Nutritional and Environmental Impacts of Foods on Human Health

Abstract

Suboptimal diet is a major public health concern, responsible for ~10 million death/year globally associated with nutrition, plus additional deaths associated with environmental emissions from food production. Informing consumer choices is crucial and would require to consistently combine latest epidemiological evidence on the impact of diet and pollution, with life cycle assessment (LCA) of food systems to analyze relevant trade-offs.

This dissertation aims to address four critical challenges for assessing the life cycle impact and benefits of food systems on human health: (1) The failure to capture both environmental impacts and nutritional effects of foods consistently. (2) The lack of nutritional assessment metrics that evaluate the performance of individual food items based on health burden. (3) The overly simplified assessment of impacts of particulate matter (PM2.5) on human health, which do not consider spatial variation in exposure, nor evidence for non-linear exposure-response. (4) The need for a consistent approach to evaluate multi-ingredient mixed dishes, a central component in modern diets.

Chapter 2 developed a novel Combined Nutritional and Environmental Life Cycle Assessment (CONE-LCA) framework that evaluates and compares in parallel the environmental and nutritional effects of foods or diets in a common metric, disability adjusted life years (DALYs). A proof-of-concept case study indicated that nutritional health net benefits of adding a serving of milk to the average U.S. diet exceeded environmental impacts and highlighted the need for considering nutrition as a new LCA impact category.

Chapter 3 operationalized the nutritional approach by establishing the Health Nutritional Index (HENI). This health burden-based nutritional index quantifies the health burden of one food serving in minutes of healthy life lost or gained, using epidemiological evidence for a comprehensive set of 16 dietary risks. Application to ~7,000 food items in the U.S. diet revealed substantial variability in HENI scores between and within food categories, thus the importance of informed choices at the level of individual food items.

In Chapter 4, we developed spatially-explicit intake fractions for ground-level PM2.5, NH3, SO2, and NOx emissions in the contiguous U.S. for agriculture and other relevant sectors. Using a non-linear exposure-response function and state-specific burden data, we developed the corresponding characterization factors considering a marginal and an average slope. Spatial estimates varied by three orders of magnitude, sector-specific estimates by a factor of four, and the average slope doubled estimates compared to marginal. This work stressed the importance of spatially-explicit and sector-specific estimates in LCA.

Finally, in Chapter 5 we established a new nutritional impact category for LCA, providing both inventory flows and nutritional characterization factors, and a systematic approach to decompose mixed dishes into individual components for which environmental life cycle inventory is available. Using a case study of pizzas, we quantified and compared environmental and nutritional impacts on health and found that nutrition dominates health damages. Nutritional and environmental impacts were correlated with red meat pizzas generating the highest and vegetable pizzas the lowest health damages.

This dissertation provides the foundation for evaluating nutritional and environmental impacts of foods and diets comprehensively and systematically in food sustainability assessments and LCAs. It introduces a new nutritional LCA impact category, pioneers a powerful nutritional health based index that can inform healthier dietary choices and substitutions, and improves PM2.5 impact assessment. Findings can inform sustainable decision making for foods and diets within and beyond LCA.