Why should women who are nearing menopause be concerned about the new report by the Institute of Medicine (IOM) of the National Academies about intakes of calcium and vitamin D? Well, let’s start with kidney stones.
The IOM report’s authors noted that postmenopausal women who are taking calcium supplements may be consuming too much calcium, which increases their risk for kidney stones. Vitamin D consumption is more complicated. “While the average total intake of vitamin D is below the median requirement, national surveys show that average blood levels of vitamin D are above the 20 nanograms per milliliter that the IOM committee found to be the level that is needed for good bone health for practically all individuals,” the report authors stated. “These seemingly inconsistent data suggest that sun exposure currently contributes meaningful amounts of vitamin D to North Americans and indicates that a majority of the population is meeting its needs for vitamin D. Nonetheless, some groups – particularly those who are older and living in institutions or who have dark skin pigmentation – may be at increased risk for getting too little vitamin D.”
So what should you be aiming for? The Institute now recommends that most adults take 600 international units of vitamin D a day while adults over 70 need 800 international units. While that’s more than the previous recommendation of 400 units for people over 50, it is much less than the daily doses of 1,000 to 4,000 units that advocates often suggest, according to a story by NPR’s Richard Knox. As far as calcium is concerned, adults up to age 50 need 1,000 milligrams daily. However, once women reach 51 years of age, they need to get 1,200 milligrams daily.
The committee set an upper level intake for both calcium (2,500 IU for women ages 31-50 and 2,000 IU for women 51-70) and vitamin D (4000 IU), but noted that this information should not be misunderstood as a target that people should strive to consume. “While these values vary somewhat by age…the committee concludes that once intakes of vitamin D surpass 4,000 IUs per day, the risk for harm begins to increase,” the report authors wrote. “Once intakes surpass 2,000 milligrams per day for calcium, the risk for harm also increases.”
NPR’s Knox explained, “The Institute of Medicine experts worry that taking vitamin D in large doses over a long period might harm some people. The evidence is inconclusive, but the panel points to studies hinting at higher levels of pancreatic and esophageal cancer. Panelists say there’s reason to worry about excess deposits of calcium in arteries from too much vitamin D.” A New York Times story reported an additional warning that high levels of vitamin D can increase the risk for bone fractures and the overall death rate. “While those studies are not conclusive, any risk looms large when there is no demonstrable benefit,” New York Times report Gina Kolata wrote.