The potential for environmental sustainability-driven dietary change to improve health: a systematic review with modelling analyses
What we eat is important to our health and longevity. Unfortunately current diets are a major contributor to the burden of non-communicable disease, with interventions for individuals and the food environment required to improve dietary intakes. Interventions motivated by individual-health status however, may have unintended consequences such as feelings of shame and stigma, resulting in poor adherence. Because healthy dietary patterns are often of low environmental impact, there is potential to frame healthy diet messages around environmental sustainability. I have conducted a systematic review to identify what environmental sustainability-driven scalable initiatives aimed at improving dietary intakes have been undertaken previously. The results from this review identified the scarcity of such initiatives, providing justification for the use of simulation modelling to estimate the potential impact of population-wide environmental sustainability-driven dietary change on health outcomes, environmental measures, and costs to the individual. One of the primary contributors to increased greenhouse gas emissions and land use is food production, however the environmental burden varies considerably between food groups. The largest contributor to greenhouse gas emissions within the diet is red meat production. Conversely, some of the lowest contributors to greenhouse gas emissions within the diet are those food groups often promoted in red meat replacement, such as legumes, soy, nuts and seeds. From a health perspective high red and processed meat intakes are associated with increased risk of premature mortality, heart disease, type 2 diabetes, and certain cancers, while legume, soy, nut, and seed intakes are protective. To better understand the effects of red and processed meat replacement in Aotearoa New Zealand, I have modelled five scenarios and their expected effect on health and environmental outcomes, as well as grocery cost to the individual in a multistate lifetable model using Adult Nutrition Survey data. The scenarios were in line with Heart Foundation (1) or EATLancet (2) recommendations, or a replacement with minimally-processed plant-based alternatives (3), ultra-processed plant-based alternatives (4), or cellular meat (5). The change in food group intake for each scenario was calculated, with the nutrient adequacy of each scenario considered. Replacing red and processed meats, regardless of the scenario, would have beneficial consequences in terms of health and health system costs, reduced health inequities, and greenhouse gas emissions, with some scenarios reducing the expected grocery cost to the individual. Replacing red and processed meat intakes did not result in sub optimal intakes of key nutrients associated with red meat, such as protein, iron, zinc, or vitamin B12. Findings extend and confirm current dietary advice to reduce red and processed meat intake. For the greatest health and environment benefits, as well as greatest cost saving to the individual of the scenarios modelled, red and processed meat replacement should first and foremost be with minimally-processed plant-based foods such as legumes. Replacement with ultra-processed plant-based alternatives was costlier to the individual and increased the sodium content of the diet. Future research should consider if environmental sustainability-driven, rather than health-driven, interventions prompt dietary change, and how food environments may promote behaviour change to encourage minimally-processed plant-based eating patterns.
Advisor: Cleghorn, Cristina; Ni Mhurchu, Cliona
Degree Name: Master of Public Health
Degree Discipline: Public Health (Wellington)
Publisher: University of Otago
Keywords: Dietary modelling; Red meat reduction; QALY; Environmental sustainability; Equity; Grocery cost
Research Type: Thesis