Hate Exercise? Blame It On Mom’s Shampoo.

From the depths of PubMed to the most amateur lifestyle blog, there is perhaps one thing that scientists and health gurus can agree on: the importance of exercise. From kindergarten gym classes to undergraduate nutrition courses, we’ve been indoctrinated with the essentiality of regular exercise. But still, barely 20% of Americans over the age of 18 meet the CDC’s Physical Activity Guidelines for aerobic, physical, and muscle-strengthening activities. [1]


What happened to the other 80% of American adults? Is it lack of education? Lack of resources? Lack of time? Or maybe just pure laziness?


via GIPHY MTV | The Hills


From personal experience, one might easily point to any of these reasons. However, according to a recent article by The New York Times, the answer to those questions may in fact be: none of the above.


Health and fitness journalist Gretchen Reynolds, reviewed a new study for the journal, “Medicine & Science in Sports & Exercise,” that investigates the relationship between exercise behavior and phthalate exposure in utero. Phthalates are a group of chemicals, often referred to as plasticizers, which are used to make plastics pliable. [2] Reynolds explains that phthalates are also used as solvents in “a boggling array of everyday products,” so, “from food containers to shampoos and perfume, they are virtually ubiquitous in the environment and in our bloodstreams.” [3]



Andrea Fabry, It Takes Time, 2015.


Phthalates are known endocrine disruptors, and previous studies have shown that the chemicals can easily pass through the womb into an offspring. From this, and the link between sex hormones and activity levels, researchers at Texas A&M chose to investigate how disrupted levels of estrogen and testosterone caused by in-utero phthalate exposure might influence the offspring’s level of activity.


Reynolds reports that after mating pairs of healthy male and female mice, researchers injected one group of pregnant female mice with benzyl butyl phthalate at a level just above the safety threshold for humans, while the control group was injected with harmless oils. After birth, the mice pups were provided with running wheels to exercise at their will. While their body sizes and structure did not vary significantly, male mice exposed to the phthalate ran 20% less than their unexposed counterparts while exposed female mice ran 15% less. The exposed mice did not suffer from any obvious health complications that would limit their activity but instead, were inactive “by choice, not necessity.” [3] This choice, researchers proposed, seems to have been dictated by the hormonal disruptions caused by the phthalate exposure, given that exposed mice demonstrated lower levels of sex hormones persisting beyond early life.


As we all know, there can obviously be no human conclusions from this study, since, as Reynolds shrewdly remarks “mice are obviously not people.” However, the implication that phthalate-induced endocrine disruption in utero could have lifelong consequences on activity levels may just give us another possible explanation as to why so many of us fail to get out of bed for that dreadful morning run.



[1] http://www.cdc.gov/nchs/data/nhis/earlyrelease/earlyrelease201506_07.pdf
[2] http://www.cdc.gov/biomonitoring/phthalates_factsheet.html
[3]  http://well.blogs.nytimes.com/2016/06/29/could-environmental-toxins-shape-our-exercise-habits/?&moduleDetail=section-news-0&action=click&contentCollection=Health&region=Footer&module=MoreInSection&version=WhatsNext&contentID=WhatsNext&pgtype=Blogs&_r=0


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Elizabeth Borowiec

Elizabeth Borowiec is in her third year at Georgetown University, majoring in Biological Physics, and set to matriculate to the Georgetown School of Medicine Class of 2021. When she’s not studying—though sometimes while—she enjoys singing, playing the piano, exploring the nation’s capital and drinking Earl Grey tea.