Bodybuilders Take Breast Cancer Drug

Tamoxifen, an endocrine therapy for women with breast cancer, is found in a supplement marketed to bodybuilders.

Written byJef Akst
| 1 min read

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Tamoxifen pillsWIKIMEDIA, NCIFor decades, some bodybuilders who’ve taken steroids to help increase their muscle mass have illegally purchased the breast cancer drug tamoxifen to prevent breast enlargement. But according to new research from Liverpool John Moores University in the U.K., others may simply have bought the dietary supplement Esto Suppress, which was found to contain the drug in three out of four samples tested by the investigators, who published their results last week (February 13) as a letter in the British Medical Journal (BMJ).

“Since the 2000s, a growing number of off-the-shelf ‘food,’ ‘herbal,’ or ‘dietary’ ‘supplements’—aimed at gym goers and people wanting to lose weight or enhance their sex lives—have contained pharmacologically active substances,” the authors wrote. “Most users will be unaware that they are taking these substances.”

The amount of tamoxifen varied by sample, with one sample containing 3.8 mg per pill. The suggested dose of Esto Suppress is two pills per day; when the drug is prescribed for early-stage breast cancer, patients typically take 20 mg a day. The researchers noted, however, that their samples were purchased two years ago, and it is not known whether the supplement still contains tamoxifen.

“This research highlights the need for consumers to be aware when choosing their sports supplements,” ...

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  • Jef (an unusual nickname for Jennifer) got her master’s degree from Indiana University in April 2009 studying the mating behavior of seahorses. After four years of diving off the Gulf Coast of Tampa and performing behavioral experiments at the Tennessee Aquarium in Chattanooga, she left research to pursue a career in science writing. As The Scientist's managing editor, Jef edited features and oversaw the production of the TS Digest and quarterly print magazine. In 2022, her feature on uterus transplantation earned first place in the trade category of the Awards for Excellence in Health Care Journalism. She is a member of the National Association of Science Writers.

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