Women with high vitamin D levels in their blood following a breast cancer diagnosis are more likely to survive the disease, a new study said Thursday.
While the mechanisms for how vitamin D influences breast cancer outcomes are not well understood, researchers believed it may be related to its role in promoting normal mammary-cell development, and inhibiting the reproduction of and promoting the death of cancer cells.
The current study, published by the USjournal JAMA Oncology, included 1,666 women who were diagnosed with breast cancer between 2006 and 2013.
These participants provided blood samples within two months of diagnosis and answered questions about diet, lifestyle and other risk factors, with follow-ups at six months and at two, four, six and eight years.
Vitamin D is a nutrient best known for its role in maintaining healthy bones, and vitamin D deficiency has been associated with the risk for several cancers.
Common sources of vitamin D include sun exposure, fatty fish oils, vitamin supplements, and fortified milks and cereals.
"We found that women with the highest levels of vitamin D levels had about a 30 percent better likelihood of survival than women with the lowest levels of vitamin D,"senior author Lawrence Kushi at the Kaiser Permanent Northern California Division of Research, said in a statement.
Although the study did not examine the effects of vitamin D intake from foods versus supplements, Kushi noted that it supports the recommended daily levels of vitamin D -- 600 international units for those one to 70 years old and pregnant or breastfeeding women, and 800 international units for those over 71 years old.
"The more we know about vitamin D, the more we understand that it may play a key role in cancer prevention and prognosis," Kushi said. "This study adds to the evidence that vitamin D is an important nutrient."