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  • Writer's pictureAlan Frischer, MD, MPH

Hormones in Food

Growth in humans and other animals is stimulated by naturally produced growth hormones. In the 1950s, the FDA approved the use of artificial growth hormones to enhance the growth rate of cattle and poultry, as well as to increase egg, dairy, and meat production.

Artificial growth hormones are quite effective at expanding our food supply and increasing profits for the food industry, but just how safe is it when we end up consuming them in the foods we eat? Concerns include cancer, early puberty in girls, and other issues. Consumer advocates have fought for years to support a ban similar to one in Europe, where regulations are generally more stringent.

One of the earliest artificial growth hormones to be approved was recombinant bovine growth hormone (RBGH), which increases milk production by dairy cows. Although RBGH has been shown to have no discernible direct effect in humans, is it possible that using growth hormone may increase the presence of another hormone, insulin-like growth factor (IGF)? One study found that milk from cows that had been given RBGH contains up to 10 times more IGF. Higher levels of IGF have been associated with an increased risk of breast, prostate and colon cancers in humans, and there may be a higher risk for diabetes as well.

However, even if consuming milk, other dairy, and some fish does indeed raise human blood levels of IGF, the amount appears to be negligible compared to the much higher amount that is naturally found in our body. To match the amount of IGF found in our saliva and digestive tract, we would need to drink about 95 quarts of milk, or eat 170 three-ounce servings of genetically modified salmon in a single day. It is possible, however, that even negligible increases might be enough to cause harm. Unfortunately, this question has not been conclusively answered yet.

Also dating from the 1950s, ranchers began to fatten up cattle with sex hormones, including estrogen. Today, most beef cows in the United States have an implant in an ear that delivers these hormones. One major concern is that once this beef enters the human food supply, it may lead to earlier puberty (note that today’s children, on average, enter puberty at a younger age than did those of a generation ago). However, once again, the amount of estrogen found in beef is tiny compared to the levels that are naturally in our bodies. Could even miniscule amounts of estrogen affect prepubescent girls and boys? One study showed that children who consumed the most protein from animal sources entered puberty about seven months earlier than those who consumed the least. However, it is still not clear whether this is purely a result of hormones added to the food supply, and not due to a number of other factors.

Note that organic meat, poultry, eggs and dairy products are certified by the U.S. Department of Agriculture to have no hormones or antibiotics added. These foods also come with a much higher price tag. While some experts recommend staying away from all hormone-treated beef and milk, others suggest simply limiting consumption of meat to twice per week and dairy to three servings per day.

The data gathered does not yet show conclusive serious harmful effects from the use of these hormones, but in my opinion, concerns are valid. More research is needed, and in the meantime, we each must come to our own conclusions as to whether changing our diets, or our shopping habits, is worth it.

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