Safety of Soy Factsheet

The Safety of Soya
The VVF examines the latest science on soya. We
give you the facts on the wealth of health benefits
By Dr Justine Butler and the supposed risks of the humble soya bean.
VVF Senior Health Campaigner

Over the last few years we have heard how soya is a very good source of nutrients and can protect
against heart disease, certain cancers and may reduce the risk of osteoporosis and menopausal
symptoms – it might even help boost brain power. However, not all the reports on soya are favoura ble and
th e health benefits have b een q uest ion ed by so me while o thers ha ve gon e even fu rth er, launching a
vigorous anti-soya crusade. The result is confusion – people don’t know what to believe. The VVF has
looked at the research in its entirety and this fact sheet sets the record straight.

The history of soya consumption The UK government’s Joint Health Claims Initiative (JHCI) offers
There is a long history of people safely consuming soya beans, market advice and a code of practice for both the UK food
dating back to the 11th century BC (3,000 years ago) in the industry and consumers to ensure that health claims on foods are
eastern part of Northern China. The period from the first century both scientifically truthful and legally acceptable. In 2002 the
AD to the 15th-16th century saw the introduction of soya beans in JHCI approved the health claim: “the inclusion of at least 25
many parts of Asia, including Japan and India, and in 1765 the grams soya protein per day as part of a diet low in saturated fat
soya bean was introduced to the USA (JHCI, 2002). Since then, it can help reduce blood cholesterol” (JHCI, 2002a).
has become an important part of the diets of many populations
and in more recent years has found favour with vegetarians and Exactly how soya protein does this is not yet clear. In 2005, a
vegans because of its many nutrients and health benefits. However, review of 23 trials, published in the American Journal of Clinical
as the popularity of soya has grown, so has the number of critics Nutrition, examined the cholesterol-lowering effects of soya
questioning the benefits of this humble bean. protein containing isoflavones (a phytoestrogen or plant hormone
– see below). It confirmed that soya protein significantly lowers
Nutritional value cholesterol levels but suggested that isoflavones alone did not
Soya (Glycine max) is a particularly good source of protein as it (Zhan and Ho, 2005).
contains the eight essential amino acids which the human body
needs. Soya milk and other soya products provide a rich source of Another study looked at the cholesterol-lowering effects of soya
polyunsaturated fatty acids (including the ‘good’ fats – omega-3) proteins in healthy young men, a sub-group that has been
and are free of cholesterol. Compared to cow’s milk, soya milk somewhat overlooked. It showed that soya protein, regardless of
contains lower levels of saturated fat and higher levels of its isoflavone content, reduces cholesterol (McVeigh et al., 2006).
unsaturated essential fatty acids, which can lower cholesterol levels.
These studies suggest that this effect involves a combination of
Soya products provide an excellent source of disease-busting factors in soya, including: isoflavones, soya protein peptides (small
antioxidants, B vitamins (including folate) and iron. Calcium- chains of amino acids – the building blocks of protein) and its
fortified soya products such as soya milk and tofu provide a amino acid content (the sequence of amino acids that make up
valuable source of this important mineral without the saturated soya protein and which may differ significantly to that of animal
animal fat, animal protein (casein) and cholesterol found in dairy protein). These factors appear to work together to lower
products. One serving of 200ml (7 fl oz) of Alpro soya with added cholesterol and so reduce the risk of heart attack and stroke.
calcium and vitamins (blue pack) contains 30 per cent of the
recommended daily amount (RDA) of calcium – equivalent to Menopausal symptoms
cow’s milk. It is also fortified with vitamin B12 and 200ml In Japan, where soya consumption is higher than most other places
provides 100 per cent of the RDA of this important nutrient. in the world, the incidence of menopausal hot flushes is much
lower than in the West. However, within Japan there are
Many soya foods also contain valuable fibre which is important for variations. A six-year study of over 1,000 Japanese women showed
good bowel health and can also lower cholesterol. Soya foods, that those who consumed the most soya foods had less than half
particularly those made from whole soya beans, offer a wide range the number of hot flushes compared to women consuming the
of nutritional and health benefits. least amount of soya (Nagata, 2001).

