However even though studies have shown this to be true , the FDA says that there is no evidence of biologically active growth hormone being absorbed by humans. In other words, although rBGH appears at higher levels in milk from treated cows, the FDA is not convinced it has any effect on humans who drink it.
Other public interest groups and governments have reached different conclusions. The FDA, for its part, says that the thyroid and prostate changes were the same in the test and control groups, and that Canadian reviewers simply misinterpreted the study results.
IGF-1 occurs naturally in both cattle and humans, but there have been possible connections drawn between higher levels of IGF-1 in humans and increased risk of some cancers , including studies linking IGF-1 to breast cancer. Additionally, after rBGH was approved in , the FDA ignored appeals from consumers, food safety organizations, and scientists to reverse its approval of the hormone, or to even require labeling of foods containing rBGH. While the potential ramifications of rBGH use for humans are certainly worth examining, so are the risks for the cows being given them.
In cows treated with rBGH, health problems often develop. According to a meta-analysis published in , injecting cows with rBGH increases the risk of three important health conditions:. An increased risk of mastitis is particularly concerning—for cows and the rest of the world—because these infections are treated with antibiotics, and the high use of antibiotics in livestock can create antibiotic-resistant bacteria.
Given that growth hormones are produced naturally by cows, they can be expected to register at some level in all milk samples. On top of this, BGH is not active in humans, so even if it were absorbed from drinking milk, it wouldn't be expected to cause health effects. Of greater concern is the fact that milk from rBGH-treated cows has higher levels of IGF-1, a hormone that normally helps some types of cells to grow.
Several studies have found that IGF-1 levels at the high end of the normal range may influence the development of certain tumors. Some early studies found a relationship between blood levels of IGF-1 and the development of prostate , breast , colorectal , and other cancers, but later studies have failed to confirm these reports or have found weaker relationships.
While there may be a link between IGF-1 blood levels and cancer, the exact nature of this link remains unclear. But this same finding has also been reported in people who drink soy milk. This suggests that the increase in IGF-1 may not be specific to cow's milk, and may be caused by protein, minerals, or some other factors in milk unrelated to rBGH. There have been no direct comparisons of IGF-1 levels in people who drink ordinary cow's milk vs.
At this time, it is not clear that drinking milk, produced with or without rBGH treatment, increases blood IGF-1 levels into a range that might be of concern regarding cancer risk or other health effects.
These were:. At least 8 other national and international review committees have evaluated the evidence concerning potential health effects of rBGH on humans and dairy cows. Our Work. Take Action. Press Releases. Healthy Home. About rbGH. Share this:.
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