We know vitamin D is good for us — it helps keep our bones strong and supports our immune system. But some 42 percent of the U.S. population doesn’t get enough of the sunshine vitamin. Those living in colder climates can’t get their daily sun dosage from November through April because of the sun’s angle and strength, and are often bundled up against the cold so much that the little bit of skin that is exposed is too small to absorb daily requirements. Perhaps surprisingly, in regions where it’s easier to get year-round sun exposure, fewer people get breast cancer than in colder regions, according to a review of multiple studies in Environmental Health Perspectives in 2020.
Because of these regional differences, scientists have looked at link between vitamin D and breast cancer for years. While there have been reports that suggested vitamin D could prevent breast cancer, the studies in people are unclear. A scientific review of dozens of studies published in Nature in 2018 found inconclusive results overall. The meta-analysis concluded high levels of vitamin D in younger women has a protective effect, but researchers wrote they could not conclude whether taking vitamin D supplements have any preventative benefit.