There are also many studies showing that supplementing the diet
Health benefits with soya foods or soya protein isolates can substantially reduce
the frequency or severity of hot flushes and other menopausal
Heart health symptoms in some women.
Scientists agree that soya protein can promote heart health – a fact
supported by dozens of controlled clinical trials. In 1995, a review It was shown in 1995 that the incidence of hot flushes was
published in the New England Journal of Medicine investigated the reduced by 40 per cent in women consuming 45 grams of soya
Charity numb er : 1 037 486

effect of soya protein on cholesterol levels (Anderson et al., 1995). flour for 12 weeks compared to a 25 per cent reduction among
In 34 of the 38 studies reviewed, replacing animal protein with those consuming wheat flour (Murkies et al., 1995). In 1997,
soya protein decreased cholesterol levels (in the remaining four another study found that hot flushes were reduced by 54 per cent
trials the subjects had low cholesterol levels to start with). The role in women consuming tofu, soya milk and miso, compared to a 35
of soya protein in heart health has since been widely accepted and per cent reduction in the control group (Brzezinski et al., 1997). A
approved by many different health bodies. third study, in 1998, showed that 60 grams of an isolated soya

VVF, Top Suite, 8 York Cou rt, W i l d e r S t r ee t , B r i s t o l B S2 8QH. Tel: 0117 970 5190. Email: info@vegetarian.org.uk Web: www.ve getarian.org. uk FS10

protein supplement containing 76mg total isoflavones significantly
reduced hot flushes by 45 per cent compared to a 35 per cent The calcium paradox
reduction in the control group (Albertazzi et al., 1998). As food is digested, acids are released into the blood in varying
proportions, depending upon the food. The body tries to
More recently, in 2002, Faure et al. showed that a soya isoflavone neutralise this acid by drawing calcium from the bones and the
extract reduced the incidence of hot flushes by 61 per cent after 12 calcium is then excreted in the urine (the calciuric response).
weeks compared to a 21 per cent reduction in the control group Animal protein from cow’s milk and dairy products, as well as
(Faure et al., 2002). Not surprisingly, some of these researchers meat, fish and eggs, has a particularly strong acidic effect
suggest that soya protein may provide an alternative to hormone compared to plant protein because of the sulphur-containing
replacement therapy (HRT) for reducing menopausal symptoms. amino acids it contains. As increasing amounts of animal products
are eaten, the sulphur content of the diet increases and so does
The safety of specific amounts of isoflavones has not yet been the level of calcium in the urine. This increases calcium loss and
established and so it is better to obtain isoflavones from whole may be a risk factor for the development of osteoporosis.
soya foods rather than as isolates extracted from soya.
This so-called calciuric response is well-documented in the
Bone health scientific literature – the more cow’s milk, meat, fish and eggs
The first published human trial investigating the effects of soya foods you eat, the more calcium is lost from the body. The irony is that
on bone health and osteoporosis indicated that soya protein may be cow’s milk is promoted as the best source of calcium but it is
effective in reducing the risk of this debilitating disease (Potter et al., also a powerful source of calcium loss. The World Health
