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ConditionsNot-so-healthy eating: the trouble with soy

Not-so-healthy eating: the trouble with soy

For four days during the Third International Soy Symposium, heldin Washington, DC in November 1999, well-funded scientists who gatheredin the nation's capital made presentations to an admiring press and totheir sponsors, including the likes of Monsanto and numerous soybeanassociations

For four days during the Third International Soy Symposium, held in Washington, DC in November 1999, well-funded scientists who gathered in the nation's capital made presentations to an admiring press and to their sponsors, including the likes of Monsanto and numerous soybean associations.

The symposium marked the apogee of a decade-long marketing campaign to gain consumer acceptance of tofu (bean curd), soy milk, soy ice cream, soy cheese, soy sausage and soy derivatives, particularly soy isoflavones such as genistein and diadzein, the oestrogen-like compounds found in soybeans.

The meeting coincided with the US Food and Drug Administration (FDA) decision, announced October 25, to allow a health claim for products 'low in saturated fat and cholesterol' that contain 6.25 grams of soy protein per serving. Breakfast cereals, baked goods, convenience food, smoothie mixes and meat substitutes can now be sold with labels touting benefits to cardiovascular health as long as these products contain one heaping teaspoon of soy protein per 100-gram serving.

Marketing the perfect food
What was once a minor crop - listed in the 1913 USDA handbook not as a food, but as an industrial product - now covers 72 million acres of American farmland. Part of this harvest will be used to feed chickens, turkeys, pigs, cows and salmon. Most of the rest will be squeezed to produce oil for margarine, shortenings and salad dressings.

Advances in technology make it possible to produce isolated soy protein from what was once considered a waste product - the defatted, high-protein soy chips - and then transform something that looks and smells terrible into products that can be consumed by human beings. Flavourings, preservatives, sweeteners, emulsifiers and synthetic nutrients have turned soy protein isolate, the food processors' ugly duckling, into a New Age Cinderella.

Lately, this new fairy-tale food has been marketed not so much for her beauty as for her virtues. Early on, products based on soy protein isolate were sold as extenders and meat substitutes, a strategy that failed to produce the requisite consumer demand. The industry changed its approach. 'The quickest way to gain product acceptability in the less affluent society,' said an industry spokesman,'. . . is to have the product consumed on its own merit in a more affluent society' (J Am Oil Chem Soc, 1975; 52: 238A).

So, soy is now sold to the upscale consumer not as a cheap poverty food, but as a miracle substance that will prevent heart disease and cancer, whisk away hot flushes, build strong bones and keep us forever young. The competition - meat, milk, cheese, butter and eggs - has been duly demonised by the appropriate government agencies. Soy serves as meat and milk for a new generation of politically correct vegetarians.

Unfit for consumption
The propaganda that has created the soy sales miracle is all the more remarkable because, only a few decades ago, the soybean was considered unfit to eat - even in Asia. During the Chou Dynasty (1134-1246 BC), the soybean was designated one of the five sacred grains along with barley, wheat, millet and rice. However, the pictograph for the soybean, which dates from earlier times, indicates that it was not first used as a food since, whereas the pictographs for the other four grains show the seed and stem structure of the plant, the pictograph for the soybean emphasises the root structure.

Agricultural literature of the period speaks frequently of the soybean and its use in crop rotation. Apparently, the soy plant was initially used as a method of fixing nitrogen (Katz SH, Food and biocultural evolution: a model for the investigation of modern nutritional problems, in Nutritional Anthropology, Alan R. Liss, 1987: 50).

The soybean did not serve as a food until the discovery of fermentation techniques, some time during the Chou Dynasty. The first soy foods were fermented products like tempeh, natto, miso and soy sauce. At a later date, possibly in the second century BC, Chinese scientists discovered that a pur'ee of cooked soybeans could be precipitated with calcium or magnesium sulphate (plaster of Paris or Epsom salts) to make a smooth, pale curd - tofu or bean curd. The use of fermented and precipitated soy products soon spread to other parts of the Orient, notably Japan and Indonesia.

