Up to 85 percent of all Americans have vitamin D levels that are too low.
Cancer cells and vitamin D
Instead of differentiating into normal cells, cancer cells divide so rapidly they do not turn into the specialized cells needed by the body. Instead they divide forever overwhelming the host with nonfunctional cancer cells.
Vitmain D3 helps regulate cell growth and differentiation. It also increases the self destruction of damaged cells, while at the same time reducing the growth of new blood vessels cancer cells need to spread.
Studies on vitamin D
A study by Dr. William Grant, internationally recognized research scientist and vitamin D expert, found that about 30 percent of cancer deaths – which amounts to two million worldwide and 200,000 in the United States – could be prevented each year with higher levels of vitamin D.
A large 2007 study supported a protective effect of dietary vitamin D on premenopausal breast cancer risk.
The findings of a 2008 study strongly suggested that post-menopausal women with a higher blood level of vitamin D had less breast cancer.
Additionally, another study presented at an American Society of Clinical Oncologists meeting found that breast cancer patients deficient in vitamin D were 94 percent more likely to have their cancer spread. However, low levels of vitamin D may be the result of disease related inflammation, not the cause.
Even though several previous studies had shown higher blood levels of vitamin D correlated with a 50 percent reduction in breast cancer risk, a large 2014 Lancet meta-analysis found no evidence of reduced cancer risk with vitamin D supplementation.
Sources of vitamin D
Food sources of vitamin D include cod liver oil, fish, dairy products, and egg yolk. However, the conversion of vitamin D to its active form can be inhibited by overconsumption of animal foods and high blood calcium levels.
Since the human body was designed to produce vitamin D in response to sunlight, 20 minutes of sun exposure without sun screen is the best way to get your “D”. Just make sure you never get burned. A study by UC San Diego researchers confirmed that UVB sun exposure was inversely associated with breast cancer rates.
Unfortunately, since the amount of sun reaching most of the U.S. is insufficient for less than half of the year, some supplementation may be necessary. Ask your doctor about taking a vitamin D supplement.
Only supplement with natural vitamin D3 (not the synthetic, highly inferior and more expensive vitamin D2 often covered by insurance). D2 does not work nearly as well.
How much D3 to take
Even though the RDA for vitamin D is 600 IU, some experts recommend getting 1,000 IU or even more. According to a 2010 study by Dr. Creighton Garland, from UC San Diego Moores Cancer Center: “daily intakes of vitamin D by adults in the range of 4000-8000 IU are needed to maintain blood levels of vitamin D metabolites.”
If you take vitamin D supplements, periodic blood tests must be done to make sure you are getting enough D3, but not too much.
Checkout Dr. Mercola’s article for more tips on vitamin D and cancer prevention.
DCIS Redefined 
Am I the only one concerned with the part about the Lancet Meta-analysis article mentioned above on low vit D levels perhaps being a RESULT of inflammation from disease and not a CAUSE? This would put a whole new light on taking vit D to reduce chances or help get rid of cancer..
Cynthia,
You bring up a good point.There really are no intervention studies that show by taking vitamin D supplements, the risk of cancer decreases. However, since there seems to be a correlation between low levels of vitamin D and disease, it might be prudent to get as much vitamin D as possible from sun exposure, which is the body’s way of supplying us with that vitamin naturally. Additionally the conversion of vitamin D to its active form can be inhibited by overconsumption of animal foods and high blood calcium levels. To get maximum D it would also be a good idea to incorporate a healthy low fat, low sugar whole foods primarily plant based diet.