1998). It was found that supplementing the diet of postmenopausal Organisation (WHO) calls this the ‘calcium paradox’, where the
women with 40 grams of soya protein a day (containing 90mg of damaging effects of animal (but not vegetable) protein may
isoflavones) for six months significantly increased both the bone outweigh the positive effects of the calcium it contains (WHO,
mineral content and density of the lumbar spine. 2004). In other words, you’re better off getting calcium from
plant foods such as cereals, nuts, seeds and pulses, which don’t
These findings were supported by a later study that looked at the cause such huge losses of calcium from the bones (See VVF fact
effect of 80mg of soya isoflavones a day on bone density (Alekel et sheet, Boning up on Calcium).
al., 2000). This also showed that isoflavones reduced bone loss
from the lumbar spine of women who may otherwise be expected
to lose two to three per cent of bone per year. In 2003, a review The evidence indicates that soya isoflavones are good for bone
of the published research concluded that diets rich in health. Importantly, some researchers suggest that soya foods could
phytoestrogens (and therefore isoflavones) were likely to benefit provide an alternative treatment to HRT for women at risk of
bone health (Setchell and Lydeking-Olsen, 2003). osteoporosis and this may offer a cheap, drug-free prevention for
this debilitating condition (Lydeking-Olsen et al., 2004).
Studies from Japan and China show that postmenopausal women
with the highest intake of isoflavone-rich soya foods have the
highest bone mineral density in the lumbar spine compared with Cancer risk
women with low intakes of soya (Somekawa et al., 2001; Mei et
al., 2001). A more recent study of Chinese women, published in The low rates of breast and prostate cancers seen in Asian
the European Journal of Nutrition, confirmed a strong link countries have encouraged scientists to investigate the role of soya
between soya isoflavones and a reduction of bone loss in foods on these and other hormone-related cancers.
postmenopausal women who were not obese (Ye et al., 2006).
Breast cancer
In this study, a total of 90 women aged 45-60 years were randomly There is some evidence that soya intake during adolescence may
assigned to one of three treatment groups – taking daily doses of 0 reduce the risk of breast cancer later in life. The Shanghai Breast
(placebo), 84 and 126mg of isoflavones for six months. Bone mineral Cancer Study investigated 1,400 breast cancer cases in China (Shu
density of the spine and hip was measured at the start of the trial and et al., 2001) and found that women who consumed the most soya
when it ended after six months. It showed that as the intake of soya as teenagers had half the risk of breast cancer as adults.
isoflavones increased, the degree of
bone loss decreased, possibly caused A year later, scientists investigated the link between adolescent soya
by soya isoflavones inhibiting the intake and breast cancer in Asian-American women (Wu et al., 2002).
process where minerals are They found that women who consumed soya at least once a week
leached from the bone (bone during adolescence had a significantly reduced risk of breast cancer.
resorption) – see The calcium Over 1,000 women, including 501 breast cancer patients, were asked
paradox below. how often they ate soya foods such as tofu, soya milk and miso.

