Ounce of Prevention | Should I ever have soy?
For decades there has been a steady stream of ‘anti-soy’ publicity and I am often send Internet articles from readers and my patients warning about the dangers of soy. In my experience however, soy is a virtual super food.
I personally have consumed soy products daily for more than 25 years and regularly recommend this humble bean to my patients. As a vegetarian, I emphasise the importance of dietary protein and am always seeking ways to supplement my protein intake. Soy is a great protein source as it is a complete protein containing all the essential amino acids.
The ‘anti-soy‘ lobby has actually encouraging intensive scientific research into the benefits or dangers of eating soy foods, so the issue can be dealt with using facts instead of anecdotes.
Overwhelmingly, medical and nutritional research has shown that soy offers protection against the killer diseases - heart disease, cancer and osteoporosis while helping to ease the symptoms of the menopause. It also is an economical and complete source of high quality protein that can safely replace animal protein in the diet.
The major accusations against soy are that it may cause cancer and may disturb thyroid function.
SOY AND CANCER
Much of the worry about soy has to do with naturally occurring compounds called phytoestrogens, the most abundant of which is the isoflavone, genistein. As their name suggests, phytoestrogens have chemical structures similar to that of the hormone oestrogen. This enables them to fit into the body’s oestrogen receptor sites, much as a key fits into a lock.
Instead of causing breast cancer, this ability to bind to oestrogen receptors allows phytoestrogens to block the effects of the much stronger oestrogen produced in the body or come from toxic chemicals like insecticides. The weak soy phytoestrogens are actually oestrogen blockers and this is one way by which soy protects women against breast cancer.
Most research as well as the experience of Asian populations, where soy has been a dietary staple for thousands of years, confirms the protective role of soy. A report published back in 2001 in the journal Cancer, Epidemiology, Biomarkers, and Prevention provides compelling evidence of the anti-cancer effects of soy foods. This study found that an increase in soy intake by adolescent girls reduced theirlater risk of breast cancer. Women with the highest consumption of soy had only half the risk of those with the lowest intake. Other studies have also shown a reduced risk of prostate and colon cancers with increasing soy consumption.
SOY AND THE THYROID
Another charge against soy is that it contains “anti-thyroid agents” that can disturb the function of the thyroid gland. This is largely theoretical. Certain compounds in soy can affect thyroid tissue in test tube studies, but this does not appear to be the case in live human beings.
Population studies show no increased prevalence of thyroid disease in countries with a high intake of soy, and the clinical research has been inconclusive. That debate aside, most researchers agree that consuming soy at optimal healthy levels (about 25 to 40 grams per day) is most unlikely to impair thyroid function. After using soy with hundreds of patients, I have detected no disturbance of thyroid function that I could blame on soy.
However, if you have an under-active thyroid, a bit of caution may be in order. Keep your soy intake within the above range and have your thyroid function monitored periodically. Also, be aware that taking thyroid medication at the same time as any food (soy or otherwise) may decrease the drug’s absorption. Take it on an empty stomach.
Have some soy in your daily diet. Soy is now available in many, many forms: soymilk, shakes, soy cheese, soy nuts, soups, drinks, protein bars, tofu and tempeh. There are also textured vegetable protein products like veggie mince and soy burgers. My favourite way to have high quality soy each day is with a soy protein shake. This is a delicious nutritious drink that can conveniently replace a meal.
With the tremendous increase in commercially processed soy products there are justifiable concerns about their quality. Not all soy products are equal. I use mainly non-GMO soy products from the most reputable sources. Avoid foods containing hydrogenated or partially hydrogenates soybean oil.
Select high quality soy products as many so-called soy products have low levels of the substances that provide the health benefits of soy. Look for the term ‘soy protein isolate’ and check the protein content on labels as a guide in assessing soy products.