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Serum 25-hydroxyvitamin D status of the US population: 1988-1994 compared with 2000-2004. Looker AC, Pfeiffer CM, Lacher DA, Schleicher RL, Picciano MF, Yetley EA. Am J Clin Nutr. 2008 Dec;88(6):1519-27. PMID: 19064511 doi:10.3945/ajcn.2008.26182 Conclusions: Overall, mean serum 25(OH)D was lower in 2000-2004 than 1988-1994. Assay changes unrelated to changes in vitamin D status accounted for much of the difference in most population groups. In an adult subgroup, combined changes in BMI, milk intake, and sun protection appeared to contribute to a real decline in vitamin D status. In summary, age-standardized mean serum 25(OH)D concentrations based on observed values were significantly lower in 2000-2004 than in 1988-1994 in all groups examined. Adjustment for assay changes noticeably reduced the difference between surveys. However, mean serum 25(OH)D concentrations remained significantly lower in males (except Mexican Americans) in NHANES 2000-2004 than in NHANES III, even after adjustment for assay differences. This remaining difference likely represents a real decline in vitamin D status. Changes in BMI, milk intake, and sun protection appeared to contribute to this decline in a subgroup of non-Hispanic white adults. The possibility that trends in overweight, sun protection, and milk intake may continue supports the need to continue monitoring the serum 25(OH)D status of the population

Upper levels of vitamin D intake were set at 50 microg/d (2000 IU/d) for all ages. Some individuals would require higher levels than these to achieve serum 25-hydroxyvitamin D concentrations for optimal calcium absorption. So much new information on vitamin D and health has been collected since the requirements were set in 1997 that this nutrient is likely the most in need of revised requirements. Vitamin D requirements: current and future. Weaver CM, Fleet JC. Am J Clin Nutr. 2004 Dec;80(6 Suppl):1735S-9S. Review. Erratum in: Am J Clin Nutr. 2005 Mar;81(3):729. PMID: 15585797

Assessment of dietary vitamin D requirements during pregnancy and lactation. Hollis BW, Wagner CL. Am J Clin Nutr. 2004 May;79(5):717-26. Review. PMID: 15113709 We found that high-dose maternal vitamin D supplementation not only improves the nutritional vitamin D status of breastfeeding infants but also elevates the maternal concentrations into the mid-normal range. Thus, a dual benefit is achieved from high-dose maternal supplementation. It is noteworthy that in the Finnish study, the authors added a disclaimer, "A sufficient supply of vitamin D to the breastfed infant is achieved only by increasing the maternal supplementation up to 2000 IU/d. Such a dose is far higher than the RDA [DRI] for lactating mothers [and therefore] its safety over prolonged periods is not known and should be examined by further study." This point of concern was valid when this study was conducted in 1986 (92); however, on the basis of the current findings of Vieth et al (2) and of Heaney et al (3)-which showed that vitamin D intakes <= 10 000 IU/d (250 µg) are safe for prolonged periods (up to 5 mo)-we believe that it is time to reexamine the understated DRI of vitamin D for lactating mothers. This work is now being conducted in our clinics and laboratory.