title: Frequency of leisure-time physical activity and serum 25-hydroxyvitamin D levels in the US population: results from the Third National Health and Nutrition Examination Survey.
abstract: The decline in vitamin D status among older people is probably due to decreased synthesis of vitamin D by sun-exposed skin and/or decreased outdoor activity. The authors examined the association between outdoor leisure physical activity and serum 25-hydroxyvitamin D in the Third National Health and Nutrition Examination Survey (1988-1994) (n = 15,148 aged >/=20 years). The mean 25-hydroxyvitamin D concentration declined with increasing age, with 79, 73, and 68 nmol/liter for persons aged 20-39, 40-59, and 60 or more years. The proportion that engaged in outdoor activity in the past month was 80% for persons aged 20-39 and 40-59 years but 71% for those aged 60 or more years. In contrast, the mean difference in 25-hydroxyvitamin D between those who participated in outdoor activities daily compared with those who did not participate in the past month was similar for the youngest and oldest age groups: 13 and 16 nmol/liter, respectively. Those persons aged 60 or more years who participated in daily outdoor activities had a mean 25-hydroxyvitamin D concentration similar to that of persons aged 20-39 years: 77 versus 79 nmol/liter, respectively. These nationally representative data suggest that persons aged 60 or more years can synthesize enough vitamin D from daily outdoor activities to maintain vitamin D levels similar to those of young adults.
authors.affiliation: School of Population Health, University of Auckland, Auckland, New Zealand. r.scragg@auckland.ac.nz
authors.forename: Robert
authors.initials: R
authors.lastname: Scragg
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Camargo
mesh_terms: D000328:Adult; D017677:Age Distribution; D003430:Cross-Sectional Studies; D004032:Diet; D005260:Female; D006801:Humans; D007899:Leisure Activities; D008297:Male; D008875:Middle Aged; D009043:Motor Activity; D009749:Nutrition Surveys; D010808:Physical Examination; D011159:Population Surveillance / Q000379:methods*; D017678:Sex Distribution; D014481:United States; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D