The findings were published in the Journal of Nutrition in a study commissioned by the World Health Organization (WHO) and the Food and Agriculture Organization (FAO) to update their vitamin D recommendations for young children. The previous 2004 FAO-WHO vitamin D recommendation for that demographic was 5 mg per day.
“The vitamin D requirement estimates arising from this work differ partly from previous recommendations due to differences in the body of evidence used, the thresholds selected, the analyses conducted, and the type of recommendations derived,” the international team of researchers wrote. “Compared with the 2004 FAO-WHO vitamin D recommendation for infants and young children, these new estimates, arising from the current modeling for the FAO-WHO update exercise, represent a more data-driven derivation of the vitamin D dietary requirement.”
Beyond sunlight exposure
Twenty years ago, the FAO and WHO published their global nutrient intake requirements that many countries incorporated into their food standards and dietary guidelines. Considering new evidence for vitamin D, the FAO and WHO decided to update their recommendations.
Additionally, previous vitamin D requirements have focused on regions, such as the United Kingdom, Europe or the Nordic regions, where there is minimal UV-B sunlight. The organizations wanted to be more inclusive to provide global vitamin D recommendations, regardless of sunlight exposure.
“Accounting for sunlight exposure when setting vitamin D intake requirements is very challenging for a number of reasons, not least because often it is not possible to quantify the contribution sunlight exposure makes to serum 25OHD concentrations within the general population,” the researchers noted.
Instead, they incorporated several systematic reviews in the mega-regression to establish this update. The researchers used randomized controlled trials of healthy children from two weeks to 3.9 years of age who received daily vitamin D supplement or vitamin D-fortified foods. A total of 31 trials were included from North America, Europe, Asia and Australasia/Oceania with latitudes ranging from 61°N to 38°S. Participants likely had light or medium skin pigmentation. Of the studies, 29 included children who received vitamin D supplements, and in two of the studies children received vitamin D-fortified milk with or without supplements.
One review focused on serum 25OHD as a useful biomarker for vitamin D status in these young children. Two others about breast milk vitamin D content and the volume of breast milk intake demonstrated new consumption exposure data. Another review defined a serum 25OHD threshold to reduce nutritional rickets in young children.
Study limitations
The researchers identified several limitations of the study, including a lack of examination of skin pigmentation and its affect on cutaneous vitamin D synthesis. Forty-two percent of the studies did not report pigmentation, although these studies likely included people of light or medium complexion. Although some included people of mixed variety of skin types, none had participants of only dark skin types.
This review highlights a key research gap: little published data from Africa and South America.
“The majority of the studies were conducted in countries where the predominant racial group is white,” the researchers wrote. “This is an inherent limitation of the data rather than of the analysis. Nevertheless, this limitation should be a consideration as agencies make local context adjustments to these new estimates. In this regard, one cautious interpretation of the present vitamin D intake estimates is that they are most protective of those young children not synthesizing vitamin D in the skin.”
Source: Journal of Nutrition
doi: 10.1016/j.tjnut.2024.04.031
“The Relationship Between Vitamin D Intake and Serum 25-hydroxyvitamin D in Young Children: A Meta-Regression to Inform WHO/FAO Vitamin D Intake Recommendations”
Authors: Magali Rios-Leyvraz et al.
