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Vitamin D

What is the recommended intake for vitamin D?

Recommendations for vitamin D are provided in the Dietary Reference Intakes (DRIs) developed by the Institute of Medicine (IOM) of the National Academy of Sciences [4]. Dietary Reference Intakes is the general term for a set of reference values used for planning and assessing nutrient intake for healthy people. Three important types of reference values included in the DRIs are Recommended Dietary Allowances (RDA), Adequate Intakes (AI), and Tolerable Upper Intake Levels (UL). The RDA recommends the average daily intake that is sufficient to meet the nutrient requirements of nearly all (97-98%) healthy individuals in each age and gender group [4]. An AI is set when there is insufficient scientific data available to establish a RDA. AIs meet or exceed the amount needed to maintain a nutritional state of adequacy in nearly all members of a specific age and gender group. The UL, on the other hand, is the maximum daily intake unlikely to result in adverse health effects [4].

The IOM determined there was insufficient scientific information to establish a RDA for vitamin D. Instead, the recommended intake is listed as an Adequate Intake (AI), which represents the daily vitamin D intake that should maintain bone health and normal calcium metabolism in healthy people.

AIs for vitamin D may be listed on food and dietary supplement labels as either micrograms (μg) or International Units (IU). The biological activity of 1 μg vitamin D is equal to 40 IUs [4]. AIs for vitamin D for infants, children, and adults, are listed in table 2 in micrograms and IUs [4].

Table 2: Adequate Intake for vitamin D for infants, children, and adults

According to the IOM's report on the Dietary Reference Intakes for vitamin D, food consumption data suggest that median intakes of vitamin D for both younger and older women are below current recommendations [4]. Median intake refers to a statistical mid-point. Half of the population surveyed consumed more than the median intake while half consumed less. In this case, data suggest that more than 50% of younger and older women are not consuming recommended amounts of vitamin D.

In 2002, the vitamin D intakes of 1,546 non-Hispanic African American women and 1,426 non-Hispanic white women of reproductive age (15 to 49 years) were estimated by analyzing intake of milk and fortified cereals, two common dietary sources of vitamin D [16]. Blood levels of vitamin D were also examined in these groups. Data examined were from the National Health and Nutrition Examination Survey (NHANES) III survey, which interviewed people from randomly selected households all across the U.S. The prevalence of hypovitaminosis D, a term used to describe low blood levels of vitamin D, was 42.4% among African American women and 4.2% among white women. In both groups, blood levels of vitamin D were higher when milk or fortified cereals were consumed more than 3 times per week. Among African American women, the risk of hypovitaminosis D decreased as milk and fortified cereal intake increased. These numbers suggest that large numbers of African American women may not consume recommended amounts of vitamin D. More frequent intake of vitamin D fortified milk and fortified cereals may help prevent hypovitaminosis D in this group.

What is vitamin D?

What are the sources of vitamin D?

What is the recommended intake for vitamin D?

When can vitamin D deficiency occur?

What are some current issues and controversies about vitamin D?