In this global assessment of different dietary patterns across 185 countries in 1990 and 2018, we found modest overall dietary quality, but with important variation by age, sex, education, urbanicity, time and world region, as well as by dietary component. These results, based on the systematic collection and standardization of more than 1,100 individual-level dietary surveys worldwide, provide the most current and comprehensive estimates of global, regional and national dietary quality among adults and children, in subgroups according to educational attainment and urban versus rural residence, and comparing three validated dietary patterns including the AHEI, DASH and MED17. These results have important implications for public health and inform priorities in each nation and subnational subgroup to improve nutrition security and health equity.
As one example, our findings highlight the regional differences between insufficient intakes of healthful foods versus excess intakes of unhealthful foods. For instance, the highest dietary pattern scores in 2018 were identified in low-income countries in South Asia and Sub-Saharan Africa, where relatively low consumption of SSBs and red/processed meats is consistent with national data on food or beverage volume sales19. However, consumption of healthy components, such as fruit, non-starchy vegetables, legumes/nuts, seafood omega-3 fat and PUFAs, were also far from optimal in these nations. This suggests that a major focus on policies and innovations to increase intakes of produce, seafood and plant oils will have the largest impact on dietary quality in these countries.
By contrast, in high-income countries, Central/Eastern Europe and Central Asia, and the Middle East and Northern Africa, increasing intakes of fruit, non-starchy vegetables, legumes/nuts and whole grains have improved dietary quality over time, but have been offset by stable trends or only minor reductions in red/processed meats, SSBs and sodium. We found that red/processed meat and sodium have each significantly increased over time in Asia and Latin America and the Caribbean, consistent with previous nation-specific reports from China, Japan and Mexico20,21,22. These findings suggest that a dual focus on increasing healthful foods and lowering of harmful factors is essential in these regions, especially for nations in Asia and Latin America and the Caribbean.
Several studies have documented that the AHEI is associated with the risk of non-communicable diseases23. For example, pooled findings from two US cohorts found a 24%, 33% and 6% reduction in the incidence of cardiovascular disease, diabetes mellitus and cancer, respectively, for the highest AHEI quintile (median 64.5) compared with the lowest quintile (median 36.9; comparable to the global mean in our study, 40.3 (95% UI 39.4, 41.3)) (ref. 24). Cohorts have also found that a moderate increase (20-percentile increase) in the AHEI score during follow-up was associated with significantly lower risk of cardiovascular disease mortality and cancer mortality25. Similar relationships have been observed in France26, the United Kingdom27 and Singapore28,29. Such associations suggest that the current quality of global diets identified in this study is leading to preventable chronic disease and mortality, and that modest improvements in dietary quality can contribute to reductions in fatal and non-fatal diet-related diseases over time.
Our findings on global diet patterns among infants, children and adolescents have important implications for child nutrition and health. We found that diet quality was generally highest among infants and young children and worsened into adolescence, emphasizing the need for initiatives to aim to improve dietary quality in older children, as well as promote healthy eating habits in early childhood to translate into improved dietary quality in adolescence and adulthood. Although, diet quality was highest among children in Sub-Saharan Africa and South Asia, we found that diet quality worsened or remained stable over time in these regions. Children with more educated parents had higher dietary quality in all regions except South Asia and the Middle East and Northern Africa, while better diet quality was found among children residing in urban areas in Central/Eastern Europe and Central Asia and Southeast and East Asia, and rural areas in the Middle East and Northern Africa. Worse dietary quality in children is associated with stunting, cardiometabolic risk factors (for example, blood pressure, blood lipid levels, glucose control and obesity) and lower health-related quality of life30,31,32,33,34,35, and dietary habits and food preferences established during early life influence later habits throughout childhood and into adulthood36,37,38.
