Doubts over whether soy prevents cancer

Reported by Susan Aldridge, PhD, medical journalist

A review of the evidence suggests that soy probably does not have a protective effect against breast cancer.
Because Asian women, who consume a lot of soy in their diet, are much less likely to develop breast cancer than Western women, it has long been assumed that soy products, like tofu, can protect against the disease. This has led to increasing popularity of soy supplements, especially among breast cancer survivors. But, say researchers at Johns Hopkins University, good evidence the benefits of soy is lacking.

They looked at 18 different studies and found, at best, only weak evidence that soy is protective. It is also hard to separate the impact of soy from other effects. For instance, women who eat tofu and the like tend to have diets lower in calorie-dense foods and lower body mass index. This, not soy, may be protective.

As far as Asian women are concerned, there are factors other than soy which might protect from breast cancer. They have children earlier, drink less alcohol and are more physically active. The researchers think that soy supplements, in particular, could actually be harmful because some experiments have suggested they can promote tumor growth. The take-home message is - don't abandon soy because foods like soy nuts and milk, and tofu, have benefits for the heart. But stay away from soy supplements.

Source
Journal of the National Cancer Institute 5th April 2006

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