EPIC-Oxford: benefits and risks of plant-based diets

Plant-based diets, which include little or no food from animal sources, might have benefits for both health and the environment. The available evidence supports substantial advantages for such diets in reducing diet-related greenhouse gas emissions and other environmental impacts, but the evidence for health is sparse and there may be both benefits and risks. For example, the low intakes of saturated fat and high intakes of fibre characteristic of plant-based diets may reduce risks for some cardiovascular and gastrointestinal diseases, but the low intakes of high quality protein, some vitamins and calcium might increase risks for conditions such as some types of stroke, and bone fractures. To address this gap in the evidence we aim to enhance and extend a mature longitudinal population study in the UK to establish the world's most informative resource for studying the health benefits and risks of plant-based diets. The EPIC-Oxford cohort, which has 65,000 participants living throughout the UK, was initiated 30 years ago with recruitment targeted to oversample people following vegetarian diets, and 50% of the participants do not eat meat. This resource has detailed information on diet, a large biobank (collection of stored blood samples), and comprehensive linkage to NHS datasets on all hospital admissions, cancer diagnoses and deaths, making it unique in the world for research on the long-term health impacts of plant-based diets. We aim to enhance the existing resource by a resurvey of all surviving participants, and to extend it by recruitment of 80,000 new participants to increase statistical power and the number of people following close to 100% plant-based diets (i.e. vegan, or very low intakes of any animal products), as well as to improve the ethnic diversity of the resource. We will also extend the biobank, collecting blood samples from a further 5,000 participants selected with regard to diet group, age, gender and ethnicity, to enable further research on the impacts of plant-based diets on the functioning of the body. We have completed a pilot study recruiting 6,000 new participants, 3,000 plant-based, which has demonstrated the success and cost-effectiveness of our internet-based recruitment method, and allowed us to refine our dietary questionnaire and obtain up-to-date information on the food and nutrient intakes of these people. To make the proposed new EPIC-Oxford resource widely accessible, we will transfer the data we collect on diet and lifestyle to the UK Longitudinal Linkage Consortium (UK LLC) trusted research environment. The UK LLC will then extend the linkage to all NHS datasets providing details of diseases and conditions diagnosed in participants throughout the UK, and manage access to the resource for analyses by other researchers. The research made possible by creating this resource will provide, for the first time, robust evidence on the long-term benefits and risks of plant-based diets, and on whether any risks identified can be mitigated.