Soy Toxins There's plenty yet that you didn't know about soy!
Soy contains several naturally occurring compounds that are toxic to humans and animals. The soy
industry frequently refers to these toxins as anti-nutrients, which implies that they somehow act to
prevent the body getting the complete nutrition it needs from a food. The soy toxins (such as phytic
acid) can certainly act in this manner, but they also have the ability to target specific organs,
cells and enzyme pathways and their effects can be devastating.
The soy toxins that Soy Online Service have concerns about are protease inhibitors, phytic acid, soy
lectins (or haemagglutins), nitrosamines, manganese concentrations and the mysterious soyatoxin.
Nitrosamines are not naturally occurring in soybeans but form during the processing of products such
as isolated soy protein (ISP).
As with any toxin there will be a dose at which negative effects are not observed. Soy Online
Services have examined the scientific data on the soy toxins and have uncovered several
alarming truths:
There is no legislation to protect consumers from soy toxins in raw soy products.
With the possible exception of soy lecithin, all soy products, no matter how well treated, contain
low to moderate levels of soy toxins; processing cannot remove them all of any of them.
The soy industry has little in the way of quality control to protect consumers from exposure to
inadequately treated soy products.
Protease Inhibitors
Perhaps the best known of the soy toxins are the protease inhibitors (also referred to as
trypsin inhibitors) which, as the name suggests, are able to inhibit the action of proteases
(including trypsin) which are enzymes that are involved in the process of dismantling proteins
for use by the body.
In the rat, high levels of exposure to protease inhibitors (such as that found in raw soy flour)
cause pancreatic cancer whereas moderate levels cause the rat pancreas to be more susceptible to cancer-
causing agents. The validity of the rat model to humans has been questioned and the USFDA have
examined the effects of protease inhibitors on the Cebus monkey (JP Harwood et al., Adv Exp Med Biol
1986 199: 223-37).
The parameters of the Cebus Monkey study were as follows:
Group Number of monkeys Dietary Protein Trypsin Inhibitor (mg/g of diet) 1 8 Lactalbumin 0.12 2 10
Soy Isolate 0.54 3 6 Casein 0.08 4 2 Soy Concentrate 2.41
After five years of chronic ingestion to low levels of trypsin inhibitors, there was no discernible
pancreatic damage effect in monkeys from groups 1-3. However, one monkey in group 4 exhibited
moderate diffuse acinar atrophy, moderate diffuse interstitial fibrosis and moderate chronic
pancreatitis in all three sections of tissue examined. Minimal lymphoid hyperplasia was noted in the
other group 4 monkey.
Therefore, there is good reason to question claims that low levels of soy protease inhibitors pose
no threat to human health. Such a statement has even been made by the USFDA in response to a health
claim petition by Protein Technologies. The USFDA reported that:
'Concerns have been raised in the past about exposure to trypsin inhibitors contained in soybeans
because these compounds had been found to stimulate pancreatic hyperplasia and hypertrophy in
animals. These concerns have been allayed because heat treatment removes most of the activity of
these proteases. In addition, recent studies have questioned the applicability of the animal models,
which differ from humans in the type of diet, sensitivity of the pancreas to trypsin inhibitors, and
the anatomic sites of pancreatic cell proliferation and have found low rates of cancer in
populations with dietary patterns that include soy foods' (FR 63, 217:62977-63015, 1998).
This statement brought an angry response from Professor Irvin Leiner, the foremost expert on
protease inhibitors. In his reply to the FDA Liener wrote:
'The impression one gets from reading this section is that that there is little cause for concern as
far as the human exposure to soybean trypsin inhibitors is concerned.... In the interests of a
balanced treatment of the subject, I trust you will give due consideration to the opposing view that
the soybean trypsin inhibitors do in fact pose a potential risk to humans when soy protein is
incorporated into the diet.'
So, if there is valid concern about low levels of protease inhibitors in soy foods, what about
exposures to levels higher higher than those in the Cebus monkey study? Is there any chance that
such exposures could occur in human diets?
Soy Online Service has noted that there is considerable variability in the levels of protease
inhibitors in commercially available foods and that there is little to protect consumers from
exposure to high levels of protease inhibitors. For example, a study entitled 'Trypsin inhibitor
levels in soy-based infant formulas and commercial soy protein isolates and concentrates (RW Peace
et al., 1992, Food Res Int, 25: 137-141) found that trypsin inhibitor levels were as high as 2.72
mg/g in ready to feed soy formulas and 7.30 mg/g in soy protein concentrate.
Since there is no established acceptable levels of protease inhibitors in foods and no protection
from short-term high level (acute) exposures or long term low level (chronic) exposures, Soy Online
Service offer the following advice:
Don't feed your baby or infant a soy formula; there are alternatives!
Avoid the direct consumption of raw or partially processed soy products such as soy flour or soy
protein concentrate. Traditionally fermented soy foods are relatively free of protease inhibitors.
When preparing your own soy foods, such as boiled or roasted soybeans or soy milk, ensure that they
are adequately heated. The traditional Chinese method for preparing soybeans was a time consuming
job that was left to monks. It involved soaking the beans first and then boiling them twice over
'the full length of an incense'.
Phytates
The term phytate refers to several compounds that are based on phytic acid (inositol hexaphosphate).
It is the presence of multiple phosphates in phytates that makes them effective chelating agents,
i.e. they have the ability to bind to certain metal ions. Obviously if metals are bound up in a phytate-
complex, they are less available to the body ( i.e. less bioavailable) for nutritive purposes.
