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International Journal of Applied Science and Research
127
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Traditional fermented foodsin Nigeria and Covid-19: A Possible Approach for Boosting Immune
System
P.N. Anyiam1*, P.N. Onwuegbuchu2, C.L. Ekemezie3
1Department of Biochemistry, College of Natural Sciences, Michael Okpara University of Agriculture, Umudike,
PMB 7262, Umuahia, Nigeria
2Department of Microbiology, Faculty of Biological Sciences, Abia State University, P.M.B 2000, Uturu, Abia State,
Nigeria.
3Department of Microbiology, College Of Natural Sciences, Michael Okpara University of Agriculture, Umudike,
PMB 7262, Umuahia, Nigeria
IJASR 2020
VOLUME 3
ISSUE 6 NOVEMBER – DECEMBER ISSN: 2581-7876
Abstract: Covid-19 has spread all over the world since itoriginated from Wuhan City, China in late 2019.While a
careful search for an effective treatment is still on-going, nutritional strategies to promote immunity to possibly face
the infection should not be ignored. Recently, there hasbeen anincreased interest on fermented foodsdue to their
enhanced nutritional values and health benefits.In Nigeria, the most common of these traditional fermented foods
are; tuber based fermented products (Fufu, Garri, Lafun), cereal based foods and beverages (Kwunu, Pito, Agidi, Pap or
Akamu), vegetable-based fermented condiments (Ogiri, Dawadawa, Ugba) and animal fermented products
(NonoandKilishi). In addition to their improved nutritional quality, these fermented foods may also deliver viable
microbes know as probiotics to balance the gut microbioataand therefore have the potential to boost immunity
which in turn protects the body against infectious diseases like Covid-19 and other diseases.
Keywords: Covid-19, Fermented foods, Health benefits, Immune system, Nutrition, Probiotics
1. Introduction
Since the beginning of Covid-19 outbreakwhich is caused by a severe acute respiratory syndromecoronavirus 2
(SARS-CoV-2)-in late 2019 from Wuhan City,China, it has spread all over the world exhibiting large and significant
geographical variations in the number of infected people and death rates between and within countries[1].Ithas also
brought social and economic crisis not just in Nigeria but also in other developing countries, which is rapidly
exacerbating theon-going food insecurity in the country.Malnutrition and other co-morbidities (such as Diabetes,
cancer hypertension, tuberculosis, obesity) are considered risk factors for complications in people with Covid-
19[2,3]mainly due to a compromised immune system with oxidative stress as a common pathway.
Thoughdemographic factors such as such as age, sex, occupation and education level, seasonal variations, immunity
and timing of interventions are more relevant factors that are associated with increased incidence of Covid-19 and
its mortality rate[4], other factors like nutrition, probiotics, nutraceuticals, environment and diet should not be
ignored completely because these factors can as well beof interesting options in mitigating the impact of Covid-19
and preventing itscomorbidity.While a deep search for effective vaccines or drugswhich can be able to interfere with
the SARS-CoV-2 pathway is on-going, nutritional strategies to boost the immunity against the infection and its
spreadare imperative.
Certain fermented foods may deliver viable microbes with the potential of providing some health benefit to the host
by boosting the immunity [4]. Such foods have long been an integral part oflocal cultures and traditions of human
diet in developing countries [5,6]due to their nutritional and health benefits.Fermented foods are a very diverse
family of foods, which differ in their nutritional values, microbiological compositions and metabolites with potential
health effects[7]. Fermentation itself is a food processing technology whereby the growth and metabolic activities of
microorganisms are used to transform and preserve foods. It is an inexpensiveand simple process that requires
comparatively little energy, prolongs the shelf life of the original food, and making food nutrients more digestible[8-
10]. Production methods of different traditional fermented foods were passed down to subsequent generations in
different regions as family traditions where they are generally produced using plant or animalingredients in
combination with microorganisms which are either sourced spontaneously from the environment, or carefully kept
as starter cultures.
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Mostrural communities in Nigeria are economically depending on fermented foods as the primary source of
nutrition for nourishment, as well as for cultural traditional practices, since the major staples in the region (Cassava,
yam, maize) though provide enough calories butthey are poor in essential nutrients needed to support life
[8,11].Each region in Nigeria has its own distinctiveness in terms of food culture and heritage where fermented
foods are included which depends on type of raw food material available in that particular place, which play very
important role in the socio-economics development of the country as well as make major contributions to the
protein requirements of the rural population which couldplay a mitigating role against the economic effects of
Covid-19 especially on food security by reducing the rate of malnutrition and hunger in the region.
