Methods and participant characteristics in the Cancer Risk in Vegetarians Consortium: A cross-sectional analysis across 11 prospective studies

Background: The associations of vegetarian diets with risks for site-specific cancers have not been estimated reliably due to the low number of vegetarians in previous studies. Therefore, the Cancer Risk in Vegetarians Consortium was established. Objective: To describe and compare the baseline characteristics between non-vegetarian and vegetarian diet groups and between the collaborating studies. Methods: We harmonised individual-level data from 11 prospective cohort studies in the UK, US, India, China, and Taiwan. Comparisons of food intakes, sociodemographic and lifestyle factors were made between diet groups and between cohorts using descriptive statistics. Results: 2.3 million participants were included; 66% women and 34% men, with mean ages at recruitment of 57 (SD: 7.8) and 57 (8.6) years, respectively. There were 2.1 million meat eaters, 60,903 poultry eaters, 44,780 pescatarians, 81,165 vegetarians, and 14,167 vegans. Food intake differences between the diet groups varied across the cohorts; for example, fruit and vegetable intakes were generally higher in vegetarians than in meat eaters in all the cohorts except in China. BMI was generally lower in vegetarians, particularly vegans, except for the cohorts in India and China. In general, but with some exceptions, vegetarians were also more likely to be highly educated and physically active and less likely to smoke. In the available resurveys, stability of diet groups was high in all the cohorts except in China. Conclusions: Food intakes and lifestyle factors of both non-vegetarians and vegetarians varied markedly across the individual cohorts, which may be due to differences in both culture and socioeconomic status, as well as differences in questionnaire design. Therefore, care is needed in the interpretation of the impacts of vegetarian diets on cancer risk. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This work has been funded by the World Cancer Research Fund UK (grant 2019/1953). The funder was not involved in any of the following: study design, collection, analysis, interpretation of data, and writing of the report. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Each study in this consortium received ethical clearance from their respective ethical committees which covered future research. The Loma Linda University Institutional Review Board gave ethical approval for the Adventist Health Study 2. Ethical approval for the CARRS study was provided by Institutional Review Boards of PHFI, AIIMS, MDRF Chennai, India, AKU and Emory University. In addition, the study has received regulatory approval from the Health Ministry Screening Committee of India. The EPIC Oxford study was given ethical approval by Royal College of General Practitioners Clinical Research Ethics Committee, the Central Oxford Research Ethics Committee and local research ethics committees. The South Central Oxford C Research Ethics Committee gave ethical approval for the Oxford Vegetarian Study. The Institutional Review Board for ethics in the Buddhist Dalin Tzu Chi Hospital waived ethical approval for the Tzu Chi Health Study. The National Research Ethics Service Committee for Yorkshire and the Humber, Leeds East provided ethical approval for the UKWCS. The Ethical Review Committee of the Chinese Centre for Disease Control and Prevention, Oxford Tropical Research Ethics Committee, University of Oxford gave ethical approval for the China Kadoorie Biobank. The NHS Health Research Authority (approval provided by Anglia and Oxford Multi centre Research Ethics Committee) gave ethical approval for the Million Women Study. The Special Studies Institutional Review Board of the U.S. National Cancer Institute provided ethical clearance for the NIH AARP study. The North West Multi Centre Research Ethics Committee provided ethical approval for the UK Biobank study. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Data described in the manuscript will not be made available because studies pooled by the Cancer Risk in Vegetarians Consortium are not owned by the writing group and so are not available from this consortium. Individual studies may be contacted to request access to their data.