Which Types of Milk Have the Most IGF-1?

Recombinant bovine growth hormone, or rBGH, is a synthetic hormone commonly injected into cows in the commercial dairy industry to increase milk production. Sometimes referred to as bovine somatotropin, or rBST, rBGH has sparked controversy and questions regarding the safety of drinking milk from cows treated with this hormone. One concern is its impact on insulinlike growth factor 1 -- a hormone normally found in your body.

The levels of IGF-1 in commercial milk have not been tested in recent years. However, the International Journal of Health Services published a paper in 1996 that stated IGF-1 levels are significantly higher in milk from cows treated with rBGH. That means that most traditionally farmed milk in the U.S. will contain elevated IGF-1. Some people question whether your body can digest IGF-1 through the intestinal tract. However, animal data suggest IGF-1 is indeed absorbed through the intestines and is biologically active, according to the paper.

IGF-1 is a hormone that promotes cell division and growth. As you age, its levels decline. While IGF-1 is necessary for growth in children and teens, it may not be good to have higher levels as you age. Clinical data indicates that in adults, higher IGF-1 levels are linked to an increased risk for cancer, according to the Physician's Committee for Responsible Medicine. In addition, the journal Aging Cell reported in its August 2014 issue that lower IGF-1 levels are associated with an increased life expectancy.

Your diet influences the level of IGF-1 in your blood, according to the PCRM. A diet high in calories or animal protein increases your IGF-1 levels. Milk appears to raise IGF-1 as well. The PCRM explains that evidence from clinical data found that drinking three 8-ounce glasses of milk for 12 weeks causes a 10 percent increase in IGF-1 levels. The concern is that if milk raises IGF-1 levels, then it may lead to an increased risk for cancer.

More studies are needed to determine whether drinking milk with a higher IGF-1 content is harmful to human health. In the meantime, if you're concerned about your exposure to IGF-1, choose brands that make their dairy products -- yogurt, ice cream and cheese -- and get their milk from farmers that do not treat their cows with rBGH. Check the product for a label that says "rBGH free" or "rBST free." Foods labeled certified organic are always rBGH-free.