A soy burger. (The Solae Company/Associated Press)

Tofu, miso, tempeh and textured vegetable protein — there are many different names for the soybean, a truly versatile plant. It's garnered a lot of attention in the media, and has been described as a "wonderfood," with potential to lower the risk of breast cancer and heart disease.

It's also been suggested that soy is damaging and should be avoided. An article published in Britain's Guardian newspaper in July 2006 linked numerous health problems to the consumption of soy, including thyroid damage and reproductive difficulties. At the heart of the problem, says the article, is a chemical found in soy.

Dr. Mike Fitzpatrick, who was quoted in the article, said he found that soy contains a chemical that acts much like the hormone estrogen.

History of soy

The edible soybean is a fairly recent creation. Charles Zavitz, a professor at the Ontario Agriculture College in Guelph, Ont., brought the soybean plant to Canada from the United States at the end of the 19th century. The first Canadian-developed soybean, OAC-21, was introduced in the 1920s. Originally, the soybean was used in North America to feed animals. This all changed during the Second World War. Wartime rationing and the unreliability of imports in the 1940s created demand for locally produced oil that could be used for machinery as well as for cooking. The soybean was a viable solution. And the crop can be adapted to grow anywhere from Central America to Northern Ontario. Over the past 60 years, the demand for the soybean crop has continued to increase. Canada produced three million metric tonnes of soybeans in 2005, according to the UN Food and Agriculture Organization (FAO).

So should we eat it, or avoid it at all costs?

Soybeans are widely used as an alternative protein source for vegetarians and vegans, such as tofu and soymilk. British estimates suggest soy is present in about 60 per cent of food. A comparable percentage is not available for the Canadian grocery shelf, but according to Istvan Rajcan, associate professor of soybean breeding and genetics at the University of Guelph, soy is found in more than 300 products.

Rajcan says the reason soy is used so widely as a protein source is "because it is comparatively cheaper than meat, and cheaper to produce. Soy is also a high-quality protein."

Recent research has shown that soy contains all the essential amino acids, as well as Omega-3 fatty acids, which are essential because they cannot be synthesized by the body and must be obtained from food.

Health Canada currently does not provide any recommendations or guidelines on the consumption of soy in regards to potential health benefits or risks. In the United States, the Food and Drug Administration in 1999 concluded, "25 grams of soy protein a day, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease."

"The fact that the FDA has released this statement means that it is a well substantiated claim," Rajcan said. In addition to reducing the risk of heart disease, Rajcan said soy may reduce the symptoms of menopause. It can also decrease the risk of strokes, osteoporosis, breast cancer, prostate cancer and Alzheimer's disease.

The evidence in support of these claims is not always clear. However, Rajcan says these inconsistencies are because of the differing nature of the studies. Research on soy intake as a preventative measure has shown to be beneficial in lowering risk, however, post-diagnosis it can be ineffective.

A dangerous food?

There are questions around which part of the soybean is responsible for health benefits.

"It's hard to determine what component of soy can help in the prevention of these ailments – the protein, or the isoflavones," Rajcan said.

Isoflavones, also known as phytoestrogens, are naturally occurring chemicals that act like the hormone estrogen. It is because of the comparison to estrogen that phytoestrogens, and therefore soy, is considered controversial.

The Guardian article is among the voices urging the public to avoid soy-based products, comparing isoflavone content to someone adding hormones to food.

"The allegation is false," says Rajcan.

He said that it's wrong to compare isoflavones to estrogen because they have one-thousandth the potency.

"This would be equal to comparing one gram of estrogen with one kilo of pure isoflavones. Comparing the two is completely out of the question."

So, is soy good for everyone? Rajcan says no.

"There is no food that is good for everyone," he says.

Soy is a common food allergy, like gluten or lactose. It can also have negative reaction with some medications. Rajcan suggests that infants should not be fed soy-based products.

A formula for good health?

"Soy is fine in moderation," said Daina Kalnins, a registered dietician at Toronto's Hospital for Sick Children. "Concerns for infants are mainly reproductive issues – isoflavones mimic estrogen, which could affect the reproductive system."

The article in Britain's Guardian newspaper claims that infants raised solely on soy formula ingest the equivalent of five birth control pills-worth of estrogen per day, based on body weight. It also quotes studies in birds that entered puberty prematurely.

But Kalnins said that these results are species specific.

"There is no proof that it harms humans," she says. "We haven't seen any results. There's no reason for soy-based formulas to be taken off the market."

A 2001 study released in the Journal of the American Medical Association examined the association between exposure to soy formula and health in young adulthood, with regard to reproductive health. The study concluded that women raised on soy formula reported having slightly longer, more painful periods, but no statistically significant differences were observed.

When asked about the long-term benefits for infants exposed to soy, such as decreased risk of cancer, Kalnins said she "hadn't heard about benefits."

The Hospital for Sick Children recommends breastfeeding wherever possible. But if that isn't possible, the hospital "still recommends milk-based or lactose-free formulas" as better alternatives.

Whether or not soy contains properties that reduce disease, some of its healthy properties cannot be disputed. Soybean oil remains a healthy, and cheaper alternative to other cooking oils. Some oils remain healthier, but soybean oil remains a good alternative to many.

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