What is the optimal vitamin D status for health?
The most objectively substantiated health-related reason for tanning is that it improves vitamin D status. The serum 25-hydroxyvitamin D concentration (25(OH)D) is the measure of vitamin D nutrition status. Human biology was probably optimized through natural selection for a sun-rich environment that maintained serum 25(OH)D higher than 100 nmol/L. These levels are now only prevalent in people who spend an above-average amount of time outdoors, with the sun high in the sky. The best-characterized criteria for vitamin D adequacy are based on randomized clinical trials that show fracture prevention and preservation of bone mineral density. Based upon these studies, 25(OH)D concentrations should exceed 75 nmol/L. This concentration is near the upper end of the 25(OH)D reference ("normal") range for populations living in temperate climates, or for people who practice sun-avoidance, or who wear head coverings. Officially mandated nutrition guidelines restrict vitamin D intake from fortified food and supplements to less than 25 mcg/day, a dose objectively shown to raise serum 25(OH)D in adults by about 25 nmol/L. The combined effect of current nutrition guidelines and current sun-avoidance advice is to ensure that adults who follow these recommendations will have 25(OH)D concentrations lower than 75 nmol/L. Therefore, advice to avoid UVB light should be accompanied by encouragement to supplement with vitamin D in an amount that will correct for the nutrient deficit that sun-avoidance will cause.
Vieth
Reinhold
R
Department of Nutritional Sciences, University of Toronto, Mount Sinai Hospital, Toronto, Canada. rvieth@mtsinai.on.ca
D002170:Canada; D019587:Dietary Supplements; D017408:Guidelines as Topic; D006304:Health Status; D006801:Humans; D018673:Nutrition Policy; D009752:Nutritional Status; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood* / Q000627:therapeutic use*; D014808:Vitamin D Deficiency / Q000097:blood* / Q000517:prevention & control*
D014807:Vitamin D; C104450:25-hydroxyvitamin D