The Contributions of Solar Ultraviolet Radiation Exposure and Other Determinants to Serum 25-Hydroxyvitamin D Concentrations in Australian Adults: The AusD Study

Abstract

The Quantitative Assessment of Solar UV [ultraviolet] Exposure for Vitamin D Synthesis in Australian Adults (AusD) Study aimed to better define the relationship between sun exposure and serum 25-hydroxyvitamin D (25(OH)D) concentration. Cross-sectional data were collected between May 2009 and December 2010 from 1,002 participants aged 18-75 years in 4 Australian sites spanning 24° of latitude. Participants completed the following: 1) questionnaires on sun exposure, dietary vitamin D intake, and vitamin D supplementation; 2) 10 days of personal ultraviolet radiation dosimetry; 3) a sun exposure and physical activity diary; and 4) clinical measurements and blood collection for 25(OH)D determination. Our multiple regression model described 40% of the variance in 25(OH)D concentration; modifiable behavioral factors contributed 52% of the explained variance, and environmental and demographic or constitutional variables contributed 38% and 10%, respectively. The amount of skin exposed was the single strongest contributor to the explained variance (27%), followed by location (20%), season (17%), personal ultraviolet radiation exposure (8%), vitamin D supplementation (7%), body mass index (weight (kg)/height (m)(2)) (4%), and physical activity (4%). Modifiable behavioral factors strongly influence serum 25(OH)D concentrations in Australian adults. In addition, latitude was a strong determinant of the relative contribution of different behavioral factors.

Association between physical activity and vitamin D: A narrative literature review

“…These results suggest that modifiable factors related to sun exposure could help maintain the healthy state of vitamin D, such as decreased clothing coverage, rather than increasing the duration of exposure to ultraviolet rays. 43 Van den Heuvel et al evaluated the contribution of different physical activity characteristics, such as duration, intensity and location, in relation to plasma levels of vitamin D and concluded that physical activity performed at high intensity had the strongest positive association with vitamin D levels. 44 It is important to emphasize that exposure of the body to the sun during physical activity should have some particularities in order to raise the plasma concentrations of vitamin D, since it depends on the amount of melanin present in the skin, the type of clothing and the use of sunscreen, as well as hour of the day, season of the year, latitude of the place and age of the individual.…”

Probability of Vitamin D Deficiency by Body Weight and Race/Ethnicity

“…20 In addition to body weight and skin color, other determinants of vitamin D status include season, sunlight intensity and exposure, and use of vitamin D supplements. [21][22][23][24] Research suggests that low vitamin D in obese women is not caused by reduced sun exposure. 25 In addition, US health professionals consider age to be the primary determinant of vitamin D status.…”

Weekly cholecalciferol supplementation results in significant reductions in infection risk among the vitamin D deficient: results from the CIPRIS pilot RCT

“…Follow-up was during the winter months, from May to October 2012, much of which is when ambient UV is too low to generate vitamin D [7].…”

“…In persons who are vitamin D deficient, as occurs in winter at high latitudes and year-round for long-term medical inpatients [6,7], there is a potential for significant dysfunction in the innate immune response, leading to a greater frequency of infections.…”