Interesting ... After writing about how high serum levels of vitamin D may be linked to pancreatic cancer last week, this report by the Institute of Medicine (IOM: responsible for setting recommended intake levels) is warning about over-supplementing with vitamin D, as well as calcium:
Dietary Reference Intakes For Calcium And Vitamin D, IOM, November 30, 2010
"Overall, the committee concludes that the majority of Americans and Canadians are receiving adequate amounts of both calcium and vitamin D. Further, there is emerging evidence that too much of these nutrients may be harmful."So they decided not to raise vitamin D intake levels after all, well, not too much, just a few hundred IUs.
Click to enlarge.
Vitamin D deficiency may be overstated:
"Before a few years ago, tests for vitamin D were conducted infrequently. In recent years, these tests have become more widely used, and confusion has grown among the public about how much vitamin D is necessary. Further, the measurements, or cut-points, of sufficiency and deficiency used by laboratories to report results have not been set based on rigorous scientific studies, and no central authority has determined which cut-points to use. A single individual might be deemed deficient or sufficient, depending on the laboratory where the blood is tested. The number of people with vitamin D deficiency in North America may be overestimated because many laboratories appear to be using cut-points that are much higher than the committee suggests is appropriate."In the end, according to the IOM, most adults require about 800 mg of calcium and 400 IUs of vitamin D a day (assuming "minimal sun exposure"). I really thought they'd go higher on the vitamin D.
"The committee concludes that once intakes of vitamin D surpass 4,000 IUs per day, the risk for harm begins to increase. Once intakes surpass 2,000 milligrams per day for calcium, the risk for harm also increases."
"Kidney stones have been associated with taking too much calcium from dietary supplements. Very high levels of vitamin D (above 10,000 IUs per day) are known to cause kidney and tissue damage."