Innovative indicator tracks diet impact on health and environment

In order to monitor and operationalize food system shifts, it is essential to understand how diets affect health and the environment.

A recent Nature Food study put forward a health–environment efficiency indicator to evaluate how diets have historically supported healthy lives, environmental pollution, and resource consumption across 195 countries.

Study: Health–environment efficiency of diets shows nonlinear trends over 1990–2011. Image Credit: Foxys Forest Manufacture/Shutterstock.com

Background

Altering dietary patterns for health benefits and lowering the harmful effects on the environment has become extremely important in policy agendas worldwide.

Poor diets, besides having an adverse impact on health, may also cause damage to the environment through higher water consumption to manufacture, anthropogenic greenhouse gas (GHG) emissions, and so on. 

In order to attain Sustainable Development Goals, such as good health and well-being and zero hunger, it is imperative to engage in sustainable food consumption patterns.

Prior research has not fully explored the joint association between changes in socio-economic development and environmental and health outcomes of diets.

About the study

Addressing the aforementioned gap in the literature, this study assessed the environmental–health interactions of diets with socioeconomic development for 195 countries.

The study sample was the time period between 1990 and 2011. A health–environment efficiency indicator was constructed. This was taken as the ratio between environmental impacts and health benefits stemming from food production and consumption.

Lowering disability-adjusted life years (DALYs) was an indicator of health benefits. DALY quantifies the years of healthy life lost due to diet-associated disability or mortality.

The health environment efficiency was based on four indicators, namely, GHG emissions, acidifying emissions, eutrophying emissions, and scarcity-weighted water withdrawal. Associations between these indicators and a country’s Socio-Demographic Index (SDI) were noted. 

The SDI is a concept that is related to the human development index (HDI), but the difference is that SDI does not include direct health outcomes.

This prevents the confusion of outcomes and determinants. In varied socio-economic contexts, the SDI compares health outcomes across countries. 

Study findings

A non-linear N-shaped response of the health–environment efficiency was noted in response to an increase in SDI. In other words, the correlation between the two variables was positive, negative, and positive.

The first stage’s positive association was driven by the elimination of maternal and child malnutrition due to higher food supply.

In contrast, the second stage’s negative relation was driven by adverse environmental impacts due to a shift to more aminal products. The final stage of positive association in some developed countries was largely due to their shift towards healthier diets.

The proposed indicator is useful for integrating environmental and health impacts, whether contradicting or conforming.

The indicator is versatile and can be modified for a wider ecological concern spectrum. Furthermore, it can account for the technological progress and other dynamic factors that drive temporal changes in environmental effects.

Policymakers can use the health-environment efficiency indicator to make cross-country comparisons, thereby identifying areas for improvements and best practices.

They can even use this indicator to assess the effectiveness of dietary trends and policy interventions in their own countries. 

Countries should aim to shift to healthier diets while minimizing adverse environmental impacts.

Developed countries, which are at the right end of the SDI, can follow the methods of Japan and Norway by simultaneously reducing meat consumption and augmenting the consumption of fruits, vegetables, and whole grains. 

Other measures, such as urban planning and guidance on dietary behavior through education, are crucial for low- and middle-income countries.

Demand and supply-side issues can be difficult to change if deeply rooted in specific physical and socio-economic contexts. However, urgent action is needed, considering the high medical costs associated with diets high in fat and meat content.

Limitations of the study

The first limitation centers around potential endogeneity issues in the regression analysis.

There were many observable and unobservable factors that could have influenced diet-related DALYs and environmental impacts.

Given that environmental problems affect the SDI, there is also the possibility of reverse causality. A second limitation of the data used was the heterogeneity in production technologies across countries, which made it difficult to assess the regional differences in the environmental impacts of producing a particular food item. 

Due to better data availability, there was more information on developed countries. This could lead to an incorrect assessment of the environmental impacts when applied globally.

However, the ranking of food items with regard to their environmental impacts should remain the same across regions.

This study also ignores within-country heterogeneity by focussing on the national average for food consumption.