Vitamin D Nutritional Status in the Middle East and North Africa Region: A Systematic Review and Meta-analysis.

Background: Adequate vitamin D status is crucial for health, especially for skeletal health. The prevention of vitamin D deficiency disorders represents a major public health challenge in countries with low sunlight exposure. Nonetheless, several studies conducted in the Middle East and North Africa (MENA) region have reported surprisingly high prevalences of vitamin D deficiency, despite high sunlight availability. Even in those countries, dietary and lifestyle recommendations, including nutritional fortification policies, may be needed. Objectives: The present study aimed to systematically update and assess the vitamin D status in the MENA region using a meta-analysis approach. Methods: This meta-analysis included 41 studies (2000-2022) evaluating serum vitamin D levels in healthy MENA adult populations, using pooled analyses and meta-regressions to assess the overall levels, sex differences, and the impact of covariates such as age and body mass index (BMI). Some studies identified as source of heterogeneity were excluded, and random-effects models were used in meta-analyses to control variability of effect sizes. Registration ID https://doi.org/10.17605/OSF.IO/FK4WM. Results: High variability from country to country was observed in vitamin D status in the MENA region, ranging from 9 ± 7 to 88 ± 76 nmol/L. The overall mean serum vitamin D concentration was 46 (95% confidence interval: 40, 52) nmol/L (below the recommended cutoff of 50 nmol/L), with a 4 nmol/L higher level in men compared with women, and no significant impact of age or BMI. Conclusions: This meta-analysis provides a comprehensive assessment of vitamin D status in adults from the MENA region, highlighting the widespread vitamin D deficiency in the region, with potential gender differences, but no clear impact of age or BMI-findings that could reinforce targeted, regional public health strategies to improve vitamin D status through lifestyle and nutrition.