Calcium may help to protect against colorectal cancer

Abstract

Dairy products, largely or entirely because of calcium, help to protect against colorectal cancer according to the authors of a recent study.¹

“This is the most comprehensive single study ever conducted into the relationship between diet and bowel cancer, and it highlights the potential protective role of calcium in the development of bowel cancer,” says the lead author of the study, Keren Papier, PhD, a nutritional epidemiologist in the Cancer Epidemiology Unit of the Nuffield Department of Population Health at the University of Oxford.

The finding adds to the already well-established evidence for positive associations between alcohol use as well as the consumption of red and processed meat and colorectal cancer risk, which also were found in this study.

The study was performed because of the limitations of studies looking more comprehensively at dietary factors and colorectal cancer risk and other limitations such as dietary measure error and small sample sizes.

Using a large prospective study of 542,778 women in the United Kingdom, the investigators performed a systematic analysis that examined 97 dietary factors and the subsequent risk of colorectal cancer. Each participant completed a detailed dietary questionnaire.

Seventeen of the 97 dietary factors assessed were associated with colorectal cancer risk. Among these 17 dietary factors, alcohol and calcium intake had the strongest associations (based on the lowest p value) with colorectal cancer risk, with a positive association for alcohol (relative risk [RR] per 20 g/day, 1.15; 95% confidence interval [CI], 1.09–1.20; p < .0000001) and an inverse association for calcium (RR per 300 mg/day, 0.83; 95% CI, 0.77–0.89; p < .000001). Consumption of red meat and processed meat also was positively associated with colorectal cancer risk, with an RR per 30 g/day of 1.08 (95% CI, 1.03–1.12; p < .01), but the association was not as robust as that for alcohol.

When the researchers looked at types of dairy-related foods and nutrients, an inverse risk association was seen with all dairy-related factors, including dairy milk, yogurt, riboflavin, magnesium, phosphorus, and potassium. The inverse association of these nutrients primarily was due to the calcium associated with these nutrients. Dairy milk in particular was associated with a 14% lower risk per 200 g/day.

These findings were not changed when the researchers adjusted for potential lifestyle factors, with alcohol, calcium, and dairy milk remaining significantly associated with colorectal risk. An independent look at the association of calcium with colorectal cancer risk and dairy milk with that risk showed calcium, but not dairy milk, to be independently associated with colorectal cancer risk.

Investigators also found an inverse risk association with other foods and nutrients, including breakfast cereal, fruit, whole grains, carbohydrates, fiber, total sugars, folate, and vitamin C, but the magnitude of the risk was attenuated with further adjustment. This suggests an influence of lifestyle factors.

“Our study provides robust evidence that dairy products may help prevent colorectal cancer, largely due to the calcium they contain,” says Dr Papier, adding that the research highlights the potential protective role of calcium in the development of colorectal cancer.