Vitamin D for Cancer Prevention?
Reviewers Recommend Vitamin D Dose That's Far Above Recommended Level
Sept. 5, 2007 -- Getting enough vitamin D might cut colon cancer and breast
cancer in North America, according to a new research review.
The reviewers suggest that adults should daily take 2,000 international
units (IU) of vitamin D -- in a form called vitamin D3 (cholecalciferol) -- to
help prevent some cancers, including colon cancer and breast cancer.
But that's not a prescription or a guarantee. The review is based on
observational studies, which didn't directly test vitamin D for cancer
The 2,000-IU daily dose of vitamin D suggested by the reviewers is currently
considered the "tolerable upper limit" for vitamin D, according to the
National Academy of Sciences' Institute of Medicine (IOM).
The IOM hasn't set a "recommended intake" for vitamin D. But it has
previously determined that "adequate intake" of vitamin D is 200
IU per day for the first 50 years of life, 400 IU per day from 51-70, and 600
IU per day after age 71.
Vitamin D and Cancer Review
The new research review on vitamin D and cancer comes from scientists
including Cedric Garland, DrPH, of the University of California at San Diego's
family and preventive medicine department.
They cite 29 observational studies in their report, which appears in the
journal Nutrition Reviews.
Garland and colleagues combined data from the observational studies. They
conclude that in North America, "a projected 50% reduction in colon cancer
incidence would require a universal intake of 2,000 IU per day of vitamin
"A similar reduction in breast cancer incidence would require 3,500 IU
per day," write the reviewers, cautioning that such a dose exceeds the
Institute of Medicine's tolerable upper limit for vitamin D.
Vitamin D may help prevent cancer in several ways, including maintaining
healthy cells with normal life spans, discouraging out-of-control cell
reproduction, and hindering the formation of new blood vessels for tumors,
according to the reviewers.
Vitamin D doesn't just come in supplements. It's also found in some foods --
including salmon, tuna, and some fortified dairy products and
The body also makes vitamin D when exposed to sunshine. Garland's team
recommends getting three to 15 minutes of sun exposure on sunny days, with 40%
of the skin exposed without sunscreen.