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If there’s one food that can polarise opinion it’s soy. Depending on who’s talking, soy gets the thumbs up for protecting against heart disease and breast and prostate cancer - or the thumbs down for contributing to these cancers, along with thyroid problems. Now the Harvard T.H. Chan School of Public Health has shed some light on the debate in Straight Talk About Soy, a new report that says that the complex nature of soy’s effects on the body is one reason why research results can be conflicting.

Soy isoflavones and soy protein can have different effects depending on:

• Whether a study is animal or human. Soy may be metabolised differently in animals so the results may not apply to humans.
• Ethnicity. Soy may be broken differently in people of some ethnicities - which may explain why people in some countries who consume soy-rich diets seem to benefit from the food.
• Hormone levels. Soy’s effects can depend on the existing level of hormones in the body. Before menopause when a woman has higher levels of oestrogen, for instance, soy may act more like an anti-oestrogen but after menopause when levels of oestrogen are lower, soy may act more like oestrogen.
• The type of soy food being studied. Is it a whole food like tofu or soybeans - or a more processed food like soy-based veggie burgers or protein powder? While half a cup of cooked soybeans has 55mg of isoflavones, for example, a soy burger has only 5mg.

The bottom line according to the report? Results of recent population studies suggest soy has either a beneficial or neutral effect on a range of conditions and that it can be safely consumed several times a week. To find out more, read Straight Talk About Soy  which includes summaries of research into the effects of soy on heart disease, thyroid disease, breast and prostate cancer, hot flushes and memory and cognition.