3. Lower Risk of Cancer
In 1980 epidemiologists reported that low vitamin D levels were associated with a greater risk of developing colorectal cancer.
Since then, researchers from around the world have linked low vitamin D levels to a higher risk of breast, ovarian, kidney, pancreatic and aggressive prostate cancer.
Would vitamin D supplements or greater sun exposure help protect against these cancers? The answer is yes, according to research by Cedric F. Garland, DrPH, of the University of California, San Diego.
Garland and his colleagues calculated that the incidence of colon cancer in the United States and Canada could be cut in half if people took 2,000 IU of vitamin D daily, and that women would reduce the incidence of breast cancer by half if they took 3,500 IU of vitamin D daily.
How Much Should You Take?
So all this comes back to the questions: Should you take vitamin D? And if so, how much? Hereís the best advice culled from experts.
ē The ideal approach is to ask your doctor for a vitamin D blood test, which will eliminate the bulk of the guesswork ó but not all of it. Because of individual differences in absorption and use, people may need to take differing quantities of vitamin D to achieve a healthy blood level. Make sure your doctor orders a ď25-hydroxy vitamin DĒ test. Other tests might result in a false normal. Although levels below 30 ng/ml indicate a deficiency, many physicians havenít kept up with the research on vitamin D and believe that this level is just fine. The optimal level is at least 40 ng/ml and perhaps 50 ng/ml, says Heaney. But higher amounts, within reason, arenít necessarily bad. Surfers, lifeguards and people who spend a lot of time outdoors typically have levels of 70 to 90 ng/ml.
ē If you donít currently have a significant deficiency, and if during the summer you spend a lot of time in the sun, with at least your arms and legs exposed, and you are not always slathered with sunscreen, you probably donít need to take vitamin D supplements. Holick, who wrote The Vitamin D Solution (Hudson Street Press, 2010), suggests getting approximately 10 minutes of sun exposure (depending on time of day, season, latitudinal location and skin pigmentation) before applying sunscreen. Vitamin D made from the sun actually lasts longer in the body, compared with vitamin D from supplements or foods (also note that with the exception of wild salmon and shiitake mushrooms, most foods arenít great sources of vitamin D).
ē If itís fall, winter or early spring, if you donít get a lot of sun exposure, or if you know you are D-deficient, you should definitely take vitamin D supplements (most health pros recommend vitamin D3, also known as cholecalciferol). Your need will be greater if you are north of the latitude of Atlanta, since you will make little if any vitamin D from sun exposure during the months of November through March.
ē If you have not taken a vitamin D blood test and youíre looking for general guidelines, Holick suggests that children take 1,000 to 2,000 IU and adults take 2,000 to 3,000 IU daily. “The bottom line for me is that there is probably no evidence that these amounts pose any risk,” he says. Cannellís recommendation: Don’t drive yourself crazy with all the qualifications. “Just take 5,000 IU a day, unless youíre going outside to work or to the garden or beach.” The higher amount might be particularly helpful for people with a chronic illness, such as fibromyalgia, arthritis or lupus, adds Hunninghake. “These high doses of vitamin D, while generally safe, should be monitored with follow-up blood level [tests],” he says.
And what of the risks? For most people, vitamin D toxicity occurs after taking more than 40,000 IU daily for months, says Cannell. So as long as you’re being moderate in your intake, don’t sweat.