Despite the importance and potential health benefits of fermented foods in Nigeria, their preparation methodsstill
remains a household art till date.Very little is known about these traditional fermented foods and their benefitsdue
to scarcity of informationin the literature and the fact that they are only knownto those people residing in the area
where such foods are produced and consumed. Therefore, this reviewis aimed at assessing the standard methods of
preparation and consumption of common traditional fermented foods in Nigeria, and also discussed thehealth
benefitsassociated with the consumption of these fermented foods.
1.1 Traditional fermented Foodsin Nigeria: Production methods
A wide range of fermented foods and beverages are produced in Nigeria. Such foodsare derived from the local
staples (cassava, yam, rice, maize, wheat etc.) whichare prevalent in various localities within the country. Many
names are applied to these traditional fermented foods throughout Nigeria which differ by region and ethnic
groups. Most common fermented foods produced from these staples in Nigeria are; Garri, Fufu, Lafun, Amala,
Massa, Agidiand Ogi (Akamu). Fermented beverages include Kwunu, Mmanya-ngwo (palm wine), Pito, Burukutu and
fermented condiments include Dawadawa and ogiri.Fermented animal products include Nono (fermented milk),
WashainuandKilishi (fermented meat) (Table 1). These fermented foods are inexpensive and affordable for many
individuals in the community.They are of sociocultural and nutritional value and are marketed for income
generation. Most of the traditional fermented foods are primarily produced at household level usingN largely
uncontrolled spontaneous inoculation methods in which microorganisms associated with the raw food material and
the processing environment serve as inoculants [12]. The preparation method and mode of consumption of these
fermented foods are highlighted according to food types;
1.2 Fermented Tubers (Cassava and yam meal)
1.2.1 Garri: Thisis a high energy food commonly consumed in Southern parts of Nigeria but it is also popular
among the inhabitants of Northern and Eastern Nigeria. Itisa creamy-white granular flour with a slightly sour taste
made from fermented gelatinized fresh cassava tubers. Nigeria is one of the leading producers of cassava in the
world with an annual production of 35-40 million metric tons [9,12]. Over 40 varieties of cassava are grown in
Nigeria and cassava is the most important dietary staple in the country accounting for majority of all food crops
consumed in Nigeria [9,12]. Despite its vast potentials, the presence of hydrogen cyanide (HCN) is the most
important problem limiting cassava utilization in the country [9]. Many varieties of cassava grown in the country are
poisonous due to presence of HCN and would cause death in man and animals if consumed directly without
fermentation which detoxifies HCN.
In preparation of garrifrom cassava, the tubers are harvested, cleaned, peeled and washed in clean water. The
washed cassava is groundin a mill and the pulp is transferred into a cloth bag and tied before being subjected to
heavy pressure at room temperature for 3 or 4 days to remove excess water and ferment. The fermented pulp is
then sieved and dry-fried with or without palm oiladded (optional) to produce garri flour. The flour can be
reconstituted in hot water into a paste, cooled and consumed with various soups and stews or it can be soaked in
cold water with salt or sugar added before consumptionwith groundnut or coconut as snack.The flour, when
properly fried and stored away from moisture, has a shelf life of about three months.
1.2.2 Fufu (Fermented Cassava meal)
Fufu is a fermented white paste made also from cassava which is ranked next to garri as an indigenous food of most
Nigerians. It is widely consumed in Eastern Nigeria, especially among the Igbos but also available in the Western
part of the nation. In preparation of fufu, thecassava tubers are peeled, washed, cut into thick chucks (say 20cm
long) and soaked in water in earthen ware pots or plastic bucket for 4 to 5 days. During cold weather, the tubers
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should be properly submerged in the waterand the container may be kept closer to the cooking stand in the
kitchento fasten the fermentation and softening process.
During this period, the cassava tuber ferments and softens, releasing the poisonous hydrogen cyanide (HCN) in the
soaked water and producing a characteristic flavor [9]. The softened tubers are then disintegrated in clean water,
sieved and the starchy particles that go through the sieves are allowed to settle for about one or two hours. The
water is decanted while the sediments is packed into a cloth and bag, tied, squeezed and subjected to heavy pressure
to expel excess water. The resulting starch is rolled into balls, cooked in boiling water (100oc) for about 30 to 40
minutes. The cooked mass is pounded in a mortar with a pestle to producefufu paste which can be eaten with sauce,
soup or stew.
