For women diagnosed with breast cancer, high vitamin D levels in the blood may be bound to have a better chance to survive and have tumors with less lethal characteristics, suggests a new study.
While the new study supports earlier research on vitamin D and cancer of the breast, it can not prove that the vitamin D level will improve outcomes for women with breast cancer.
“Overall, we found a 30 percent reduction in mortality associated with vitamin D levels at the time of the diagnosis,” said study lead author Song Yao, of the Roswell Park Cancer Institute in Buffalo, New York.
The researchers used data from an ongoing study of California women started in 2006. The women were usually registered within two months after the diagnosis with invasive breast cancer. icipants average age was around 59. They were evaluated when they entered the study and periodically thereafter.
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The women were divided into three approximately equally-sized groups, with approximately 520 participants, based on their blood levels of a marker for vitamin D.
The researchers found a low level in women with more advanced forms of cancer. The lowest levels were in women who had not yet entered menopause, and the diagnosis of triple-negative cancer, which has a tendency to poorer results than other forms of breast cancer.
Over an average of seven years follow-up, about 100 women with the lowest vitamin D levels died, compared to 76 women with the highest levels of vitamin D.
The women with the highest vitamin D levels were 28 percent less likely to die of any cause during the study than women with the lowest vitamin D levels, after accounting for tumor characteristics and other factors, the researchers report in JAMA Oncology.
The link was stronger in pre-menopausal women. In that group, high vitamin D levels were also bound to have a better chance of not having breast cancer come back, and not die.
Yao told Reuters Health that the a randomized controlled trial that is the gold standard of medical research, to investigate whether a high vitamin D ensures that women with breast cancer to live longer.
Dr. Wendy Chen, a breast cancer specialist at the Dana-Farber Cancer Institute in Boston, agreed that a trial would be necessary to say that there is a direct link.
“I would not be able to obtain a causal relationship from these data, because of all the things that are related to vitamin D and survive,” said Chen, who was not involved in the new research.
For example, she told Reuters Health, obesity can affect vitamin D levels and breast cancer prognosis.
Chen said that women with breast cancer who are currently on a low dose of vitamin D supplements should be allowed to stay during the treatment.
Vitamin D performs a number of functions in the body, but is best known for the help of the bones calcium. Other than exposure to the sun, one of the best sources of vitamin D is fatty fish such as salmon or tuna, according to the U.S. National Institutes of Health. Milk and other products, such as cereals and some beverages contain added vitamin D, too.
People need to get 600 international units (IU) of vitamin D per day in the age of 1 to 70, according to the Institute of Medicine. Older people should get 800 IU of vitamin every day.