Global estimation of dietary micronutrient inadequacies: a modelling analysis

Abstract

Background: Inadequate micronutrient intakes and related deficiencies are a major challenge to global public health. Analyses over the past 10 years have assessed global micronutrient deficiencies and inadequate nutrient supplies, but there have been no global estimates of inadequate micronutrient intakes. We aimed to estimate the global prevalence of inadequate micronutrient intakes for 15 essential micronutrients and to identify dietary nutrient gaps in specific demographic groups and countries.

Methods: In this modelling analysis, we adopted a novel approach to estimating micronutrient intake, which accounts for the shape of a population's nutrient intake distribution and is based on dietary intake data from 31 countries. Using a globally harmonised set of age-specific and sex-specific nutrient requirements, we then applied these distributions to publicly available data from the Global Dietary Database on modelled median intakes of 15 micronutrients for 34 age-sex groups from 185 countries, to estimate the prevalence of inadequate nutrient intakes for 99·3% of the global population.

Findings: On the basis of estimates of nutrient intake from food (excluding fortification and supplementation), more than 5 billion people do not consume enough iodine (68% of the global population), vitamin E (67%), and calcium (66%). More than 4 billion people do not consume enough iron (65%), riboflavin (55%), folate (54%), and vitamin C (53%). Within the same country and age groups, estimated inadequate intakes were higher for women than for men for iodine, vitamin B12, iron, and selenium and higher for men than for women for magnesium, vitamin B6, zinc, vitamin C, vitamin A, thiamin, and niacin.

Interpretation: To our knowledge, this analysis provides the first global estimates of inadequate micronutrient intakes using dietary intake data, highlighting highly prevalent gaps across nutrients and variability by sex. These results can be used by public health practitioners to target populations in need of intervention.

Funding: The National Institutes of Health and the Dutch Ministry of Foreign Affairs.

Figure 1:. Methods for estimating the prevalence of inadequate micronutrient intakes

Iron intakes in Kazakhstan are used as an example. The top row illustrates the procedure for males aged 15–19 years and the bottom row illustrates the results for all age–sex groups. (A) First, we derived a skewed (gamma or log-normal) intake distribution, for which the median (blue line) of distribution was drawn from the GDD and the shape of the distribution was drawn from the nutriR database. (B) Second, we derived a normal requirement distribution, for which the mean of the distribution was drawn from the study by Allen and colleagues and the SD of the distribution was derived assuming a coefficient of variation of 0·25 for vitamin B12 and 0·10 for all other nutrients based on the work of Renwick and colleagues. (C) Finally, we derived the percentage of inadequate intake by intersecting these two distributions using the probability approach. We calculated the number of people with inadequate intakes using population estimates from the World Bank. In A–C, the vertical dotted line indicates the average requirement. (D) We repeated this process for every age–sex group. The points represent the median intake based on the GDD, the boxes represent the inner 50% of the intake distribution, and the whiskers represent the inner 95% of the intake distribution. The grey lines show the sex-specific and age-specific average requirements. GDD=Global Dietary Database.

Figure 2:. Estimated prevalence of intake inadequacies by country and nutrient in 2018

The estimated number and proportion of the global population with inadequacies is stated alongside each map. Countries with land areas of less than 25 000 km² are shown as points to increase visibility. DFE=dietary folate equivalents. RAE=retinol activity equivalents.

Figure 3:. Prevalence of intake inadequacies by World Bank region and nutrient in 2018

Nutrients and regions are arranged in order of decreasing prevalence of inadequate intakes. For a map of the World Bank regions, see appendix (p 15). DFE=dietary folate equivalents. RAE=retinol activity equivalents.

Figure 4:. Distribution of subnational differences in the prevalence of intake inadequacies between females and males by World Bank region

Values greater than 0 indicate a higher prevalence of intake inadequacies in females than in males in the same country and age group, whereas values less than 0 indicate a higher prevalence of intake inadequacies in males than in females in the same country and age group. In the boxplots, the solid line indicates the median, the box indicates the IQR, the whiskers indicate 1·5 times the IQR, and the points beyond the whiskers indicate outliers. For a map of the World Bank regions, see appendix (p 15). DFE=dietary folate equivalents. RAE=retinol activity equivalents.