With so many people developing allergies to dairy there has been a mass flocking to soy. Unfortunately though, this interest has lead to the marketing of soy derived products. The negative consequences of consuming these foods are currently being collated in both the USA and New Zealand for what is believed will be one of the biggest court cases in history. So what went wrong with the soy bean?

The original Chinese character for soy depicts little roots at the bottom which revive the soil. This was the purpose of the noble soybean – the important task of fixing nitrogen in the soil during crop rotation to restore exhausted fields. This technique of using a bean crop to revitalise the soil is still common practice today. The crop is grown, then rather than being harvested for consumption, it is dug back into the soil.

History reveals to us that the soy bean was not used as a food until the technique of fermentation was discovered. Science shows us that unfermented soy contains enzyme inhibitors that block the actions of trypsin and other enzymes required for protein digestion. The soybean also contains hemaglutinin, a clot promoting substance that causes red blood cells to clump together. Trypsin inhibitors and hemaglutinin have been referred to as “growth depressant substances”. Both of these negative factors are neutralised during fermentation. In precipitated products (tofu/bean curd), enzyme inhibitors concentrate in the soaking liquid rather than in the curd. Enzyme inhibitors are reduced in quantity, although they are not completely eliminated. Once fermented or precipitated, only then was the soy bean recognised a wholesome food, worthy of consumption. Fermented soy products include tempeh, natto, miso and properly fermented soy sauce – known as shoyu (wheat based) and tamari (wheat free).

Even when fermented or precipitated, there are some other ugly facts one needs to be aware of. Soybeans also contain goitrogens that depress the thyroid function. This is why traditionally the Japanese have always balanced their soy consumption with daily use of seaweeds, ie. miso soup prepared with stock made from kombu seaweed, sushi – rolled in nori seaweed, agar agar for jelly, kombu and wakame for cooking beans and grains, hijiki and arame for salads and stir fry dishes. Seaweeds are rich in iodine, needed for proper thyroid function and counterbalance the effects of soy on the thyroid. The Japanese also consume soups made with bone broths; this also balances the negative effects of soy, particularly its effect on blocking calcium absorption.

We are under a misconception that Asians consume vast quantities of soy. The Japanese consume approximately 2 tablespoons a day and the Chinese, only 2 teaspoons a day. This is usually always a fermented food, not the modern soy protein isolate version.

Folklore suggests large quantities of soy can decrease sexual energy. For this reason it was given as food in the monasteries. This is supported by research showing that soy may interfere with zinc absorption—a decrease in zinc effects the healthy functioning of sex glands (1). In the food seminars I run, many women have told me stories of their husband’s libido being directly affected by the level of soy they were consuming! Soy products are currently recommended to lower cholesterol. Interestingly, low cholesterol often equates to both a low libido and a decreased ability to cope with stress. In females, unfermented soy can disrupt endocrine function and may contribute to infertility and breast cancer.

Of all the beans, the soy bean is plagued with the highest levels of phytic acid. Phytic acid blocks the uptake of essential minerals, including calcium, magnesium, copper, iron and especially zinc. Soaking the beans prior to cooking usually neutralises phytic acid in beans. Soy however seems highly resistant to phytate reducing techniques. It is only in fermentation that this is overcome and the beans become easy to digest. Soy foods also increase the body’s requirement for vitamin D and B12. The effect of these phytates in soy-formulas is a great concern. The iron and zinc requirements of infants are well documented, particularly those that relate to cognitive function. There is also a link with diabetes with “twice as many soy fed children developing diabetes as those in a control group that were breast fed or received milk based formula” (6). Soy infant feeding is also linked to early puberty in girls (7) and testosterone inhibition in males (8).

What about the modern soy drink, known as soy “milk”? This was never a traditional beverage of either Japan or China. The earliest reference to it being consumed as a beverage appears in 1866, although due to its undesirable flavour and odour, consumption didn’t pick up until the late 1970’s following a successful marketing campaign (2). In these early years, production of soy milk always began with a long soak of the beans. The beans were then ground with water to a mush. This was placed in a cloth bag and squeezed to remove most of the liquid. This liquid was discarded and the soy paste was then boiled in fresh water. The large amounts of scum that rose to the surface were carefully removed (3).

