My father (79) had colon cancer two years ago. My wife's mother developed breast cancer at 58. Researchers have discovered that vitamin D has anti-cancer effects. Will regular sunbathing and/or a plant-based (vegan or semi-vegan) diet protect my wife and me from these diseases?

Dr Fred Kavalier answers your health question:

You pose two important questions. Are you two at increased risk of cancer because you each have one parent who has had it? And can you reduce your risk by changing your diet and sunbathing?The truth is that if you have one close relative who develops cancer, your risk of developing the same cancer is not significantly higher. It is clear that the great majority of cancers are not caused by simple genetic factors. The only exception might be if a relative developed cancer at an unusually young age, which could indicate a genetic tendency. One in nine UK women will develop breast cancer at some time in their lives, and about one in 20 men and women will develop colon cancer.The second question is more difficult. Vitamin D does seem to have anti-cancer properties, particularly against colon cancer. And sunlight helps the body to make more vitamin D. But sunbathing can increase the risk of skin cancer. We don't know where the balance of risk and benefit lies, so can't tell you how much risk reduction (if any) you could expect. But on diet, the evidence is clear; people who eat more fruit and vegetables get less cancer.

Please mail your questions for Dr Fred to He regrets that he is unable to respond personally to questions.