Phytates are particularly adept at binding metals in their so-called divalent state, metal ions such
as calcium (Ca2+), copper (Cu2+), iron (Fe2+), manganese (Mn2+) and zinc (Zn2+).
Soybeans contain very high levels of phytate and their are numerous reports of reduced
bioavailablity of various metals from foods containing soy; this has particular significance for
vegetarians and infants fed soy-formulas.
Vegetarians, particularly young women vegetarians, need to be aware that soy products affect their
iron and zinc requirements and it has been recommended that they utilise strategies that minimise
the intake of dietary phytate.
The effects of phytate in soy-formulas are a great concern. The iron and zinc requirements of
developing infants are well documented, particularly those that relate to cognitive function. There
is no question that infants fed soy-formulas are at greater risk of reduced uptake of various
essential minerals compared with breast-fed infants or infants fed other formulas.
Copper bioavailability is significantly lower in rhesus monkeys fed low-phytate soy formula from 2
to 4 months. Iron absorption in infants is approximately doubled by the removal of phytate from soy
formula; a similar effect is observed by doubling the ascorbic acid content of a soy formula.
Manganese absorption is also doubled by the removal of phytate from soy formula, but increasing the
ascorbic acid content of a soy formula containing the native amount of phytic acid did not improve
manganese absorption. Zinc bioavailability from soy formulas is also reduced by phytate. In rhesus
monkeys, zinc absorption was 2.0 times greater from monkey milk compared with soy formula, 2.2 times
greater from whey-predominant formula compared with soy formula and 1.7 times greater from casein-
predominant formula compared with soy formula. Zinc absorption from dephytinized soy formula was
approximately the same as that from casein-predominant formula.
Soy formulas are typically over-supplemented with minerals and vitamins to account for the
deficiencies caused by phytate, but it is evident that this does not take care of the problems.
Removal of phytate from soy formulas is altogether a better solution but manufactures have not shown
any inclination do this. Why not? Phytate removal will cost $$$ and it seems to us that soy formula
manufacturers consider economics to be more important than the well being of infants.
Manganese
The soybean plant has the ability to absorb manganese from the soil and concentrate it to an extent
that soy-based infant formulas can contain as much as 200 times the level of manganese found in
natural breast milk. In babies, excess manganese that cannot be metabolised is stored in body
organs. Around eight percent of the excess manganese in the diet is stored in the brain in close
proximity to the dopamine-bearing neurons responsible, in part, for adolescent neurological
development.
The implications are that the one in eight infants raised on soy formula during the first six months
of life may be at risk of brain and behavioural disorders that do not become evident until
adolescence. The following two links discuss the issue of manganese toxicity further.
Is soy-based infant formula brain damaging?
Press Release written by David Goodman, Ph.D.
"How safe is soy infant formula?".
Aluminium
Aluminum and bone disorders: with specific reference to aluminum contamination of infant nutrients.
Koo WW, Kaplan LA. J Am Coll Nutr. 1988 Jun;7(3):199-214.
Enteral nutrients including human and whole cow milk have low Al, whereas highly processed infant
formulas with multiple additives, such as soy formula, preterm infant formula, and formulas for
specific disorders are heavily contaminated with Al.
However, even with normal renal function, only 30-60% of an Al load from parenteral nutrition is
excreted in the urine, resulting in tissue accumulation of Al.
To minimize tissue burden, Al content of infant nutrients should be similar to "background" levels,
i.e., similar to whole milk (less than 50 micrograms/L).
Full Abstract Here
Vitamin B12 Deficiency
Vitamin B 12 deficiency has been recognised as a serious result of soy consumption for many years.
For instance JJ Rackis discusses it in January 1974 in "Biological and Physiological Factors in
Soybeans' in the J. Am. Oil Chemists Soc, pp 161", and Irvin E Liener examines it in 1994 in
"Implications of Anti-Nutritional Components in Soybean Foods in Soybean" in Critical Reviews in
Food Science and Nutrition
There is a simple explanation of some of the physical effects that can result from a deficiency of
this important nutrient at. "Vegans Deficient in Nutrients".
If the Moorhead trial judge had known this, would these people now be serving a jail term for the
death of their child?
Read about the Seventh Day Adventist Moorheads Here and Here.
Other Toxins
Letter to FDA CONSUMER magazine fda.gov400 ltrs.htmlOpen ↗ August 2000
The FDA Consumer article on soy spoke of the possible risks of plant estrogens, but made no mention
of the carcinogenic effects of protease inhibitors found in soy. McGuinness et al. report rats fed
raw soya flour develop cancer of the pancreas ("The effects of long-term feeding of soya flour on
the rat pancreas," Scandinavian Journal of Gastroenterology, 1980;
15:497-502). They say that preheating the flour protected the animals, but others have said that the
high heat required (130 degrees Celsius) to deactivate the carcinogenic trypsin inhibitors in
soya flour denatures the soy proteins to the point that they become virtually useless. If this is
so, one either chooses less heating, resulting in more surviving trypsin inhibitors, or more
heating, resulting in useless protein.
William Jarvis, Ph.D.
Department of Health Promotion and Education
Loma Linda University
Loma Linda, Calif.
Soyatoxin
The soy industry funds millions of dollars of research each year; what chance is there for the
discoverers of soyatoxin to get funding to continue their work?