Even though individuals living near the Equator receive sufficient year-round sun exposure to allow vitamin D synthesis, the need to avoid exposure to prevent skin cancer and darker skin pigmentation can still lead to low vitamin D status in this geographic location. Existing literature supports the ability of vitamin-D fortified foods to improve vitamin D status, but it is not known if this is also true for those living in low- to middle-income countries near the Equator. This void in our knowledge was addressed by a study conducted by Villamor and colleagues and reported in the April 2023 issue of The Journal of Nutrition.
Columbian families (n=80) with a mother and child aged 12-14.5 years were randomized to receive skim milk or skim milk fortified with 2400 IU (60 µg) of cholecalciferol for 6 weeks. The children were to consume 500 ml daily and that remaining from the milk provided was consumed by the mothers. Differences in serum total and free 25(OH)D, and vitamin D binding protein from baseline to the end of follow up were determined.
Fortification increased serum total 25(OH)D (5.4 nmol/L), and free 25(OH)D (0.6 pmol/L), and decreased vitamin D binding protein (416 nmol/L) in adolescents. The impacts were greater in those with lower vitamin D binding protein, darker skin, less sunlight exposure, and high compliance. The effects on mothers were lower than those observed in adolescents. The authors concluded that cholecalciferol-fortified skim milk was able to improve total 25(OH)D in the serum of Columbian adolescents and women.
In an editorial, Calvo describes some of the methodological challenges and limitations to the study conducted by Villamor and colleagues, but states these observations provide information needed to develop food fortification plans to address vitamin D deficiency in Latin America. Calvo suggests efforts to certify clinical assays for 25 (OH)D, validation of standards and efforts to harmonize assays will enable comparisons of findings from different regions and populations.
References
Villamor E, Oliveros H, Marín C, López-Arana S, Agudelo-Cañas S. Increased serum total and free 25-hydroxyvitamin D with daily intake of cholecalciferol-fortified skim milk: A randomized controlled trial in Colombian adolescents. Journal of Nutrition, Volume 153, Issue 4, April 2023, Pages 1189-1198, doi.org/10.1016/j.tjnut.2022.11.026.
Calvo MS. Lessons learned from a randomized controlled trial with vitamin D fortified milk in Colombian adolescents: Importance to vitamin D fortification policies in Latin America. Journal of Nutrition, Volume 153, Issue 4, April 2023, Pages 917-919, doi.org/10.1016/j.tjnut.2023.02.006.
Images via canva.com.
