DAIRY PRODUCTS AND PROSTATE CANCER
Most North Americans grew up being quite sure that milk was an essential part of a healthy diet. The incredibly successful campaigns such as “Got Milk?” and “Milk does a body good” have cemented that in our brains.
However, as it became obvious that people following Western diets had way higher rates of cancer than populations following mostly plant-based diets, researchers started to realize that the likely culprits were not only meat and other fatty foods, but also dairy products. In 1998 a large Harvard study of health professionals showed that men who consumed more than two servings of milk a day had a 60% increased risk of prostate cancer over those who generally avoided milk.
There are over 24 000 new cases of prostate cancer a year in Canada. In BC there are about 3600 new cases a year with about 600 men dying in BC each year from the disease.
Reviewing the biological purpose of milk helps us understand why dairy products could promote cancer. The key point is that all mammal’s milk is designed to promote rapid growth of the newborn. It contains protein, fat, sugar and dozens of hormones and other natural substances to promote growth. Cow’s milk is very different in composition to human milk. A baby calf weighing 70 pounds will gain weight at a rate of 75 pounds per month to grow to over 550 pounds in just 9 months from its mother’s milk alone!
When humans drink cow’s milk it causes some concerning changes in the body, one of the most worrying being the increase in Insulin-like growth factor 1 (IGF-1). IGF-1 is a powerful driver of cancer cell growth, with higher levels being associated with increased risk of prostate and breast cancer. There are a few other ways in which milk may raise prostate cancer risk. Milk is high in fat and has no fibre so it may increase the body’s production of testosterone, which is linked to prostate cancer risk.
High calcium foods such as milk also interfere with the activation of vitamin D in the body. As the load of calcium from ingested dairy products, including cheese, yogurt and ice cream, hits the blood stream it signals the body to reduce its vitamin D activation to ensure the body doesn't absorb too much calcium. Lower levels of vitamin D are associated with higher cancer risk, as we learned from our previous column on vitamin D.
The question most people ask at this stage, is “Where do I get my calcium if I cant have dairy?” It is easy to get enough calcium from plant sources. Green leafy vegetables and legumes such as peas, beans and lentils are an excellent source of calcium and unlike milk, also provide fibre and valuable phytonutrients to help prevent cancer. Tofu, broccoli cabbage, cauliflower and fortified soy and rice milks are also healthy options.