dietary guidelines

Better adherence to dietary guidelines is known to reduce mortality risk but as per a recent study, it is also associated with lower environmental impact. The study shows the importance of dietary guidelines in reducing mortality risks, as well as greenhouse gas emissions and land use.

 

The food that we eat greatly influences our health and has a major impact on the state of the environment we all share. High body weight and unhealthy diets are the greatest contributors to premature mortality. At the same time, the food sector is responsible for more than a quarter of all greenhouse gas (GHG) emissions. The whole world recognizes the effects of global warming which has led to an interest in healthy and environmentally friendly dietary patterns. However, there is not enough information about the magnitude of impact dietary changes on the environment. Can adhering to dietary guidelines both reduce mortality risk and help the environment?

Current Dietary Guidelines

Current dietary guidelines such as those suggested by the World Health Organization (WHO) and Dietary Approaches to Stop Hypertension (DASH) are primarily based on health outcomes. Researchers measured the levels of adherence to these dietary guidelines using the Healthy Diet Indicator (HDI) and DASH score, respectively.  The HDI score (from 0 to 7) consists of six nutrients (SFA, PUFA, cholesterol, protein, dietary fiber, and free sugars) and one food group (fruits and vegetables). The DASH score (from 8-low adherence to 40-highest adherence) is based on the sum of consumption of nutritional components including fruits, vegetables, nuts and legumes, whole grains, low-fat dairy products, sodium, red and processed meats, and sweetened beverages.

Adherence to WHO guidelines by European and American elderly has been shown to increase longevity, while the DASH diet is associated with lower risk of cardiovascular disease, congenital heart defects, and stroke. Furthermore, the Dutch dietary guidelines of Netherlands were recently updated and adherence is measured by the Dutch Healthy Diet index 2015 (DHD15-index).

Effect of Adherence to Dietary Guidelines

A recent study published in the British Journal of Nutrition compared the effect of adherence to dietary guidelines on indicators of environmental impact and health outcomes. The study used data from the Dutch sub-cohort of the European Prospective Investigation into Cancer and Nutrition (EPIC-NL) that included 40,011 men and women aged 20-70 years between 1993 and 1997. The daily dietary intake of the participants was assessed using a 178-item questionnaire. The HDI, DASH score and DHD15-index were evaluated in relation to GHG emissions, land use, and all-cause mortality risk. All analysis was stratified by sex since the diets of men and women differ with respect to energy intake and environmental impact. Based on the level of adherence to dietary guidelines, the DASH scores and DHD15-index were grouped into tertiles. HDI was categorized into three groups with a score of 0-2, 3 and 4-7. The vital status of participants was obtained from municipal population registries and participants were followed up over time until death or mean follow-up of 19.2 years. Environmental impact was calculated based on life cycle assessments (LCA) of food items. The LCA data was combined with the EPIC-NL questionnaire data to calculate the GHG emissions (kg CO2 equivalents/d) and land use (m2xyear/d).

The comparison of dietary guidelines and environmental impact revealed that men’s diets, on average, have a higher total impact on the environment than women’s diets. In men, dietary GHG emissions are significantly lower for the HDI (-9.1%) and for the DHD15-index (-5.5%) but not for the DASH score. In women, better adherence to the guidelines is associated with statistically lower GHG emissions for HDI and DHD15-index but higher DASH scores were associated with higher GHG emissions (2.3%). All dietary guideline indices showed that a higher score is associated with lower land use for both men and women.

Reduced Mortality Risk

The comparison of dietary guidelines and all-cause mortality showed that there is significantly reduced mortality risk in the highest compared with the lowest category of the HDI for both men and women. A better adherence to both DASH and DHD-15 index is also found to be associated with reduced mortality risk.

In men, for the highest scores of HDI, there was the largest difference in environmental impact whereas for women, it is observed for the DHD15-index. In addition, higher DHD-15 index scores are associated with the lowest all-cause mortality risk in both men and women.

Moderate Reductions in Greenhouse Gas Emissions

Despite the conceptual differences in the dietary guidelines and the indices, the HDI, DASH and DHD15-index show similar associations with all-cause mortality but based on the results of this study, only HDI and DHD15-index are associated with possible reductions in GHG emissions and land use. The reductions in GHG emissions observed in this study were only moderate but there was a clear reduction in mortality risk.

A large population-based cohort with a long follow-up of 19 years is the main strength of this study. The study used both dietary and environmental data of the same population and linked it with the registered mortality data. In addition, three different indices for healthy diets were compared thus making the results more robust. Some limitations of the study include assessment of dietary intake and its environmental impact only at baseline and only in adults.

This study highlights the benefits associated with adhering to a healthy diet, both to reduce mortality risk and benefit the environment. A better adherence to dietary guidelines reduces mortality risk and positively impacts our environment by lowering GHG emissions and land use. Clearly, eating more plant-based diets and limiting our energy intake can help us achieve good health while limiting the environmental impact of what we eat.

Written by Preeti Paul, MS Biochemistry

Reference:

Sander Beisbroek, W.M. Monique Verschuren et al. Does a better adherence to dietary guidelines reduce mortality risk and environmental impact in the Dutch sub-cohort of the European Prospective Investigation into Cancer and Nutrition, British Journal of Nutrition (2017), 118, 69-80

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