1.2.3 Lafun or Elubo (Cassava Flour)
Lafun is a fibrous powdery form of fermented cassava similar to fufu but the production process slightly differs from
that of fufu. It is commonly produced and consumed in Western States of Nigeria and is also available in Eastern
part of the country. Lafunis prepared from cassava tuber. Basically, the cassava tuber is peeled and soaked in water
for 3 to 4 days to ferment. Afterwards, the soaked water is drained off and the fermented cassava dried in the sun.
The dried product is ground in a mill into flour known as Elubo. The flour is added into boiling water with constant
stirring until a smooth thick paste is formed. The paste is allowed to cool and is then served with any kind of
vegetable sauce or soups.When properly stored, lafun have a shelf-life of up to six months [9].
1.2.4 Amala (Fermented Yam flour)
Amala is a popular food consumed in Western Nigeria. It is prepared from yam (Discoreaspp) tuber. Theyam tuber is
washed and peeled, then cut into very thin slices and left in the sun on a tray or mat for 4 to 5 days to ferment and
dry. The dried yam slices are milled into flour then cooked for few minutes in hot water with constant stirring until
thick dark brown dough like paste (amala) is formed. The characteristic flavor and dark color of amala which is
found objectionable by some people is due to enzymatic and non-enzymatic browning reactions and the presence of
polyphenols in the yam [9], which can be minimized or prevented completely by blanching the yam slices in boiling
water for 2 minutesbefore fermentation or drying to inactivate the enzyme responsible for the browning reactions.
1.3 Cereal based fermented food products
Generally, grains lack some basic nutrients such as essential amino acids and certain vitamins [9,10]. Fermentation
of cereals is a simple way to improve their nutritional value as well as their sensory and functional qualities [10].
Fermentation decreases the level of carbohydrates and non-digestible polysaccharides and oligosaccharides in
cereals and increases the synthesis of certain amino acids and the bioavailability of the vitamins [13]. In addition,
fermentation also significantly reduces the content of non-nutrients in cereals, such as polyphenols, phytates and
tannins [10]and increases the content of nutrients like free amino acids and their derivatives. The activities of some
enzymes such as amylase, phytase, hemicellulase and protease increase, which results in improved shelf-life,
digestibility and nutritional value [13]. It has been noted that during fermentation, cereals also have increased
antioxidants activity [14]. Some of the cereal based fermented foods in Nigeria are as follows;
1.3.1 Ogi/Akamu/pap (Fermented maize starch)
Ogi (Akamu or pap) is another traditional fermented food consumed in Nigeria which is prepared from fermented
maize (Zea mays). It is a staple cereal product of mainly the theYorubas, and is the first natural food given to babies
at weaning [9]. The process of preparation basically consists of soaking the maize in water for one to three days to
ferment and develop a characteristic odour. The softened maize is washed, ground into a meal with a blender or
mill. The ground material is mixed with water and sieved to remove parts of the hull and other fibrous materials.
The filtrate which is almost pure starch suspension is placed in a pot so that starchy material sediments at the
bottom of the pot. The supernatant is decanted and the wet starch poured into cloth bags, squeezed and dewatered
until a semi-solid corn starch is produced. This is stored in a cool place from where samples can be taken from the
stock and cooked into ogi or akamu which is usually served hot with table sugar to enhance the taste and can be eaten
withakara (bean cake), fried yam or bread.
1.3.2 Massa (fermented rice meal)
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Massa is a fermented product made from rice or millet. It is consumed in various forms by all groups especially in
Northern States of Nigeria. It is the principal ingredients for a variety of cereal-based foods and is a good source of
income for the women who prepare the traditional product for sale. The problem of Massa apart from the short
shelf-life is that of low protein content [9]. However, cowpea, groundnut or soybeans flour could be added into
Massa during preparations to improveits nutritional quality. Basically, Massa is prepared from rice flour. The raw rice
is firstly soaked in water for 8 hours or overnight and washed. Then blend together with already precooked rice with
a gradual addition of water while controlling the texture and thickness. Add the yeast and set the mixture aside for 5
to 8 hours or overnight to ferment. After the fermentation process is completed, fry the batter in batches with little
oil in a pan until they turn golden brown. Massa can be served with honey, sauce or any condiment of choice.
