大豆の毒はプロテアーゼ・インヒビター(蛋白質分解阻害酵素)、フィチン酸、大豆レクチン(ヘマグルテン)、ニトロソアミン、高濃度マンガン、そして不可思議な大豆毒。ニトロソアミンは、自然な状態ではないが大豆蛋白などの加工過程で発生する。

プロテアーゼ・インヒビター(トリプシンインヒビター)；蛋白質分解阻害酵素葉は蛋白質を分解して体がつかえる形に変えるための酵素が働かなくするもので、

プロテアーゼ(タンパク質分解酵素)阻害酵素
恐らく最もよく知られた大豆の毒はプロテアーゼ阻害酵素(トリプシン・インヒビターとも呼ばれる)で、これはその名のとおり蛋白質を分解して体が使えるようにするための酵素(トリプシンを含むプロテアーゼ)の働きを止めることが出来る。

ネズミではプロテアーゼ阻害酵素に高濃度(生大豆の粉の量）で曝されると膵臓ガンを引き起こし、中濃度では膵臓が発ガン物質に侵され易くなる。ネズミの実験の人体への有効性が疑問視され、米国食品医薬品局はセブ島の猿でプロテアーゼ・インヒビターの影響を調べた (JP Harwood et al., Adv Exp Med Biol 1986 199: 223-37).

セブモンキーのパラメーターは以下の通り:

5年間低レベルのトリプシン・インヒビターを摂取した結果、1-3群の猿には識別できる膵臓障害は全く見られなかったが、4群の中の一頭に軽度のびまん性細葉萎縮、軽度のびまん性間質性腺維症、軽度の慢性膵炎が検査した3箇所全てに見られた。第4群のその他の猿には僅かにリンパ球肥厚が見られた。

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:
従って、低レベルの大豆プロテアーゼ・インヒビターは人体に全く影響がないというのは検討すべき十分な根拠がある。　

'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 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?".

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 http://www.fda.gov/fdac/departs/2000/400_ltrs.html 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.

Phytoestrogens

The endocrine disruptors in soy.

You've probably heard quite a bit about phytoestrogens.  The plant compounds that mimic estrogen are touted by some as miracle agents that will prevent cancer, coronary heart disease and osteoporosis (just to name a few).

But there is a much darker side to these compounds which are phyto-endocrine disruptors by any other name.  You'll be shocked to learn that these compounds may actually increase the risk of breast cancer and cause thyroid disease, and angry to discover that soy formulas manufacturers refuse to remove them from their products despite knowing that babies fed soy-formulas risk irreversible damage.

And for a touch of the bizarre how about:

Archer Daniels Midland (ADM) Company informing the FDA that they had found that soy phytoestrogens were generally recognised as safe (GRAS).

or how about:

Protein Technologies International (PTI) determining that the soy phytoestrogens reduced the risk of coronary heart disease.  The PTI petition was so bad it was even contradicted by the American Soybean Association (ASA).

Follow the links to the following topics:

Phytoestrogens in the Environment

Hormonally active agents in the environment.

Phytoestrogens and the risk of cancer.

They can promote Cancer!!!

Do phytoestrogens prevent cancer? The evidence to support the industry claim is scant and recent work indicates that phytoestrogens may actually increase the risk of breast cancer. And in HOT OFF THE PRESS are two articles that propose a link between bioflavonoids and soy and infantile leukemia.

Phytoestrogens and the thyroid.

We're sick of hearing that there are no harmful effects of  phytoestrogens.  However, like many endocrine disruptors, phytoestrogens disrupt thyroid function.  The damage can be permanent but obviously the soy industry think that goitre and hypothyroidism doesn't qualify as evidence of harm!

Phytoestrogens and Male Health

Phytoestrogens can affect male animals health and fertility, what about people?

Phytoestrogens and your baby.

Don't doubt it - phytoestrogens are bad for your baby.   If you are feeding your infant a soy formula our advice is STOP immediately.   Why? Soy formula fed infants receive the same daily dose of phytoestrogens that has been shown to be biologically active in adults!  By exposing your baby to such large amounts of phytoestrogens you are risking permanent endocrine system damage to your child.   There are alternatives to soy formulas that are both lactose and dairy protein free; use one of those instead of soy.  But don't just take our word for it, read for yourself the work of FDA's Dr Dan Sheehan, sex-hormone and thyroid expert Professor Cliff Irvine and phytoestrogen researcher Professor Kenneth Setchell.

If you have fed your child a soy formula and have evidence that they have developed thyroid or developmental disorders we invite to contact us.

Phytoestrogens and infertility.

Phytoestrogens can make animals infertile, what about people?  There is clear potential for phytoestrogens to reduce male fertility.   And If you are a woman trying to conceive our advice is AVOID soy.

Phytoestrogens and cognitive function.

Do phytoestrogens rot the brain?

Archer Daniels Midland's GRAS application for soy phytoestrogens.

It's almost too weird to contemplate, but food giant ADM applied to the FDA for Generally Recognised as Safe (GRAS) status to be granted to compounds that are known reproductive toxins!  Read for yourself ADM's bizarre determination that soy phytoestrogens exhibit no adverse affects in humans or animals!   Read also the counter submissions that led to ADM withdrawing their application.

Protein Technologies International's Health Claim petition.

For more soy industry deceit, read excerpts of PTI's Health Claim petition for yourself and how PTI have petitioned the FDA to approve labelling that will promote the consumption of between 25 and 100g per day of soy protein as lowering the risk of coronary heart disease.  But, oops, PTI forgot to mention that such an amount of soy protein could easily result in a megadoses of phytoestrogens; up to 600mg per day!