Features
U of G Scientists Stand Up for Soy
Researchers counter soy's recent bad press with studies showing health benefits
BY RACHELLE COOPER
There have been some mixed messages lately about the dangers of consuming too much soy, but U of G researchers say that making soy products a regular part of a balanced diet will only improve your health.
News coverage in recent months has linked soy to health problems, including thyroid damage and reproductive difficulties, because of the hormone estrogen that's found in soy.
Prof. Istvan Rajcan, a soybean breeding expert in the Department of Plant Agriculture, says the misconception occurred because isoflavones — non-nutritive, naturally occurring plant chemicals found in soybeans — are related to estrogens.
“The isoflavones in soybeans are a thousand times less potent than estrogen, so one would have to consume huge amounts of soybeans to have any estrogen effect,” he says. “A small percentage of the population has food allergies to soy, but I have yet to see a study showing that an adult was negatively affected from consuming too much soy.”
Rather than doing people harm, soy isoflavones are known to offer some protection against hormone-related disorders, including certain forms of cancer, says Rajcan.
“Isoflavones have been shown to reduce prostate, breast and colon cancer; to slow the onset of osteoporosis; and to alleviate symptoms of menopause.”
Adds Prof. Alison Duncan, Human Health and Nutritional Sciences: “In the research studies I've done so far, I haven't observed any negative effects of consuming soy.”
In her study of the impact of soy protein consumption on reproductive hormones related to prostate cancer risks in healthy adult men, she found that some hormones changed in a direction beneficial for prostate cancer risk. The research, published in the Journal of Nutrition, also found that hormone levels remained within normal range, not suggesting any negative effects related to male fertility.
Duncan is also looking at the impact of soy on circulating thyroid hormones.
“My research found no effects from soy consumption on thyroid hormones among healthy young men, which adds to results from other studies that had similar findings. Overall, foods made from soybeans have many healthy attributes. They are often high in protein, low in fat and high in fibre.”
Adds Rajcan: “Soybeans produce one of the healthiest vegetable oils, and soy protein has all the essential amino acids. It has a good balance of fatty acids and a relatively small amount of saturated fat. Soybeans are also one of the main sources of vitamin E, which is a byproduct of processing the oil from soybean seeds.”
The U.S. Food and Drug Administration has approved a health claim for soy foods stating that 25 grams of soy protein a day may reduce the risk of heart disease.
“A health claim in the United States would not be approved unless there was sufficient evidence to support its validity,” says Duncan. “Canada's Food Guide stresses moderation and variety as key concepts to a healthy diet, and soy foods have many excellent attributes that fit into that recommendation.”
In a study recently published in the American Journal of Clinical Nutrition, she found that soy protein can reduce blood fats in healthy men in a direction that reduces the chances of cardiovascular disease.
“That study showed that it's never too early to start incorporating soy into a balanced diet and that there are benefits even for people who are healthy.”
Soybeans weren't grown in Canada until U of G professor Charles Zavitz brought a soybean plant to Guelph from the United States at the end of the 19th century and developed the first Canadian soybean, OAC-21, in the 1920s. Soy is now found in more than 300 products, and Canada produced three million metric tonnes of soybeans in 2005.
Guelph continues to be a leader in soybean research. Rajcan is working to make soybean oil even healthier, is developing soybean crops that will do well in shorter seasons and is developing soybean seeds with different levels of isoflavones. Duncan is studying the effects of consuming soy on Type 2 diabetes and is working with Rajcan to see whether isoflavones from soy actually get absorbed into the human system.
“I think the uniqueness the University of Guelph brings to the Canadian platform on soy research is that we've got a continuum all the way from agriculture to human health and everything in between,” says Duncan.