1.4 Fermented beverages:
1.4.1 Kwunu: This is a non-alcoholic fermented beverage prepared from millet andwidely consumed in Northern
parts of Nigeria. To prepare kwunu, first, the millet is ground in a mortar with pestle to remove the husk and release
the kernels. The kernels are washed and left to dry on a mat under the sun for 8-12 hours. The dried kernels are
then ground into flour and mixed with little cold water before pouring it into a pot of hot water with constant
stirring until a thick smooth paste is formed. The paste is left to ferment for 1 to 3 days so as to develop a sour
flavor after which it can be consumed. The flour can also be made into a watery gruel known as kwunuzaki and
consumed hot or cold with ginger, pepper and sugar to taste. The product has a shelf-life of about 24 hours at
ambient temperature, which can be extended to 8 days by pasteurization at 60 0C for 1 hour [9] and stored under
refrigeration condition.
1.4.2 Pito/burukutu
Pito is cream colored liquor while burukutu is a brown colored suspension, both of which are brewed from sorghum,
millet, maize or a mixture of these cereals. Both drinks are brewed concurrently by fermentation of malted or
germinated cereals. For instance, sorghum grains are soaked in water for 24hrs, drained and kept for 2 days to
germinate. After sprouting, the grains are sun dried and ground into flour. The flour is mixed with water and boiled
for 3 to 4 hours to form slurry. The boiled mash is allowed to settle at the bottom and water is decanted while the
sediment which is a thick brown suspension is known as burukutu. Each fraction is decanted into a clean calabash
pot where it is allowed to stand and ferment for 24 hours at room temperature for proper flavor development, after
which the drink can then be consumed. Pito and burukutu are widely consumed in Northern Nigeria. The alcoholic
content of burukutu is slightly higher than that of pito.
1.4.3 Mmanya-ngwo (Palm wine)
Thisis the fermented sap of palm tree which is obtained in Nigeria by the tapping of the inflorescence of the palm
tree. The wine is a milky suspension of microorganisms (especially yeasts) in a fermenting palm sap. It is a popular
refreshing and nourishing beverage consumed in most parts of Nigeria, especially Southern and Eastern Nigeria,
and is also a major ingredient in the manufacture of local bread because of its naturally high content of yeasts. Fresh
palm wine is sweet and has virtually zero alcohol contents, but the palm sap ferments easily and become sour in few
hours after collection.
1.5 Fermented condiments
The fermentation of fruits and vegetablesis very popular as a means of preservation in various local communities in
Nigeria, because untreated fruits and vegetables are highly perishable.The fermentation of fruits and vegetables is
mainly by lactic acid fermentation that acts spontaneously when conditions are favorable for the fermenters,
especially lactic acid bacteria, which are the dominant microorganism in this type of fermentation [8, 15, 16]. The
conventional substrates for condiments productions from vegetables are diverse and each can be produced from
more than one raw material. The methods employed in the production of these condiments foods differ slightly
from one region of the country to another because these processes are based on traditional systems. Common
traditional fermented condiments in Nigeria are as follow;
1.5.1 Dawadawa or Iru:
This is an important fermented food condiment and protein source produced from African locust bean
(Parkiabiglobosa) and consumed extensively throughout Nigeria as a condiment to add flavor to various dishes and
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soups. In the unfermented state, African locust bean is non-edible because it contains high quantity of trypsin
inhibitors and flatulence causing oligosaccharides which are anti-nutrients [8,9]. After fermentation, the hard
inedible beans are converted into a soft and palatable nutritious condiment with a sweet pleasant flavor and
improved vitamin content. Basically, production of Dawadawa consists of boiling the locust bean seeds for 1 to 2
days to soften the hard seed coat.
After softening, the seed coats are removed by finger pressure, releasing the cotyledons which are reheated for up to
2 hours. After the second boiling, the cooked water is decanted and the cotyledons spread in basket lined with
blanched banana leaves. The seeds are also covered with several layers of banana leaves and left 2 or 3 days to
ferment in the natural heat of the tropics. Wood ash may also be added which is then sun dried for 2 days before
consumption. When properly dried, Dawadawa can be kept for up to a year in a shelf under tropical conditions [8].
Production of Dawadawaprovides useful nutritional supplements in a nutrient deficient region at a little cost in
capital among traditional processing techniques. In poor families, it can be consumed generously as a low cost
substitute to meat.
1.5.2 Ogiri:
This is also a fermented condimentprepared from the castor seed (Ricinuscommunis) which is a major oil seed
common in Africa and other parts of the tropics [8]. Different types of ogiri exist depending on the starting raw.
