The Impact of Dietary Macronutrient Composition on Noncommunicable Diseases and Aging: A Life Course Approach

Abstract

Background: Nutrition is vital for human health and is a key modifiable risk factor in the development of noncommunicable diseases (NCDs), which account for 74% of global annual deaths. Aging increases disease risk, and nutritional associations vary across life stages. However, current research often focuses on individual nutrients rather than complex associations. Therefore, this thesis investigates the association of macronutrients with NCDs and aging throughout the lifespan using a multi-nutrient approach known as the Geometric Framework for Nutrition.

Aims: Six studies were conducted to explore the following aims at varying stages of the life course:

1) How are macronutrients linked to NCDs?

2) Is dietary macronutrient composition associated with markers of biological aging?

3) What roles do diet quality, food groups, and factors like the microbiome play in macronutrient-NCD and aging relationships?

Results: Findings from this thesis revealed a complex nonlinear relationship for macronutrients with aging (Chapters 4, 6), metabolic health (Chapters 4, 5), and disease outcomes (Chapter 7). These relationships suggest that there is no single optimal macronutrient composition for all outcomes. Notably, the microbiome was shown to play a potential effect-modifying role in how diet impacts cardiometabolic health (Chapter 8). Furthermore, the final study revealed that macronutrient composition associations with NCDs widely differ according to diet quality (Chapter 9).

Conclusions: Dietary macronutrient composition is intricately linked to metabolic health, aging, and NCD risk, with variations based on diet quality, life stage, and potential modification by factors like the microbiome. The findings emphasize the need for a comprehensive and standardized approach to nutritional research that considers each of these aspects before providing dietary guidance or making public health recommendations.