega-3 fatty acids and
inflammatory processes: Effects, mechanisms and
clinical relevance. Biochemistry Biophysics Acta, 1851
(4), 469–484. https://doi.org/10.1016/j.bbalip.2014.
08.010
Calderón-Montaño, J. M., Burgos-Morón, E., Pérez-
Guerrero, C., & López-Lázaro, M. (2011). A review on
the dietary flavonoid kaempferol. Mini-Reviews in
Medicinal Chemistry, 11(4), 298–344. https://doi.org/
10.2174/138955711795305335
Calvo, M. M. (2005). Lutein: A valuable ingredient of fruit
and vegetables. Critical Reviews in Food Science and
Nutrition, 45(7–8), 671–696. https://doi.org/10.1080/
10408690590957034
Cao, G., Sofic, E., & Prior, R. L. (1997). Antioxidant and
prooxidant behavior of flavonoids: Structure-activity
relationships. Free Radical Biology and Medicine, 22
(5), 749–760. https://doi.org/10.1016/S0891-5849(96)
00351-6
Carlson, D., Daxenbichler, M., Vanetten, C., Kwolek, W., &
Williams, P.(1987). Glucosinolates in crucifer vegeta-
bles : Broccoli, brussels sprouts, cauliflower, collards,
kale, mustard greens, and kohlrabi. Journal American
Socity Horticultural Science, 112(1), 173–178. https://
naldc.nal.usda.gov/download/23901/PDF
Cartea, M. E., Francisco, M., Soengas, P., & Velasco, P.
(2011). Phenolic compounds in Brassica vegetables.
Molecules, 16(1), 251–280. https://doi.org/10.3390/
molecules16010251
Catak, J., & Yaman, M. (2019). Determination of nicotinic
acid and nicotinamide forms of Vitamin B3 (Niacin) in
fruits and vegetables by HPLC using postcolumn
derivatization system. Pakistan Journal of Nutrition,
18(6), 563–570. https://doi.org/10.3923/pjn.2019.563.
570
Catani, M. V., Savini, I., Rossi, A., Melino, G., & Avigliano, L.
(2005). Biological role of vitamin C in keratinocytes.
Nutrition Reviews, 63(3), 81–90. https://doi.org/10.
1301/nr.2005.mar.000-000
Cerdó, T., García-Santos, J. A., Bermúdez, M. G., & Campoy,
C. (2019). The role of probiotics and prebiotics in the
prevention and treatment of obesity. Nutrients, 11(3),
1–31. https://doi.org/10.3390/nu11030635
Chandrasekara, A., & Josheph Kumar, T. (2016). Roots and
tuber crops as functional foods: A review on phyto-
chemical constituents and their potential health
benefits. International Journal of Food Science, 2016,
1–15. Article ID3631647. https://doi.org/10.1155/
2016/3631647
Charron, C. S., Novotny, J. A., Jeffery, E. H., Kramer, M.,
Ross, S. A., & Seifried, H. E. (2020). Consumption of
baby kale increased cytochrome P450 1A2 (CYP1A2)
activity and influenced bilirubin metabolism in a
randomized clinical trial. Journal of Functional Foods,
64(8), 103624. https://doi.org/10.1016/j.jff.2019.
103624
Cheynier, V. (2012). Phenolic compounds: From plants to
foods. Phytochemistry Reviews, 11(2–3), 153–177.
https://doi.org/10.1007/s11101-012-9242-8
Chinyere, G. C., & Obasi, N. A. (2011). Changes in the
amino acids contents of selected leafy vegetables
subjected to different processing treatments. African
Journal Biochemistry Research, 5(6), 182–187. http://
www.academicjournals.org/app/webroot/article/
article1380186785_Chinyere%20and%20Obasi.pdf
Chiplonkar, S. A., Tarwadi, K. V., Kavedia, R. B., Mengale, S.
