Posted on behalf of Tiffany O’Callaghan
A new report concludes that huge doses of the vitamin D are unwarranted and may even be harmful, and it suggests that most Americans and Canadians aren’t suffering from a deficiency in the “sunshine vitamin”. The Institute of Medicine (IOM) report analyzed findings from more than 1,000 studies of vitamin D and calcium intake.
In recent years, there have been a flurry of studies examining the potential benefits of vitamin D for everything from helping equip the immune system to fight infections to potentially inhibiting the growth of cancerous cells. Yet all this research has failed to indicate just how much vitamin D is needed to stave off deficiency. The last recommendations from the IOM released in 1997 suggested that, depending on age, 200 to 600 international units (IUs) of vitamin D was an “adequate intake” to maintain health.
Yet, as the Associated Press points out, as more studies have emerged suggesting protective benefits, some advocates have recommended that people consume amounts as high as 2,000 IUs per day, and many supplements are now sold in doses of 1,000 IUs.
The new report goes beyond the earlier adequate intake recommendations to establish dietary reference guidelines that are nowhere near those high levels. According to the report, people under age 70 need no more than 600 IUs of vitamin D per day, while seniors may require up to 800 IUs to maintain bone health.
Why the discrepancies? The report authors believe that inconsistency in blood tests — and in the cut off points used to determine deficiency — may have contributed to inconsistencies in recommendations as well as inflated numbers of people with D deficiency. (As they point out, whether or not someone was deemed deficient could have hinged on which lab processed the blood test.) In fact, according to the report, an analysis of vitamin D levels in national blood samples found that the majority of Americans and Canadians are getting plenty of both vitamin D and calcium.
Regarding further benefits of vitamin D — for cancer prevention or for treating diabetes, as some studies have suggested — the IOM committee pointed to inconsistent and conflicting results and found that there was not yet enough rigorous evidence to suggest a substantial benefit beyond the amount needed to maintain healthy bones.
Of course, with so many hopes hinging on vitamin D, these new recommendations certainly won’t put the subject to rest. Yet, until there is more definitive science beyond the benefits to bone health, the IOM committee recommends proceeding with caution. After all, as committee chair and nutrition expert A. Catharine Ross said in a statement about the findings: “Past cases such as hormone replacement therapy and high doses of beta carotene remind us that some therapies that seemed to show promise for treating or preventing health problems ultimately did not work out and even caused harm. This is why it is appropriate to approach emerging evidence about an intervention cautiously, but with an open mind.”
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