Multiple studies have shown that vitamin D can reduce the risk of breast cancer; vitamin D is especially important for women with triple negative breast cancer, as they have been found to be more deficient in the vitamin than other cancer patients.
Natural sources of vitamin D are more effective than supplements, with the best source being UV rays from the sun. According to the National Institutes of Health, researchers recommend five to 30 minutes of sun exposure from 10 a.m. to 3 p.m. at least twice a week to the the face, arms, legs, or back without sunscreen.
However, those of us in sun-challenged areas of the country—a line above 42 degrees latitude, or roughly above the northern border of California and Boston—don’t get enough sun between November and February. Smog, shade, and cloud cover all reduce the sun’s effectiveness elsewhere. And UV rays cannot penetrate glass, so sitting in front of a window may feel good, but if offers little vitamin D benefit.
The NIH says the average adult can tolerate up to 2000 IUs of vitamin D a day. But where do we get it if not from the sun? Some of the best sources:
Cod liver oil (1 tablespoon): 1360 IU
Sockeye Salmon (3 ounces): 794 IU
Vitamin D-fortified milk (1 cup): 115-124 IU
Vitamin D-fortified orange juice (I cup): 100 IU
One egg yolk: 25 IU
See the entire list here.
If you cannot get enough natural vitamin D, go for supplements. Studies show that vitamin D3 is as much as three times as effective as other forms of vitamin D. A form of vitamin D known as Gemini 0097 is being studied by researchers at Rutgers for benefit to both hormone-positive and hormone-negative breast cancers, reducing the former by 60 percent and the latter by 50 percent. At this point, Gemini 0097 is still in the testing stage and is not yet available to consumers.