The Chinese did not eat unfermented soybeans as they did other legumes such as lentils because the soybean contains large quantities of natural toxins or 'antinutrients'. First among them are potent enzyme inhibitors that block the action of trypsin and other enzymes needed for protein digestion. These inhibitors are large, tightly folded proteins that are not completely deactivated during ordinary cooking. They can produce serious gastric distress, reduced protein digestion and chronic deficiencies in amino acid uptake. In test animals, diets high in trypsin inhibitors cause enlargement and pathological conditions of the pancreas, including cancer (Rackis JJ et al, The USDA trypsin inhibitor study. I. Background, objectives and procedural details, in Qualification of Plant Foods in Human Nutrition, vol 35, 1985).

Soybeans also contain haemagglutinin, a clot-promoting substance that causes red blood cells to clump together.

Trypsin inhibitors and haemagglutinin are growth inhibitors. Weanling rats fed soy containing these antinutrients fail to grow normally. Growth-depressant compounds are deactivated during the process of fermentation so, once the Chinese discovered how to ferment the soybean, they began to incorporate soy foods into their diet. In products made using precipitation techniques, enzyme inhibitors concentrate in the soaking liquid rather than in the curd. Thus, in tofu, growth depressants are reduced in quantity, but not completely eliminated.

Depressed thyroid function
Soy also contains goitrogens - substances that depress thyroid function. Scientists have known for years that soy-based formula can cause thyroid problems in babies. Goitre and hypothyroidism were reported in infants fed soybean diets until the early 1960s (N Engl J Med, 1960; 262: 1099-103). In fact, recent reports indicate that thyroid disorders may be attributable to feeding soy-based infant formulas (J Am Coll Nutr, 1990; 9: 164-7; J Am Coll Nutr, 1997; 16: 280-2).

Further, a study of 37 adults showed that diffuse goitre and hypothyroidism appeared in half the subjects after consuming 30 g per day of pickled roasted soybeans for three months (Nippon Naibunpi Gakkai Zasshi, 1991; 67: 622-9). These findings are consistent with the recently proposed mechanism by which soy isoflavones affect thyroid hormone synthesis (Biochem Pharmacol, 1997; 54: 1087-96).

It is likely that soy isoflavones may be the cause of thyroid disorders in soy consumers and, hence, there is every indication that many cases of goitre and hypothyroidism in infants were caused by soy isoflavones. Unless diets that include soy isoflavones are adequately supplemented with iodine, goitre will result (J Trop Pediatr, 1988; 34: 110-3).

High in phytic acid
Soybeans are high in phytic acid, which is present in the bran or hulls of all seeds. It's a substance that can block the uptake of essential minerals - calcium, magnesium, copper, iron and especially zinc - in the intestinal tract. Although not a household word, phytic acid has been extensively studied; there are literally hundreds of articles on the effects of phytic acid in the current scientific literature. Researchers are in general agreement that grain- and legume-based diets high in phytates contribute to widespread mineral deficiencies in Third World countries (Nutr Cancer, 1983: 4: 206-16; Am J Clin Nutr, 1988; 47: 729-34; J Am Diet Assoc, 1988; 88: 1562-6). Analysis shows that calcium, magnesium, iron and zinc are present in the plant foods eaten in these areas, but the high phytate content of soy- and grain-based diets prevents their absorption.

The soybean has one of the highest phytate levels of any grain or legume studied (J Food Comp Anal, 1989; 2: 6778), and the phytates in soy are highly resistant to normal phytate-reducing techniques such as long, slow cooking (J Food Sci, 1984; 49: 199-201). Only a long period of fermentation significantly reduces the phytate content of soybeans. When precipitated soy products like tofu are consumed with meat, the mineral-blocking effects of the phytates are reduced (J Nutr, 1989; 119: 48-53; J Res Soc Health, 1983; 103: 74-7).

The Japanese traditionally eat a small amount of tofu or miso as part of a mineral-rich fish broth, followed by a serving of meat or fish. Vegetarians who consume tofu as a substitute for meat and dairy products risk severe mineral deficiencies. The results of calcium, magnesium and iron deficiency are well known; those of zinc are less so.

