Total and Soluble Oxalate Content of Some Indian Spices

Abstract

Spices, such as cinnamon, cloves, cardamom, garlic, ginger, cumin, coriander and turmeric are used all over the world as flavouring and colouring ingredients in Indian foods. Previous studies have shown that spices contain variable amounts of total oxalates but there are few reports of soluble oxalate contents. In this study, the total, soluble and insoluble oxalate contents of ten different spices commonly used in Indian cuisine were measured. Total oxalate content ranged from 194 (nutmeg) to 4,014 (green cardamom) mg/100 g DM, while the soluble oxalate contents ranged from 41 (nutmeg) to 3,977 (green cardamom) mg/100 g DM. Overall, the percentage of soluble oxalate content of the spices ranged from 4.7 to 99.1% of the total oxalate content which suggests that some spices present no risk to people liable to kidney stone formation, while other spices can supply significant amounts of soluble oxalates and therefore should be used in moderation.

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ORIGINAL PAPER
Total and Soluble Oxalate Content of Some Indian Spices
Sumana Ghosh Das &G. P. Savage
#Springer Science+Business Media, Inc. 2012
Abstract Spices, such as cinnamon, cloves, cardamom,
garlic, ginger, cumin, coriander and turmeric are used all
over the world as flavouring and colouring ingredients in
Indian foods. Previous studies have shown that spices
contain variable amounts of total oxalates but there are
few reports of soluble oxalate contents. In this study, the
total, soluble and insoluble oxalate contents of ten dif-
ferent spices commonly used in Indian cuisine were
measured. Total oxalate content ranged from 194 (nutmeg)
to 4,014 (green cardamom) mg/100 g DM, while the soluble
oxalate contents ranged from 41 (nutmeg) to 3,977 (green
cardamom) mg/100 g DM. Overall, the percentage of soluble
oxalate content of the spices ranged from 4.7 to 99.1% of the
total oxalate content which suggests that some spices present
no risk to people liable to kidney stone formation, while other
spices can supply significant amounts of soluble oxalates and
therefore should be used in moderation.
Keywords Total oxalate .Soluble oxalate .Insoluble
oxalate .Spices
Introduction
Spices and herbs are popular ingredients in Indian cuisine,
they are used to improve and to add a variety of flavours and
tastes and they also have antimicrobial and radical-
scavenging properties [1,2]. Many spices such as, turmeric,
cumin, garlic, pepper, cinnamon, coriander, and cardamom
are used as preservatives and flavourings in pickles and
chutneys [1,3]. Several spices, particularly garlic, ajowan,
black pepper, cloves, ginger, cumin, and caraway seeds are
also used extensively in Indian medicine [1]. Spices have
been shown to contain a number of phenolic and flavo-
noid compounds with antioxidant, anti-inflammatory,
anti-mutagenic, and anti-carcinogenic activities [3]. In
contrast to these beneficial compounds, spices including
cinnamon, ginger, cloves, fennel, coriander, and turmeric
have been shown to contain high levels of oxalates while
other spices, such as caraway and cardamom (both black
and green cardamom) contain moderate levels of oxalates
[4–6].
Oxalates exist in two different forms in plant foods,
water-soluble salts with sodium, potassium and ammonium
ions, and insoluble salts with calcium, magnesium and iron
ions, rendering these minerals unavailable to animals [7–9].
Current practice is to extract the soluble fraction of oxalates
from foods using hot water (80 °C) and the total (soluble
and insoluble) fraction using hot acid (e.g.,2MHCl,80°C).
