Soy is a staple in many meat-free diets, but there are many myths surrounding this plant-based protein. Dr Sue Shepherd weighs in on the great soy debate.
Soy beans are a complete plant protein – meaning they contain all the essential amino acids that our body can’t make. Soy is also high in soluble fibre, low in fat and is low GI. So, with all these health benefits, why hasn’t soy been embraced by all? We address some common myths.
Myth: Soy reduces nutrient absorption
Some people believe soy reduces nutrient absorption because it contains phytates, which can interfere with the absorption of some vitamins and minerals. However, phytates naturally occur in many common foods such as seeds, nuts, and grains (including wheat and oats). Given that the amount of phytates in soy is much lower than in oats or wheat, it is unlikely soy will have a significant impact on reducing the absorption of nutrients. In fact, phytates have been shown to be beneficial for cancer protection and lowering cholesterol.
Myth: Soy causes male fertility issues
Soy contains isoflavones, a type of phytoestrogen. Phytoestrogens are plant oestrogens with a structure similar to the female sex hormone oestrogen, but with a much weaker effect. A recent study assessing soy impact on male fertility found no effect on semen volume or sperm concentration, count, morphology or motility when men consumed test drinks containing either high or low levels of soy isoflavones.
Myth: Soy causes goitres
A goitre (pronounced ‘goy-ter’) is an enlarged thyroid gland. Food sources of goitrogens, which can contribute to the formation of goitres, include some vegetables (such as spinach, broccoli and Brussels sprouts), strawberries, peaches, peanuts and soy.
Although soy contains goitrogens, researchers state that for it to cause toxicity, there must also be several other factors present including iodine deficiency, defects in the body’s ability to make thyroid hormones, or additional goitrogens in the diet. Soy is no more likely to cause goitres than any of these other goitrogen-containing foods.
Myth: All soy is genetically modified (GM)
GM food has been subject to bad press and many consumers wish to avoid it. Compared to the rest of the world, Australia has a low incidence of GM soy products – and all labelling must state whether a product has GM ingredients. In Australia, most of the major brands of soy products, do not contain GM soy.
The bottom line
Including soy products (such as soy milk, soy protein, edamame etc) in your diet is not bad for you, and may have health benefits.