S., Paknikar, K. M., & Agte, V. V. (1999). Fortification of
vegetarian diets for increasing bioavailable iron
density using green leafy vegetables. Food Research
International, 32(3), 169–174. https://doi.org/10.
1016/S0963-9969(99)00070-8
Choo, Y. M., Yapa, S. C., Ooi, C. K., Ma, A. N., Goh, S. H., &
Ong, S. H. (1996). Recovered oil from palm-pressed
fiber: A good source of natural carotenoids, vitamin
E, and sterols. Journal of the American Oil Chemists’
Society, 73(5), 599–602. https://doi.org/10.1007/
BF02518114
Chung, M. J., Lee, S. H., & Sung, N. J. (2002). Inhibitory
effect of whole strawberries, garlic juice or kale juice
on endogenous formation of N-nitrosodimethyla-
mine in humans. Cancer Letters, 182(1), 1–10. https://
doi.org/10.1016/S0304-3835(02)00076-9
Satheesh & Workneh Fanta, Cogent Food & Agriculture (2020), 6: 1811048
https://doi.org/10.1080/23311932.2020.1811048
Page 25 of 31
Cleary, B. V. M. (2003). Dietary fibre analysis. Proceedings
of the Nutrition Society, 62(1), 3–9. https://doi.org/10.
1079/pns2002204
Clifton, P. M., & Keogh, J. B. (2017). A systamatic review of
the effect of dietary saturated and polyunsaturated
fat on heart disease. Nutrition, Metabolism and
Cardiovascular Diseases, 27(12), 1060–1080. https://
doi.org/10.1016/j.numecd.2017.10.010
Coleman, J. (2015). Threonine: Food sources, functions
and health benefits. Nova Science, Hauppauge.
Connie, M. W., & Aren, L. P. (1994). Dietary calcium:
Adequacy of a vegetarian diet. The American Journal
of Clinical Nutrition, 59(5), 1238S–1241S. https://doi.
org/10.1136/bmj.2.6095.1105-a
Davani-Davari, D., Negahdaripour, M., Karimzadeh, I.,
Seifan, M., Mohkam, M., Masoumi, S. J., Berenjian, A.,
& Ghasemi, Y. (2019). Prebiotics: Definition, types,
sources, mechanisms, and clinical applications.
Foods, 8(3), 1–27. https://doi.org/10.3390/
foods8030092
De Azevedo, C. H., & Rodriguez-Amaya, D. B. (2005).
Carotenoid composition of kale as influenced by
maturity, season and minimal processing. Journal of
the Science of Food and Agriculture, 85(4), 591–597.
https://doi.org/10.1002/jsfa.1993
De Sá, M. C., & Rodriguez-Amaya, D. B. (2003). Carotenoid
composition of cooked green vegetables from res-
taurants. Food Chemistry, 83(4), 595–600. https://doi.
org/10.1016/S0308-8146(03)00227-9
Denke, M. A., & Grundy, S. M. (1991). Effects of fats high in
stearic acid on lipid and lipoprotein concentrations in
men. The American Journal of Clinical Nutrition, 54(6),
1036–1040. https://doi.org/10.1093/ajcn/54.6.1036
Dennis, M. J., & Wilson, L. A. (2003). Nitrates and nitrites.
In C. Benjamin (Ed.), Encyclopedia of Food Sciences
and Nutrition,2 ed (pp. 4136–4141). Academic Press.
Di Noia, J. (2014). Defining powerhouse fruits and vege-
tables: A nutrient density approach. Preventing
Chronic Disease, 11(6), 3–7. https://doi.org/10.5888/
pcd11.130390
Doleman, J. F., Grisar, K., Van Liedekerke, L., Saha, S., Roe,
M., Tapp, H. S., & Mithen, R. F. (2017). The contribution
of alliaceous and cruciferous vegetables to dietary
sulphur intake. Food Chemistry, 234(1), 38–45.
https://doi.org/10.1016/j.foodchem.2017.04.098
Dunbar, B. S., Bosire, R. V., & Deckelbaum, R. J. (2014).
