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Posted by christian Henriquez on Thursday, May 3, 2012
What are hormones? Hormones are chemicals that are produced naturally in the bodies of all animals, including humans. They are chemical messages released into the blood by hormone-producing organs that travel to and affect different parts of the body. Hormones may be produced in small amounts, but they control important body functions such as growth, development and reproduction. Hormones can have different chemistry. They can be steroids or proteins. Steroid hormones are active in the body when eaten. For example, birth control pills are steroid hormones and can be taken orally. In contrast, protein hormones are broken down in the stomach, and lose their ability to act in the body when eaten. Therefore, ordinarily, protein hormones need to be injected into the body to have an effect. For example, insulin is a protein hormone. Diabetic patients need to be injected with insulin for treatment.
Why are consumers concerned about hormones in foods? While a variety of hormones are produced by our bodies and are essential for normal development of healthy tissues, synthetic steroid hormones used as pharmaceutical drugs, have been found to affect cancer risk. For example, diethylstilbestrol (DES), a synthetic estrogen drug used in the 1960s was withdrawn from use after it was found to increase the risk of vaginal cancer in daughters of treated women. Lifetime exposure to natural steroid hormone estrogen is also associated with an increased risk for breast cancer (see BCERF Fact Sheet #09 Estrogen and Breast Cancer Risk: What is the Relationship?). Hence, consumers are concerned about whether they are being exposed to hormones used to treat animals, and whether these hormones affect human health. We try to address this complex issue based on scientific evidence that is currently available.
Can steroid hormones in meat affect the age of puberty for girls? Early puberty in girls has been found to be associated with a higher risk for breast cancer. Height, weight, diet, exercise, and family history have all been found to influence age of puberty (see BCERF Fact Sheet #08, Childhood Life Events and the Risk of Breast Cancer). Steroid hormones in food were suspected to cause early puberty in girls in some reports. However, exposure to higher than natural levels of steroid hormones through hormone-treated meat or poultry has never been documented. Large epidemiological studies have not been done to see whether or not early puberty in developing girls is associated with having eaten growth hormone-treated foods. A concern about an increase in cases of girls reaching puberty or menarche early (at age eight or younger) in Puerto Rico, led to an investigation in the early 1980s by the Centers for Disease Control (CDC). Samples of meat and chicken from Puerto Rico were tested for steroid hormone residues. One laboratory found a chicken sample from a local market to have higher than normal level of estrogen. Also, residues of zeranol were reported in the blood of some of the girls who had reached puberty early. However, these results could not be verified by other laboratories. Following CDC's investigation, USDA tested 150 to 200 beef, poultry and milk samples from Puerto Rico in 1985, and found no residues of DES, zeranol or estrogen in these samples. In another study in Italy, steroid hormone residues in beef and poultry in school meals were suspected as the cause of breast enlargement in very young girls and boys. However, the suspect beef and poultry samples were not available to test for the presence of hormones. Without proof that exposure to higher levels of steroid hormones occurred through food, it is not possible to conclude whether or not eating hormone-treated meat or poultry caused the breast enlargement in these cases.
Conclusions Studies done so far do not provide evidence to state that hormone residues in meat or dairy products cause any human health effects. However, a conclusion on lack of human health effect can only be made after large-scale studies compare the health of people who eat meat or dairy products from hormone-treated animals, to people who eat a similar diet, but from untreated animals.
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