Sustainable Diet Index: Associations with Obesity and Mortality in the US
Open AccessBackground: The concept of sustainable diets has recently received extensive attention due to its value in coping with current challenges including the expansion of diet-related chronic diseases and abnormal climate change. Sustainable dietary patterns should be defined using a multidimensional approach with comprehensive consideration of all potential dimensions of diet, consistent with the United Nation’s Food and Agriculture Organization definition. A composite index developed in France assessed sustainable dietary patterns by encompassing four dimensions of diet, including nutritional, environmental, economic, and sociocultural, and reported its beneficial role in health risks. However, a similar index has not yet been examined among US adults.Objectives: The overall aims of this study were to assess multidimensional sustainable dietary patterns in US adults and to examine their effects on health risks using a nationally representative sample of US adults from 2007 to 2018. Specifically, 1) we developed a sustainable diet index for US adults (SDI-US) and characterized its trends over time; 2) we examined the cross-sectional association between the SDI-US and obesity; and 3) we examined the prospective association between the SDI-US and mortality. Methods: This study used nationally representative data for adults aged 20 years and older from six National Health and Nutrition Examination Survey 2-year cycles, 2007–2018. SDI-US consisted of 4 sub-indices corresponding to 4 dimensions of sustainable diets (nutritional quality, environmental impacts, affordability, and sociocultural practices) using data from a 24-hour dietary recall interview, environmental impacts of foods, food expenditures, and food choices. A higher SDI-US score (range: 4–20) indicated a more sustainable dietary pattern. For the first aim of this study, mean SDI-US across survey cycles were estimated, and linear and quadratic trends was examined using orthogonal polynomial contrasts in regression models. For the second aim of this study, obesity was defined as a body mass index ≥30 kg/m2, and logistic regression models were used to estimate multivariable-adjusted odds ratios (ORs) with 95% confidence intervals (CIs). For the third aim of this study, all-cause mortality from baseline until December 31, 2019, was obtained through linkage to the National Death Index. Multivariable-adjusted hazard ratios (HRs) with 95% CIs were estimated using Cox proportional hazards models. All analyses accounted for the complex survey design. Results: For the first aim of this study (n=25,543), there were no significant trends in total SDI-US between 2007 and 2018 (overall mean SDI-US=13.1). Although nutritional or sociocultural indicators did not change, the economic indicator increased and environmental indicators decreased between 2007 and 2018. Despite a significant interaction between SDI-US and age, there were no substantial differences in SDI-US trends by age group. For the second aim of this study (n=25,262), obesity prevalence in US adults was 38.2% (95% CI 37.0-39.3) between 2007 and 2018. In a multivariable-adjusted model, a higher SDI-US score was associated with a lower odds of obesity, especially in women. For the third aim of this study (n=22,414), 2,100 total deaths occurred during 150,386 person-years of follow-up. A higher SDI-US score was associated with a lower mortality risk, especially in adults < 65 years after controlling for demographic and lifestyle characteristics. Conclusion: The SDI-US can be used to assess multidimensional sustainable dietary patterns in US adults and a current score was 13 out of 20 points. From 2007 to 2018, total SDI-US largely remained unchanged. More sustainable dietary patterns were inversely associated with lower risks of obesity and mortality. Continued monitoring and simultaneous improvements in all dimensions are needed to be more closely aligned with sustainable dietary patterns. These findings support the potential benefit of adopting sustainable dietary patterns for both human health and planet health. Evidence based on SDI-US may provide novel insights into obesity, chronic disease, and mortality research.
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