The growth hormone was developed using recombinant DNA technology, a feat of genetic engineering in which naturally occurring genes are “recombined” to create virtually identical versions of the originals. Of course, it’s the “virtually” part that gets people upset. But the same technology has successfully yielded new vaccines and insulin products. Recombinant bST (sometimes written rBST) is manufactured in the U.S. by Monsanto under the name Posilac.

The risks of drinking milk from injected cows are unsubstantiated.

A leading criticism is that recombinant bST increases an insulin-like hormone in cows and cow milk, and that increased levels of the same hormone in humans have been associated with cancer. Cornell University’s Dale Bauman, former president of the American Society for Nutrition, helped us unpack the facts regarding this hormone, IGF-1. Bauman has been on the front lines of the bST controversy since the beginning.

“The amount of IGF-1 in milk is insignificant compared to the amount already produced in our bodies every day,” he asserts. “We swallow it in our saliva, and the amount we swallow daily is equal to the amount of IGF-1 in 95 quarts of milk. The amount produced in our whole body every day is equal the amount in 3,000 quarts of milk.”

Bauman further explains—and the American Cancer Society concurs—that there is no cause-and-effect chain linking bST, high levels of IGF-1, and cancer. “In fact, elevated levels are actually to be expected [when cancer is present] because IGF-1 is involved the turnover and repair of cells, including tumor cells.”

No one has been able to determine any differences in treated cows or in their milk.

“If one cow was treated with bST and you tested every cow in the herd, you could not determine any difference in the milk of the treated cow. There really is no difference that can be tested,” says Bauman. He and a team of nutritional biochemists analyzed over 200 herds—and over 200,000 lactations—looking for bST-related problems and came up empty-handed.

“We compared the five years before and five years after bST was used, analyzing herds that did and did not use it. We looked at all sorts of indexes for animal health, infection, health problems, reproduction. … There just were no differences. The only distinction was that in herds that used bST, the cows gave more milk per day and were more efficient in their use of nutrients.”

It is established that bovine growth hormones are harmless in the human body.

Back in the early 1960s, biotechnologists had hoped that growth hormones from cows might be used to treat a certain type of dwarfism, just as insulin from pigs was being used to treat diabetes. To test the theory, bovine somatotropin was injected directly into the bloodstream of human subjects. It was found to be biologically inactive. The human body simply broke down and absorbed the bST with no consequence.

Experiments in recombinant DNA were in their infancy at the time and withstood close evaluations by virtually every regulatory agency concerned with human health. To date, not even staunch opponents of recombinant bST can cite a known hazard.

Growth hormones are not steroids.

Some confusion arises around the term “growth hormone.” Human growth hormones come with their own distinct set of risks. But neither bovine growth hormone nor human growth hormone is a type of steroid. In fact, the corticosteroids sometimes used by bodybuilders and athletes actually stunt growth.

Milk cartons are designed to sell milk.

Food and Drug Administration regulations state that the labels on milk cartons must be truthful. Cartons can advertise that the milk is produced with no added growth hormones, appealing to the sensibilities of many consumers (especially as the $2 billion organic market thrives).