Omega-3 and omega-6 fatty acids in human and
animal health: An African perspective. Molecular and
Cellular Endocrinology, 398(1–2), 69–77. https://doi.
org/10.1016/j.mce.2014.10.009
Edelman, M., & Colt, M. (2016). Nutrient value of leaf vs.
seed. Frontiers in Chemistry, 4(1), 2–6. https://doi.org/
10.3389/fchem.2016.00032
Ejtahed, H. S., Angoorani, P., Soroush, A. R., Mortazavian, A.
M., Larijanid, B., Atlasi, R., & Hasani-Ranjbara, S.
(2019). Probiotics supplementation for the obesity
management; A systematic review of animal studies
and clinical trials. Journal of Functional Foods, 52, 228–
242. https://doi.org/10.1007/s00223-017-0339-3
El Khoury, D., Cuda, C., Luhovyy, B. L., & Anderson, G. H.
(2012). Beta glucan: Health benefits in obesity and
metabolic syndrome. Journal Nutrition Methods,
2012. Article ID851362. https://doi.org/10.1155/
2012/851362
El-Seedi, H. R., El-Said, A. M. A., Khalifa, S. A. M.,
Goransson, U., Bohlin, L., Borg-Karlson, A. K., &
Verpoorte, R. (2012). Biosynthesis, natural sources,
dietary intake, pharmacokinetic properties, and bio-
logical activities of hydroxycinnamic acids. Journal of
Agricultural and Food Chemistry, 60(44), 10877–
10895. https://doi.org/10.1021/jf301807g
Emebu, P., & Anyika, J. (2011). Proximate and mineral
composition of kale (brassica oleracea) grown in
Delta State, Nigeria. . Pakistan Journal of Nutrition, 10
(2), 190–194. https://doi.org/10.3923/pjn.2011.190.
194
Eppendorfer, W. H., & Bille, S. W. (1996). Free and total
amino acid composition of edible parts of beans,
kale, spinach, cauliflower and potatoes as influenced
by nitrogen fertilisation and phosphorus and potas-
sium deficiency. Journal of the Science of Food and
Agriculture, 71(4), 449–458. https://doi.org/10.1002/
(SICI)1097-0010(199608)71:4<449::AID-JSFA601>3.
0.CO;2-N
Erdogan, B. Y., & Onar, A. N. (2011). Determination of
nitrates, nitrites and oxalates in kale and sultana pea
by capillary electrophoresis. Journal of Animal and
Veterinary Advances, 10(15), 2051–2057. https://doi.
org/10.3923/javaa.2011.2051.2057
Fadigas, J. C., Dos Santos, A. M., de Jesus, R. M., Lima, D.
C., Fragoso, W. D., David, J. M., & Ferreira, S. L. (2010).
Use of multivariate analysis techniques for the char-
acterization of analytical results for the determina-
tion of the mineral composition of kale? Micro
Chemistry Journal, 96(2), 352–356. https://doi.org/10.
1016/j.microc.2010.06.0060
Fahey, J. W. (2003). Brassica. In C. Benjamin (Ed.),
Encyclopedia of Food Sciences and Nutrition, 2nd ed
(pp. 606–615). Academic Press.
Fischer Walker, C. L., Ezzati, M., & Black, R. E. (2009).
Global and regional child mortality and burden of
disease attributable to zinc deficiency. European
Journal of Clinical Nutrition, 63(5), 591–597. https://
doi.org/10.1038/ejcn.2008.9
Flores, P., Hellín, P., & Fenoll, J. (2012). Determination of
organic acids in fruits and vegetables by liquid chro-
matography with tandem-mass spectrometry. Food
Chemistry, 132(2), 1049–1054. https://doi.org/10.
