Milk and Cancer Risk

Milk and Cancer Risk - How Foods Fight Cancer

Milk drinkers have more IGF-1 in their bloodstreams. IGF-1 is a powerful
stimulus for cancer cell growth.

To understand why dairy products might play a role in cancer, it helps to
remember their biological purpose. Milk is produced by mothers to support
the rapid growth of their newborns. It contains plenty of protein, fat,
and sugar (lactose), as well as dozens of hormones and other natural
chemical substances that direct infants’ growth and development. Milk
differs from species to species—cow’s milk is quite different in its nutrient
profile from human milk—but all mammals’ milk is designed to encourage
rapid growth.

After the age of weaning, of course, all mammals stop drinking their
mothers’ milk. A few thousand years ago, however, humans began to
domesticate animals and to consume milk taken from cows and a few
other mammals.

When humans drink cow’s milk, it causes some worrisome biological
changes in the body, one of which is a rise in the amount of insulin-like
growth factor 1 (IGF-1) in the bloodstream.3,4 IGF-1 is a powerful stimulus
for cancer cell growth. When breast cancer cells are mixed with IGF-1
in a test tube, for example, they grow rapidly.

Researchers have known for many years that men and women with higher levels of IGF-
1 in their blood are at higher risk for prostate and premenopausal breast cancer, respectively,
compared to those with lower levels.5,6 So one way that milk may influence cancer risk
is by increasing the amount of IGF-1 in the blood. Individuals who have been diagnosed
with cancer may be quite right to be concerned that milk drinking boosts IGF-1 levels in their
bloodstreams, given that IGF-1, in turn, can encourage cancer cell growth.

Milk causes other chemical changes in the body as well, some of which
relate to specific types of cancer. Generally speaking, these mechanisms relate
not only to the likelihood that cancer will strike, but also to how rapidly it
will grow and spread once it has occurred.