Results showed that those who were high soya consumers as both
adolescents and adults had a 47 per cent reduction in risk of breast
cancer. Those who ate little soya as adults but had eaten it
regularly during adolescence showed a 23 per cent reduction in
risk. Women who were low consumers during adolescence and
high consumers during adulthood showed little reduction in risk.

These studies suggest that high soya intake during adolescence
reduces breast cancer risk and the risk continues to fall if people
continue to eat soya as an adult.

Drawing the evidence together, Trock et al. performed a review of
18 studies on soya exposure and breast cancer risk published
between 1978 and 2004 (Trock et al., 2006). Results show a

modest association between a high soya intake and a reduced Researchers at the Centre for Neuroscience at King’s College,
breast cancer risk. However, the authors warn that this result London, investigated the effects of a high soya diet (100mg
should be interpreted with caution and that recommendations for isoflavones per day) compared to a low soya diet (0.5mg
high-dose isoflavone supplementation to prevent breast cancer or isoflavones per day) in student volunteers (File et al., 2001).
prevent its recurrence would be premature. In other words, the After just 10 weeks, those receiving the high soya diet exhibited
research looks promising but more evidence is needed. significant improvements in short-term and long-term memory and
in mental flexibility.
The low rate of breast cancer in Japan and the high rate of survival
amongst those who are affected is often used to promote soya A second study investigated the effects of soya isoflavones
foods as being beneficial – or at least, not being harmful – for (60mg per day) in the cognitive ability of a group of
breast cancer patients. Some researchers, however, are cautious postmenopausal women aged between 50 and 65 years of age
and think that even the small oestrogen-like effect of soya foods (Duffy et al., 2003). After 12 weeks, significant improvements
may be detrimental for women who have gone through the were seen in the soya group, including their recall of pictures
menopause, whose natural oestrogen levels have dropped and who and in a sustained attention task. Although the groups did not
have been diagnosed with oestrogen-receptor positive (hormone- differ in their ability to learn rules, the soya group showed
sensitive) breast cancer (PCRM, 2002). significantly greater improvements in tests learning rule reversals
and planning. Its conclusion was that significant cognitive
Their concern is that the weak oestrogen activity improvements in postmenopausal women can be
of soya isoflavones may stimulate the growth gained from 12 weeks of consumption of soya
of tumours which are sensitive to isoflavones.
oestrogen. This is not a concern for
premenopausal women, who have Another study investigated the effects
much higher levels of oestrogens of soya supplements (60mg
which are many times more potent isoflavones per day) on
than phytoestrogens. These postmenopausal women and found
concerns are based largely on the that after just six weeks, the soya
results of in vitro (test tube) and group showed a greater
animal studies but as these have improvement of nonverbal
produced mixed results their (identifying objects, for example)
relevance to human breast cancer short-term memory than the
patients remains unclear. placebo group (File et al., 2005).
What’s more, those on soya
To date there have only been two produced significantly better
human studies on this subject, the performances in mental flexibility and
findings of which were also unclear planning ability. There were, however,
(Petrakis et al., 1996; Hargreaves et al., no improvements in long-term memory,
1999). The cautious approach would be for category generation or sustained attention.
postmenopausal women at risk of breast cancer to
limit the amount of soya products they eat to three or These studies show that soya isoflavones can have a
four a week. significant positive effect on cognitive ability but the benefits
may be restricted to people under the age of 65 (Kritz-Silverstein
On the whole, the evidence suggests that consuming moderate et al., 2003; Kreijkamp-Kaspers et al., 2004). Certainly, further
amounts of soya foods is much more likely to benefit health investigation is warranted.
rather than harm it, both in terms of breast cancer risk and other
chronic diseases.
Soya infant formula
Prostate cancer
Prostate cancer rates also vary widely around the world, tending to Nutritional adequacy
peak in developed, wealthy countries. Japan is the exception, where The VVF supports the World Health Organisation’s
prostate cancer rates are surprisingly low, despite its high standard recommendation that babies should be fed only breast milk for
of living, and some evidence suggests that soya may be responsible. their first six months of life. However, some mothers are unable
to, or choose not to, breast feed and in these circumstances
There are a limited number of studies investigating the role of soya specially formulated milks are recommended until the child is one
in prostate cancer but in 1998 a large-scale study in 59 countries year old. Soya-based infant formulas can provide all the nutrients
found that, overall, soya products were significantly protective required by a growing infant.
(Hebert et al., 1998). It showed that death from prostate cancer
increases with an affluent diet, specifically dairy milk, meat and A number of studies confirm that infants fed soya-based formulas
poultry, while a diet based on cereals, soya beans, nuts and oilseeds show normal growth and development. One study compared
reduces the death risk. The authors of this review believe that their weight, length and head circumference of healthy, full-term infants
findings are strong enough to warrant more work on the potential up to one year old who were fed either soya-based formula or who
use of soya products in preventing prostate cancer. were fed only breast milk for at least two months and were then
weaned on to cow’s milk formula. Both groups showed similar
In summary, there are no human studies that show an increased growth rates in the first year of life (Lasekan et al., 1999).
risk of cancer due to soya consumption but plenty of evidence
suggesting that it provides protection. Another, more recent study compared the nutritional status and
growth of 168 infants who were allergic to cow’s milk and were
Cognitive effects fed either soya-based infant formula or hydrolysed whey formula.
Several studies indicate that soya intake may improve both short- In both groups, nutrient intake and growth were ‘within reference
term and long-term memory, mental flexibility and planning. values’ – in other words, they grew normally (Seppo et al., 2005).