Zinc and soy
Zinc is called the intelligence mineral because it is needed for optimal development and function of the brain and nervous system. It plays a role in protein synthesis and collagen formation; it is involved in the blood-sugar control mechanism and thus protects against diabetes; it is needed for a healthy reproductive system. Zinc is a key component in numerous vital enzymes and plays a role in the immune system. Phytates found in soy products interfere with zinc absorption more completely than with other minerals (Leviton R, Tofu, Tempeh, Miso and Other Soyfoods: The 'Food of the Future', New Canaan, CT: Keats Publishing, 1982: 1415).

Milk drinking has been given as the reason why second-generation Japanese in America grow taller than their native ancestors. Some investigators postulate that the reduced phytate content of the American diet - whatever its other deficiencies - is the true explanation, pointing out that both Asian and Western children who do not get enough meat and fish products to counteract the effects of a high-phytate diet frequently suffer rickets, stunting and other growth problems (Lancet, 1972; i: 771-3).

Soy protein isolate
Soy processors have worked hard to get the antinutrients out of the finished product, particularly soy protein isolate (SPI), the key ingredient in most soy foods that imitate meat and dairy products, including baby formulas and some brands of soy milk.

SPI is not something you can make in your own kitchen. Production takes place in industrial factories where a slurry of soy beans is first mixed with an alkaline solution to remove fibre, then precipitated and separated using an acid wash and, finally, neutralised in an alkaline solution. Acid washing in aluminium tanks leaches high levels of aluminium into the final product. The resultant curds are spray-dried at high temperatures to produce a high-protein powder. A final indignity to the original soybean is high-temperature, high-pressure extrusion processing of the SPI to produce textured vegetable protein (TVP).

Much of the trypsin inhibitor content can be removed through high-temperature processing, but not all. Trypsin-inhibitor content of SPI can vary as much as fivefold. In rats, even low-level trypsin-inhibitor SPI-feeding results in reduced weight gain compared with controls (Qual Plant Foods Hum Nutr, 1985; vol 35). But high-temperature processing has the unfortunate side-effect of so denaturing the other proteins in soy that they are rendered largely ineffective (J Sci Food Agr, 1971; 22: 526-35). That's why animals on soy feed need lysine supplements for normal growth.

Nitrites, which are potent carcinogens, are formed during spray-drying, and a toxin called lysinoalanine is formed during alkaline processing (Evaluation of the Health Aspects of Soy Protein Isolates as Food Ingredients, prepared for FDA by Life Sciences Research Office, Federation of American Societies for Experimental Biology (9650 Rockville Pike, Bethesda, MD 20014, USA, Contract No. FDA 223-75-2004, 1979). Numerous artificial flavourings, particularly MSG, are added to SPI and TVP products to mask the strong 'beany' taste and impart the flavour of meat.

In feeding experiments, the use of SPI increased requirements for vitamins E, K, D and B12, and created deficiency symptoms of calcium, magnesium, manganese, molybdenum, copper, iron and zinc (J Am Oil Chem Soc, 1974; 51: 161A-70). Phytic acid remaining in these soy products greatly inhibits zinc and iron absorption; test animals fed SPI develop enlarged organs, particularly the pancreas and thyroid gland, and increased deposition of fatty acids in the liver (J Am Oil Chem Soc, 1974; 51: 161A-70A).

Soy and cancer
'In addition to protecting the heart,' says a vitamin company brochure, 'soy has demonstrated powerful anticancer benefits . . . the Japanese, who eat 30 times as much soy as North Americans, have a lower incidence of cancers of the breast, uterus and prostate.'

Indeed they do. But the Japanese - and Asians in general - have much higher rates of other types of cancer, particularly cancer of the oesophagus, stomach, pancreas and liver. Asians throughout the world also have high rates of thyroid cancer (Harras A, ed, Cancer Rates and Risks, 4th edn, NIH, National Cancer Institute, 1996).

