HOW TO PREVENT CANCERS

The new report released today by the Institute of Medicine on recommended vitamin D intake is a bit like getting that shirt you wanted for your birthday, but it turned out to be the wrong color and the wrong size (report).  It’s sort of what you wanted but not really.

While the new report kicks up recommended intake of vitamin D to 600 IU daily for adults up to age 70 and 800 IU daily for those over 70, these amounts fall short of the levels shown in research studies that could have benefit for conditions such as heart disease and cancer^{1, 2, 4}.  Looking at colon cancer alone, studies have found that high levels of vitamin D could cut the risk of the disease in half compared to low levels⁴ (previous post).

And it's estimated that over half of all women, and over 40 percent of all men, in the United States have less than optimal blood levels of vitamin D, often suggested to be 75 nmol/dL of a type of circulating vitamin D called 25(OH)D ^{5, 6} .  Those prone to very low sun exposure or low vitamin D levels are even worse off:  the elderly, the very overweight, people with dark skin, and those who largely live in northern areas (where vitamin D-producing UV-B sunlight can be low for much of the year).

To reach beneficial blood levels of vitamin D, most people would need to take about 1000 IU per day, with those prone to lower levels taking perhaps 1500 IU per day.  This is well above the new guidelines of 600 per day for most adults.

The IOM report takes a typically conservative approach to assessing studies of potential benefits and potential risks related to vitamin D intake, as well as to the blood levels of vitamin D that qualify as “sufficient.” Such an approach often minimizes potential benefits while highlighting potential risks.  This can help safeguard the nation’s health from the zeitgeist of diet crazes, but when it comes to vitamin D it seems more like a missed opportunity.