There is currently only one vegan infant soya formula on the UK type of phytoestrogen found in soya beans and include genistein
market: Farley’s Soya Formula, produced by Heinz. This dairy-free and daidzein. Each gram of soya protein in traditional soya foods
infant formula is nutritionally complete and can be used from provides about three to four milligrams (mg) of isoflavones
birth. It contains no animal products so it is suitable for both (Messina and Redmond, 2006).
vegetarians and vegans and infants who require a diet free from
lactose or casein. Many of the beneficial effects – and supposed health risks – of
soya foods are thought to be related to the presence of
In summary, soya-based infant formulas continue to provide a safe phytoestrogens. Phytoestrogens can act in a similar way to the
feeding option for infants. They meet all a baby’s nutritional hormone oestrogen, although they are far less potent (Coldham et
requirements but have none of the detrimental effects associated al., 1997). Some phytoestrogens (isoflavones) are estimated to be
with cow’s milk formulas. For more information on the health between 100 and 100,000 times weaker than the oestrogens that
consequences of consuming cow’s milk, see the VVF’s White Lies occur naturally in humans (Messina et al., 2006).
report online at www.vegetarian.org.uk/campaigns/whitelies or
order a copy by telephoning the VVF on 0117 970 5190 Mon-Fri It is thought that phytoestrogens can have a normalising effect on
9am-6pm. For more information on soya infant formulas see the the body’s natural oestrogen levels (Kurzer, 2000) – if a woman has
VVF fact sheet Soya-Based Infant Formula. a high oestrogen level, perhaps from taking the contraceptive pill or
HRT, phytoestrogens may reduce it by binding to oestrogen
Is soya safe for babies? receptors and blocking access from the stronger
Soya-based nutrition during infancy has a long oestrogens. When oestrogen levels are low, such
history of safe use around the world dating as in postmenopausal women, the weak
back centuries. The first report of soya- effect of phytoestrogens can return the
based infant formula in the West was in body’s oestrogen to more normal levels
1909 (Ruhrah, 1909) and soya-based and so relieve menopausal symptoms.
infant formula was used in cases of
infantile eczema as early as in the Soya isoflavones have been a part
1920s (Hill and Stuart, 1929). of the diet of millions of adults
Since these early days, formulas and children in Asia for centuries
have come a long way. They now and are generally regarded as
contain all the necessary nutrients healthy. A recent review came to
and can be used as a safe the conclusion that the current
alternative to breast milk or as a scientific literature, taken as a
supplement to it. whole, shows that isoflavones
from soya foods are quite safe
Use of soya-based infant formulas in (Munro et al., 2003).
the UK has grown since the 1960s and
are currently fed to about one per cent of Interest in phytoestrogens has increased
all formula-fed babies aged four to 10 weeks, dramatically over the last decade, particularly
rising to about two per cent of infants aged 10- in soya-based infant formulas. The concerns
14 weeks (Hamlyn et al., 2002). raised are based on animal experiments which suggest
that phytoestrogens can affect sexual development and
In the US, soya infant formulas are consumed by 20-25 per cent reproduction function. These experiments are fundamentally
of all babies who are fed formulas of whatever type (USDA, flawed on many levels.
2006). Despite this, the UK Food Standards Agency’s (FSA)
advice is that you should only give your baby soya-based infant Firstly, isoflavones behave differently in different species so
formula if your GP or health visitor advises it (FSA, 2007). It animal studies bear little relevance to humans. Secondly, the
also says that in almost all cases, breast-feeding or another type intestines act as a barrier to isoflavones so artificially boosting
of formula will be a better choice and that if you are currently levels in animals by injection has no relevance. Finally, many of
feeding your baby soya-based formula, talk to your GP or health these experiments have exposed animals to isoflavones at levels
visitor about changing it (FSA, 2007). This highly-cautious many, many times higher than those absorbed by infants fed with
approach is based largely on unfounded anecdotal evidence and infant formula. More and more scientists and doctors are
animal-based experiments. acknowledging that the results of animal experiments should not
form the basis of a public health policy. Dr Kenneth Setchell,
This controversial issue has yet to be resolved (see Phytoestrogens Professor of Pediatrics at Cincinnati Children’s Hospital Medical
below). The FSA says that, until a full review of the evidence both Centre, states that mice, rats and monkeys all metabolise soya
for and against soya formula has been completed, there is no isoflavones differently from humans and that the only appropriate
reason to stop your baby having a soya formula – but only if it has model for examining human reproductive development is the
been suggested by a health professional. human infant (Setchel, 2006).

This is an extremely cautious approach given that literally millions In 1998, a review of isoflavones, soya-based infant formulas and
of infants have been raised on soya formulas in the UK and US, hormone function in those who had soya formulas as infants,
many of whom are now well into their late 30s and early 40s. reported that growth was normal and no changes in timing of
What’s more, there are no reports from Japan and China that the puberty or in infertility rates were reported (Klein, 1998). The
use of soya has affected fertility rates. In fact, the absence of any author concluded that soya-based infant formulas continue to be a
reported ill effects on millions of babies would suggest there are no safe, nutritionally complete feeding option for most infants. They
adverse effects, either biological or clinical (Klein, 1998). would not, of course, be suitable for infants with a soya allergy
(see Allergies below).
Phytoestrogens
Phytoestrogens are natural substances found in many fruits, Just one single human study has specifically examined the effect of
vegetables, dried beans, peas, and wholegrains. Isoflavones are a soya-based formula on sexual development and fertility (Strom et al.,

