Milk and Breast Cancer

On the blog posts titled "Hormone Imbalance" and "Estrogen and Breast Cancer" I wrote that estrogen is a stimulating hormone and that it promotes the growth of cells. And on the post "Could Sugar Be the Fuel of Cancer Cells", it says that a hormone called insulin like growth factor (IGF-1) promotes cancer cells growth. So you can see that I've been researching and studying the subject of hormonal changes, specially in women for a long time. And now I'd like to present a little on how diet can affect especially, estrogen and IGF-1 levels and one of its possible consequence - cancer.

Lewis Cantley, director of the Cancer Center at Beth Israel Deaconess Medical Center at Harvard Medical School, says that up to 80 percent of all human cancers are driven by either mutations or environmental factors that work to enhance or mimic the effect of insulin on the incipient tumor cells. Cantley is now studying precisely this link between a specific insulin-signaling gene (known technically as PI3K, which is the gene that estrogen activates) and tumor development in breast and other cancers common to women. 

Foods rich in, or that increases the circulating level of IGF-1 and estrogen in the blood may highly increase someone's risk of developing cancer, especially cancers of the breast, lung and colon. So which food do you think has high levels of IGF-1 and estrogen at the same time? COW'S MILK!!!

The primary biologic purpose of cow’s milk is to cause growth—from a 60 pound calf to a 600 pound cow in less than 8 months. And the main ingredient in milk that causes this growth spurt is the powerful hormone IGF-1. But, when cow’s milk is fed to people, their IGF-1 levels also increase. Studies show a 10% increase in IGF-1 levels in adolescent girls from one pint daily and the same 10% increase for postmenopausal women from 3 servings per day of nonfat milk or 1% milk. This rise in IGF-1 level is an important reason for the “bone-building” effects of cow’s milk. But IGF-1 promotes undesirable growth too—like cancer growth and accelerated aging. Increased serum IGF-I concentrations have also been found in women with breast cancer compared to healthy women.
 

Milk also raises estrogen levels in a person’s body. The main source of this estrogen is the modern factory farming practice of continuously milking cows throughout pregnancy. As gestation progresses the estrogen content of milk increases from 15 pg/ml to 1000 pg/ml. 


 

Estrogen Production in Cows
Non-pregnant	15 pg/ml
First half of pregnancy	151 pg/ml
Last days of pregnancy	1000 pg/ml

The American Dietetic Association reports that breast cancer is most prevalent in countries where women consume high fat and animal based diet. The saturated fat in meat and milk products increases the risk of breast cancer because fat cells produce estrogen, therefore the more fat a woman has, the more estrogen she is likely to be making in her body, even after menopause. 

In the American Journal of Clinical Nutrition, Patricia Moorman has presented some hypothesis on how milk is related to breast cancer. Here are some points of the article that summarizes very well the relationship between milk consumption and breast cancer:

• A pregnant cow produces extra estrogen which ends up in her milk, and excess estrogen is known to make breast cancer cells multiply

• Fat in milk causes the release of excess estrogen in the woman's body

• The body uses fiber to eliminate estrogen, and milk contains no fiber.

• Mother's milk, either human or cow, helps the tiny baby to grow rapidly. It may be that the growth factors in milk, such as insulin-like growth factor (IGF-1), are encouraging the growth of cancer cells. In test tube studies, IGF-1 was found to accelerate the growth of breast cancer cells, and this compound may be more potent than estrogen in this regard. Bovine growth hormone (BGH) is now being given to cows to boost their milk production, as well as the dairy farmers' profits, and cows receiving BGH produce two to four times more IGF-1 than normal.

• Finally, milk contains pesticides and industrial pollutants. Breast cancer deaths declined in Israel when three carcinogens found in Israeli milk were banned.