The level of insoluble oxalate is determined by subtracting the
soluble oxalate from total oxalate content [10,11]. After
consumption by humans, insoluble oxalates are excreted in
the faeces. Soluble oxalates are able to bind to calcium and
other minerals under acidic to near-neutral conditions in the
intestine making these minerals unavailable. It has been
reported that after ingestion of food only 2–12% oxalate out
of the total oxalate eaten is absorbed, and the remaining free
oxalate combines with calcium to form calcium oxalate in the
intestinal lumen, making calcium unavailable for absorption
[7,8]. Unabsorbed oxalate in the intestinal track is voided in
the faeces as calcium oxalate [12]. There are two main effects
of oxalate on human health: first, oxalate can form insoluble
salts in the digestive tract by binding to cations such as
calcium, iron and magnesium, decreasing the bioavailability
S. Ghosh Das :G. P. Savage (*)
Food Group, Agriculture and Life Sciences, Lincoln University,
Canterbury, New Zealand
e-mail: savage@lincoln.ac.nz
Plant Foods Hum Nutr
DOI 10.1007/s11130-012-0278-0
Author's personal copy

of these essential minerals [7,13]. Secondly, soluble oxalate,
once absorbed into the body has to be excreted in the urine. In
this process oxalates can bind to calcium and form insoluble
calcium oxalate, which then accumulates in the kidneys. It has
been estimated that approximately 75% of all kidney stones
are composed of this calcium oxalate [6]. Excessive urinary
excretion of oxalate (hyperoxaluria) is a primary risk factor for
this disorder [14,15]. The diet plays an important role in the
incidence of stone formation [15–18], avoiding the excessive
consumption of high-oxalatecontaining foods and consuming
calcium containing dairy foods [19] are logical ways to limit
calcium oxalate stone formation in the kidney. A summary of
all the limited data available on the oxalate content of spices is
shown in Table 1.
Early studies by Singh [5] suggested that some spices
contained relatively low levels of total oxalates when
expressed on a dry matter (DM) basis (Table 1)[1].
Singh used an oxalate precipitation method followed by
titration with potassium permanganate. This method has
now been superseded by more accurate HPLC methods. In
contrast to Singh’s work using a titration method, Ram-
asastri [4] showed that many spices contained high levels
of total oxalates. In this later study, Ramasastri was able
to show that caraway seeds, cinnamon and cloves also
contained soluble oxalates. Caraway seeds were unusual
as they contained between 80 to 90% soluble oxalates.
The cinnamon supplement used by Tang et al.[6]
contained 1,789 mg total oxalates/100 g DM which is
much higher than the range (398–826 mg/100 g DM) reported
earlier [4]. The value reported for the total oxalate content
(1,969 mg/100 g DM) of turmeric was similar to the
range 1,526–1,935 mg/100 g DM reported earlier by
Ramasastri [4], but in contrast to the single value
(12.4 mg/100 g DM) reported by Singh [5].
It is interesting to note that Tang et al. [6] in a urinary
oxalate excretion study found that the percent of ingested
oxalate absorbed up to 6 h following turmeric ingestion was
significantly higher (8.2%) than that following cinnamon
ingestion (2.6%). Turmeric contained 91% soluble oxalates
compared to 6% in cinnamon, suggesting that the ratio of
soluble oxalates to total oxalates in a food is an important
determinant in oxalate absorption and excretion. This was
supported by later studies comparing oxalate absorption
from almond and black pepper. Almonds contained 31%
soluble oxalate and 5.9% of total oxalate was absorbed
while black pepper contained 5% soluble oxalate and
1.8% of total oxalate was absorbed over the same time period
[20]. Therefore, cinnamon can be considered a low oxalate
food while the consumption of moderate amounts of turmeric
would not be recommended for people with a tendency to
form kidney stones. There is a need to measure the oxalate
content of common spices that are regularly added to Indian
cooking and are sometimes taken in larger amounts, for their
other perceived nutritional benefits. It is also important to
measure the soluble oxalate content of many of these spices
to confirm whether the earlier results, quoting only total
oxalate content, are useful as the percent soluble oxalate of a
food is a major determinant of absorption. It is possible that
spices may attribute more oxalates in Indian diets than previ-
ously thought and understanding the levels involved with a
reduction of their use could well reduce the incidence of
kidney stone formation. For these reasons, the total and solu-
ble oxalate contents of condiments and spices commonly
imported into New Zealand were analyzed for their oxalate
contents.
Materials and Methods
Sample Material
Dried spices were purchased from Moshims Indian Super-
market in Christchurch, NZ in October 2010; the spices
were produced and packed in India and exported to NZ by
M.V. Exports, Mumbai, Maharashtra, India. A sub-sample
of each spice was subsequently ground to a fine powder in a
coffee mill (Sunbeam, model: EM0400, China).