2001). It looked for links between the feeding of soya-based infant Despite this, they recommended that research should be
formula and reproductive health in adulthood. There was no evidence undertaken as a matter of high priority to determine whether
of adverse effects on either sexual development or reproductive health consumption of soya-based formulas can affect infant reproductive
of either males or females. The authors said that their findings were development in any way. Interestingly, the UK and New Zealand
reassuring about the safety of soya-based infant formula. are the only countries to have issued such advice on
phytoestrogens and soya-based formulas.
In 2003, in response to concerns about phytoestrogens, the UK
Department of Health’s committee of independent experts, the Oestrogen in cow’s milk
Committee on Toxicity of Chemicals in Food, Consumer Products The hormonal content of cow’s milk has not been widely discussed
and the Environment (COT) reviewed the health implications of amongst scientists and very little research has been published on it.
phytoestrogens and other naturally-occurring chemicals (COT, Cow’s milk has been shown to contain over 35 different hormones
2003). It tried to assess, on the basis of current evidence, if soya- and 11 growth factors (Grosvenor et al., 1992).
based infant formulas pose any risk for babies.
Some scientists are particularly concerned about the oestrogen
The COT report compared isoflavone intakes in Western and content of cow’s milk, suggesting that it is one of the main ways we
Eastern populations and found that Eastern populations have a are exposed to it (Ganmaa and Sato, 2005). What concerns them is
significantly higher intake. In the UK, the US, Australia and New that cow’s milk has changed drastically over the last 100 years. For
Zealand, intakes tend to range from around 0.8mg per day to most of the time that a cow is milked, she is also pregnant and
17mg per day, while in Japan, China and Korea they range from therefore secreting hormones into the milk. Hormone levels
18mg per day to 200mg per day. These figures do not include data increase markedly during pregnancy and have been linked to a wide
collected from a group of vegans in New Zealand whose intake range of illnesses and diseases, including certain hormone-
was found to be 140mg per day. dependent cancers such as ovarian and breast cancer.

The average UK consumer, the COT report states, consumes These hormones and growth factors act as signalling molecules,
around 1mg of isoflavones per day, while vegetarians who eat carrying important messages from the mother to the infant animal
soya-based meat and dairy replacement foods, consume around that encourage rapid growth and development. Cow’s milk is
3mg a day. They concede that these figures may be underestimated designed to turn a small calf into a big cow in just one year.
given the increasing amount of soya used in processed foods.

More recently, the isoflavone intake of a small group of
vegetarians and omnivores was estimated using a new isoflavone
database which lists the isoflavone content of 6,000 foods (Ritchie,
2006). Vegetarians were found to consume around 7.4mg per day
compared to an estimated 1.2mg for omnivores (Ritchie et al.,
2006). The main source for each group were soya milks and
yogurts, soya and textured vegetable protein foods, breads and
dried fruit.

Previous work showed that a group of UK vegetarians consumed
an average of 10.5mg of isoflavones per day (Clarke et al., 2003).
Only one report has measured the isoflavone intake of vegans (11
breast-feeding UK vegan mothers) which was estimated to be 75mg
a day (MAFF, 1998). This is above the average Western intake but
well within the range of Eastern countries. The table below shows
the isoflavone content of a range of soya-based foods.

Food Isoflavone Isoflavone
(mg/100g) (mg in average portion size)
Miso 43-60 4-16
Soya cheese 6-31 1-24
Soya milk 5-10 3-53
TVP 68.3* 29-67
Soya yoghurt 16 5-85
Soya sauce 0.1-1.6 -
Tempeh 29-53 4-38
Tofu 13.5-67 19

Source: COT, 2003. *Ritchie et al., 2006.

COT estimated that the daily isoflavone intake of infants fed soya-
based infant formula is approximately 40mg per day. Again, above
the average Western intake but well within the range of intakes
seen in Eastern countries. The COT report acknowledged that
there is no evidence that populations which regularly eat high
quantities of soya, such as the Chinese and Japanese, have altered
sexual development or impaired fertility. China is the world’s most
populous nation, with over 1.3 billion citizens.

