Is it true that eating white flour and sugar fuels cancer growth? —B.T., El Macero, Calif.

It’s unclear. Many population studies have examined the possible link between the intake of refined (white) carbohydrates such as flour and sugar and various types of cancer, with mixed results. The largest review we could find, involving 39 studies, found an association between refined-carb intake and colorectal and endometrial cancer, but not breast or pancreatic cancer. But a smaller review of 23 studies found no increased risk of colorectal cancer.

Regardless of any possible cancer risk, there are other good reasons to limit your intake of refined carbs: They provide plenty of calories and have little nutritional value. Instead choose healthful, complex carbohydrates such as whole grains, brown rice, and vegetables.

Find out why successful dieters recommend restricting refined carbs.