The purpose of this study was to investigate the role of lifestyle (farming vs nonfarming), age, season, and percent body fat on serum 25-hydroxyvitamin D (25-OHD) and parathyroid hormone (PTH). Serum 25-OHD concentrations were lower in winter than in summer and in older than in younger individuals. Dietary intake of vitamin D was associated with greater serum 25-OHD concentrations. A significant inverse relationship between PTH and 25-OHD was observed in older but not younger individuals. Trabecular volumetric bone mineral density was inversely associated with serum PTH, but not 25-OHD concentrations. Modern farm practices do not necessitate excessive sunlight exposure and that may help explain the lack of differences between farming and nonfarming populations.
Ethel Austin Martin Program in Human Nutrition (Drs Weidauer and Specker) and Health and Nutritional Sciences Department (Dr McCormack), South Dakota State University, Brookings; and Exercise and Sports Sciences Department, Augustana College, Sioux Falls, South Dakota (Dr Gorres-Martens).
Correspondence: Lee Weidauer, PhD, Post-Doctoral Research Associate, Ethel Austin Martin Program in Human Nutrition, South Dakota State University, 1021 Medary Ave N, Wecota Hall, Brookings, SD 57007 (Lee.Weidauer@sdstate.edu).
This material is based upon work supported by the National Institutes of Health (R01-AR47852), the National Science Foundation/Experimental Program to Stimulate Competitive Research Grant #EPS-0091948, and by the Ethel Austin Martin Endowed Program in Human Nutrition at South Dakota State University.
The authors have disclosed that they have no significant relationships with, or financial interest in, any commercial companies pertaining to this article.