The Truth About Soya

  • 15 Oct 2009
  • Reading time 8 mins
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Soya is increasingly hailed as a wonderfood - balancing hormones, staving off cancer, lowering cholesterol - all at good value for money. So what’s all this about it being dangerous? Natalie Savona unravels the conflicting evidence.

An Unbiased Opinion?

Before you come down on either side, it’s important to remember that, as with many issues, people will have their own agenda; every study is funded by a party with a vested interest in the results. The big soya companies (many of whom advocate genetic modification) obviously want us to think of their product as a good purchase, and have very powerful lobby pushing for official endorsement of health claims. While on the other hand, equally powerful pharmaceutical companies are loathed to have any natural (and unpatentable) products reduce the need for drugs such as HRT. What with dairy producers, who certainly don’t want trends to shift from milk to soya - there is little room for unbiased research and information.

Hormonal Superfood

In the world of optimum nutrition though, soya is regarded a superfood, and indeed, many studies have shown it to be not just a valuable part of any healthy diet but also therapeutic in certain cases. Perhaps soya’s most widely known benefit is its effect on hormonal balance. It is one of the richest natural sources of isoflavones, a type of phytoestrogen, or plant oestrogen. Many hormonally-related problems such as premenstrual syndrome, polycystic ovaries, breast and prostate cancers are partly attributed to an increasing exposure to oestrogen-like, hormone-disrupting chemicals in our environment. Phytoestrogens are said to help to block the effect of any such excess oestrogen. This may initially seem contradictory, given that they are oestrogen-like, but this is how it works: phytoestrogens dock onto oestrogen receptor sites on cells, basically blocking out the stronger, more harmful, oestrogen-like substances.

At the same time, if a woman is actually low in oestrogen, such as during the menopause, they will actually act as a weak oestrogen, helping relieve her symptoms by increasing levels i.e. the phytoestrogens balance oestrogens, whether they are too high or too low. Soya is one of the richest source of phytoestrogens and countless studies have shown that eating soya or taking soya supplements can provide relief from menopausal symptoms and conditions caused by hormonal problems. Hormone balance is just one of the benefits of eating soya that is backed up by scientific evidence. Others are the lowering of cholesterol, reducing the risk of cancer and osteoporosis and helping athletes build muscle. There is a particularly strong link between protection from hormone-related cancers such as breast and prostate and the inclusion of soya in the diet. Soya is a rich source of nutrients: protein (like animal and fish protein, it contains all eight amino acids), calcium, iron, zinc, omega 6 fats, lecithin, vitamin E and isoflavones.

So Where’s the Drawback?

Given all these good points, it may be difficult to imagine that soya has any enemies. The truth is though, that soybeans do, like many foods, contain some antinutrients. A key one is an enzyme (trypsin) inhibitor which blocks the digestion of protein, thus reducing the intake of protein and sometimes causing digestive problems. Similar enzyme inhibitors are actually present in several foods such as other beans and peanuts. Soya beans also contain a substance called haemagglutinin which encourages the red blood cells to clump together and reduces the take-up of oxygen. However, both the enzyme inhibitors and haemagglutinin are deactivated when soya is fermented (such as in miso, soy sauce, tamari and tempeh), and when it is ‘precipitated’ as with tofu, the enzyme inhibitors remain in the liquid remnants that are discarded. Soya is also high in a substance called phytic acid which can block the absorption of important minerals such as calcium and zinc.

So critics say that eating soya could lead to deficiencies in minerals but what they fail to point out is that many other foods, notably wheat - a British staple - are also rich in phytates. Mineral deficiencies are unlikely to be caused by one ingredient of a diet, unless it is eaten in particularly large amounts or the diet is not varied. Studies have also shown that the blocking action of phytates is reduced if foods such as tofu are eaten with meat or fish.

A fact that is often overlooked, especially in relation to the consumption of soya products as a replacement for milk or other dairy produce, is that soya itself is a common allergen. In fact, people who are intolerant of dairy produce or even allergic to it, may well be sensitive to soya milk. Although this is only a relatively small number of people. Another drawback for soya is that it contains goitrogens - substances which interfere with the function of the thyroid. But so do broccoli, kale, cabbage and other foods. Bear in mind also that much of the research on which the no-nos for soya hangs, was on animals or birds that were fed raw soya. Birds are not designed to digest soya, and certainly not raw.

Soya and Babies

There is some genuine concern over the safety of soya in foods such as baby formulas, so much so that the government has set up a committee to look into the implications of dietary phytoestrogens. The fears are largely based on speculation that the phytoestrogens may interfere with hormonal mechanisms, in children and later in life. One anti-soya campaigner has calculated that a baby fed exclusively on soya formula receives the oestrogen equivalent of at least five birth control pills daily, based on body weight. To equate phytoestrogens in soya to actual oestrogen is invalid, given that phytoestrogens are at least a hundred times weaker than oestrogens. What’s more, research on the effects of phytoestrogens on babies was done on baby rats.

Studies show ......

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