Women with higher vitamin D levels in their bloodstream after a breast cancer diagnosis had significanly better long-term outcomes, according to a new study from Kaiser Permanente and Roswell Park Cancer Institute in Buffalo, New York.
While the new study supports previous research on vitamin D and breast cancer, it can't prove that increasing vitamin D blood level will improve outcomes for women with breast cancer.
The researchers used data from an ongoing study of California women started in 2006. Women were usually enrolled within two months of being diagnosed with invasive breast cancer. Participants' average age was about 59. They were evaluated when they entered the study and periodically afterward.
The women were split into three roughly groups, about 520 participants each, based on their blood levels of a marker for vitamin D.
The researchers found low levels among women with more advanced cancers. The lowest levels were in women who had not yet entered menopause and were diagnosed with triple-negative cancer, which tends to have worse outcomes than other types of breast cancers.
Women with highest vitamin D levels almost 30% less likely to die
Over an average of seven years of follow-up, about 100 women with the lowest vitamin D levels died, compared to 76 women with the highest level of vitamin D.
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 link was stronger among premenopausal women. In that group, high vitamin D levels were also tied to a better chance of not having breast cancer recur, and not dying from it.
The researchers noted it would take a randomized controlled trial, the gold-standard of medical research, to examine whether high vitamin D causes women with breast cancer to live longer.
Women with breast cancer who currently take low-dose vitamin D supplements should be able to continue during treatment, experts said.
How much vitamin D?
Vitamin D’s best-known role is helping the body absorb calcium and phosphorus from foods, nutrients critical for building and maintaining bone. Low levels of vitamin D can speed up bone loss and increase the risk of fractures.
The Institute of Medicine's recommendations for vitamin D intake are based on bone health. Adults are advised to consume 600 international units (IU) of vitamin D each day from ages 1 through 70. Older people should get 800 IU of the vitamin each day. The safe upper limit is 4000 IU per day.
Some people, though, may need more vitamin D to maintain a sufficient blood level.
How to get your vitamin D
Foods that provide vitamin D naturally, which are few and far between, include salmon (447 IU per 3 ounces) and tuna (154 IU per 3 ounces). Eggs (41 IU per yolk) and cheese (14 IU per 2 ounces of cheddar) provide a little. Fluid milk, many non-dairy beverages and some brands of orange juice are fortified with vitamin D (100 IU per one cup).
Most multivitamins contain 400 IU of vitamin D3 but some manufacturers have started adding 1000 IU. Single supplements of vitamin D typically come in 400 and 1000 IU doses.
All research on this web site is the property of Leslie Beck Nutrition Consulting Inc. and is protected by copyright. Keep in mind that research on these matters continues daily and is subject to change. The information presented is not intended as a substitute for medical treatment. It is intended to provide ongoing support of your healthy lifestyle practices.