Key food categories affect cancer risk

Alcohol intake appears to be a strong risk factor for cancer, while dairy, fruits and vegetables, and coffee exert protective effects, reveals a recent umbrella review of meta-analyses of observational studies.

The study involved 860 meta-analytic comparisons, most of which were of continuous exposures (91 percent; n=779); only 81 comparisons used dichotomous contrasts. The review aimed to assess the strength and validity of evidence regarding the association between dietary intake and the risk of developing or dying from primary cancer at 11 anatomical sites.

Only 10 of the meta-analyses (1.2 percent) were supported by strong evidence and had no suggestion of bias. Five of these associations showed a significantly increased risk of colorectal cancer related to high alcohol consumption (summary relative risk [RR] per 10 g/day, 1.07, 95 percent confidence interval [CI], 1.05–1.08). Alcohol intake had a similar impact on postmenopausal breast cancer.

On the other hand, higher intake of dairy products (RR per 400 g/day, 0.87, 95 percent CI, 0.83–0.90), milk (RR per 200 g/day, 0.94, 95 percent CI, 0.92–0.96), calcium (RR high vs low, 0.83, 95 percent CI, 0.79–0.87) and whole grains (RR per 90 g/day, 0.84, 95 percent CI, 0.78–0.90) were all protective against colorectal cancer.

Thirteen more meta-analyses provided highly suggestive evidence, particularly as regards the link of alcohol and different subtypes of breast cancer, oesophageal cancer in men, head and neck cancer, and liver cancer mortality. In addition, coffee intake showed an inverse correlation with liver cancer and skin basal cell carcinoma risk, while fruits and vegetables also exerted a protective effect against pharyngeal and oral cancer.