Just how much soy do Asians eat? A 1998 survey found that the average daily amount of soy protein consumed in Japan was about eight grams for men and seven grams for women - less than two teaspoons (J Nutr, 1998; 128: 209-13). The famous Cornell China Study, conducted by C.T. Campbell, found that legume consumption in China varied from 0 to 58 g per day, with a mean of about 12 g (Campbell CT, The Cornell Project in China). Assuming that two-thirds of legume consumption is soy, then the maximum consumption is about 40 g, or less than three tablespoons per day, with an average consumption of about nine grams, or less than two teaspoons. A survey conducted in the 1930s found that soy foods accounted for only 1.5 per cent of calories in the Chinese diet compared with 65 per cent of calories from pork. (Asians traditionally cooked with lard, not vegetable oil; Chang KC, ed, Food in Chinese Culture: Anthropological and Historical Perspectives, New Haven, 1977).

Traditionally fermented soy products make a delicious, natural seasoning that may supply important nutritional factors in the Asian diet. But, except in times of famine, Asians consume soy products only in small amounts as condiments, not as a replacement for animal foods - with one exception. Celibate monks living in monasteries and leading a vegetarian lifestyle find soy foods quite helpful because they dampen the libido.

It was a 1994 meta-analysis by Mark Messina that fuelled speculation on soy's anticarcinogenic properties (Nutr Cancer, 1994; 21: 113-31). Messina noted that, in 26 animal studies, 65 per cent reported protective effects with soy. He conveniently neglected to include at least one animal study in which soy caused pancreatic cancer (Rackis JJ et al., Qual Plant Foods Hum Nutr, 1985, vol 35).

In the human studies he listed, the results were mixed. A few showed some protective effect, but most showed no correlation at all between soy consumption and cancer rates. Messina concluded that 'the data in this review cannot be used as a basis for claiming that soy intake decreases cancer risk'. Yet, in his subsequent book, The Simple Soybean and Your Health, Messina makes just such a claim, recommending one cup or 230 g of soy products per day in his 'optimal' diet as a way to prevent cancer.

Thousands of women are now consuming soy in the belief that it protects them against breast cancer. Yet, in 1996, researchers found that women consuming SPI had an increased incidence of epithelial hyperplasia, a condition that presages malignancies (Cancer Epidemiol Biol Prev, 1996; 5: 785-94). A year later, dietary genistein was found to affect breast cells, leading the authors to conclude that women should not consume soy products to prevent breast cancer (Environ Health Perspect, 1997; 105 [Suppl 3]: 633-6).

Birth control pills for babies
In 1998, investigators reported that the daily exposure of infants to isoflavones in soy infant formula is six to 11 times higher on a bodyweight basis than the dose that has hormonal effects in adults consuming soy foods. Approximately 25 per cent of bottlefed children in the US receive soy-based formula - a much higher percentage than in other parts of the Western world. Fitzpatrick estimated that an infant exclusively fed soy formula receives the oestrogenic equivalent (based on bodyweight) of at least five birth control pills per day (NZ Med J, 1995; May 24: 318). By contrast, almost no phytoestrogens have been detected in dairy-based infant formula or in human milk, even when the mother consumes soy products.

An alarming number of girls are entering puberty much earlier than normal, according to a recent study (Pediatrics, 1997; 99: 505-12). Investigators found that 1 per cent of all girls now show signs of puberty, such as breast development or pubic hair, before the age of three; by age eight, 14.7 per cent of white girls and almost 50 per cent of African- American girls have one or both of these characteristics.

In the 1986 Puerto Rico Premature Thelarche study, the most significant dietary association with premature sexual development was soy infant formula (Am J Dis Child, 1986; 140: 1263-7).

Dissension in the ranks
Dr Lon White reported on a study of Japanese-Americans living in Hawaii that showed a significant statistical relationship between two or more servings of tofu a week and 'accelerated brain ageing'. Those participants who consumed tofu in midlife had lower cognitive function in later life and a greater incidence of Alzheimer's disease and dementia. 'What's more,' said Dr White, 'those who ate a lot of tofu, by the time they were 75 or 80, looked five years older.' White and his colleagues blamed the negative effects on isoflavones - a finding that supports an earlier study in which postmenopausal women with higher levels of circulating oestrogen experienced greater cognitive decline.