Dietary disparities by education or income level have been reported in specific, mostly high-income nations or selected groups of nations8,39,40,41, but not globally. Our findings demonstrate that more educated individuals had higher overall dietary quality in most, but not all, world regions, with largest impacts of education among nations in Central/Eastern Europe and Central Asia, Latin America and the Caribbean, and South Asia. We also identified key exceptions in the Middle East and Northern Africa, and Sub-Saharan Africa, where dietary quality did not vary by education level. Notably, higher education was generally linked to greater consumption of fruits, non-starchy vegetables, whole grains and plant oils, but not always to lower consumption of SSBs and red/processed meat. Interestingly, urbanicity differentially influenced dietary quality in different world regions, with better dietary quality among urban versus rural residents in Central/Eastern Europe and Central Asia and Southeast and East Asia, but the opposite in the Middle East and Northern Africa, related to specific differences in the consumption of the underlying healthful versus unhealthful components among urban versus rural residents in these regions.
In agreement with our earlier analysis of healthy and unhealthy dietary scores16, we found that, compared with lower-income countries, higher-income countries had better scores for healthy components (for example, fruit and whole grains) but worse scores for unhealthy components (for example, red/processed meats and sodium).
This investigation has several strengths. Our data and findings build upon and expand the previous literature by including the largest number of individual-level dietary surveys, providing a more contemporary estimate of trends in global dietary quality and estimating global dietary quality in children and adolescents, which has not been previously reported. We included 1,139 dietary surveys, most of which were nationally representative and collected at the individual-level using 24 h recalls or food-frequency questionnaires (FFQs). We standardized all data inputs including dietary factor definitions, units and age-specific energy adjustment, and incorporated Bayesian modelling with survey and country covariates to address heterogeneity and sampling and modelling uncertainty42. We assessed subnational differences by age, sex, education and urbanicity, including the first global estimates of dietary patterns by educational attainment and urban versus rural residence. We characterized three established metrics for diet quality, each validated against major health outcomes17, including the similarities and differences in global, regional and national dietary quality depending on the dietary metric.
Potential limitations should be considered. While we made extensive efforts to minimize bias and incorporate heterogeneity and uncertainty, individual-level dietary data are subject to measurement errors, and survey availability was limited or incomplete for some nations, dietary factors, demographic groups and years16,42. For example, less than a quarter of surveys included data on children aged 3–9 years and adults ≥85 years. The Bayesian hierarchical models incorporated additional uncertainty to account for these limitations, but sampling and/or information bias cannot be ruled out16. To allow for comparability between population subgroups, we standardized dietary intakes to 2,000 kcal per day before computing the dietary patterns, but the unadjusted dietary intakes may be lower among populations with lower energy requirements (for example, infants and young children, and seniors) or higher among populations consuming >2,000 kcal per day. We did not have information on trans fat (AHEI) or alcohol use (AHEI and MED), and our findings should be interpreted as dietary quality based on the other components of these scores. The dietary patterns selected (AHEI, MED and DASH) were originally developed and validated for adult populations in high-income countries but have been used to characterize dietary quality among children and seniors33,43,44. It is important to note that a single or suite of dietary metrics has not been developed or validated to assess micronutrient quality of the diet in all age groups17, and the AHEI, MED and DASH may be inadequately correlated with nutrients of concern, particularly among children and in low- and middle-income countries. Caution is warranted when interpreting the findings in relation to nutrient adequacy. However, in the absence of validated metrics for the double burden of malnutrition, the AHEI, MED and DASH are appropriate metrics for assessing dietary quality across populations17. We did not consider other, less validated dietary indices and scores16,17,45,46, which can be assessed once these have been better validated for use in diverse global populations.
In conclusion, we found global dietary quality to be only modest today, and with only some improvement, although inconsistent by world region, over the past three decades.
These results provide comprehensive global information about individual-level dietary patterns among children and adults, by age, sex, education and urbanicity. Our findings highlight the substantial variation in dietary quality and inform the need for specific national and subnational policies to improve nutrition security and nutrition equity.