Are there dietary patterns that have been proven to reduce your risk of cancer?

Vegetables and fruit help modestly: every additional 200 grams per day is associated with a 3% lower risk of cancer in general, up to a ceiling of around 600 grams per day. That may sound small, but the association has been shown to be statistically robust in a large meta-analysis. Keep in mind that this is an association, not a proven cause-and-effect relationship. The Mediterranean diet has the strongest evidence base of all dietary patterns. People who follow this diet most closely have, in large cohort studies, on average a 6 to 14% lower risk of dying from cancer. Colorectal cancer stands out: the risk was 18% lower for that cancer, and that finding was the most consistent across studies. For stomach cancer the figure was even 28%, but that is based on only four studies. Prostate cancer shows no noteworthy association. The only large randomised trial in this area, the PREDIMED study, tested the Mediterranean diet supplemented with extra virgin olive oil in older women. The incidence of breast cancer in that trial was 68% lower than in the control group. That sounds impressive, but there were only 35 cases of breast cancer in total, and it was a secondary analysis in a study that was not designed for this purpose. The researchers themselves say that confirmation is needed. The same diet but with nuts instead of olive oil showed no significant difference. Diet also rarely works in isolation. A long-running study with more than 110,000 participants shows that women who combine four or five healthy habits at age fifty (not smoking, a healthy weight, physical activity, low alcohol consumption and good dietary quality) live on average more than ten years longer free of disease than women without such habits. The contribution of diet alone cannot be isolated from this. Conclusion for practice: the Mediterranean diet, rich in vegetables, fruit, legumes, whole grains and olive oil, is the best-studied dietary pattern in relation to cancer. The protection is consistent but modest, and in all available studies the findings are associations, not demonstrable causes. Colorectal cancer has the strongest evidence base. Smoking, body weight and physical activity each probably have a greater effect than diet alone.