Diet and nutrition: health of vegetarians and vegans
Diet and nutrition
Diet is an important determinant of good health, but many questions remain about whether and how dietary and nutritional factors may affect a wide range of diseases. Our research is examining a number of prominent hypotheses in relation to diet and health. Diet has been measured in EPIC-Oxford and the Million Women Study, and we are also leading dietary analyses in the UK Biobank, for which we have developed the Oxford WebQ. We have assessed diet with traditional methods such as food frequency questionnaires, and we are now also using internet-based measures of diet as well as a range of biomarkers of nutritional status and metabolic profile. Current analyses include the role of diet in the aetiology of cancers of the prostate (see prostate section), breast and colorectum, and in relation to the risk of a range of other cardiometabolic, musculoskeletal and gastro-intestinal disorders.
Health of vegetarians and vegans
Our group has been studying the long-term health of vegetarians and vegans since the establishment of the pioneering Oxford Vegetarian Study in 1980. Recent estimates suggest that up to 3 million people in the UK are vegetarians, but the long-term effects on health of a vegetarian diet are not well understood, and comparatively little is known about the health effects of a vegan diet. Our previous research has demonstrated lower risks of obesity, ischaemic heart disease, diabetes, stomach cancer and perhaps haematological cancers in vegetarians compared with non-vegetarians (Davey and Key 1996, Tong et al 2019, Papier et al 2019; Key et al 2014), but also higher risks of stroke and fractures (Tong et al 2019, Tong et al 2021), and further research is needed to assess both the beneficial effects of a vegetarian diet and possible hazards associated with relatively low intakes of some nutrients, such as protein, long-chain n-3 fatty acids, vitamin B12, vitamin D and calcium (particularly in vegans). Recruitment into EPIC-Oxford was targeted at vegetarians and other people interested in diet and health, as well as the general population, and the participants comprise 34,000 meat eaters, 10,000 people who eat fish but not meat, 19,000 lacto-vegetarians and 2,500 vegans. Participants have been followed-up for nearly 30 years by means of repeat questionnaires and linkage to NHS medical records (see EPIC-Oxford). We are also examining the impacts of vegetarian and vegan diets on physiology and metabolic profile and disease risk in the UK Biobank, and leading a worldwide consortium focused on cancer risk in vegetarians.