Development and Application of the Dietary Environmental Index for the Assessment of Foods and Dietary Patterns in the United States
El-Abbadi, Naglaa.
2018
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Abstract: Introduction: Identifying and promoting food intake patterns that enhance overall diet quality and health outcomes within ecologically viable parameters is crucial for dietary sustainability and food security. Diet composition strongly influences dietary environmental impact because of the wide variation in life cycle impacts among foods, even among those with similar nutrition and healt... read moreh effects. Often processed foods high in sugar, fat, or refined carbohydrates are low in greenhouse gas emissions; therefore, focusing solely on minimizing environmental impact risks leaning too much on foods that are less healthy. At the same time, diets that are nutrient-rich and diverse may be associated with a heavy environmental burden. Future dietary recommendations must place nutritional health in the context of environmental effects; to date, we lack methods for aligning health and sustainability concerns in our dietary choices. Objectives: The central objective of this dissertation research was the construction of a Dietary Environmental Index as a comprehensive scoring system that includes both nutritional and environmental impact assessment, to be utilized in scoring a wide range of foods consumed in the United States. This tool is further applied to evaluate observed food intake patterns, and ultimately used to project how they may be modified to optimize nutritional health while mitigating environmental harm. Methods: For Aim 1, the DEX was developed as the ratio of a Nutrient Density Score (NDS), derived from the Nutrient Rich Foods Index 9.3, to an Environmental Impact Score (EIS) composed of four life cycle environmental impacts representing climate change potential, land use, water resource depletion, and marine eutrophication. DEX scores were calculated for 8,076 food products from USDA databases. For Aim 2, the DEX scores were applied to evaluate 24-hr dietary intake reported by adults in the 2007-08 National Health and Nutrition Examination Survey (NHANES), standardized to 2000 kcal. Each participant's total food intake for the day was classified into one of five patterns: lacto-ovo vegetarian (plant-based foods plus dairy and egg); pesce-pollotarian (vegetarian plus any seafood and/or poultry); and omnivore at 3 levels (all foods, with the proportion of red meat (in grams) out of total food consumed at <5%, 5-15%, and >15%). For Aim 3, DEX-modeled food patterns were constructed based on the NHANES 2007-08 reported food intake. A single high-DEX food was selected to represent each of the 150 What We Eat in America food categories, and used to substitute any reported food within that category which ranked below the 75th percentile for DEX, at equal mass as originally reported per participant. The DEX-modeled food patterns were standardized to 2000 kcal, and resultant changes in DEX, NDS, and EIS scores were evaluated. Results from Aims 2 and 3 were compared against nutritional intake recommendations in the 2015 Dietary Guidelines for Americans (DGA), and the direct environmental impacts were calculated. Results: Aim 1: DEX scores were calculated for 8,076 foods from the 2007-2008 National Health and Nutrition Examination Survey, median [25th, 75th percentiles]: 39.1 [34.0, 43.7], higher scores favored. Median DEX scores for food groups, highest to lowest, were legumes/nuts/seeds (48.2), grains (44.7), vegetables (43.0), fruits (41.8), dairy (40.4), poultry (36.8), seafood (32.7), pork (32.0), eggs (31.3), beef (28.1). The coefficient of variation of the DEX score within food group categories ranged from 13% to 32%. Aim 2: Average DEX score of dietary intake among NHANES participants was 39.6 ± 3.0. Among the food intake patterns, more favorable DEX scores were associated with lower consumption of meat, particularly red meat. The mean DEX of the lacto-ovo vegetarian category was highest (41.8), with similar mean scores between pesce-pollotarian (40.8) and light-meat omnivore (40.9), slightly lower for medium-omnivore (40.0), and with the lowest for heavy-meat omnivorous intake (37.6). Overall, participants in the highest DEX tertile category had superior HEI-2010 scores (p<0.001), and were better able to meet most DGA recommendations (p<0.01). Aim 3: Eliminating foods below the 75th percentile of DEX per WWEIA food category still allowed over 2000 food options, for which DEX, NDS, and EIS scores showed improvement by 15%, 9%, and 7%, respectively. After substituting all lower-scoring foods consumed with the high-DEX category representative, average DEX score of the modeled dietary intake was 44.0 ± 3.0. DEX-modeled diets showed overall higher intake of fruits, vegetables, and whole grains, and lower intake of meat. As a result, the distribution of DEX-modeled food intake patterns shifted significantly from their original counterparts observed in NHANES data. DEX-modeled diets were also associated with greater levels of beneficial nutrients, including fiber, iron, calcium, and vitamins A, C, and E, ranging from 32% to 82%. Levels of nutrients to discourage were modestly reduced, including saturated fat, added sugar, and sodium, from -12% to -16%. Individual direct environmental impacts improved by 11-17%. Conclusions: Our results demonstrate the importance of considering the relative nutrition-to-environmental impact of food choices, as only a modest correlation was found between nutrient density of foods and their environmental impact, and substantial variation was seen in DEX scores even within food groups. Our application of the DEX towards the assessment of observed versus modeled food intake patterns provides insight on how dietary intake reported by a nationally representative sample of the American population fares in aligning diet quality and sustainability, and how moving towards food decisions which incorporate environmental consideration may improve these results. Future evaluations may explore the potential association between the DEX and diet-related health outcomes. Additional considerations to enhance this research would be the inclusion of food prices as an economic indicator of sustainability. This work can further the development of a usable tool to promote sustainable public health nutrition, and aid individuals trying to identify ways to be environmentally conscientious in their dietary choices.
Thesis (Ph.D.)--Tufts University, 2018.
Submitted to the Dept. of Nutritional Epidemiology.
Advisor: Paul Jacques.
Committee: Timothy Griffin, Miriam Nelson, and Christian Peters.
Keywords: Nutrition, Epidemiology, and Environmental science.read less - ID:
- gq67k3886
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