Serum 25-hydroxyvitamin D Status of the US Population: 1988-1994 Compared With 2000-2004

Am J Clin Nutr. 2008 Dec;88(6):1519-27. doi: 10.3945/ajcn.2008.26182.

Abstract

Background: Changes in serum 25-hydroxyvitamin D [25(OH)D] concentrations in the US population have not been described.

Objective: We used data from the National Health and Nutrition Examination Surveys (NHANES) to compare serum 25(OH)D concentrations in the US population in 2000-2004 with those in 1988-1994 and to identify contributing factors.

Design: Serum 25(OH)D was measured with a radioimmunoassay kit in 20 289 participants in NHANES 2000-2004 and in 18 158 participants in NHANES III (1988-1994). Body mass index (BMI) was calculated from measured height and weight. Milk intake and sun protection were assessed by questionnaire. Assay differences were assessed by re-analyzing 150 stored serum specimens from NHANES III with the current assay.

Results: Age-adjusted mean serum 25(OH)D concentrations were 5-20 nmol/L lower in NHANES 2000-2004 than in NHANES III. After adjustment for assay shifts, age-adjusted means in NHANES 2000-2004 remained significantly lower (by 5-9 nmol/L) in most males, but not in most females. In a study subsample, adjustment for the confounding effects of assay differences changed mean serum 25(OH)D concentrations by approximately 10 nmol/L, and adjustment for changes in the factors likely related to real changes in vitamin D status (ie, BMI, milk intake, and sun protection) changed mean serum 25(OH)D concentrations by 1-1.6 nmol/L.

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.

MeSH terms

  • Adolescent
  • Adult
  • Age Distribution
  • Aged
  • Body Mass Index
  • Bone Density Conservation Agents / administration & dosage*
  • Child
  • Cross-Sectional Studies
  • Dairy Products
  • Female
  • Humans
  • Male
  • Middle Aged
  • Nutrition Surveys
  • Nutritional Status*
  • Population Surveillance
  • Radioimmunoassay
  • Sex Distribution
  • Sunscreening Agents / adverse effects
  • Surveys and Questionnaires
  • Vitamin D / administration & dosage*
  • Vitamin D / analogs & derivatives*
  • Vitamin D / blood
  • Vitamin D Deficiency / blood
  • Young Adult

Substances

  • Bone Density Conservation Agents
  • Sunscreening Agents
  • Vitamin D
  • 25-hydroxyvitamin D