Plasma 25-Hydroxyvitamin D Responses of Younger and Older Men to Three Weeks of Supplementation with 1800 IU/day of Vitamin D

Abstract

Objective: The objective of this study was to compare changes in plasma 25-hydroxyvitamin D (25(OH)D) levels of younger and older men after three weeks of oral vitamin D supplementation.

Methods: Nine younger men (22 to 28 years) and nine older men (65 to 73 years) with self-reported vitamin D intakes below 200 IU/d were enrolled in February and randomized to 1800 IU/d of ergocalciferol (vitamin D₂, n=11) or to a control group (n=7) and followed for three weeks. Blood was collected at baseline, and after one, two and three weeks for measurement of plasma concentrations of total 25(OH)D, 25(OH)D₂ and 25(OH)D₃.

Results: In both the younger and older supplemented men, 25(OH)D₂ and total 25(OH)D concentrations increased significantly during the study, whereas values of these metabolites did not change in younger or older control subjects. No group showed significant changes in 25-hydroxyvitamin D₃. There was a significant interaction between age group and supplement group, suggesting that the effect of vitamin D₂ supplementation on changes in 25(OH)D₂ changes with age. The mean increase in 25(OH)D₂ was greater in the younger supplemented men than in the older supplemented men (37±9 nmol/L vs. 19.5 nmol/L, p=0.027), and this accounted for their significantly greater increase in total 25(OH)D.

Conclusion: These data are consistent with an age-related decline in the absorption, transport or liver hydroxylation of orally-consumed vitamin D.

• vitamin D supplementation
• 25-hydroxyvitamin D
• vitamin D absorption
• aging

The authors thank Ms. Amanda Yeaton in the Calcium and Bone Metabolism Laboratory, Ms. Irene Ellis, Ms. Bella Gindelsky and Dr. Elias Seyoum in the Nutrition Evaluation Laboratory and the staff of the Metabolic Research Unit for their substantial contributions to this study.

Notes

This material is based upon work supported by the U.S. Department of Agriculture, under agreement No. 58-1950-9-001. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors, and do not necessarily reflect the view of the U.S. Department of Agriculture.