In summary, a cow’s milk contains many hormones and growth Iodine is also be found in cereals and grains, such as whole wheat
factors and often in concentrations much higher than those found and rye, but levels vary depending on the amount of iodine in the
naturally in her blood (Grosvenor et al., 1992). In other words, soil where the plants are grown.
powerful hormones and growth factors are synthesised in the
cow’s mammary gland and excreted into her milk – milk which It is important not to take too much iodine as this can be harmful.
humans then drink. Considering the main complaint about soya is The FSA consider that 500 micrograms or less a day is unlikely to
that it contains phytoestrogens, many thousand times weaker than cause any harm (FSA, 2007a).
animal oestrogens, it begs the question: what is the real motivation
behind the anti-soya crusade? Allergies
Although severe reactions to food are rare, approximately six per
When considering the health benefits and/or risks of soya versus cent of children under three years old are thought to be affected
cow’s milk, think about which is the more natural drink? Plant by food allergy, the most common culprits being cow’s milk and
‘milk’, produced from a bean, consumed by millions for centuries, eggs. The number of people affected by food allergies tends to
or animal milk, taken from another species and one which is decline with age, with around four per cent of adults being
generally pregnant? Humans are the only mammal to consume affected, with shellfish and nuts being the most common causes
milk after weaning and then from another species. Over three- (Department of Health, 2006).
quarters of the world’s population do not drink cow’s milk at all;
they are lactose intolerant and cannot digest the sugar in milk after Just a small number of foods are responsible for 90 per cent of
weaning. It is clear that for most humans, cow’s milk isn’t and all allergic food reactions and include: cow’s milk and dairy
never has been ‘natural’. products, eggs, peanuts, tree nuts (including Brazil nuts,
hazelnuts, almonds and walnuts), fish, shellfish, including
Soya and thyroid function mussels, crab and shrimps, wheat and soya (FSA, 2007b). The
The thyroid is a small gland found in the front of the neck. It symptoms of soya allergy are similar to those of cow’s milk
produces the important hormone thyroxine, which helps control allergy and include rashes, diarrhoea, vomiting, stomach cramps
how fast the body makes and uses the energy it obtains from and breathing difficulties. Very rarely, soya can cause
food. The thyroid gland needs iodine from food to function and anaphylaxis (FSA, 2007c) – a severe and potentially fatal ‘toxic
a lack of it can make the gland enlarge, forming a goitre. It can shock’. Since November 2005, food labelling rules require pre-
happen whether the thyroid is overactive or underactive. An packed food sold in the UK to show clearly on the label if it
overactive thyroid causes an illness called hyperthyroidism while contains soya (FSA, 2007c).
an underactive gland causes hypothyroidism. The concerns
about soya and thyroid focus on two components – goitrogens There are concerns that genetically modified (GM) soya may
and isoflavones. be more likely to cause an allergic reaction than non-GM soya
(Soil Association, 2007). These concerns have been met by
Goitrogens are found naturally in soya, broccoli, kale, cabbage, biotechnology companies producing even more GM soya, but
turnips, millet, peanuts and pine nuts. They can interfere with the with the specific proteins thought to cause the allergic
uptake of iodine and lead to a goitre. However, this is not a reactions removed. GM products, especially soya and maize,
problem if the diet provides enough iodine. are now in so many foods that it can be difficult to avoid
them. If you want to avoid GM foods then choose foods that
A limited number of studies have suggested that isoflavones may are certified organic.
affect thyroid function by lowering free thyroxine concentrations.
In a cautionary statement, COT advises physicians and other Environmental impact of soya
health care workers to be aware of possible links between Some people attempt to condemn soya by citing the
isoflavones in soya-based infant formulas and thyroid function, environmental impact soya farming is having on the Amazonian
particularly in cases of congenital hypothyroidism (COT, 2003). rainforest. They are right to be concerned but people eating soya
are not the problem – 80 per cent of the world’s soya production
However, a recent review of 14 trials which investigated the is fed to livestock so that people can eat meat and dairy foods
effects of soya on thyroid function concluded that there was (Greenpeace, 2006). Much of the remainder is used as padding in
little evidence that it had an adverse effect in people whose a wide range of mainstream food products such as meat pies and
thyroid function is normal and whose diet contains adequate pasties. Both the rainforests and our health would benefit
iodine (Messina and Redmond, 2006). The authors raise the tremendously if more people became vegetarian or vegan, even if
possibility that soya foods may interfere with absorption of they ate more soya.
medications containing synthetic thyroid hormone taken by
hypothyroid patients, but say that hypothyroid adults need not Soya production
avoid soya foods. Long-established soya foods such as soya sauce, tamari, miso,
tempeh, tofu and soya milk were originally developed in Asia
There is a theoretical concern that in individuals with using traditional fermentation or precipitation methods. Many of
compromised thyroid function and/or whose iodine intake is these foods use the whole bean and the foods made from them
marginal, soya foods may increase risk of developing differ from soya protein isolates, which are extracts from soya
hypothyroidism. The general consensus is that all people, beans and include textured vegetable protein (TVP) and other
whether soya consumers or not, should ensure their intake of meat substitutes.
iodine is adequate.
As with all processed foods, the nutrient content is partly
The Department of Health recommends that toddlers aged one to determined by the processing method. The VVF does not
three should get 70 micrograms of iodine per day and adults 140 recommend over-consumption of any highly-processed foods as
micrograms (Department of Health, 1991). You should be able to they tend to contain high levels of fat – sometimes including
get all the iodine you need by eating a varied and balanced diet hydrogenated fats – salt, sugar and artificial additives, which have
(FSA, 2007a). Good sources of iodine include seaweed such as all been linked to health problems. However, many of the ‘mock
nori and kelp and Vecon vegetable stock. Adults can supplement meats’ do provide a valuable low-fat and cholesterol-free source of
their diet with kelp tablets but these are not suitable for children. good protein and increasingly they do not contain hydrogenated

