Global prevalence and disease burden of vitamin D deficiency: a roadmap for action in low- and middle-income countries

Abstract

Vitamin D is an essential nutrient for bone health and may influence the risks of respiratory illness, adverse pregnancy outcomes, and chronic diseases of adulthood. Because many countries have a relatively low supply of foods rich in vitamin D and inadequate exposure to natural ultraviolet B (UVB) radiation from sunlight, an important proportion of the global population is at risk of vitamin D deficiency. There is general agreement that the minimum serum/plasma 25-hydroxyvitamin D concentration (25(OH)D) that protects against vitamin D deficiency-related bone disease is approximately 30 nmol/L; therefore, this threshold is suitable to define vitamin D deficiency in population surveys. However, efforts to assess the vitamin D status of populations in low- and middle-income countries have been hampered by limited availability of population-representative 25(OH)D data, particularly among population subgroups most vulnerable to the skeletal and potential extraskeletal consequences of low vitamin D status, namely exclusively breastfed infants, children, adolescents, pregnant and lactating women, and the elderly. In the absence of 25(OH)D data, identification of communities that would benefit from public health interventions to improve vitamin D status may require proxy indicators of the population risk of vitamin D deficiency, such as the prevalence of rickets or metrics of usual UVB exposure. If a high prevalence of vitamin D deficiency is identified (>20% prevalence of 25(OH)D < 30 nmol/L) or the risk for vitamin D deficiency is determined to be high based on proxy indicators (e.g., prevalence of rickets >1%), food fortification and/or targeted vitamin D supplementation policies can be implemented to reduce the burden of vitamin D deficiency-related conditions in vulnerable populations.

Keywords: 25-hydroxyvitamin D; cholecalciferol; developing countries; dietary supplementation; fortification; micronutrients; nutrition; rickets; vitamin D.

Figure 1.

Serum25-hydroxyvitaminD(25(OH)D)concentrationthresholdsforvitaminDdeficiency, insufficiency, andsufficiency developed by the Institute of Medicine (IOM), the Scientific Advisory Committee on Nutrition (SACN), the European Food Safety Authority (EFSA), and the Endocrine Society. Dashed lines are shown for 25(OH)D ranges in which the consensus group did not make a direct statement regarding vitamin D deficiency, adequacy, or risk of harm.

Figure 2.

Association between serum 25-hydroxyvitamin D (25(OH)D) concentrations (in late winter) and total vitamin D intake (i.e., from diet plus supplemental vitamin D) in healthy persons aged 4–86 years living at northerly latitudes (between 51° N and 60° N) based on individual patient data (IPD) meta-regression analysis (n 882 individuals). The solid and dashed lines through the IPD data points (black circles) correspond to the lines on the basis of the=two-step (adjusted for age and baseline 25(OH)D) and one-step IPD analyses, respectively, and the corresponding 95% prediction bands are shown in gray (the lightest being the band for the one-step IPD analysis). Reproduced with permission from Nutrients.

Figure 3.

Radiographs of a normal knee (left) and a knee with nutritional rickets (right). The arrows indicate the regions with the widening of the growth plate and the frayed margins.

Figure 4.

Edible oil that is used, fortifiable, and fortified with vitamin A. Examples of household utilization of edible oil (dark gray bars), as reported in the Fortification Assessment Coverage Toolkit (FACT) surveys, by potential for fortification (fortifiable, light gray bars), and actual content of fortificant (fortified, white bars). Oil fortification was voluntary in India but mandatory in all other settings shown. Adapted from Aaron et al.

Figure 5.

Countries where edible oils are fortified with vitamin A (yellow) or vitamins A and D (green). While 36 countries allow fortification of edible oils with vitamin A, 10 countries (Afghanistan, Djibouti, India, Morocco, Mozambique, Oman, Papua New Guinea, Sierra Leone, Yemen, and Zimbabwe) allow mandatory or voluntary fortification with vitamin A, and mandate edible oils to include vitamin D as an optional or mandatory cofortificant in their standards.

Figure 6.

Schematic representation of the Roadmap for Action.