The Overall, Healthful, and Unhealthful Plant-Based Diet Indices: Relative validation and associations with weight gain and mortality Restricted; Files Only
Cousineau, Benjamin (Fall 2025)
Abstract
Poor diet quality is a leading risk factor for many non-communicable diseases and pre-mature mortality. Dietary guidelines recommend diets rich in plant foods such as fruits, vegetables, whole grains, and legumes to support optimal health. Plant-based diets are generally considered to have high diet quality. Vegetarians and vegans have lower rates of obesity, cardiovascular disease, and certain cancers when compared with those following traditional Western diets. Historically, longitudinal studies have relied primarily on dichotomous classifications of plant-based diet patterns (e.g., vegetarian, vegan) and are limited in their ability to assess differences in diet quality among various plant-based diets and whether these differences are related to long-term health outcomes.
In this dissertation, we applied three recently developed plant-based diet quality indices, the Overall Plant-based Diet Index (PDI), the Healthful Plant-based Diet Index (hPDI), and the Unhealthful Plant-based Diet Index (uPDI), to examine their validity in a comprehensive food frequency questionnaire and their longitudinal associations with weight change and mortality in several US prospective cohorts.
In Aim 1, we evaluated the performance of each diet index by examining their performance using repeated measures of a comprehensive food frequency questionnaire (FFQ), multiple 24-hour dietary recalls, and nutritional blood and urine biomarkers in the Cancer Prevention Study-3 Dietary Assessment Sub-study (n=677). We observed good reproducibility and moderate to good validity across all three indices in both women and men, with slightly lower validity among non-white and Hispanic adults. Performance metrics were higher for hPDI and uPDI compared to PDI.
In Aim 2, we examined associations between adherence to PDI, hPDI and uPDI and 6-year changes in body weight in women and men from the larger Cancer Prevention Study-3 cohort (n=99,756). Highest adherence to plant-based diets rich in healthy or total plant-foods was associated with lower 6-year weight gain compared to those with low adherence, with the stronger associations among females adhering to a healthy plant-based diet, younger adults, and females with a lower BMI.
Lastly, in Aim 3, we investigated associations between each plant-based diet index and risk of cardiovascular disease, cancer, and all-cause mortality among women and men in the Cancer Prevention Study-II (n=84,978). Over a mean ± SD follow-up of 16.9 ± 5.5 years, we observed that higher adherence to a plant-based diet rich in healthy or total plant-based foods was associated with 21-24% lower CVD mortality and 18-25% lower all-cause mortality, whereas higher adherence to uPDI was associated with 22% and 23% higher mortality risk for both respectively. Only PDI was associated with lower cancer mortality risk of 17%.
Collectively, these findings provide insight to the performance of three popular indices and support the promotion of diets emphasizing healthy, minimally processed plant foods and limited animal foods to improve weight management and reduce mortality risk.
Table of Contents
Contents
Chapter 1: Introduction 1
Chapter 2: Background 12
2. 1 Burden of chronic disease 12
2. 2 Diet quality and chronic disease 12
2. 3 Dietary intake assessment 13
2. 4 Diet quality indices 14
2. 5 Defining plant-based diet patterns 15
2. 6 Vegetarian, vegan, and Mediterranean diet patterns 16
2. 7 Health promoting mechanisms of plant foods 17
2. 8 Plant-based diet quality indices 18
Chapter 3: Reproducibility and validity of plant-based dietary indices in the Cancer Prevention Study-3 Diet Assessment Sub-Study. 26
3. 1 Introduction 27
3. 2 Methods 28
3. 3 Results 35
3. 4 Discussion 38
3. 5 Conclusions 42
Chapter 4: Associations between plant-based diet quality and 6-year body weight change in the Cancer Prevention Study-3 61
4. 1 Introduction 62
4. 2 Methods 63
4. 3 Results 69
4. 4 Discussion 72
4. 5 Conclusion 76
Chapter 5: Quality of plant-based dietary patterns in association with cardiovascular disease, cancer, and all-cause mortality in the Cancer Prevention Study-II Nutrition Cohort. 103
5. 1 Introduction 104
5. 2 Methods 105
5. 3 Results 110
5. 4 Discussion 113
5. 5 Conclusions 118
Chapter 6: Expanded Discussion 148
6. 1 Summary of key findings 148
6. 2 Implications to public health 150
6. 3 Strengths & limitations 152
6. 4 Future directions and considerations 153
6. 5 Conclusions 154
About this Dissertation
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File download under embargo until 12 January 2032 | 2025-12-18 12:39:19 -0500 | File download under embargo until 12 January 2032 |
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