Soy
The soybean (Glycine max) provides a cheap and nutritious alternative to animal protein in populous countries such as China, Korea and Japan. There are many cultivars available and a crop of soy is highly productive, producing large amounts of beans. The beans are usually pressed for their oil and the remaining meal used for animal feed, or included as an ingredient in vegetarian meals and baked goods. Traditional methods of preparation of soybean included boiling to make soymilk and tofu, roasting the beans, and fermentation to make tempeh.
They contain 30% carbohydrate, of which about 10% is fibre; almost 40% protein, including all the essential amino acids; and 20% fat, half of which is omega-6 and omega-3 fatty acid. There are also high amounts of B-vitamins in soybeans (excluding vitamin B12), as well as vitamin C, E and K. In addition, soybeans contain the minerals calcium, magnesium, manganese, iron, potassium and zinc.
Soybeans have to be cooked before eating because they contain protease inhibitors which prevent the enzyme trypsin breaking down the protein during digestion. Furthermore, soybeans contain phytates (inositol hexaphosphate), phytic acid, and oxalate which can lock up minerals making them unavailable for absorption. While soaking and sprouting lessens the problem, soy is also goitrogenic, inhibiting thyroid hormone synthesis, a potential problem if the diet is already deficient in iodine.
Most soy is now also genetically modified (GM) and soy isolates, flour or vegetable protein present in processed foods imported into Australia are derived from GM soy. This crop is designed to tolerate an increased level of herbicide use which results in higher levels of residues in the finished products, which are active at a level of parts per billion.1 While the long-term health impact of GM food consumption is largely unknown, animal studies have shown liver and pancreatic cell alterations in animal studies, hinting at the contribution of these ultra-processed foods to our epidemic of diabetes, obesity and other degenerative diseases.2,3
Modern oil extraction also differs markedly from traditional methods. The oil is removed from the beans by rolling, pressing and using the solvent hexane. The oil is then degummed in order to remove its valuable lecithin, refined using alkali, bleached, hydrogenated and deodorised. Most of the remaining meal is then dried and milled to make de-fatted soy flour, soy protein concentrate or isolate, as well as textured soy protein (TVP). Additional industrial techniques include ‘extraction, isoelectric precipitation, salt precipitation, thermocoaggulation, and ultrafiltration procedures.’4
Soy contains a number of biologically active compounds including saponins, lunasin and isoflavones. The protein content in soybeans was the initial focus of research because of an apparent cholesterol-lowering effect; however, research has now largely shifted towards the isoflavones present in the bean. Of particular interest are genistein and daidzein, as well as the isoflavan equol. Equol is produced by the gut of between 25-50% of individuals who have the specific intestinal bacteria needed to synthesise it from daidzein.5 Other isoflavones are glycitein, biochanin A, and formononetin, also present in red clover; however, soy has higher levels of genistein and daidzein than red clover.
To begin with, isoflavones enhance nitric oxide, a substance that dilates vessels and therefore helps to reduce blood pressure. This also stabilises blood vessel walls, and combined with the oestrogenic activity, makes soy a useful addition to the diet for women suffering menopausal hot flushes. Nevertheless, you would have to eat tofu in the amount of about 50% of your daily protein intake to enjoy these beneficial effects.6 The oestrogenic activity, albeit weak, also means that when consumed in a context of existing high circulating oestrogen levels (pre-menopause) they reduce oestrogenic activity overall, while on the other hand, in an environment of low oestrogen (peri-menopause, post menopause), they have an advantageous stimulating effect.
A finding by the Women’s Health Initiative in 2002, that hormone replacement therapy (HRT) increased the risk of breast cancer, helped turn the use of alternative soy products, as well as flaxseed and red clover, into one of the biggest selling categories of alternative medicines. Soy in particular can help with hot flushes, vaginal atrophy, and bone loss.7
This hormone-modulating effect also unfortunately classifies soy as an endocrine disruptor. The disruptive nature of phytoestrogens was initially discovered when it was noted that sheep which grazed on red clover became infertile. It was thought that eating large amounts of soybean products may therefore have serious implications for infants fed soymilk formula, adolescent men, and people at risk of cancer.