Such as Ogiri-uguwhich is made from fluted pumpkin (Telfaireaoccidentalis) seeds whereas Ogiri-egusi is prepared from
melon (citrullus vulgaris) seeds. All types of ogirihave similar preparation method. Raw castor seed is not edible
because of its toxic constituents such as ricin and hemagglutinis as well as trypsin inhibitor [9]. However, the seed
can be fermented and detoxified into a seasoning called Ogiri, used as a condiment in soups or stews. Basically, the
preparation consists of dehaulling the castor seeds, wrapping the dehaulled seeds in blanched plantain leaves and
boiling for to 8 hours and allowed for 4 days to ferment. Later, the seeds are mixed with ash from burnt palm leaves
and then ground into a paste. The resulting paste is rewrapped and left for another 3 days to complete the
fermentation process. Heat and characteristic foul odour from the product indicates that fermentation has been
completed.
1.5.3 Ugba (fermented African oil bean)
Ugba is prepared from oil bean (Pentaclethramacrophylla) seeds and are eaten by many people in Eastern Nigeria, which
comprises mainly the Igbo ethnic groups as well as other ethnic groups in Southern Nigeria. The condiment is
produced in a traditional way at home with rudimentary utensils and can be also consumed either as snacks, salads
or as a soup flavor. The unfermented oil bean seed is bitter to taste and contains a toxic alkaloid. Fermentation
renders the Ugba seed nutritious and non-toxic [9].
To prepare Ugba, the seeds are boiled in water for over 12 hours to soften the hard seed coats. The boiled seeds are
then dehaulled to produce the cotyledons or kernels while the seed coats are discarded. The kernels are cut into long
narrow slices (about 0.2 cm thick), washed, boiled for 1 or 2 hours to remove the bittering substances and the cook
water discarded. Then the Ugba slices are soaked overnight (12 hours) in a pan fully covered with water. The soaked
water which also contains part of the bitter substance is now discarded and the sliced samples washed and placed in
a basket to drain completely. Then the Ugba is placed in small portions in blanched banana leaves, wrapped and left
to ferment for 2 to 3 days at room temperature. Fermentation for more than 4 days produces very soft Ugba used
only in soups.
Table 1: Traditional fermented foods in Nigeria
Fermented food
Raw material
Location
Type of product
Ogi/Akamu/pap
Maize
West
Beverage
Kwunu
Millet
North
Beverage
Fufu
Cassava tuber
East/South
Food
Garri
Cassava tuber
All region
Food
Lafun
Cassava tuber
West
Food
Massa
Rice or Maize
North
Food
Ugba
Oil bean
East/South
Food
Dawadawa
African Locust bean
West
Condiment
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Ogiri
Castor or Melon seed
East/south
Condiment
Mmanya-ngwu
Palm sap
East
Beverage
Pito/burukutu
Maize/Millet
West
Beverage
Nono/washainu
Cow milk
North
Beverage
Kilishi
Cow meat
North
Meat
1.6 Fermented Meat products:
Kilishi
Fermentation of meat produces desirable organoleptic properties, such as aroma, texture and taste [17], good
nutritional valueand important health benefits [18]. A popular Nigerian locally prepared meat product is known as
Kilishi.It is the most popular traditional dry-cured semi-fermented meat product in Nigeria which is made from
whole muscle of cow. It is the cheapest means of preserving meat and widely consumed and enjoyed by mostly
Northern Nigerians. The production ofKilishi involves drying, curing and pressing the meat and then adding a
cemenpowder-which is a traditional spice made from the combination of red pepper and garlic [9]. Many physical,
microbial, biochemical and organoleptic changes occur during the production of kilishi, such as proteolysis, which
increases the levels of free amino acids, and the addition of cemenimproves the taste and flavor of Kilishi
1.6.2 Nono/Maishanu
Nono is a cow milk-based fermented delicious and refreshing beverage which is widely produced in Northern
Nigeria for nutrition and income generation. It varies according to sociocultural and taste preferences and generally
practiced among the Fulani herdsmen. Traditionally, milk is obtained freshly from cow and boiled for 3hrs and
inoculated with a little of leftover as starter and then is allowed to ferment for 24 hours at room temperature.
During fermentation, some of the lactose is converted to lactic acid by the fermenting microorganisms. At the end
of the fermentation, the milk butter (Maishanu) is removed by churning for further use and the remaining sour milk
which is nono has youghurt-like taste and is usually taken with sugar. It is an excellent source of proteins and
minerals especially, calcium, phosphorous and vitamins [9]. It is more readily available in the northern states of
Nigeria. The collected Nono can also be molded into Wara (soft cheese) which is also delicious.
