Dissertations & Theses (Open Access)

Date of Award

Spring 5-2020

Degree Name

Doctor of Philosophy (PhD)

Advisor(s)

Alexandra E.M. Van Den Berg, Phd, Mph

Second Advisor

Deanna M. Hoelscher, Phd, Rdn, Ld, Cns, Fisbnpa

Third Advisor

Baojiang Chen, Phd, Ms

Abstract

Both globally and within the United States, chronic disease has become a major driver of mortality and morbidity. In the United States in 2017, the top ten causes of mortality accounted for 74% of all deaths [2]; of these causes, half are closely linked to diet (heart disease, cancer, stroke, Alzheimer’s and diabetes). [3] In 2013, Ioannidis estimated that 26% of deaths and 14% of disability adjusted life years (DALYs) in the United States may be attributable to dietary risk factors, controlling for obesity. [4] At the same time, diet also has an important impact on the environment. Direct emissions from food production contribute 9% to global Greenhouse Gas (GHG) emission totals, while the livestock sector contributes 50% to that total [5]. Indirect impacts from land use and habitat destruction are also influential, reducing the ability of the environment to sequester carbon while contributing to widespread species extinction. Incorporating both direct and indirect mechanisms, Herrero (2013) estimates that switching from the current dietary pattern to a plant-based dietary pattern may reduce global Greenhouse Gas (GHG) emissions by 28% [6]. Clearly, there is a need to define and encourage dietary patterns that reduce the risk of chronic diseases while also protecting the environment from the threats of climate change and mass extinction. Proposed solutions must address both proximal impacts, such as human health outcomes, as well as distal outcomes, such as climate change and biodiversity loss. In order to do so, any proposed remedy must also be feasible and equitable for diverse 2 populations. A plant-based diet may offer the best option for achieving these multi-factorial goals. Because animal products are reduced rather than eliminated, a plant-based diet may be more acceptable to a greater number of individuals. In addition, including some animal products in the diet can reduce the likelihood of nutrient deficiencies (B12 and Vitamin D) that are associated with total elimination of animal products from the diet. Finally, advocating for a plant-based diet is less likely to become mired in the ever-changing and confusing minutiae of dietary advice, allowing for a simple message that allows for great variation and adaptability across cultures and socioeconomic circumstances. Therefore, this dissertation intends to assess the impact and the utility of a plant-based diet as a means of improving health and mitigating the environmental impacts of diet. This literature review aims to first explore the association of a plant-based diet to several prevalent chronic disease outcomes: obesity, cardiovascular disease (CVD), type II diabetes (T2D), and cancer. In addition, the impact of consuming meat in the diet will be explored separately, as this has been found to be separate both behaviorally and physiologically. Next, the intersection of diet and the environment will be assessed, with particular focus on the impact of a plant-based diet on GHG emissions, land use and biodiversity. The implications on climate and health equity are also addressed, since these aspects of the current system, as well as the potential impacts of policies intended to influence diet, must be examined in order to ensure all populations may participate and benefit. Finally, the psychosocial determinants of behaviors around consumption of both plants and animals are explored, with the intention to understand how best to intervene and possibly improve dietary patterns at the population level.

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