Residual Moisture Determination
The residual moisture content of each sub-sample of
driedspiceswasdeterminedbydryingtheminanoven
Table 1 Total and soluble oxalate content (mg/100 g DM) of some
Indian-origin condiments and spices [4–6]
Spices Total
oxalates
Soluble
oxalates
Ajowan (Trachyspermum ammi)[5] 1166–1458 –
a
Ajowan (Apium Graveolens var. Dulce) [4] 350 –
Cardamom (black) (Amomum subulatum)[5] 452–553 –
Cardamom (green) (Ellettaria cardamomum)[4] 16.9 –
Caraway seeds (Carum caarvi)[5] 655–913 587–688
Cinnamon (Cinnamomum zealanicum)[5] 398–826 108–200
Cinnamon (Cinnamomum zealanicum)[6] 1798 –
Cloves (Syzygium aromaticum)[5] 3245–3969 1520–1677
Coriander seeds (Coriandrum sativum)[5] 990–1480 –
Cumin (Cuminum cyminum)[4] 76.3 –
Fennel seeds (Foeniculum vulgare)[5] 815–1118 –
Garlic (Allium sativum)[4] 8.8 –
Ginger (Zingiber officinale)[4] 91.4 –
Turmeric (Curcuma domestica)[5] 1526–1935 –
Turmeric (Curcuma domestica)[6] 1969 –
Turmeric (Curcuma domestica)[4] 12.4 –
True cardamam (Ellettaria cardamomum)[5] 493–522 –
a
Not detected
Plant Foods Hum Nutr
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(Watvic, Watson Victor Ltd., NZ) set at 105 °C to a
constant weight [20]. All determinations were performed
in triplicate.
Extraction and Analysis of Oxalates
The measurement of total and soluble oxalate was per-
formed following the method outlined by Savage et al.
[21].Theoxalicacidpeakwasidentifiedbycomparing
the retention time with an oxalate standard solution and
by spiking the sample with a known quantity of oxalic
acid standard solution. The content of insoluble oxalate
was calculated by subtracting the amount of soluble oxalate
from the total oxalate content [10]. All determinations were
performed in triplicate.
Results and Conclusions
The mean residual moisture content of the 10 spices was
89%, which is typical of dried foods (Table 2).
The total oxalate content of the spices measured in this
study ranged from 194 mg/100 g DM for nutmeg to
4,014 mg/100 g DM for green cardamom (Table 2), while
the soluble oxalate levels ranged from none detected in
cinnamon and very low levels in nutmeg 41 mg/100 g to
3,977 mg/100 g DM in green cardamom. Green cardamom
contained the highest proportion of soluble oxalate (99.1%)
of the total oxalate content followed by turmeric powder
(95%). Although the level of total oxalate in ginger was
lower than most other spices, around 88% of it existed in
soluble form. All the other spices contained soluble oxalates
which ranged from 4.7 to 59.2% of the total oxalates.
Cinnamon was the only spice which contained insoluble
oxalate alone.
Earlier studies [4–6] have shown that spices including
cinnamon, caraway, black cardamom, ginger, cloves, fennel
seeds, coriander and turmeric were high in total oxalates,
whereas other spices such as true cardamom, cumin, garlic
and ginger contained low levels of total oxalates (Table 1).
Table 2shows that the total oxalate found in locally sourced
turmeric (but produced in India) was significantly higher
than the values published by Singh [5], with 95% existing as
soluble oxalate. Later studies [4], suggest that caraway
seeds contained principally soluble oxalates, while the
present study found much higher levels (95.3%) of insoluble
oxalates and very low levels (4.7%) of soluble oxalates. The
level of soluble oxalate found in turmeric (95%) in this study
was similar to the value reported by Tang et al. [6] which was
91.2% soluble oxalate.