2.1 Nutritional benefits of fermented foods
Nutritional benefits associated with food fermentation include extension of shelf life, enhancement of food quality
and nutrients, improving digestibility and bioavailability of nutrients, enhancement of the sensory properties (flavor,
aroma and texture, taste, colour), reduction in toxic and anti-nutritional factors, decreases in cooking time and
energy requirement and delivery of probiotic bacteria [4,10,19]. Lactic acid bacteria and yeast create a low moisture
content and pH which are unfavorable conditions for growth of spoilage and pathogenic microorganismsthat may
decompose or spoil the food, thereby extending the shelf-life of the foods, especially for highly perishable foods.
Fermentation can also enhance nutritional properties in a safe and effective manner. The enzymatic activity of the
raw material and the metabolic activity of microorganisms in fermented food can change the nutritive and bioactive
properties of the food matrices in a manner that has beneficial consequences for human health.Traditional
fermented foods are among the most affordable sources of vitamins, minerals and plant-based proteins, which are
essential for good health [10]. During fermentation, bacteria synthesize vitamins, minerals, organic acids and
produce biologically active peptides with enzymes such as proteinase and peptidase and remove some non-nutrients
[9,10].The B-vitamins including folate (B9), riboflavin (B3), and cobalamin (B12) are synthesized from various non-
vitamin precursors by certain bacteria during fermentation [20,21]. The microorganisms involved in the
fermentation of indigenous foods also improve the sensory properties by producing favorable volatile end products
which promote the growth of fermenting bacteria and protect against pathogenic microorganisms [22].
Also during fermentation, microbial amylase hydrolyses carbohydrate into sugars which are then readily digestible
by humans. Galactinase, (another microbial enzyme) soften the texture of the seeds and liberate sugars for digestion
[23]. Most legumes which contain large amount of non-digestible carbohydrates are associated with abdominal
distention and flatulence in humans but fermentation reduces the total flatus in legumes [10]. In most fermented
high protein products, the extent of protein hydrolysis is one of the most important factors responsible for texture
and flavor seen after fermentation. Soluble low molecular weight peptides and amino acids that contribute to flavor
are also produced through the enzymatic breakdown of proteins [10,24]. Some polysaccharides produced
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duringfermentation act as prebiotics which are further fermented by the microbiota in the colon to favorable short
chain fatty acids with health benefits.
Additionally, fermentation results in the removal of toxic or undesirable food constituents such as phytic acid (9,10]
which is an anti-nutritional compound that chelates divalent importantmetal ions reducing their absorption and
bioavailability. The reduction of pH as a result of lactate production during fermentation optimizes endogenous
phytase activity thus removing most phytate and increase the bioavailability of essential mineralsthat helps maintain
immune system.
2.2 Fermented foods and probiotics
Microorganisms contributing to the food fermentation process have recently been associated with many health
benefits and these microorganisms (probiotics)have become another focus of attention in nutrition and wellbeing.
By definition, probiotics are live microorganisms that when administered in adequate amounts confer a health
benefit on the host [25,26]. Studies have found that the intake of probiotics resulted in minor but consistent
improvements in several metabolic risk factors in subjects with metabolic diseases and particularly in insulin
resistance [1,4,27].
Different types of bacteria (e.g, Lactobacillus, Bifidobacterium, Streptococcus, Bacillus) and yeast or mold (e.g, Saccharomyces,
Aspergillus, Candida) are used as probiotics [28]and studies showed that indigenous fermented foods and beverages
may serve as a suitable carrier for these probiotics. Many fermented foods and beverages products are processed
such that viable microorganisms are present at the time of consumption and a relatively large fraction of those
microbes survives passage through the human digestive tract [29,30]. The ingestion of fermented foods containing
probiotics potentially increase the numbers of microbes in the diet by up to 10, 000-fold [31] and consuming these
fermented foods could be equivalent to introducing new beneficial microorganisms into the intestinalmicrobiota.
It is very important to note that fermented foods are not same as probioticsbecause not all fermented foods contain
live microorganisms. Taking beer and wine as example, which undergo further steps after production that removes
the organisms and other fermented foods such as bread are heated at higher temperature which inactivates the
microorganisms in the food. Therefore, the strain composition and stability of the microorganisms in traditional
fermented foods arenot clearly understood [7]. However, when fermented foods and beverages are supplemented
with probiotic bacteria, they serve as nutraceuticals and provide numerous extra nutritional and health benefits.
