Global patterns, temporal trends, and inequalities in micronutrient intake inadequacy among women of reproductive age: a modelling analysis

Women of reproductive age (WRA, 15-49 years) have elevated micronutrient requirements because of menstruation, pregnancy, and lactation and their central role in maternal and child health; however, globally comparable evidence on inadequate micronutrient intake in this population remains limited. We therefore estimated the prevalence of inadequate intake of 15 essential micronutrients among WRA across countries, regions, and time and assessed inequalities according to the sociodemographic index (SDI). Using an established probabilistic dietary modelling framework, we estimated micronutrient intake inadequacy among WRA in 185 countries from 1990 to 2018 by combining median intake estimates from the Global Dietary Database with distribution-shape estimates from nutriR and applying harmonised age- and sex-specific average requirements. Absolute and relative inequalities were assessed using the slope index of inequality and the concentration index. In 2018, vitamin E had the highest estimated prevalence of inadequate intake among WRA (77.7%; 95% UI: 38.3%, 95.0%), followed by iron (72.0%; 95% UI: 53.0%, 85.1%) and calcium (70.5%; 95% UI: 61.8%, 77.1%). More than 90% of WRA in South Asia had estimated inadequate intakes of five micronutrients. Iron inadequacy worsened between 1990 and 2018, whereas magnesium and niacin inadequacy declined. Most micronutrients had a higher prevalence of inadequate intake in lower-SDI countries, although magnesium showed the opposite pattern in 2018. These findings suggest that micronutrient intake inadequacy among WRA is widespread globally, with marked regional variation, temporal change, and substantial SDI-related inequalities, and may inform nutrition policy, intervention prioritisation, and global monitoring efforts.