“I have been seeing a lot of information about milk and dairy raising levels of IGF1 in our bodies. The claim is that will increase the growth of cancer cells, particularly in hormonal based cancers like prostate and breast cancer. Apparently, high levels of IGF1 are good if you are growing but less important once you have matured. Can you put our minds at ease, please? ”
Drinking a lot of milk might raise your IGF-1 levels, but it’s not because of the hormones in the milk itself. Any IGF-1 that may be present in foods such as dairy products is broken down during digestion and doesn’t have any biological effect in humans. The amount of protein you take in, on the other hand, has a more direct effect on IGF-1 levels.
Dairy contains protein, of course, but so does meat, fish, beans, legumes, and so on.
What does IGF-1 Do?
IGF-1 (insulin-like growth factor-1) is critical to proper growth when we are kids. When we reach adulthood and stop growing (taller, anyway), levels of IGF-1 decline, but not to zero. The hormone continues to play an important role throughout life, helping to preserve bone and muscle tissue, for example. (That could explain why a higher protein intake is associated with stronger bones.)
Growth is a double-edged sword, however. We want to promote the growth of bones and muscles but we certainly don’t want to promote the growth of cancer cells or tumors. There is some epidemiological evidence that shows an association between higher IGF-1 levels in the blood and higher cancer risks. But correlation is not causation. We don’t know whether high IGF-1 levels promote cancer or are an unrelated phenomenon.
Does Dairy Promote Cancer?
I previously reviewed the literature to see if there was a link between dairy intake and breast cancer in humans–and found none. For prostate cancer, men with the highest intake of dairy products (more than 4 servings per day) have a slightly increased risk.
Dairy products–if you choose to consume them–can be a good source of protein and calcium, which help to maintain strong bones and muscles as we age. And when consumed in moderation , they appear to pose little risk of cancer.
See also: How much dairy is too much?