1016/j.foodchem.2011.10.064
Forouhi, N. G., Krauss, R. M., Taubes, G., & Willett, W.
(2018). Dietary fat and cardiometabolic health:
Evidence, controversies, and consensus for guidance.
The Bmj, 361(K2139), 1–8. https://doi.org/10.1136/
bmj.k2139
Gonçalves, Á. L. M., Lemos, M., Niero, R., De Andrade, S. F.,
& Maistro, E. L. (2012). Evaluation of the genotoxic
and antigenotoxic potential of Brassica oleracea L.
var. acephala D.C. in different cells of mice. Journal of
Ethnopharmacology, 143(2), 740–745. https://doi.org/
10.1016/j.jep.2012.07.044
Gopalan, C., Sastri, B. V. R., & Balasubramanian, S. C. (1989).
Nutritive value of Indian foods. National Institute of
Nutrition, Indian Council of Medical Research.
Górska-Warsewicz, H., Laskowski, W., Kulykovets, O.,
Kudlińska-Chylak, A., Czeczotko, M., & Rejman, K.
(2018). Food products as sources of protein and
amino acids-The case of Poland. Nutrients, 10(12),
1977–1997. https://doi.org/10.3390/nu10121977
Grembecka, M. (2015). Sugar alcohols—their role in the
modern world of sweeteners: A review. European
Food Research and Technology, 241(1), 1–14. https://
doi.org/10.1007/s00217-015-2437-7
Gupta, K., & Rana, M. K. (2003). Salad crops, leaf-types. In
C. Benjamin (Ed.), Encyclopedia of Food Sciences and
Nutrition,2nded (pp. 5060–5073). Academic Press.
Gupta, R. K., Gangoliya, S. S., & Singh, N. K. (2013).
Reduction of phytic acid and enhancement of bioa-
vailable micronutrients in food grains. Journal of
Food Science and Technology, 52(2), 676–684. https://
doi.org/10.1007/s13197-013-0978-y
Gupta, S., Gowri, B. S., Lakshmi, A. J., & Prakash, J. (2013).
Retention of nutrients in green leafy vegetables on
Satheesh & Workneh Fanta, Cogent Food & Agriculture (2020), 6: 1811048
https://doi.org/10.1080/23311932.2020.1811048
Page 26 of 31
dehydration. Journal of Food Science and Technology,
50(5), 918–925. https://doi.org/10.1007/s13197-011-
0407-z
Hagen, S. F., Borge, G. I. A., Solhaug, K. A., & Bengtsson, G. B.
(2009). Effect of cold storage and harvest date on bioac-
tive compounds in curly kale [Brassicaoleracea L. var.
acephala]. Postharvest Biology and Technology, 51(1), 36–
42. https://doi.org/10.1016/j.postharvbio.2008.04.001
Hasan, M. N., Akhtaruzzaman, M., & Sultan, M. Z. (2013).
Estimation of Vitamins B-complex (B2, B3, B5 and B6)
of some leafy vegetables indigenous to bangladesh
by HPLC Method. Journal Analysis Science Methods
Institute, 3(3), 24–29. https://doi.org/10.4236/jasmi.
2013.33a004
Hassan, F. A., Ismail, A., Hamid, A. A., Azlan, A., & Al-
Sheraji, S. H. (2011). Characterisation of fibre-rich
powder and antioxidant capacity of Mangifera
pajang K. fruit peels. Food Chemistry, 126(1), 283–
288. https://doi.org/10.1016/j.foodchem.2010.11.019
Hayes, C. (2001). The effect of non-cariogenic sweeteners
on the prevention of dental caries: A review of the
evidence. Journal of Dental Education, 65(10), 1106–
1109. https://doi.org/10.1002/j.0022-0337.2001.65.
10.tb03457.x
Heaney, R. P., Weaver, C. M., Hinders, S., Martin, B., &
Packard, P. T. (1993). Absorbability of calcium from
brassica vegetables: Broccoli, Bok Choy, and Kale.
