For many years soya has been hailed as the ‘wonder food’ of the health food world, but there has also been controversy in the media over the potential for negative effects of soya consumption. Let us fill you in on some of the facts.

The soybean, part of the legume family, has been grown in the Far East for thousands of years, where its health benefits have become common knowledge. In Japan, certain soybean based dishes such as miso soup have long been considered as a cure-all. With the Eastern reputation for good health, long life expectancy and healthy diets, soya products have now been accepted into the Western diet as a healthy ingredients.

However, soya products are being consumed in the West in rather different ways compared to as they are in the East. While the Japanese tend to stick to fermented soya products such as miso, natto and soy sauce, and only eating refined soya products such as tofu in moderation and accompanied by other ingredients (such as iodine-rich sea vegetables), Westerners have adopted various soya and soya isolate products as a substitute for a multitude of meat and dairy ingredients, eating them in much larger quantities than the Japanese would. Also, with products such as tofu it is better to stick to organic or traditionally made products which use natural ingredients and setting agents.

In terms of nutritional value, soya has the highest protein content of any bean. It has the unique advantage over other legumes of containing all 8 essential amino acids and it has fatty acids including omega-3 and -6. On top of this it is also very low in saturated fat and has potential cholesterol lowering properties.

Over the years studies have suggested that soy products can be beneficial to human health in numerous ways. As mentioned one of these is in the reduction of cholesterol which in turn reduces the risk of heart disease, one of the biggest killers in the West. Research has indicated that the isoflavones in soya decrease LDL cholesterol (known as ‘bad’ cholesterol) but have no effect on HDL cholesterol (known as ‘good’ cholesterol) and significantly improved lipid profiles in blood [1,2,3].

These same isoflavones are also said to help in the prevention of osteoporosis (bone loss) [4], menopause symptoms (including hot flushes), and other studies are currently being done on the potential preventative effect on certain cancers (including breast [5] and prostate cancer [6]). In summary, there is a wealth of evidence and scientific research to suggest that soya has health providing properties. Research has even led the UK government’s Joint Health Claims Initiative (JHCI) to encourage the consumption of at least 25g of soya protein per day.

However, in recent months there has been a strong emphasis in the media on the potential dangers of eating soya products which are said to include adverse effects on thyroid functions and fertility. As well as all their positive attributes, isoflavones are said to be responsible for concerns over thyroid function. Despite this, recent research suggests that it is probably not necessary for people with thyroid function problems to avoid soya. The key would be to ensure that there is also enough iodine in their diet as iodine promotes healthy thyroid functions (iodine-rich foods include sea vegetables, peanuts and raisins).

With the fertility concerns a lot of the information covers the use of soya based baby formula and the consumption of tofu. There is no perfect substitute for breast milk, which is the most natural food for infants. Also refined soya products may not be as healthy as unrefined or fermented ones.

Overall, soya’s safety has been reviewed by a number of major Western committees including the UK Committee on Toxicity and the US Food and Drug Administration who still credit it to be a safe food.

Ultimately, there is no such thing as a ‘wonder food’, but soya is a valuable food source which can be beneficial in our diets. Like most things it should be consumed in moderation and as part of a balanced diet. In Asia they tend to eat between 10 and 25g of soya protein per day and this is predominantly in the form of fermented soya products such a soy sauce, miso and natto or as whole fresh or dried beans which have greater nutritional value. They almost never drink soya milk and tofu is eaten in moderation, accompanied by iodine-rich foods.

Clearspring believe that this is a sensible approach to eating soya. It is also advisable to avoid heavily processed, refined or GM soya products as they may contain higher levels of toxins and possible carcinogens with lower levels of beneficial antioxidants and isolavones than unrefined products. Research into the health benefits and possible risks of soya products is still at an early stage, but the nutritional benefits of it cannot be denied.

References:

1.Taku K et al., 2008. Soy isoflavones lower serum total and LDL cholesterol in humans: a meta-analysis of 11 randomized controlled trials. Am J Clin Nutr. 2007 Apr;85(4):1148-56

2.Zhan S, Ho Sc. 2005. Meta-analysis of the effects of soy protein containing isoflavones on the lipid profiles. AM J Nutr. 2005 Feb; 81(2): 397-408.

3.McVeigh BL et al., 2006. Effects of soy protein varying on isolavone content on serum lipids in healthy young men. Am J Clin Nutr. 2006 Feb; 83(2):244-51.

4.Yamaguchi M, 2006. Yakugaku Zasshi. Regulatory mechanism of food factors in bone metabolism and prevention of osteoporosis. 2006 Nov; 126(11) :1117-37.

5.Wu AH ey al., 2008. Soy intake and breast cancer risk in Singapore. Chinese Health Study, 2008 Jul 8:99(1): 196-200

6.Kurashi N. et al., 2007. Soy product and isoflavone consumption in relation to prostate cancer in Japanese men. 2007 Mar; 16(3): 538-45 Epub 2007 Mar.

To find out more:

The vegetarian and vegan foundation research

Safety of soya research

The whole food perspective

The British dietetic association