Vitamin D may help women fight breast cancer, new research suggests.
Women who had higher vitamin D levels when they were diagnosed with breast cancer fared significantly better than those with lower levels, according to the study, published online Nov. 10 in the peer-reviewed journal JAMA Oncology.
The researchers, from Kaiser Permanente and the Roswell Park Cancer Institute, believe the vitamin may promote normal mammary-cell development, while influencing cancer cells to stop reproducing and die.
Women with the highest levels of vitamin D had about a 30 percent better likelihood of survival than women with the lowest levels, researcher Lawrence H. Kushi said in a release.
“The more we know about vitamin D, the more we understand that it may play a key role in cancer prevention and prognosis,” he said.
Sources of vitamin D include sun exposure, fatty fish oils, vitamin supplements, and fortified milks and cereals.
The nutrient promotes calcium absorption, but it appears to also play a role in cancer risk and outcomes. In previous studies, researchers have found that people who are deficient in vitamin D are at higher risk of developing some types of cancer.
For the breast cancer study, researchers analyzed data from 1,666 Northern California patients who provided blood samples within two months of being diagnosed, between 2006 and 2013.
The study participants also answered questions about diet, lifestyle and other risk factors, and researchers followed up with them in 6 months and in 2, 4, 6 and 8 years.
Scientists adjusted the data for possible factors that can influence vitamin D levels, such as age, obesity, race and ethnicity, socioeconomic status and some tumor characteristics that are known to influence breast cancer outcomes.
A grant from the National Cancer Institute funded the research.