Almost All Women With Breast Cancer Are Also Vitamin D Deficient

We all know someone who's been affected by breast cancer, so it shouldn't come as a surprise that it's the most common type of cancer worldwide. According to a 2022 review published in The Breast, breast cancer accounts for one in eight cancer diagnoses and resulted in a total of 2.3 million new cases in 2020. 

As common as this devastating cancer is, there's very little attention paid to its link to vitamin D status. And yet, up to 96%1 of the breast cancer population is also deficient in vitamin D, per a 2017 review published in Breast Cancer. 

While research on the exact mechanisms and pathways of the sunshine vitamin's effect on breast cancer are ongoing, evidence consistently shows a clear association between circulating vitamin D [i.e., 25(OH)D serum vitamin D levels] and breast cancer risk.

In a 2015 case-control study from Breast Cancer Research and Treatment, women deficient in vitamin D [i.e., with 25(OH)D levels below 20 ng/ml] had a 27% higher risk5 of breast cancer than women with sufficient vitamin D levels.

But while clinical vitamin D sufficiency is defined as 25(OH)D levels above 30 ng/ml, other research indicates that higher levels provide greater protection against breast cancer risk.

Case in point: In one pooled analysis from Anticancer Research, a serum 25(OH)D level of 47 ng/ml was found to lower breast cancer risk by 50%6.

Evidence suggests the average person needs to consume 5,000 IU of vitamin D3 per day to reach the goal serum level of 50 ng/ml. The problem? Food sources high in vitamin D don't offer enough to help you achieve this goal (unless you're drinking 50 glasses of milk a day, that is). 

And though it's nicknamed the "sunshine vitamin," most people don't get enough safe sun exposure to achieve optimal vitamin D status. Age, latitude, skin tone, season, climate, skin tone, and biological sex all impact one's ability to produce vitamin D from sun exposure, so it's not a reliable source for most.

A whopping 96% of the breast cancer population is also deficient in vitamin D. Science shows that achieving vitamin D sufficiency (specifically, serum levels of 47 ng/ml or higher) can help cut your breast cancer risk in half.