Tang et al. [6] carried out a study to assess urinary oxalate
excretion following the consumption of supplemental doses
of cinnamon and turmeric [6]. In this study, eleven healthy
subjects consumed either 3.2 g turmeric or 3.5 g cinnamon
in an oxalate load test; this was compared to the control
regime when only water was given. The subjects consumed
63 mg total oxalate from the test spices. The cinnamon and
turmeric supplements used in this study had total oxalate
contents of 1,798 mg/100 g DM and 1,969 mg/100 g DM,
respectively. The total oxalate content of turmeric sourced
locally in New Zealand contained 1,889 ± 69 mg/100 g DM,
which is similar to the results of Tang et al. [6]. In contrast,
the total oxalate content of cinnamon sourced locally in
New Zealand contained 3,460 ± 313 mg/100 g DM and thus,
the consumption of cinnamon would have provided two
times higher level of oxalate if 3.5 g of cinnamon was
consumed in the same way. The absorption of oxalate from
turmeric was observed by Tang et al. [6] to be significantly
higher than cinnamon, and this can be explained by nothing
that turmeric analyzed in the present study contained 95%
Table 2 Total, soluble and insoluble oxalate contents of 10 different Indian-origin spices (mg/100 g DW ± SEM)
Spices Residual moisture
(g/100 g as purchased)
Total
oxalates
Soluble
oxalates
Insoluble
oxalates
Cardamom (green) (Elettaria cardamomum) 93 4014± 332 3977 ± 50 37± 8
Cardamom (black/big) (Amomum subulatum) 90 2055± 46 1204 ± 173 851 ± 107
Caraway seeds (Carum carvi) 89 945± 134 44 ± 2 901±76
Cinnamon (Cinnamomum zelanicum) 86 3460± 313 –
a
3460±181
Cumin (Cuminum cyminum) 88 1513± 94 112± 4 1401 ± 54
Curry leaf (Murraya koenigii) 86 2033± 201 119 ± 22 1914 ±120
Ginger (Zingiber officinale) 89 1528± 92 1339 ± 38 189± 35
Malabathrum leaf (Cinnamomum tamala) 86 2744± 141 1625 ± 221 1119±90
Nutmeg (Myristica fragrans) 94 194± 22 41 ± 5 153 ± 14
Turmeric powder (Curcuma domestica) 89 1889± 69 1795 ± 59 94± 35
a
Not detected
Plant Foods Hum Nutr
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soluble oxalates. This indicates that the amounts of soluble
and insoluble oxalates in foods have an important role in the
determination of oxalate absorption and excretion. Chai and
Liebman [22] also showed that almond, which contained
31% soluble oxalate, had a higher rate of absorption (5.9%)
than black pepper (1.8%) which contained only 5% soluble
oxalate content.
People susceptible to kidney stone formation should reduce
their intake of soluble oxalates; cinnamon could be considered
a low oxalate spice while turmeric a high soluble oxalate
containing spice should be avoided. The data in Table 2
suggests that green cardamom, turmeric, ginger, malabathrum
leaf and black cardamom containing 99%, 95%, 87%, 59%
and 59% soluble oxalate, respectively, could pose a threat to
an individual prone to renal stone formation.
In a household survey [23], the daily spice intake was
calculated for average Indian males using the method de-
veloped by the National Nutrition Monitoring Bureau of
India [24]. They found that the average total spice intake
for Indian males was 9.54 g/day. Using this value and the
total oxalate values determined for four spices determined in
this study, the mean daily total oxalate intake can be calcu-
lated. Using data from the present study, cumin seeds, dry
ginger, turmeric powder and caraway seeds could provide
an average of 12.1, 1.6, 16.4 and 0.8 mg of total oxalate,
respectively, on a daily basis in the diet of an average Indian
male. The American Dietetic Association [25] recommends
restricting the consumption of total dietary oxalate to less
than 40 to 50 mg/day for people prone to form kidney
stones. These calculations are based on the assumption that
only one spice is consumed each day; it is clear, however,
that cumin and turmeric powder are important and popular
constituents of many curry-based dishes and have the po-
tential to supply moderate amounts of oxalates in the diet, in
addition to the oxalates that may be found in traditional
Indian vegetables [26]. Spices are normally neither included
in diet surveys nor included in formulations of balanced diets
due to their insignificant intake. However, this may be impor-
tant if larger quantities of spices are consumed regularly in the
diet as in traditional dishes. There may also be regional
variations in types and quantities of spices used. The avail-
ability of current data in this area is insufficient and needs
further research before getting any conclusion about them.
Conclusions
Spices which are part of many cuisines are found to contain
oxalates which range from 41 (nutmeg) to 3,977 (green
cardamom) mg soluble oxalates/100 g DM. However, the
oxalate contents of spices in different locations may vary
depending on the species, cultivars, climates, processing and
extraction methods. Some spices, including turmeric
powder, green cardamom, ginger, malabathrum leaf and
black cardamom were found to have most of their oxalates in
the soluble form and, therefore, should be avoided by people
with hyperoxaluria or a tendency to form kidney stones.
However, the daily intakes of these spices are low compared
to other oxalate containing leafy vegetables as they are added
to meals in relatively small amounts. It should be noted,
however, that spices are an important part of Indian cuisine
and that spices are routinely added to many traditional meals;
therefore, these spices will constitute a frequent intake of
oxalates in the diet.
Acknowledgments The authors wish to thank Leo Vanhanen for
his help throughout the experiment and Janette Busch for proof
reading the text.
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