A recent study showed that dark skin and low exposure to sunlight increase the risk of vitamin D deficiency in children.
Vitamin D deficiency is linked to various diseases including rickets, cancer and cardiovascular disease; hence, it is vital that we maintain sufficient vitamin D levels (≥ 50 nmol/L) through sun exposure, diet or supplements containing vitamin D. Those at risk of vitamin D deficiency include children and dark-skinned individuals, particularly those living at northern latitudes with limited sun exposure. To maintain sufficient vitamin D levels, the Nordic Nutrition Recommendations suggest that fair-skinned children aged 1 week to 2 years and dark-skinned children aged 1 week to 5 years receive a daily 10-µg vitamin D supplement. After 5-years of age, vitamin D levels should be sufficiently maintained by sun exposure and diet. However, it is unclear whether 10 µg/day is sufficient for children living in northern areas with limited sun exposure. A study published in the American Journal of Clinical Nutrition determined the amount of vitamin D required by children living in Sweden to maintain sufficient vitamin D levels during winter, taking skin color and latitude into account.
The authors recruited 189 children aged 5-7 years from northern (63°N, Malmö) and southern (55°S; Umeå) Sweden for a longitudinal, double-blind, randomized, food-based intervention study during late fall and winter (November 2012-March 2013). Children were classified as having fair skin (n = 108) or dark skin (n = 98) and were randomly assigned milk-based vitamin D3 supplements containing 2 (placebo), 10 or 25 µg of vitamin D3. Supplements were consumed daily for three months. Dietary vitamin D intake, sun exposure, health and socioeconomic data were obtained from questionnaires. Blood samples were collected at baseline and following the three month supplementation period to obtain serum 25-hydroxyvitamin D [S-25(OH)D] concentrations, an indicator of vitamin D status.
Diet alone provided only 60% (6 µg) of the daily recommended vitamin D intake for all children at baseline and follow-up, and dark-skinned children had overall lower levels. Supplementing the children’s diet with 10 and 25 µg vitamin D3 increased the daily intake to 17 and 26 µg, respectively. Overall, these supplements increased S-25(OH)D concentrations more in dark-skinned children, although concentrations remained higher in fair-skinned children. To reach sufficient S-25(OH)D concentrations (≥50 nmol/L), 95.1% dark-skinned children required the 25-µg vitamin D3 supplement, whereas 90.2% of fair-skinned children needed the 10-µg supplement. Further analyses showed that daily vitamin D intakes of 20 µg and 28 µg are optimal for maintaining winter vitamin D levels in fair- and dark-skinned children, respectively.
The children in this study, particularly children with darker skin, required much higher daily vitamin D intake during winter than specified by the Nordic Nutrition Recommendations. The authors suggest that the daily vitamin D recommendations be increased and extended to include children over five years of age. Intake can be increased by providing daily vitamin D3 supplements, as diet alone is insufficient to meet the current recommendations. The authors also recommend that strategies be developed to incorporate vitamin D fortification or supplements into diets over summer and winter.
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