A study suggests a link between higher vitamin D levels in the blood and better breast cancer survival.
The researchers found that women diagnosed with breast cancer who had higher-than-average vitamin D levels were much more likely to survive breast cancer than women who had the lowest vitamin D levels.
The study was published in the March 2014 issue of Anticancer Research. Read “Meta-analysis of Vitamin D Sufficiency for Improving Survival of Patients with Breast Cancer.”
The study was a meta-analysis -- a study that combines and analyzes the results of many earlier studies. In this case, the results of 4,443 women in five studies published between 2009 and 2013 were analyzed. All the studies looked at the effect of vitamin D levels on breast cancer survival rates.
Earlier studies by the same lead researcher, Cedric Garland, professor of family and preventive medicine at the University of California-San Diego, have suggested that low vitamin D levels are linked to a higher risk of breast cancer in premenopausal women. So Dr. Garland wondered if vitamin D also might affect breast cancer survival rates.
The researchers put the women into five groups based on their blood levels of vitamin D. The highest vitamin D levels were 30 ng/ml (nanograms/milliliter) or more and the lowest were 17 ng/ml or less. Vitamin D researchers recommend a level of 40-60 ng/ml for adults. The researchers pointed out that about half the women in the United States diagnosed with breast cancer have a vitamin D level that’s higher than 17/ng/ml and half have vitamin D levels that are lower.
The researchers found that women with the high levels of vitamin D had a 44% lower risk of dying from breast cancer than women who had the lowest levels.
It’s not completely clear how vitamin D affects breast cancer survival. The researchers who did this study said that vitamin D influences how breast cancer cells divide and grow. It seems that vitamin D turns on a protein that that blocks cells from dividing quickly. If cancer tumor cells have vitamin D receptors, they don’t grow as quickly.
While the results of this study are encouraging, more research is needed before vitamin D supplements routinely become part of breast cancer treatment. It’s very important to talk to your doctor before you start taking any vitamin D supplements. Taking too much vitamin D can be harmful. Vitamin D supplements should be taken only when your vitamin D levels are too low based on blood work done by a medical professional.
You might want to ask your doctor about the results of this study and whether checking your vitamin D levels makes sense for your unique situation. If your vitamin D level is low, you and your doctor can decide if a vitamin D supplement is right for you. You also can ask your doctor about getting more direct sunlight exposure. Even short periods of direct peak sun exposure -- 15 minutes three times a week, for example -- can give you more than the recommended daily amount of vitamin D. It’s also impossible to overdose on vitamin D from the sun. Still, while sun exposure offers vitamin D benefits, it does have risks. Sun exposure can increase your risk of skin cancer, including melanoma, the most dangerous type.
For more information on vitamin D levels and how they can affect breast cancer, visit the Low Vitamin D Levels page in the Breastcancer.org Lower Your Risk section.