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Breast Cancer Health Center

Vitamin D, Calcium vs. Breast Cancer

Study Shows Vitamin D and Calcium in Diet May Lower Breast Cancer Risk
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What About the Sun

Current dietary recommendations call for people aged 50 and under to consume just 200 international units (IU) of vitamin D a day, with 400 IU recommended for those between the ages of 51 and 70, and 600 IU recommended after age 70.

Many experts now agree that these levels are too low. Longtime vitamin D researcher Cedric Garland, DrPH, says most people should get between 1,000 IU to 1,500 IU a day.

Excessive vitamin D can lead to toxicity. You should talk to your doctor about the use of supplements prior to taking them.

Dairy products and oily fish like salmon and tuna are some of the best food sources for vitamin D, but it would be difficult to get that much vitamin D in foods alone.

The easiest way for the body to get vitamin D is through sun exposure, because ultraviolet rays from the sun trigger the natural synthesis of vitamin D.

An 8-ounce glass of milk contains only 100 IU of vitamin D. By comparison, someone who spends 10 to 15 minutes in the sun on a sunny day without sunscreen can absorb 2,000 to 5,000 IU of vitamin D if 40% of their body is exposed, Garland says.

Recommending sun exposure is controversial because of the risk of skin cancer, and Garland tells WebMD that it is possible to get all the vitamin D the body needs through foods and dietary supplements.

"Ideally a mix is good, with some vitamin D coming from food, some from supplements, and some from sun if people can handle sunlight," he says.

Considering the Evidence

The American Cancer Society, the National Council on Skin Cancer Prevention, and other interested health groups from the U.S. and Canada met early last year to consider the evidence on sun exposure, vitamin D, and health.

The coalition concluded that the evidence is "strong" linking vitamin D to a decreased risk of bone fractures in the elderly. With regard to cancer risk, the group concluded that "a growing body of evidence" suggests a protective benefit for some cancers.

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