2.3 Health Benefits Associated with Fermented Foods
In the past, the health benefits of fermented foods were unknown and so many people primarily used fermentation
only to preservefoods and improve theirsensory qualities.Recently, it is increasingly understood that these fermented
foods also promote human health in ways that are not directly attributable to the starting unfermented food
materials. Nowadays, fermented foods have become an important part of the diet in many cultures and have
recently emerged as a novel functional food with many health benefits that gobeyond basic nutrition. Fermented
foods generally have the potential to lower the risk of carcinogenesis, atherosclerosis, oxidation, tumors, obesity
[32], inflammation [27], mutagenesis, hypercholesterolemia effects [33], stimulating the immune system [34,35]and
alleviating the symptoms of lactose intolerance [36].
Recent human clinical studies on fermented foods support this possibility. For instance, large cohort investigations
revealed strong associations between consumption of fermented foods and weight maintenance [37,38].Another
long-term prospective study shows reductions in risk of cardiovascular diseases and overall mortality from frequent
yogurt consumption [39]. Similarly, An et al.,[40]and Choi et al., [33] showed that kimchi ( a fermented food)
possesses health beneficial effects especially on people with pre-diabetes by inducing insulin sensitivity and
decreasing insulin resistance.In addition,fermented rice has been shown tohave beneficial effect on hypertension
and metabolic syndrome and may prevent some lifestyle diseases [41]. Another similar study showed
thatfermentedfoodsreduce fatigue and stresses [42] and protects against oxidative stress induced by DNA damage
[43]. Also, fermented foods have been proved to help the liver against the free radicals produced by copper
accumulation [44].
The health benefits provided by fermented foods could be attributable to the bioactive compounds formed during
fermentation process and other metabolites produced by the microorganisms responsible for fermentation
[45].Physiologically-active peptides with different functionalities, phytochemicals, free amino acids and their
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derivatives,volatile compounds and organic acids are all produced by various microorganisms during the food
fermentation [9,10]. Due to their bioactivities, these peptides possess the potential to be used in the formulation of
health enhancing nutraceuticals that may play different physiological roles in the body. For instance, conjugated
linoleic acidwhich is a metabolite produced during fermentation; have a blood pressure lowering effect [46].
Another bioactive compound called exopolysaccharideisnatural polymer of sugars that are produced biologically by
various microorganisms during fermentation [47,48]. Due to the potential health benefits associated with
exopolysaccharides, which include anti-oxidant, anti-diabetic, anti-carcinogenes, cholesterol lowering and
immunomodulatory properties, the compound has recently become a focus of interest by researchers [49,50].
Free amino acids and its neurotransmitter derivatives (Gama-aminobutyric acid-GABA) which regulate blood
pressure against cardiovascular and cancer and also possessimmuno-modulatory function are synthesized during
fermentation [51]. The free amino acids and GABA contents of fermented foods also contribute to its anti-diabetic
and anti-oxidant properties [52] and havealso been shown to have potential chemo-preventive[53], hypolipidemic
and anti-inflammatory effects [54]. Lactic acid (a major end-product of food fermentation) has been reported to
reduce pro-inflammatory cytokine secretion in a dose dependent manner [55]and also alters redox status by
reducing the reactive oxygen species burden in intestinal enterocytes [56].
Apart from the bioactive compounds which are produced during food fermentation, several studies have shown
that probiotics contained in fermented foodsalso provides several health benefits [10,24,28]. For example, ingestion
of vibrant probiotics through fermented foods is found to cause significant positive improvements in balancing
intestinal permeability [57], having direct effects on metabolic syndromes, atherosclerosis, inflammatory bowel
diseases [27], colon cancer enhanced immune system and improve gastrointestinal function [4,10]and indirect
effects on depression, anger, anxiety and levels of stress hormones [58].Studies have revealed that Lactobacillus
sppwhich are common organisms in fermented foods could reduce the risk of infections, including bacterial
vaginosis [59,60]. It could also reduce the occurrence of gonorrhoea, chlamydia, and other sexually transmitted
diseases and diarrhoea [61]. Many fermented foods are high in vitamin C and iron, both of which help the body to
fight against infection by contributing to a healthy immune system.
2.4 Effect of fermented foods on human immune system
Imbalance in the gut microbiota is associated with the pathogenesis of various diseases [1,62,63], including
hypertension, diabetes mellitus, cancer, obesity and cardiovascular diseases which are considered risk factors for
complications in people with Covid-19. Different levels of evidence have supported the role of nutrition and
fermented foods in balancing and promoting immunity [1,4,28,64,]andrecent reports have shown that some of the
countries with low Covid-19 mortality rate are those with a relatively high national consumption of traditional
fermented foods [3,4]. The human gut is home for over 200 species of bacteria collectively known as the gut
microbiotawhichlive mutually in gut of humans [62]. These microbes help break down food in the intestines, aid in
the digestion process, help fight off disease, and boost the immune system [3,63]. The immune isthe group of cells
and molecules that protect us from disease by monitoring our body and responding to any foreign substances they
perceive as threats, particularly infectious microbes [10].