The issue is complicated by the fact that oestrogenic compounds interact in different ways with sub-types of the oestrogen receptor (ER) in the body. This is why soy isoflavones appear to exert both anti-proliferative and stimulatory effects on breast cancer, depending on the research you read. Epidemiological studies, however, show that relatively high levels of soy consumption in traditional Asian societies is associated with a reduced breast cancer and prostate cancer risk.8,9
As for the risk of feminisation in men, the regular intake of soy has subsequently been found to have little effect on adult male hormone levels when consumed in moderate amounts.5 Moderate consumption, as occurs with the replacement of meat protein by tofu, can even be useful in treating prostate conditions because of the observed modulation of the androgens responsible, but this kind of strategy applies to older men with distinct urinary symptoms relating to prostatic enlargement.10
However, this does not apply with a very high consumption of soy as is the case with weight-trainers or athletes, where significant reductions have been noticed in circulating androgen levels. This makes the consumption of soy foods counterproductive to muscle-building. In fact, by merely consuming a few baked goods each day containing soy flour (3 scones) you can markedly lower your testosterone level.11 This begs the question: what would a fulltime factory-food diet be capable of doing for adolescent men, let alone a growing infant boy fed on soymilk formula? The key is of course moderation, with soy consumption being part of a broader nutrient-dense diet, as it was in the traditional diet of the Okinawan people whose androgen and oestrogen levels were relatively high compared to age-matched Americans.12
Infant formulas derived from soy present potential problems other than those arising from the phytoestrogen content.13 The list is extensive: they contain pesticide residues which are active in trace amounts; GM contamination is undeclared on the label; the overall effect of all the other additives in the formula, supposedly designed to nourish a growing child when replacing breast milk, is unknown; the potential allergic effect is similar to cow’s milk which it often replaces; the presence of nitrosamines and lysinealine, byproducts of processing; the lack of cholesterol which is essential for the infant’s brain and nervous system development; and lastly, the suppressive effect on thyroid function and other organs due to anti-nutrients such as goitrogens and enzyme inhibitors.
Soy can also cause an allergic reaction, including IgE-mediated responses such as anaphylaxis, food protein-induced enterocolitis syndrome, eosinophilic oesophagitis, as well as the related atopic conditions of asthma, allergic rhinitis and eczema. There is also the lesser class of food sensitivity reactions which makes identification of the cause of a food reaction difficult because soy derivatives are prevalent in processed foods. The usual approach is an elimination-and-challenge diet which excludes all the most common reactive foods for two weeks: cow’s milk, soy, wheat, egg, peanut, and seafood. Once symptoms have subsided, individual foods are then reintroduced one at a time to help identify the culprits.14
The important point is that the modern diet contains many ultra-processed ingredients, and unless you are vegan or vegetarian, you only consume soy derivatives. These soy derivatives confer few of the benefits of whole organic soybeans as were once consumed in mainland Japan before the 1950s. Along with tofu, miso and tempeh, the Japanese ate seaweed products, oily fish, fresh fruit and vegetables with plenty of fibre and other important phytonutrients, a diet able to sustain health into old age.
In the island of Okinawa the staple was mostly sweet potato instead of soybeans and this vegetable, rich in protective polyphenols, apparently conferred even greater health benefits on the population compared to the Japanese mainland, considering the higher percentage of centenarians they fostered. Meals consisted of mostly vegetables and miso soup cooked together with leaves such as daikon radish. Festival days once a month provided additional protein in the form of fish, fish pastes, goat, pork, or seaweed products. Seaweed was regularly eaten in the form of konbu, and it was often consumed together with tofu to make a clear soup, or added to meat broth.15 The traditional diet was matched to high levels of exercise and often prolonged calorie-restriction—perfect conditions for the expression of optimal genetic traits.16 Unfortunately, as the Okinawans changed their lifestyle and incorporated such staples as GM soy and polished rice into their diet, they steadily lost their advantage.
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