Journal of Food Science, 58(6), 1378–1380. https://
doi.org/10.1111/j.1365-2621.1993.tb06187.x
Holden, J. M., Eldridge, A. L., Beecher, G. R., Marilyn
Buzzard, I., Bhagwat, S., Davis, C. S., Douglass, L. W.,
Gebhardt, S., Haytowitz, D., & Schakel, S. (1999).
Carotenoid content of U.S. foods: An update of the
database. Journal of Food Composition and Analysis,
12(3), 169–196. https://doi.org/10.1006/jfca.1999.082
Hossain, A., Khatun, M. A., Islam, M., & Huque, R. (2017).
Enhancement of antioxidant quality of green leafy
vegetables upon different cooking method.
Preventive Nutrition and Food Science, 22(3), 216–
222. https://doi.org/10.3746/pnf.2017.22.3.216
Howard, G. M., Nguyen, T. V., Harris, M., Kelly, P. J., &
Eisman, J. A. (1998). Genetic and environmental
contributions to the association between quantita-
tive ultrasound and bone mineral density measure-
ments: A twin study. Journal of Bone and Mineral
Research, 13(8), 1318–1327. https://doi.org/10.1359/
jbmr.1998.13.8.1318
Hunt, J. R. (2003). Bioavailability of iron, zinc, and other
trace minerals from vegetarian diets. The American
Journal of Clinical Nutrition, 78(3), 633S–639S. https://
doi.org/10.1093/ajcn/78.3.633s
Jaishankar, M., Tseten, T., Anbalagan, N., Mathew, B. B., &
Beeregowda, K. N. (2014). Toxicity, mechanism and
health effects of some heavy metals. Interdisciplinary
Toxicology, 7(2), 60–72. https://doi.org/10.2478/
intox-2014-0009
Jandacek, R. J. (2017). Linoleic acid: A autritional quand-
ary. Healthcare, 5(2), 25–33. https://doi.org/10.3390/
healthcare5020025
Jeffery, E. H., & Stewart, K. E. (2004). Upregulation of
quinone reductase by glucosinolate hydrolysis pro-
ducts from dietary broccoli. Methods. Enzymology,
382(2), 457–469. https:// doi.org/10.1016/S0076-
6879(04)82025-1
Jo, C., Ahn, D. U., & Lee, K. H. (2012). Effect of gamma
irradiation on microbiological, chemical, and sensory
properties of fresh ashitaba and kale juices. Radiation
Physics and Chemistry, 81(8), 1076–1078. https://doi.
org/10.1016/j.radphyschem.2011.11.065
Johari, M. A., & Khong, H. Y. (2019). Total phenolic content
and antioxidant and antibacterial activities of
pereskia bleo. Advances in Pharmacological Sciences,
2019, 1–4. Article ID7428593. https://doi.org/10.
1155/2019/7428593.
Johnson, M., McElhenney, W. H., & Egnin, M. (2019).
Influence of green leafy vegetables in diets with an
elevated ω-6: ω-3 fatty acid ratio on rat blood pres-
sure, plasma lipids, antioxidant status and markers
of inflammation. Nutrients, 11(2), 1–14. https://doi.
org/10.3390/nu11020301
Johnson, M., Pace, R. D., Dawkins, N. L., & Willian, K. R.
(2013). Diets containing traditional and novel green
leafy vegetables improve liver fatty acid profiles of
spontaneously hypertensive rats. Lipids Health
Disease, 12(1), 1–7. https://doi.org/10.1186/1476-
511X-12-168
Johnson, M., Pace, R. D., & Mc Elhenney, W. H. (2018).