The modern method is of course faster and cheaper. The beans are not squeezed, the soak water is not discarded, the scum that rises to the surface during cooking remains and the pre-soaking phase is hastened with the use of an alkaline solution. This speed comes at a cost; the soaking solution destroys key nutrients and produces small amounts of the carcinogen lysinoaline (4). It also produces an “off” flavour. To counter this, major manufacturers use a deodorising process (5). Almost all commercially made soy milks are then sweetened—even those marketed as “plain”. You may note with interest that the soy milks produced in Japan and Hong Kong ie. vitasoy and bonsoy, always contain seaweed to counter-balance the negative effect on the thyroid. It’s unfortunate no other countries follow their lead in this area.

The most important soy to avoid is any food product containing soy protein isolate. Watch out for soy milk powder, protein powder, products marketed as being low fat, soy baby formulas and some brands of soy milk and soy yoghurt. The term soy protein isolate refers to the fact that the soy protein from the bean has been isolated from the carbohydrate and fatty acid components that naturally occur in the bean. To produce this, the soybeans are ground and then undergo a high temperature and solvent extraction process to remove the oils. The defatted meal is then mixed with an alkaline solution and sugars in a separation process to remove fibre. Then it is precipitated and separated using an acid wash. Finally, the resultant curds are neutralised in an alkaline solution and spray dried at high temperatures to produce a high protein powder. This is a highly refined product in which not only has the vitamin and protein quality been compromised, but even after all that processing, it still contains some of the trypsin inhibitors. Also, nitrites, potent carcinogens, are formed during spray drying and a toxin called lysinoalanine is formed during the alkaline processing. It’s no surprise that soy protein isolate has not been given USA approval as generally recognised as safe (GRAS) for human consumption. Does it make sense that a food so highly over processed could still maintain any semblance of wholesome nutrition? When nature is tampered with, there are usually unpleasant consequences.

Soy In Summary

  • Safe to consume
    • Fermented soy products: tempeh, natto and quality brands of naturally fermented soy sauce ie. tamari or shoyu.
  • Consume only in small amounts together with a diet rich in seaweed
    • Tofu.
  • Avoid
    • All products containing soy protein isolates.


  1. Food and Healing: Anne Marie Colbin
  2. Chronology of soymilk worldwide: William, Shurtleff
  3. Roasted soybean in infant feeding: RA Guy, Chinese Med J, 1938
  4. Soybeans: Chemistry, Technology and Utilization: KeShun Liu, Gaithersburg, Aspen, 1999, pg 151—153.
  5. Soy Alert!: K. T. Daniel, PhD Nourishing Traditions 2004 Pg 47.
  6. Fort P and others. Breast feeding and insulin-dependent diabetes mellitus in children. J Am Coll Nutr 1986;5(5):439-441.
  7. Freni-Titulaer LW and others. Am J Dis Child 1986 Dec;140(12):1263-1267.
  8. Sharpe RM and others. Infant feeding with soy formula milk: effects on the testis and on blood testosterone. Hum Reprod 2002 Jul;17(7):1692-703.

For further information:

What’s wrong with modern soy products?

  • High levels of phytic acid in soy reduce assimilation of calcium, magnesium, copper, iron and zinc. Phytic acid in soy is not neutralised by ordinary preparation methods such as soaking, sprouting and long, slow cooking. High phytate diets have caused growth problems in children.
  • Trypsin inhibitors in soy interfere with protein digestion and may cause pancreatic disorders and stunted growth.
  • Soy phytoestrogens disrupt endocrine function and have the potential to cause infertility and to promote breast cancer in adult women.
  • Soy phytoestrogens are potent antithyroid agents that cause hypothyroidism and may cause thyroid cancer. In infants, consumption of soy formula has been linked to autoimmune thyroid disease.
  • Soy foods increase the body’s requirement for vitamin D and B12.
  • Processing of soy protein results in the formation of toxic lysinoalanine and highly carcinogenic nitrosamines.
  • Free glutamic acid or MSG, is formed during soy food processing.
  • Soy foods contain high levels of aluminium (soy formula contains 10 times that of milk based formula and 100 times greater than fresh milk).

This information is an excerpt from http://www.westonaprice.org/

Average Isoflavone Intake Isoflavone per Kg of body weight *
Japan (1996 survey) 10 mg 0.17 mg
Japan (2000 survey) 28 mg 0.47 mg
In American women,
causing hormonal
changes after 1 month 45 mg 0.75 mg
FDA recommended amount for adults 25 mg 0.42 mg
In children receiving soy formula 38 mg 6.25 mg

* Assumed 60 kg for adults, 6 kg for infants