Exposure to bisphenol A (BPA) and phthalates—chemicals found in many types of cosmetics, plastics, and food packaging—may reduce adults’ vitamin D levels, according to a study published today.

BPA, phthalates, and other endocrine-disrupting chemicals (EDCs) have previously been linked to health and reproductive problems, and appear to be especially risky for young children and pregnant women. But this is the first research to find a link between them and vitamin D levels in a large group of adults.

That’s important, say researchers, since vitamin D is known to be important for brain, bone, and heart health. Low levels in the blood have been linked to a whole host of problems, including mental decline in older adults, chronic migraines in young people, and worse outcomes in people with diabetes and cancer. (In many of these cases, doctors still don’t know if low vitamin D is a cause or a consequence.)

The study, published online by the Journal of Clinical Endocrinology & Metabolism, includes data from 4,667 adults who participated in a national health survey between 2005 and 2010. They also provided period blood and urine samples, which researchers analyzed to determine vitamin D levels and exposure to EDCs.

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When researchers compared these measures, they found that people who were exposed to large amounts of phthalates were more likely to have low vitamin D compared to those exposed to small amounts—an association that was especially true for women. They also found a link between BPA exposure and low vitamin D levels in women, but not in men.

In a press release, lead study author Lauren Johns said that “nearly every person on the planet” is exposed to BPA and phthalates, “so the possibility that these chemicals may even slightly reduce vitamin D levels has widespread implications for public health.” Johns is a PhD candidate at the University of Michigan School of Public Health.

In fact, she told Health, these finding may provide a clue as to how, exactly, EDCs are making people sick. “It is possible that this may be one pathway through which these chemicals may adversely impact health,” she says.

The body makes its own vitamin D when sunlight is absorbed through the skin; it can also get it from fortified foods or dietary supplements. In the body, vitamin D acts like a hormone, and is believed to play a role in regulating several important physiological processes. 

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The authors can’t be sure why EDC exposure seems to affect vitamin D levels, but they believe that the chemicals may alter vitamin D in the body through some of the same mechanisms they use to impact similar reproductive and thyroid hormones. More studies are needed, they say, to determine what implications their findings could have on public health.

So how do consumers protect themselves? It’s tricky, since EDCs are prevalent in so many products; a recent study even found that phthalates are lurking in household dust. And even when people try to shop smart—by choosing canned food that’s labeled BPA-free, for example—it’s not always possible to know whether a replacement chemical is really any safer.

Industry-wide bans have helped reduce levels of some EDCs in products like children’s toys over the last decade, research has shown, but at the same time, levels of others have increased.

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“The widespread use of these chemicals, and their alternatives, makes it difficult to avoid exposure,” Johns agrees. But she does have some suggestions for people concerned about their vitamin D levels, and their overall health. 

“It is possible to reduce exposure by limiting use of plastic-containing products, finding natural alternatives to personal-care products, and limiting consumption of heavily processed and packaged foods,” she says. You can also say no to fast food (which has been shown to contain phthalates), and avoid handling receipts (which are often coated with BPA) whenever possible.

And if you’re concerned about your vitamin D levels, talk to your healthcare provider. The latest government recommendations say that regular screenings for vitamin levels aren’t necessary, but your doctor can help you decide if you might benefit from getting yours checked, and from taking a supplement if necessary.