Dr Claude Hughes reported that rats of mothers fed genistein had decreased birth weights compared with controls, and onset of puberty was earlier in male offspring. His research suggested that the effects observed in rats 'will be somewhat predictive of what occurs in humans. There is no reason to assume that there will be gross malformations of fetuses, but there may be subtle changes such as neurobehavioural attributes, immune function and sex hormone levels'. The results, he said, 'could be nothing or could be something of great concern . . . if mom is eating something that can act like sex hormones, it is logical to wonder if that could change the baby's development.'

A study of babies born to vegetarian mothers, published in January 2000, indicated just what those changes might be. Mothers who ate a vegetarian diet during pregnancy had a fivefold greater risk of delivering a boy with hypospadias, a birth defect of the penis (BJU Int, 2000; 85: 107-13). The authors of the study suggested that the cause was greater exposure to phytoestrogens in soy foods popular with vegetarians.

Sally Fallon and Mary Enig are co-authors of Nourishing Traditions: The Cookbook that Challenges Politically Correct Nutrition and the Diet Dictocrats ( and co-founders of the Weston A. Price Foundation ( Dr Enig is a nutritionist and an expert in the field of lipid biochemistry.

* High levels of phytic acid in soy reduce assimilation of calcium, magnesium, copper, iron and zinc. Soy phytic acid is not neutralised by ordinary preparation methods such as soaking, sprouting and long, slow cooking. High phytate diets can cause growth problems in children.

* Trypsin inhibitors in soy interfere with protein digestion and may cause pancreatic disorders. In test animals, these inhibitors led to stunted growth.

* Soy phytoestrogens disrupt endocrine function, and may cause infertility and promote breast cancer in 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.

* Vitamin B12 analogues in soy are not absorbed and actually increase the body's requirement for B12.

* Soy foods increase the body's requirement for vitamin D.

* Fragile proteins are denatured during high-temperature processing to make soy protein isolate and textured vegetable protein.

* Processing of soy protein results in the formation of toxic lysinoalanine and highly carcinogenic nitrosamines.

* Free glutamic acid or MSG, a potent neurotoxin, is formed during soy food processing; additional amounts are added to many soy foods.

* Soy foods contain high levels of aluminium, which is toxic to the nervous system and the kidneys.

Soy and cholesterol-lowering Protein Technologies International (a division of Dupont), requested a health claim for isoflavones, the oestrogen-like compounds plentifully found in soybeans, based on assertions that 'only soy protein that has been processed in a manner in which isoflavones are retained will result in cholesterol-lowering'. In 1998, the FDA made the unprecedented move of rewriting PTI's petition, removing any reference to the phytoestrogens and substituting a claim for soy protein, a move in direct contradiction to the agency's regulations. The FDA is authorised to make rulings only on substances presented by petition.

The abrupt change in direction was no doubt due to the fact that a number of researchers, including scientists employed by the US government, had submitted documents indicating that isoflavones are toxic. The FDA had also received, early in 1998, the final British government report on phytoestrogens, which failed to find much evidence of benefit and warned against potential adverse effects (IEH Assessment on Phytoestrogens in the Human Diet, Final Report to the Ministry of Agriculture, Fisheries and Food, UK, November 1997, p 11).

One of the strongest letters of protest came from Drs Dan Sheehan and Daniel Doerge, government researchers at the National Center for Toxicological Research (Food Labeling: Health Claims: Soy Protein and Coronary Heart Disease, Food and Drug Administration 21 CFR, Part 101 [Docket No. 98P-0683]). Their pleas for warning labels were dismissed as unwarranted.

'Sufficient scientific evidence' of soy's cholesterol-lowering properties is drawn largely from a 1995 meta-analysis by Dr James Anderson, sponsored by Protein Technologies International (N Engl J Med, 1995; 333: 276-82).