Green leafy vegetables in diets with a 25:1 omega-6/
omega-3 fatty acid ratio modify the erythrocyte fatty
acid profile of spontaneously hypertensive rats. Lipids
Health Disease, 17(1), 1–7. https://doi.org/10.1186/
s12944-018-0723-7
Joy, E. J. M., Ander, E. L., Young, S. D., Black, C. R., Watts,
M. J., Chilimba, A. D. C., Broadley, M. R., Siyame, E. W.
P., Kalimbira, A. A., Hurst, R., Fairweather-Tait, S. J.,
Stein, A. J., Gibson, R. S., White, P. J., & Broadley, M. R.
(2014). Dietary mineral supplies in Africa. .
Physiologia Plantarum, 151(3), 208–229. https://doi.
org/10.1111/ppl.12144
Kader, A. A. (2008). Flavor quality of fruits and vegetables.
Journal of the Science of Food and Agriculture, 881,
1863–1868. https://doi.org/10.1002/jsfa.3293 11
doi:10.1002/jsfa.v88:11
Kahlon, T. S., Chapman, M. H., & Smith, G. E. (2007). In vitro
binding of bile acids by spinach, kale, brussels sprouts,
broccoli, mustard greens, green bell pepper, cabbage
and collards. Food Chemistry, 100(4), 1531–1536.
https://doi.org/10.1016/j.foodchem.2005.12.020
Kahlon, T. S., Chiu, M. C. M., & Chapman, M. H. (2008).
Steam cooking significantly improved in vitro bile
acid binding of collard greens, kale, mustard greens,
broccoli, green bell pepper, and cabbage. Nutrition
Research, 28(6), 351–357. https://doi.org/10.1016/j.
nutres.2008.03.007
Kawatra, A., Singh, G., & Sehgal, S. (2001). Nutriton com-
position of selected green leafy vegetables, herbs
and carrots. Plant Foods for Human Nutrition, 56(4),
359–365. https://doi.org/1011873119620
Kayashima, T., & Katayama, T. (2002). Oxalic acid is
available as a natural antioxidant in some systems.
Biochimica Et Biophysica Acta (BBA) - General
Subjects, 1573(1), 1–3. https://doi.org/10.1016/
S0304-4165(02)00338-0
Keeton, J. T. (2011). History of nitrite and nitrate in Food. In
N. S. Bryan & J. Loscalzo (Eds.), Nitrite and nitrate in
human health and disease (pp. 69–84). Humana Press.
Kim, D., Song, H., Lim, S., Yun, H., & Chung, J. (2007). Effects of
gamma irradiation on the radiation-resistant bacteria
and polyphenol oxidase activity in fresh kale juice.
Radiation Physics and Chemistry, 76(7), 1213–1217.
https://doi.org/10.1016/j.radphyschem.2006.12.003
Kim, S. Y. (2017). Production of fermented kale juices with
lactobacillus strains and nutritional composition.
Preventive Nutrition and Food Science, 22(3), 231–
236. https://doi.org/10.3746/pnf.2017.22.3.231
Kim, S. Y., Yooun, S., Kwon, S. M., Ke, S. P., & Lee-Kim, Y. C.
(2008). Kale juice improves coronary artery disease
risk factors in hypercholesterolemic men. Biomedical
and Environmental Sciences, 21(1), 91–97. https://doi.
org/10.1016/S0895-3988(08)60012-4
Kim, Y. A., Keogh, J. B., & Clifton, P. M. (2017). Probiotics,
prebiotics, synbiotics and insulin sensitivity. Nutrition
Satheesh & Workneh Fanta, Cogent Food & Agriculture (2020), 6: 1811048
https://doi.org/10.1080/23311932.2020.1811048
Page 27 of 31
Research Reviews, 31(1), 35–51. https://doi.org/10.
1017/S095442241700018X
Klopsch, R., Baldermann, S., Hanschen, F. S., Voss, A.,
Rohn, S., Schreiner, M., & Neugart, S. (2019). Brassica-
enriched wheat bread: Unraveling the impact of