Elsevier

Bone

Volume 30, Issue 5, May 2002, Pages 771-777
Bone

Original article
Serum 25-hydroxyvitamin D status of adolescents and adults in two seasonal subpopulations from NHANES III

Presented in part at the 21st annual ASBMR meeting, St. Louis, MO, 1996.
https://doi.org/10.1016/S8756-3282(02)00692-0Get rights and content

Abstract

Subclinical vitamin D deficiency may be common in certain subgroups in the U.S., but to date vitamin D data from other groups in the population have not been available. We used serum 25-hydroxyvitamin D (25-OHD) data from 18,875 individuals examined in the Third National Health and Nutrition Examination Survey (NHANES III 1988–1994) to assess the vitamin D status of selected groups of the noninstitutionalized U.S. adolescent and adult population. Serum 25-OHD levels were measured by a radioimmunoassay kit (DiaSorin, Inc., Stillwater, MN; normal range 22.5–94 nmol/L). Because physical exams are performed in mobile vans in NHANES, data could not be collected in northern latitudes during the winter; instead data were collected in northern latitudes during summer and in southern latitudes in winter. To address this season-latitude aspect of the NHANES design, we stratified the sample into two seasonal subpopulations (winter/lower latitude and summer/higher latitude) before examining vitamin D status. Less than 1% of the winter/lower latitude subpopulation had vitamin D deficiency (25-OHD <17.5 nmol/L). However, the prevalence of vitamin D insufficiency in this group ranged from 1%–5% with 25-OHD <25 nmol/L to 25%–57% with 25-OHD <62.5 nmol/L, even though the median latitude for this subsample (32°N) was considerably lower than the latitude at which vitamin D is not synthesized during winter months (∽42°N). With the exception of elderly women, prevalence rates of vitamin D insufficiency were lower in the summer/higher latitude subpopulation (<1%–3% with 25-OHD <25 nmol/L to 21%–49% with 25-OHD <62.5 nmol/L). Mean 25-OHD levels were highest in non-Hispanic whites, intermediate in Mexican Americans, and lowest in non-Hispanic blacks. Our findings suggest that vitamin D deficiency is unlikely in the two seasonal subpopulations of noninstitutionalized adolescents and adults that can be validly assessed in NHANES III. However, vitamin D insufficiency is more common in these two seasonal subpopulations. Of particular interest is that insufficiency occurred fairly frequently in younger individuals, especially in the winter/lower latitude subsample. Our findings support continued monitoring of this vitamin in the U.S. population.

Introduction

Interest in vitamin D status in the U.S. has intensified lately due to the recognition that, despite the fortification of milk with vitamin D in this country, subclinical vitamin D deficiency may be common in certain population subgroups such as medical inpatients or homebound elderly persons.8, 35 Hypovitaminosis D status has been associated with a number of negative skeletal consequences, including secondary hyperparathyroidism, and increased bone turnover, rates of bone loss, and fracture risk.4, 8, 19, 23, 35 Although there have been many community-based studies of vitamin D status in the U.S.,26 data from a representative sample of the population have not been previously available. Furthermore, data on some groups, such as adolescents or individuals living in the southern U.S., are limited.

The inclusion of serum 25-hydroxyvitamin D (25-OHD) levels in the most recently completed National Health and Nutrition Examination Survey, or NHANES III (1988–1994), provides the opportunity to examine vitamin D status in a representative sample of the noninstitutionalized U.S. population for the first time. However, the NHANES III survey design contains an inherent season-latitude structure that affects interpretation of serum 25-OHD levels, because they vary by these factors.37 Specifically, because physical exams, including phlebotomy, in NHANES III were conducted in mobile vans that can be adversely affected by weather, data had to be collected in northern latitudes in summer and in southern latitudes in winter. In the present study, we stratified the representative sample of U.S. adolescents and adults from NHANES III into two seasonal subpopulations to assess vitamin D status while addressing the season-latitude structure of the survey design. Specifically, we examined the prevalence of vitamin D deficiency and insufficiency in the representative sample of adolescents and adults: (a) whose blood was collected during the winter at median latitude 32°N (range 25°–41°N); and (b) whose blood was collected during the summer at median latitude 39°N (range 25°–47°N). These groups may be at lower risk of inadequate vitamin D status due to potentially greater ultraviolet radiation levels present at lower latitudes in winter or during summer months at higher latitudes. In addition, we compared the vitamin D status of two minority groups in the U.S., namely non-Hispanic blacks and Mexican Americans, with that of non-Hispanic whites.

Section snippets

Subjects

NHANES III is the most recently completed survey in a series conducted periodically by the National Center for Health Statistics (NCHS), Centers for Disease Control and Prevention (CDC), to assess the health and nutrition of a large representative sample of the noninstitutionalized, civilian U.S. population. Data were collected via household interviews and direct standardized physical examinations were conducted in specially equipped mobile examination centers.29 NHANES III was designed to

Results

Mean 25-OHD values and prevalence rates of vitamin D insufficiency in the U.S. population stratified by season are shown in Table 1. Less than 1% of the winter/lower latitude subpopulation had serum 25-OHD levels indicative of vitamin D deficiency (e.g., <17.5 nmol/L) (data not shown). However, prevalence rates of values associated with vitamin D insufficiency were more common (Table 1); that is, these prevalence rates ranged from approximately 1%–5% with values <25 nmol/L to 25%–57% with

Discussion

We found little evidence of vitamin D deficiency (e.g., serum 25-OHD <17.5 nmol/L) in the two seasonal subpopulations of noninstitutionalized U.S. adolescents and adults examined in the present study. However, vitamin D insufficiency was common, especially when defined as serum 25-OHD <37.5–<62.5 nmol/L — despite the presumably more favorable UV radiation levels available at lower latitudes in winter or at higher latitudes during summer months. In particular, vitamin D insufficiency was common

Acknowledgements

The authors acknowledge Donna J. LaVoie, (MT)ASCP, and Della B. Twite, (MT)ASCP, for their outstanding efforts in performing the NHANES III vitamin D assays.

References (38)

  • B Dawson-Hughes et al.

    Effect of calcium and vitamin D supplementation on bone density in men and women 65 years of age or older

    N Engl J Med

    (1997)
  • B Dawson-Hughes et al.

    Calcium retention and hormone levels in black and white women on high- and low-calcium diets

    J Bone Miner Res

    (1993)
  • S Docio et al.

    Seasonal deficiency of vitamin D in childrenA potential target for osteoporosis-preventing strategies?

    J Bone Miner Res

    (1998)
  • T Ezzati et al.
  • M.F Gloth et al.

    Vitamin D deficiency in homebound elderly persons

    JAMA

    (1995)
  • J Guillemant et al.

    Acute PTH response to oral calcium load and seasonal variation of vitamin D status in healthy young adult subjects

    Eur J Clin Nutr

    (1996)
  • J Guillemant et al.

    Vitamin D status during puberty in French healthy male adolescents

    Osteopor Int

    (1999)
  • E.W Gunter et al.
    (1996)
  • S.S Harris et al.

    Vitamin D insufficiency and hyperparathyroidism in a low income, multiracial, elderly population

    J Clin Endocrinol Metab

    (2000)
  • Cited by (0)

    View full text