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DRI Dietary Reference Intakes Calcium Vitamin D
coupled with observational data suggesting that 400 International Units (IU) (10 μg) per day was adequate to maintain this level.
The ULs for vitamin D were especially challenging because available data have focused on very high levels of intake that cause intoxication and little is known about the effects of chronic excess intake at lower levels. The committee examined the existing data and followed an approach that would maximize public health protection. The observation that 10,000 IU (250 μg) of vitamin D per day was not associated with classic toxicity served as the starting point for adults; this value was corrected for uncertainty by taking into consideration emerging data on adverse outcomes (e.g., all-cause mortality), which appeared to present at intakes lower than those associated with classic toxicity and at serum 25OHD concentrations previously considered to be at the high end of physiological values. Possible ethnic/racial differences were taken into account as well. The UL for adults is used for 9 to 18 years olds, but is “scaled down” for children 1 to 8 years of age. Earlier studies remain the best basis for ULs for infants.
DIETARY INTAKE ASSESSMENT
Calcium remains a nutrient of concern given that median calcium intakes from foods in both the United States and Canada are close to the EAR values for most groups. In particular, girls 9 to 18 years of age are falling below desirable intakes when only food sources of calcium are considered, as are women over the age of 50 years. Available data from the United States on the total intake of calcium when dietary supplements are considered suggest that older women have noticeably increased calcium intakes with supplement. For girls, the increase in intake attributable to supplement use is small. No life stage groups exceeded the UL for calcium when foods alone were considered. However, when supplement use was taken into account (United States only), women at the 95th percentile of calcium intake appeared to be at risk for exceeding the UL. The data underscore the possible need to modestly increase calcium intake among older girls; among older women, a high calcium intake from supplements may be concerning.
Although daily median vitamin D intake from foods in both countries for all life stage groups was below the established reference value, these data should be considered in light of the average serum 25OHD concentrations. U.S. serum 25OHD concentrations on average were well above 40 nmol/L (16 ng/mL), the level established as consistent with an intake equivalent to the EAR; in fact, all mean serum 25OHD concentrations were above 50 nmol/L (20 ng/mL). In the case of serum 25OHD concentrations from Canadian surveys, mean serum 25OHD levels for all life stage groups were at or above 60 nmol/L (24 ng/mL). The fact that these values