Vitamin D status indicators in indigenous populations in East Africa.
Level 4 - case-series / case-control
Cross-sectional comparative observational study across ethnic and life-cycle cohorts
PubMed 22878781 · doi:10.1007/s00394-012-0421-6
What was done
Serum 25-hydroxyvitamin D [25(OH)D; 25(OH)D₂ + 25(OH)D₃] and erythrocyte docosahexaenoic acid (RBC-DHA, a proxy for fish intake) were measured across 5 East African ethnic groups with differing diets and traditional lifestyles (Maasai, Hadzabe, Same, Sengerema, Ukerewe). Cohorts included non-pregnant adults, pregnant women, mother-infant pairs at delivery, infants and lactating mothers at 3 days postpartum, and lactating mothers at 3 months postpartum.
What was found
Mean ± SD serum 25(OH)D was 106.8 ± 28.4 nmol/L in non-pregnant adults and 79.9 ± 26.4 nmol/L in cord blood. Pregnant women had higher 25(OH)D than non-pregnant counterparts among both Maasai (147.7 vs. 118.3 nmol/L) and Sengerema (141.9 vs. 89.0 nmol/L). Infant 25(OH)D at delivery was approximately 65% of maternal levels in Ukerewe. Serum 25(OH)D was significantly associated with pregnancy, delivery, ethnicity (used as a proxy for sunlight exposure), age (slight increase), and RBC-DHA (positively related, particularly to 25(OH)D₂).
Why it matters
This study provides an evolutionary benchmark for human circulating vitamin D, suggesting natural ancestral 25(OH)D levels centered around 115 nmol/L and indicating substantial maternal-fetal transfer.
Limits
The total sample size (n) and subgroup counts are not reported in the abstract. Sunlight exposure was not directly quantified (ethnicity served as a proxy), dietary intake was inferred from RBC-DHA rather than direct records, and the cross-sectional design cannot establish causality for physiological shifts across pregnancy and lactation.
Cited by
- contradicts Studies of traditional African tribes show natural vitamin D levels over 150 ng/mL.