fats (check the label!). This makes them a healthier option than • Soya foods can help improve cognitive skills.
their meaty milky equivalents, which contain saturated animal fat, • Millions of people have been safely consuming soya foods for
animal protein, cholesterol and hormones. thousands of years.
• Phytoestrogens (plant hormones) are much weaker than the
The key to good health is to eat a wide range of foods including natural oestrogens consumed in dairy products and red meat
plenty of wholegrains such as wholemeal bread, brown pasta and and may have a normalising effect on hormone levels.
brown rice, pulses (peas, beans – including soya – and lentils), fruit • Soya-based infant formula can be used as a safe alternative or
and vegetables and nuts and seeds. supplement to breast milk as it meets the nutritional
requirements of the child.
• Millions of healthy infants have been safely raised on soya-
Summary based infant formulas.
• There is no evidence that soya adversely affects the sexual
• Soya beans are cholesterol-free and are a good source of development or reproductive health of humans.
protein, polyunsaturated fatty acids, antioxidants, B vitamins • Intakes of phytoestrogens in the UK are no greater than those
and iron. consumed in Eastern countries for thousands of years.
• Calcium-fortified soya products such as soya milk and tofu • There is no evidence that soya foods cause impaired fertility or
provide a valuable source of this important mineral. alter sexual development in humans.
• Vitamin B12-fortified products such as soya milk provide a • For the vast majority of people, soya does not disrupt thyroid
vital source of this nutrient. function.
• Soya protein lowers cholesterol and can protect heart health. • Although soya may be responsible for some food allergies, it is
• Soya foods can reduce menopausal symptoms. not the main culprit.
• Soya protein can protect bone health and reduce the risk of • Soya ‘mock meats’ provide a valuable source of protein.
osteoporosis. • Cow’s milk contains over 35 different hormones and 11
• Soya foods may reduce the risk of breast cancer, with the growth factors, several of which have been linked to cancer.
possible exception of postmenopausal women. • 80 per cent of the world’s soya production is fed to livestock.
• Soya foods may reduce the risk of prostate cancer.

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Join the VVF
soy protein isolate on breast secretion in pre- and postmenopausal women. The Vegetarian & Vegan Foundation can help you and your
Cancer Epidemiology Biomarkers and Prevention. 5, 785–94. family to start eating healthily – giving everyone the chance of a
43. PCRM, 2002. Healthy eating for life to prevent and treat cancer. New York: brighter future.
John Wiley & Sons, Inc.
44. Potter, S.M., Baum, J.A., Teng, H., Stillman, R.J., Shay, N.F. and Erdman, For just £15 per year, you’ll receive the colourful, easy-to-read
J.W Jr. 1998. Soy protein and isoflavones: their effects on blood lipids and
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bone density in postmenopausal women. American Journal of Clinical you'll be entitled to free health advice from our nutritionists.
Nutrition. 68 (suppl) 1375S–1379S.
45. Ritchie M.R., Cummings J.H., Morton M.S., Michael Steel C., Bolton-Smith To join the VVF either write to us, telephone or join online.
C., Riches A.C. 2006. A newly constructed and validated isoflavone database
for the assessment of total genistein and daidzein intake. British Journal of VVF, Top Suite, 8 York Court, Wilder Street, Bristol BS2 8QH.
Nutrition. 95 (1) 204-213. Tel: 0117 970 5190. Email: info@vegetarian.org.uk
46. Ritchie, 2006. Phyto-oestrogen database [online]. Available from: Web: www.vegetarian.org.uk
http://medicine.st-and.ac.uk/research/docs/ritchie/ [Accessed October 17 2006].

VVF – Feeding you the Facts
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