Soy protein under attack – for no good reason

The debate around the benefits and drawbacks of soy protein has been raging for years, but Dr. David Jenkins is ready to settle it once and for all. Put simply, it’s a good thing.

Dr. Jenkins, a scientist at St. Michael’s Li Ka Shing Knowledge Institute, a professor of nutritional science at U of T and director of the Clinical Nutrition and Risk Factor Modification Centre, was the lead author of a recent study that found soy protein has the ability to lower LDL cholesterol in adults by three to four per cent—a small but significant amount.

Dr. Jenkins is the physician who developed the glycemic index, and is a longtime proponent of plant-based diets for cardiovascular health. Now he is concerned by the U.S. Food and Drug Administration’s decision to revoke a previously approved health claim that eating soy lowers the risk of heart disease. Why the move by the FDA? Apparently the decision was based on studies that showed inconsistent findings, and only a small improvement in cholesterol levels. But Dr. Jenkins says the FDA used a methodology based on drug testing, and foods are not drugs. They are more complicated to test, since they are usually taken with other foods. And he has shown that combining several small improvements from different foods can add up to the same heart benefits as taking drugs.

He recommends doing exactly that via his Portfolio Diet, which replaces animal proteins with soy, nuts and beans and adds fibre and plant sterols for further benefits for heart health.

The latest Canada’s Food Guide agrees, emphasizing plant-based protein over meat and dairy — but Dr. Jenkins worries the new direction will not last, given the huge presence of the U.S. meat and dairy industries. “What we’re left with is Health Canada saying eat more plant protein foods, and everyone saying, well, the FDA says they’re no good,” he says  “Canada still has a health claim for soy, but can we keep it up when we have neighbours we exchange goods with?”

As for the worries that soy’s mild estrogenic effect could stimulate the growth of breast cancer cells, Dr. Jenkins says that new research actually suggests the opposite. One early study widely reported in the press had used mice with compromised immune systems, which allowed the cancer cells to grow. “After that, everything had to be soy-free,” he says. “But then more data started coming in. Studies were showing that women who took soy were actually better off.”

For instance, the National Cancer Institute brought out a review of many studies that assessed women’s soy intakes over time. To their surprise, they found that pre-menopausal women in particular who ate soy saw a reduction in breast cancer incidence. And it suddenly dawned on people that women need their immune systems, and estrogen components stimulate the immune system, which then helps fight the cancer.

“So I went back and told my patients to take soy!” Dr. Jenkins says.

Dr. Jenkins points out that soy protein is part of a healthy eating picture that includes fruit, vegetables, beans and legumes, nuts, seeds and whole grain cereals. And he advises choosing organic or non-GMO soy. “I’m as much of a non-GMO person as anyone else,” he says, “not for health reasons but because there are major environmental concerns. And we have to be much more concerned with the environment, and what we eat.”

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