Oxford Vegetarian Study
The Oxford Vegetarian Study (OVS), also known as the Study of Cancer in Vegetarians, began in 1980. 11,040 participants were recruited through the Vegetarian Society of the United Kingdom, publicity in local and national media and by word of mouth between September 1980 and January 1984. Participants joined the study by voluntarily completing and returning a diet and lifestyle questionnaire. The aim of the study is to investigate the long-term health of vegetarians and comparable non-vegetarians, with particular interest in cancer risk and mortality.
The design is an observational cohort, based on recruiting healthy volunteer participants and following their long-term health through linkage to NHS information on incident cancers and causes of death. Participants in the study were flagged with the Office for National Statistics (ONS) and the cancer registries. Analysis of data arising from the study, sometimes in combination with data from the EPIC-Oxford study, has led to many publications in peer reviewed journals such as the British Medical Journal and the British Journal of Cancer.
Data were initially collected by questionnaires on diet and lifestyle, returned by post from 1980 to 1984 from all 11,040 participants. Blood samples were collected by post between 1984 and 1986 from 3,773 participants and plasma prepared and stored. Assays were conducted and papers reporting the findings were published between 1987 and 1992, and the plasma samples have subsequently been destroyed. Food diaries (four day records) were collected by post in 1985 and 1986 from 5,551 participants.
In 1994, we wrote to all surviving participants in the Oxford Vegetarian Study, informing them of the findings to date enclosing a list of published papers, and inviting them to join the European Prospective Investigation into Cancer (EPIC)-Oxford study.
Each participant in The Oxford Vegetarian Study is followed up for cancer diagnosis, and for causes of death through the NHS and the Office for National Statistics. In England and Wales this linkage is done through NHS England. To do this, details including name, NHS Number and date of birth plus a unique study identifier are supplied by the study investigators to NHS England. This linkage was carried out under Section 251 of the NHS Act 2006. NHS England provided us with information about people who may have passed away (mortality data) and cancer diagnosis data until 2019. This information includes month and year and cause of death, and month and year of cancer diagnosis and type of cancer, supplied by NHS England on behalf of the Office for National Statistics and is sourced from civil registration data. NHS England then supplied the mortality and cancer information together with the unique identifier with no names or other details back to the study. The information provided will not be linked back to the participant record, but stored in a database which will be used for analysis, where an individual participant cannot be identified. For participants in Scotland equivalent data linkage was performed by the Public Benefit and Privacy Panel for Health and Social Care, and for Northern Ireland this linkage is done by the Central Services Agency.
All subsequent analyses use only subsets of de-identified data. The data are held only at the Cancer Epidemiology Unit based at The Nuffield Department of Population Health (NDPH) at the University of Oxford. No data are released or shared in any form that would enable individual participants to be identified.
Participants can request more information about how we use their data and also find out about their options to withdraw consent for us to use their data in our Frequently Asked Questions.
Analyses of the data gathered on the cohort from 1980 to 2019 have resulted in 18 publications in peer reviewed journals as listed on the OVS publications page.
Results from the most notable publications:
- Cross-sectional analyses of study data and assays using the plasma samples showed that vegans had lower total- and LDL-cholesterol concentrations than did meat eaters; vegetarians and fish eaters having intermediate and similar values (Thorogood et al, 1987).
- Plasma total cholesterol was strongly positively associated with the Keys score (Thorogood et al, 1990).
- Meat and cheese consumption were positively associated and dietary fibre intake was inversely associated with total cholesterol concentration in both men and women (Appleby et al, 1995).
- Mortality from ischaemic heart disease was higher in participants with higher intakes of saturated fat and cholesterol (Mann et al 1997).
- Risk of colorectal cancer increased in association with smoking, alcohol, and white bread consumption, and decreased with frequent consumption of fruit (Sanjoaquin et al 2004).
Since 2019, the data from the Oxford Vegetarian Study are being used for a new collaborative initiative examining cancer risk in vegetarians.