Natural growth hormones are essential in young animals and humans alike for healthy growth and development. However, the controversy lies in artificial growth hormones that are approved for use to enhance the growth rate of cattle, poultry and other animals. These hormones are also used to increase milk production and may find their way into our food supply in more ways than one. While growth hormones increase profits for the food industry, further clinical research is needed to determine how safe and healthy they are.
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Types of Hormone
Hormones are present in most animal products including beef and poultry. They are injected directly into the animals or added to their feed to enhance the amount of eggs, dairy and meat produced. These synthetic hormones include recombinant bovine growth hormone, rbGH, which is also called bovine somatotropin, BST. This hormone is used to promote milk production in cows. The steroid hormones estrogen, progesterone and testosterone are also given to cattle and other animals to promote growth and development.
Growth Hormones in Milk
According to the Food and Drug Administration, the amount of hormones that filter into animal products such as milk and dairy is safe for human consumption. However, some researchers state that milk that comes from cows that are treated with recombinant bovine growth hormones contain much higher levels of hormones. (3) However, the Food and Drug Administration concluded that bovine growth hormones that are given to cows are based on natural hormones found in cattle. Growth hormones are natural proteins that are produced in the pituitary gland of both animals and humans. (2) The FDA approved the use of these growth hormones in 1993 after their assessment that milk from treated cows is safe and healthy. (2)
Insulin-like Growth Factor
The hormone insulin-like Growth Factor-1 or IGF-1 is also naturally present in both animals and humans. Synthetic varieties may also be given to cattle to increase milk production, bone growth and meat production. (3) Since this growth hormone is found in humans, it was assumed to be safe to get from food sources such as meat and dairy. (3) However, because IGF-1 stimulates cell division, it may be linked to an increase of certain types of cancers. (3) The FDA reports that milk from treated cows and milk from untreated, both contain the same amount of IGF-1. (3)
A study published in the Journal of Clinical Oncology in 1999 found that eating foods with natural or synthetic insulin-like growth factor-1, IGF-1, may be linked to an increase in certain cancers including prostate, breast and colon cancers. (1) Foods with this hormone such as meat, fats and oils, raise the level of IGF-1 in the blood and may increase the risk of several diseases including diabetes. (1 all under abstract) However, further clinical studies are needed to determine the link between synthetic growth hormones in foods and disease risk. (1) Another review published in 2009 in "Medical Hypotheses" reported that drinking milk from treated cows during pregnancy may affect the health of the infant in its adult years. (4)