Recently, fermented foods have regained popularity as part of diets due to the interest in their significant impact on
the gut microbiota balance and immune system. The importance of the interactions between the gut microbiota and
the immune system is clearly highlighted by the fact that majority (about 80 per cent) of the body’s immune cells are
found in the human gut[4,63]. As a consequence, the immune system and the gut microbiota developed a
mutualistic relationship regulating one another and cooperating to support each other.This means that when gut
health is imbalanced, it is difficult for the body’s immune system to function properly [65,66] and this may increase
predisposition to inflammatory and immune-mediated diseases.According to Stiemsmaet al.,[67], frequent
consumption of fermented foodswhich contain probiotics may help improve the immune system’s function by
balancing the human gut microbiota.
The administration of probiotics through fermented foods has been shown to alter the composition and
functionality of the gut microbiota thereby modulating the immune system to fight infections and diseases [4,10,65].
Moreover, having an active and natural variety of microorganisms in the gut may improve general health since the
good and healthy microorganisms in the gut make food more digestible through their enzymes which also help also
to maintain immune system [65]. Therefore, probiotics contained in fermented indigenous food may restore the
International Journal of Applied Science and Research
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composition of the gut microbiome and introduce beneficial functions to gut microbial communities and thereby
boosting the immune system to fight infections [67].
Apart from the effects of probioticson gut bacteria, the systemic effects of bioactive peptides which are produced
during fermentation also possess some immuno-modulatory effects [10]. In a study to determine the serum cytokine
profiles of healthy volunteers after consuming Kefir (fermented beverage), it was reported that immune cells (TNF-
α) levels were increased with Kefir consumption, though the increase was not significant [68]. Again, consumption
offermented foods and beverages improves the bio-accessibility and bioavailability of food bioactive components,
supplying dietary fibers, essential micronutrients, enzymes and organic acids, all of which are crucial in boosting the
immune system. Short chain fatty acids which are produced from insoluble dietary fibers by certain microbial
species in fermented foods also promote the activity of regulatory T-cells which prevent inflammatory reactions by
suppressing the abnormal activation of other immune cells [1], thereby playing a very important part in maintaining
immune tolerance and self-antigens.
In fact, the human microbiotawhich is related to immunity is a key contributor to many aspects of human health
and its composition is largely influenced by diet we eat [69]. A healthy interaction between the immune system and
the gut microbiota is crucial for the maintenance of the body’s homeostasis, immunity and wellbeing [65]. If we eat
nothing but overly processed and difficult to digest foods, then the fermentation process will occur within the
gastrointestinal track resulting into gas, bloating, diarrhea, and constipation which might possibly lead to other
diseases like cancer. However, providing the body with predigested foods such as fermented foods will help the
existing microbes within to do the job they need to do, which includes stimulating the immune system to function
properly. This is why it is important to take good care of our gut and this starts with what we eat [69]. Taking into
considerations the benefits of these traditional fermented foods, utilizing them properly at larger scale could
mitigate the economic effects of Covid-19 especially on food security and also help boost the immunity to possibly
face the infection.
3. Conclusion
Fermented foods are increasingly understood for their properties that extended well beyond preservation and
sensory attributes. They offer additional health benefits and enhanced nutrient availability far beyond the
unfermented material. Fermented foods have the potentials to boost the immune system to possibly face the
infection by balancing the gut microbiota which is linked with immunity. Nigerian traditional fermented foods and
beverages if properly developed as standard commercial products could also play a major role in the national food
security especially during and post Covid-19 by mitigating the economic effects of the pandemic in the country.
Without being a promise of efficacy against Covid-19, incorporating these locally fermented foods and beverages
into diets may help to minimize gut inflammation and enhance immunity to possibly lower the severity or the
duration of infection episodes pending when an effective vaccines or drugswhich can interfere withthe
virusmetabolismsis discovered.
4. Acknowledgement
The authors are thankful to the MobilitéUniversitaire en Afrique (MOUNAF) projectof the Intra-Africa Academic
Mobility Scheme of European union for the financial support.
Ethics statement
There are no ethical concerns in thisreview article
5. Author contributions
P.N.A reviewed the literature and wrote the manuscript. P.N.O and C.O.E read and revised the manuscript. P.N.A
wasresponsible for the concept, preparation and submission of the final article.
6. Conflict of Interest
The authors declare no conflicts of interest
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136
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