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Soy – friend or foe? What do I need to know ?

There is a lot of conflicting information and passionate debate surrounding soy consumption. This article aims to demystify the debate and provide practical information to enable people to make healthy dietary choices that are right for them.

What is soy ?  ( Botanical name Glycine max)

Soybean is a legume that is predominantly known for its use in Japanese and Chinese cuisine. Traditional types of soy include tofu (soybean curd), miso, tempeh, natto, edemame and soy sauce.

More recently soy has become popular in western diets not just as a protein alternative for vegetarians (as it contains all 8 essential amino acids) but also for its use in general food production. It is not uncommon to see soy or soy derivatives such as soy isolate used in foods such as breads, cereals, snack bars, vegetable oil, salad dressing, infant formula, stock cubes and muscle building protein powders used in the fitness industry. You may be interested to know that soybean is also used in the production of industrial products such as biodiesel, hydraulic oil, solvents and plastics.

In fact, the majority of the world’s annual soybean production is actually used for animal feed. So it is important you become aware of all the soybean sources in your diet – not just the obvious ones.

So, why is there so much debate surrounding the soybean?

Firstly, soybeans are big business and global production has skyrocketed over the past decade. The majority of annual production is now genetically modified.

Traditionally, soybeans are used in the Asian diet in a fermented form (eg tempeh, miso and natto).  The process of fermentation facilitates the breakdown of structural bonds within the bean that aids its digestion and promotes healthy levels of gut micro flora. Traditional use of the soybean is also in its wholefood state.

Western cultures use of soybean is quite different. Generally western food production uses unfermented, soy isolates ( ie components of soybean) rather than the whole bean. The high content of enzyme inhibitors in unfermented soybeans can interfere with the body’s ability to break down the macronutrients in the bean making it difficult for some people to digest. So, if you are experiencing digestive complaints such as bloating, nausea, cramping, gas or diarrhea and you consume a moderate to high level of soy in your diet seek the support of a qualified healthcare professional to help determine if soy may be contributing to your digestive symptoms.

Soybeans are known to affect human tissue in a number of ways –

Soybeans contain phytoestrogens which are plant compounds that exhibit oestrogenic activity. These compounds are known pharmacologically as selective oestrogen receptor modulators ( SERMs) and can bind to oestrogen receptors and exert either an antagonistic or agonist action on oestrogen responsive tissue in the body. The implications of this are particularly important for people with oestrogen related conditions such as breast and prostate cancer, endometriosis, heavy menstruation as well as during menopause and peri menopause.

As part of legume family, soybeans contain high levels of phytates. These compounds like to bind with metal ions in the body such as zinc, calcium and iron. So people with nutritional deficiencies should see a qualified health professional to assess the level and type of soy in the diet.

Soybeans affect the thyroid gland due to their goitrogenic action. Goitrogens are substances that suppress thyroid function by interfering with the uptake iodine. This is especially important for people with an iodine deficiency, an under active thyroid or Hashimoto’s disease. Other foods known to exhibit a goitrogenic action include cruciferous vegetables such as broccoli, brussel sprouts, cabbage, cauliflower and kale.

Researchers have known for some time that the isoflavones in soy exert a cholesterol lowering affect and have been associated with decreased risk of cardiovascular disease. A more recent study in 2011 indicated that a diet rich in legumes, not just soy alone, can decrease total and LDL cholesterol. So mixing up your peas and beans rather than relying on a diet high in soy is the healthier option.

Soybeans are a natural source of nutrients required for bone formation such as calcium, magnesium and boron. The therapeutically active isoflavones in soy have also been shown to inhibit the breakdown of bone especially in post menopausal women where osteoporosis can become a concern.

Bullet points you should know  –

1. Soy is hiding in a lot more foods than you expect. So read labels and be on the lookout for all sources of soy in your diet.

2. Soybeans contain various constituents that can affect human tissue.  Be mindful of what these actions are and how they may affect your individual health profile.

3. Fermented soy is preferred over unfermented soy or products that contain isolated soy compounds such as textured soy protein or soy isolates.

4. Insist on GM free soy.

5. Consider what other ingredients are in your soy milk. Read labels and beware of sweeteners, colourings and added fats such as palm oil.

6. Keep soybean consumption to a moderate level and seek the advice of a qualified health care professional if you have specific health care concerns such as thyroid disease, oestrogen related conditions, poor digestion or are a vegetarian and rely on soy as a form of protein in your diet.