Plant-based diets for reducing cardiovascular disease risk

Austin, Grace Elise

Title: Plant-based diets for reducing cardiovascular disease risk
Creator: Austin, Grace Elise
Relation: University of Newcastle Research Higher Degree Thesis
Resource Type: thesis
Date: 2024
Description: Research Doctorate - Doctor of Philosophy (PhD)
Description: Cardiovascular disease (CVD) continues to be the leading cause of death across the globe, and it is estimated 80% of heart disease and stroke are preventable. Lifestyle and dietary pattern modifications are the most important primary prevention of CVD as they influence metabolic pathways associated with risk factors including hypertension, type 2 diabetes (T2D), dyslipidaemia, sustained low-grade inflammation, overweight and obesity. Individuals are adopting a plant-based diet (PBD) on a global scale, and they have recently been incorporated within the Australian CVD risk guidelines and numerous dietary guidelines overseas have emphasised plant-proteins and plant-based eating patterns. PBDs are known to be beneficial for cardiovascular health, however evidence within the Australian population is nearly non-existent. The overarching aim of this thesis was to examine the CVD risk and health status in Australians following various PBDs compared to a regular meat-eating diet. The first aim of my thesis presented in chapter 3, was to investigate the effect of PBDs on weight status among individuals with T2D. A systematic review and meta-analysis of randomised controlled trials was conducted and found that when compared to a regular meat-eating diet, PBDs reduced body weight, body mass index (BMI), and waist circumference (WC). When examining the effect of PBDs compared to baseline measures, the reduction in body weight and BMI was enhanced to >5%, a level deemed clinically significant among this population. Chapters 4, 5, 6 and 7 are from a cross-sectional study, the major project of my thesis. This study recruited 240 healthy middle-aged adults to examine the health status and risk of CVD in individuals following PBDs compared to a regular meat-eating diet (RMD). Participants habitually following one of five dietary patterns were categorised into the following groups: vegan, lacto-ovo-vegetarian (LOV), pesco-vegetarian (PV), semi-vegetarian (SV) and regular meat eater (RME). The second aim of this thesis was to explore dietary intake and nutritional adequacy of PBDs compared to a regular meat-eating diet, presented in chapter 4. It was observed that those adhering to a vegan and LOV dietary pattern had the most favourable nutrient compositions, however, held greater risk of nutrient inadequacies. Vegans and LOVs had lower dietary intakes of saturated fat, trans fat, cholesterol, sodium, and higher carbohydrate, dietary fibre, thiamine, vitamin E, folate, magnesium, iron, and omega-6 polyunsaturated fatty acids (n-6PUFA), whereas PVs and SVs had moderate intakes when compared to RMEs. Individuals adhering to a vegan dietary pattern had inadequate nutrient intake of vitamin B₁₂, iodine, long-chain omega-3 polyunsaturated fatty acids (LCn-3PUFA) and calcium, although rates of inadequate nutrient intake varied among SV, LOV, and PV dietary patterns. Examining adequacy of macronutrient intake revealed all dietary patterns met adequate intake for protein, exceeded for fat, and were below for carbohydrate. Those adhering to PBDs consumed more daily serves of vegetables, fruit (vegans only), legumes/nuts and less discretionary choices/sugar sweetened beverages in comparison to the regular-meat diet. Adequacy of daily food group consumption revealed, even with the inclusion of plant-based alternatives, vegans, LOVs, and SV had inadequate serves of protein-rich foods, and SV and RMEs fell just below the daily recommended serves of dairy. The third aim of my thesis was to examine the predicted 5-year and 10-year risk of developing CVD in Australian individuals following various PBDs compared to a regular meat-eating diet, presented in chapter 5. Crude analyses demonstrated PBDs, specifically the vegan dietary pattern reduced 5-year and 10-year predicted risk of CVD in comparison to RMEs. The addition of confounders; age, sex, smoking status, and alcohol intake reduced the strength of this association, indicating that other lifestyle factors beyond dietary pattern influence predicted CVD risk estimates. Furthermore, participants had comparably low levels of chronic diseases, metabolic syndrome, use of medications and higher levels of physical activity across both PBD categories and regular-meat-eating diets, therefore most participant’s risk scores equated to low risk. PBDs reduce the 5-year and 10-year predicted risk of CVD, however, the interactions with other lifestyle factors are indicated. The fourth aim of this thesis was to examine the association between individuals following various PBDs and plasma lipids and glycaemic indices compared to a regular meat-eating diet, presented in chapter 6. Finding showed adherence to a vegan dietary pattern was associated with favourable plasma lipids and glycaemic indices characterised by lower total cholesterol (TC), low-density lipoproteins (LDL-C), non-high-density lipoprotein cholesterol (non-HDL-C), TC/HDL-ratio, fasting blood glucose (FBG), haemoglobin A1C (HbA1c) and insulin concentrations, when compared to regular a meat-eating dietary pattern. LOVs and SV had only a moderate association with lipid profiles and glycaemic indices as only some outcomes reached significance. Difference in plasma lipid levels and glycaemic indices are in line with reduced CVD risk among individuals adhering to PBDs. The fifth and final aim of this thesis was to investigate the association between PBDs and body composition, weight status and whole-body bone mineral density (BMD) compared to a regular meat-eating diet, presented in chapter 7. Findings demonstrated that WC was lower in individuals adhering to all PBDs compared to a regular-meat-eating diet. Whole-body BMD and bone mineral content (BMC) was not different between those following PBDs and regular-meat diets, except for LOVs who had borderline lower lean mass. Recommended dietary intake for calcium and protein were adequate, and serum 25-hydroxy-vitamin D (25(OH)D) was similar across groups, a likely key factor underpinning the observed comparable outcomes for whole-body BMD. There were also no differences in any other weight status nor body composition parameters. These analogous weight status outcomes may be explained by participants having comparably, healthy BMIs and low obesity rates across both plant-based and regular meat-eating diets. Adhering to a PBD is not associated with meaningful changes in BMD or body composition, provided that the dietary patterns are planned appropriately with adequate levels of calcium and protein. This thesis investigated several critical questions and concerns surrounding the possible health outcomes and nutrition implications of following PBDs, which until now have mostly been unexplored, particularly in the Australian context. This research utilised a sample of Australian habitually following PBDs, and results are reflective of the current food supply, inclusive of plant-based alternatives and their fortification status to allow better translation to clinical practice and nutrition policy. In summary, findings may 1) aid the development of national dietary strategies and guidelines to achieve nutritional adequacy for individuals following plant-based eating patterns, 2) better inform practitioners, health care providers and the community of the current health status of Australians following PBDs with particular focus on cardiometabolic health and lastly 3) given the identified nutritional implications, help guide industry product development and reformulation of plant-based alternatives which are of rising consumption in today’s climate. Findings from this study promote further investigation in larger population-based prospective cohort studies that cohesively define various PBDs, that utilise validated dietary assessment tools specific to PBDs and incorporate biochemical measures of nutritional markers to verify the observed differences across plant-based and regular meat-eating diets.
Subject: plant-based diets; cardiovascular disease; cross-sectional; thesis by publication; vegan; vegetarian; lacto-ovo vegetarian; pesco-vegetarian; semi-vegetarian; nutrition; dietetics; nutritional biochemistry
Identifier: http://hdl.handle.net/1959.13/1513653
Identifier: uon:56756
Language: eng
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