Milk and ovarian cancer

A team of scientists recently published a meta-analysis of 29 case-control and cohort studies that focused on types of dairy intake, Vitamin D and calcium intake, and the risk of ovarian cancer (Brit J Nutr https://doi.org/10.1017/S0007114520001075).

Out of those studies, the vast majority (23) looked at the association between risk of ovarian cancer and the participants' consumption of dairy products and lactose (a sugar found in dairy products). 13 studies assessed calcium intake and ovarian cancer, and 10 looked at calcium intake. (Some studies focused on more than one measure of intake.)

When the authors compared those with the highest versus the lowest intake of total dairy products, there was no association, positive or negative, found between total dairy product intake and ovarian cancer.

When the researchers drilled down into specific types of dairy products, however, they found that those with a higher intake of whole milk were 35% more likely to develop ovarian cancer than those in the lowest level of intake.

On the other hand, those who consumed the most low-fat milk were 16% less likely to develop ovarian cancer. Intakes of skim milk, yogurt, cheeses, and lactose intake in general had no effect on ovarian cancer risk.

As some of the studies did not specify whether their participants' calcium intakes were from the foods they ate as opposed to taking supplements, the authors could only report on calcium intake as a whole. Compared to those with the lowest calcium intake from all sources, those with the highest calcium intake were 29% less likely to develop ovarian cancer. When they calculated the risk only for those taking calcium supplements, however, the decrease in ovarian cancer risk was described as "marginal" (at 19%).

Higher levels of Vitamin D from dietary sources were associated with a 20% lower risk of ovarian cancer, but when the authors assessed the risk for all sources of Vitamin D there was no significant association either way.

Given these results, the authors conclude that "consumption of whole milk was positively associated with ovarian cancer risk, whereas consuming large amounts of low-fat milk, dietary calcium, and dietary vitamin D were negatively associated with ovarian cancer risk."

These result should be interpreted with caution as they are from case-control and cohort studies and not randomized controlled trials. Still, this seems to support the idea that getting your vitamins from your diet is superior to taking supplements. Further, this supports the Mediterranean Diet's emphasis on low-fat and fermented dairy instead of whole milk.

First posted: April 29, 2020