Can Soap Lower Testosterone Levels?
Could your soap or shampoo be lowering your testosterone levels? According to a new study in the Journal of Clinical Endocrinology & Metabolism, it’s a possibility.
Study results showed that men, women, and children exposed to high levels of chemicals commonly found in plastics and some personal care products showed lower testosterone levels in their blood compared to those with less exposure.
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Designed to make plastics more flexible but durable, phthalates can be found in detergents, vinyl flooring, adhesives, raincoats, and various soaps, shampoos, hair sprays, and nail polishes.
“The statistically significant associations between lower testosterone and phthalates we observed were within phthalate exposure levels that are commonly found among the general population,” says lead study author John D. Meeker, MS, ScD, of the University of Michigan’s School of Public Health in Ann Arbor, Mich.
Meeker and his co-author, Kelly K. Ferguson, PhD, conducted a cross-sectional study to examine phthalate exposure and testosterone levels in 2,208 people who participated in the US National Health and Nutrition Examination Survey, 2011-2012.
The researchers found associations between markers of phthalate exposure and testosterone levels among multiple age groups and in both sexes, including children—6- to 12-year-old boys and girls as well as girls ages 12 to 20.
“One surprising finding was that we did not observe significant associations among men ages 20 to 40, which is an age group for which previous research has reported a relationship,” Meeker says. “We were also surprised that associations in women ages 40 to 60 were among the strongest for most types of phthalates studied.”
Specifically, increased phthalate concentrations were associated with a 10.8% to 24% decline in testosterone levels among this age group in females. In boys ages 6 to 12, increased concentrations of metabolites of di-(2-ethylhexyl) phthalate were linked to a 24% to 34.1% drop in testosterone levels.
Due to the study’s cross-sectional design, Meeker says they were unable to conclude causation at this time. “Phthalates have been found to be anti-androgenic in animal and in vitro studies through a number of possible specific mechanisms,” he says. “We still don’t know how this may be happening in males or females at different life stages in humans, and it is possible that the different specific phthalate chemicals may be acting through differing or multiple mechanisms simultaneously.”
While there are still many unknowns, the authors suggest individuals and policymakers may want to take steps to limit exposure to these products, given the growing evidence of associated adverse health effects.
“Because our study was conducted on the population level, it is difficult to interpret how our findings might impact the individual, and some individuals may be more susceptible than others,” Meeker says. “Things are also complicated by the fact that most products that contain phthalates aren’t labeled as such, making it very difficult for clinicians to be able to make sound recommendations for patients to avoid or reduce exposure.”
Meeker and Ferguson plan to continue studying the potential endocrine and downstream health effects of exposure to phthalates and other commonly encountered chemicals in multiple human populations at various life stages.
—Colleen Mullarkey
Reference
Meeker JD, Ferguson KK. Urinary phthalate metabolites are associated with decreased serum testosterone in men, women and children from NHANES 2011-2012. J Clin Endocrinol Metab. 2014 Aug 14. [Epub ahead of print].