Scientists from Loma Linda University have found that higher consumption of dairy foods is associated with an increased risk of prostate cancer in men.
Dairy foods, also known as milk products, are produced from the milk of animals such as cows, water buffalo, goats, and sheep.
In Western diets, commonly consumed dairy products include yogurt, cheese, and butter.
The dairy food group provides a wide range of nutrients, including calcium, phosphorus, vitamin A, vitamin D (in fortified products), riboflavin, vitamin B12, protein, potassium, zinc, choline, magnesium, and selenium.
Prostate cancer is one of the most common cancers among men in the United States.
Previous research has suggested possible links between dairy intake—or dietary calcium—and an increased risk of prostate cancer, although the evidence has been limited and sometimes inconsistent.
In the current study, researchers aimed to further examine these associations in a large population of men, including many participants who consumed little or no dairy and obtained much of their calcium from nondairy sources.
The analysis included data from 28,737 men living in the United States and Canada. Over an average follow-up period of eight years, researchers identified 1,254 cases of prostate cancer, including 190 advanced cases.
The results showed that men with the highest intake of dairy foods had a significantly higher risk of prostate cancer compared with those who consumed the least dairy. Similar associations were observed for both advanced and non-advanced prostate cancer.
In contrast, the researchers found no evidence that higher intake of calcium from nondairy sources was linked to an increased risk of prostate cancer.
Overall, the findings suggest that higher consumption of dairy foods—but not nondairy calcium—is associated with a greater risk of prostate cancer. Notably, the greatest increases in risk were observed at relatively low levels of dairy intake.
One possible explanation for the observed association is that dairy foods, or an as-yet-unidentified factor closely linked to dairy consumption, may play a causal role in prostate cancer development.
The research team also noted that the hormone content of dairy milk could be relevant. Up to 75% of lactating dairy cows are pregnant, and prostate cancer is known to be a hormone-responsive disease. Hormonal components in dairy products may therefore influence cancer risk.
The study was conducted by Gary E. Fraser and colleagues and published in The American Journal of Clinical Nutrition.
