The categorisation of whole-grain foods in dietary recommendation models – processing and health

Suboptimal diets, including excess or inadequate intakes of individual dietary components, significantly impact health. For example, a diet low in whole grains is the leading dietary risk factor attributed to global CVD-related deaths. In contrast, the food classification system known as Nova, classifies a significant number of whole-grain foods, especially many breads and ready-to-eat cereals, as ultra-processed foods (UPF). This thesis aims to investigate whole grains in global diets, with a focus on health impacts related to the level of processing. A systematic scoping review identified bread and bread rolls, and ready-to-eat cereals as the primary sources of whole-grain intake across Australia, New Zealand, Europe, the United Kingdom and Northern America but elsewhere sources varied, and intake data was not identified for continents such as Africa and Asia. Methods of quantification of whole-grain content in foods varied across countries, resulting in calculating whole-grain intakes based on consumption of only select “whole-grain” foods. Greater consistency in whole-grain quantification methods is required to support comparative research informing current intake evidence and public health promotional efforts. Secondary analysis of nationally representative intake data from Australia and the United States (US) investigated the contribution of whole grain sourced from UPF to total whole grain intake. We further explored excluding higher whole-grain containing foods (≥50% and ≥25% based on dry weight) from the Nova UPF category to understand how this theoretically impacts previously established associations of intake of UPF with cardiometabolic risk measures. Some associations were observed for both non-ultra-processed and ultra-processed whole-grain intake and some cardiometabolic risk factors. When excluding high whole-grain foods from the UPF category, associations and adjusted R-squared values remained similar. All whole-grain foods provide some health benefit, but it may be ideal to emphasise less processed sources due to greater observed benefit to cardiometabolic risk measures. Focus groups and interviews considered how whole-grain foods, and their level of processing related to health is perceived by consumers (as purchasers of whole grain foods) and food industry personnel (producing whole-grain foods) respectively. Consumers generally perceived whole grains as less processed, while suggesting processing elements, such as additives may influence their food choices, healthfulness was typically judged based on the presence or absence of certain nutrients. Food industry personnel viewed food processing as complex but oversimplified in current food processing classification systems. They emphasised the importance of holistic consumer education to help consumers differentiate between less healthy and ‘healthier’ processed foods. Messaging around food processing should consider nutritional quality of foods to ensure consumers. This thesis demonstrates whole-grain foods of all processing levels, as defined by Nova, are associated with health benefits albeit with potential greater benefit on cardiometabolic risk measures from those that are less processed. There is a need for more primary research data to clarify the mechanisms by which different types of processing impact health outcomes, particularly to address the nuanced evidence regarding whole grains in current food processing classifications.