Impact of Skin Color and Sun Exposure on Vitamin D Deficiency in Children
Understanding Vitamin D Deficiency
A recent study has highlighted that children with dark skin and limited sun exposure are at an increased risk of vitamin D deficiency. This deficiency is associated with various health issues, including rickets, cancer, and cardiovascular diseases. Therefore, it is crucial to maintain adequate vitamin D levels (≥ 50 nmol/L) through sun exposure, dietary sources, or vitamin D supplements.
At-Risk Populations
Children and individuals with dark skin, especially those residing in northern latitudes with minimal sunlight, are particularly vulnerable to vitamin D deficiency. To ensure sufficient levels of vitamin D, the Nordic Nutrition Recommendations advise that fair-skinned children aged 1 week to 2 years and dark-skinned children aged 1 week to 5 years receive a daily supplement of 10 µg of vitamin D. After the age of 5, it is expected that vitamin D levels can be adequately maintained through sun exposure and diet. However, the sufficiency of 10 µg/day for children in northern regions remains uncertain.
Vitamin D Requirements for Children in Sweden
Research Study Overview
A study published in the American Journal of Clinical Nutrition examined the vitamin D requirements for children in Sweden during winter, considering skin color and geographical latitude. The researchers recruited 189 children aged 5 to 7 years from northern (Malmö, 63°N) and southern (Umeå, 55°S) Sweden for a longitudinal, double-blind, randomized, food-based intervention study conducted from November 2012 to March 2013.
Study Design and Findings
Participants were categorized based on skin color, with 108 classified as having fair skin and 98 as having dark skin. The children were randomly assigned to receive milk-based vitamin D3 supplements containing either 2 µg (placebo), 10 µg, or 25 µg of vitamin D3 daily for three months. Dietary vitamin D intake, sun exposure, health, and socioeconomic data were collected via questionnaires. Blood samples were taken at the beginning and end of the supplementation period to measure serum 25-hydroxyvitamin D [S-25(OH)D] levels, which indicate vitamin D status.
The results revealed that diet alone provided only 60% (6 µg) of the recommended daily vitamin D intake for all children at both baseline and follow-up, with dark-skinned children exhibiting lower overall levels. Supplementation with 10 µg and 25 µg of vitamin D3 increased daily intake to 17 µg and 26 µg, respectively. Notably, these supplements were more effective in raising S-25(OH)D concentrations in dark-skinned children, although fair-skinned children maintained higher levels.
Recommendations for Vitamin D Intake
To achieve sufficient S-25(OH)D concentrations (≥50 nmol/L), 95.1% of dark-skinned children required the 25-µg vitamin D3 supplement, while 90.2% of fair-skinned children needed the 10-µg supplement. Further analysis indicated that optimal daily vitamin D intakes for maintaining winter levels are 20 µg for fair-skinned children and 28 µg for dark-skinned children.
The findings suggest that children with darker skin require significantly higher daily vitamin D intake during winter than what is currently recommended by the Nordic Nutrition Recommendations. Consequently, the authors advocate for an increase in daily vitamin D recommendations and propose extending these guidelines to children over the age of five.
To meet these revised recommendations, daily vitamin D3 supplementation should be prioritized, as dietary sources alone are insufficient. Additionally, the authors recommend implementing strategies for vitamin D fortification or supplementation throughout both summer and winter months.
Reference
Ohlund I, Lind T, Hernell O, Silfverdal S-A, Karlsland Akeson P. Increased vitamin D intake differentiated according to skin color is needed to meet requirements in young Swedish children during winter: a double-blind randomized clinical trial. Am J Clin Nutr. 2017. Available at: doi: 10.3945/ajcn.116.147108.
Written by Natasha Tetlow, PhD