Dr Anderson discarded eight studies for various reasons, leaving 29. The published report suggested that individuals with cholesterol levels over 250 mg/dL would experience a 'significant' reduction of 7-20 per cent in levels of serum cholesterol if they substituted soy protein for animal protein. Cholesterol reduction was insignificant for those whose cholesterol was lower than 250 mg/dL.

One hundred grams of soy protein, the maximum suggested cholesterol-lowering dose and the amount recommended by PTI, can contain almost 600 mg of isoflavones, an amount that is undeniably toxic (Food Technology, January, 1982; pp 60-4).

In 1992, the Swiss health service estimated that 100 g of soy protein provided the oestrogenic equivalent of the Pill (Bulletin de L'Office F'ed'eral de la Sant'e Publique, no. 28, July 20, 1992).

Twenty-five grams of soy protein isolate, the minimum amount PTI claimed to have cholesterol-lowering effects, contains 50-70 mg of isoflavones. It took only 45 mg of isoflavones in premenopausal women to exert significant biological effects, including a reduction in hormones needed for adequate thyroid function. These effects lingered for three months after soy consumption was discontinued (Am J Clin Nutr, 1994; 60: 333-40).

It is the isoflavones in soy that are said to have a favourable effect on postmenopausal symptoms and protection from osteoporosis.

The claim that soy prevents osteoporosis is extraordinary, given that soy foods block calcium and cause vitamin D deficiencies. If Asians indeed have lower rates of osteoporosis than Westerners, it is because their diet provides plenty of vitamin D from shrimp, lard and seafood, and plenty of calcium from bone broths. The reason that Westerners have such high rates of osteoporosis is because they have substituted soy oil for butter, which is a traditional source of vitamin D and other fat-soluble activators needed for calcium absorption.

The male species of tropical birds carries the drab plumage of the female at birth and 'colours up' at maturity - at around nine to 24 months.

In 1991, Richard and Valerie James, bird breeders in Whangerai, New Zealand, purchased a new kind of feed for their birds - one based largely on soy protein (Proc Nutr Soc NZ, 1995; 20: 22-30). With this feed, the birds 'coloured up' after just a few months.

Unfortunately, the ensuing years saw decreased fertility in the birds with precocious maturation, deformed, stunted and stillborn babies, and premature deaths, especially among females, with the result that the total population in the aviaries went into steady decline. The birds suffered beak and bone deformities, goitre, immune system disorders and pathological, aggressive behaviour. Autopsy revealed digestive organs in a state of disintegration. The list of problems corresponded with many the Jameses had encountered in their two children, who had been fed soy-based infant formula.

Aghast and angry, the Jameses hired toxicologist Mike Fitzpatrick, PhD, to investigate further. A literature review uncovered evidence that soy consumption has been linked to numerous disorders, including infertility, increased cancer and infantile leukaemia and, in studies dating back to the 1950s, that genistein in soy causes endocrine disruption in animals (J Nutr, 1956: 235-40).

Dr Fitzpatrick also analysed the birdfeed and found high levels of phytoestrogens, especially genistein. When the Jameses discontinued using the feed, the flock gradually returned to normal breeding habits and behaviour.

In-vitro studies suggest that isoflavones inhibit synthesis of oestradiol and other steroid hormones (Biochem Biophys Res Commun, 1995; 215: 1137-44; PSEBM, 1995; 208: 51-9).

Reproductive problems, infertility, thyroid disease and liver disease due to dietary intake of isoflavones have been observed in several animal species, including mice, cheetah, quail, pigs, rats, sturgeon and sheep (Gastroenterology, 1987; 93: 225-33; Science, 1976; 191: 98-100; Food, Cosmetics Technol, 1980; 18: 425-7; Gen Comp End, 1991; 83: 447-57; Aust J Agr Res, 1967; 18: 335-48).

Parents who have contacted the Jameses recount other problems associated with children of both sexes who were fed soy-based formula, including extreme emotional behaviour, asthma, immune-system problems, pituitary insufficiency, thyroid disorders and irritable bowel syndrome - the same endocrine and digestive havoc that afflicted the Jameses' parrots.

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