Health of vegetarians

Health of vegetarians: lay summary
EPIC-Oxford is a large study following the health of vegetarians and similar non-vegetarians. The aim of the proposed research is to examine the long-term health of vegetarians in the UK. This will help understanding of the impact of several related dietary factors on long-term health, and will provide important information for the 1.2 million vegetarians living in the UK.
The participants in EPIC-Oxford comprise 65,500 men and women who volunteered to join the study in the 1990s. Recruitment was targeted at vegetarians and other people with an interest in diet, and 34,000 meat-eaters, 10,000 people who eat fish but not meat, 19,000 lacto-vegetarians and 2,500 vegans joined the study. All the participants completed a questionnaire about their diet and other aspects of lifestyle, and 20,000 of them also provided a blood sample to be stored frozen for future analysis. The diet and lifestyle of the participants has been followed by questionnaires completed 5, 10 and 15 years after recruitment, and their health has been followed by linkage to National Health Service data on hospital diagnoses, cancers and death.
Previous analyses in EPIC-Oxford have shown several large differences in dietary intake, nutritional status or other markers of health between vegetarians and non-vegetarians. Some of these differences might be expected to lead to better health in the vegetarians, whereas others might lead to worse health. For example, we have shown that the vegetarians have relatively low levels of overweight and obesity, low blood cholesterol, high fruit and vegetable intake and high fibre intake, all of which may reduce the risk for some types of heart disease and perhaps other diseases. In contrast, we have also shown that the vegetarians have low dietary intakes and blood levels of potentially beneficial types of fat (especially n-3 fatty acids from fish), vitamin B12 and vitamin D; these low levels might contribute to an increased risk in vegetarians for some diseases, such as stroke.
The proposed research will utilize the information we have already collected over the last 20 years on the diet and lifestyle of the participants in EPIC-Oxford, together with extended follow-up by continued linkage to data from the National Health Service, to examine the risk for a range of diseases in vegetarians compared to non-vegetarians.
The main dietary factors examined will be vegetarian and vegan diets. We will also examine the impact on health of meat, fish, dairy products, animal protein, dairy protein, saturated fats, fats from vegetable oils and fish, dietary fibre, vitamin B12, and calcium. We will then examine the health records of the participants to answer several questions:
Whether the already reported low risk of ischaemic heart disease in vegetarians is largely due to the low intake of saturated fatty acids, and whether it may also be affected by other dietary factors such as particular compounds in meat.
Whether the risk of stroke may be high in vegetarians, and this may be related to the low intake of proteins from animal foods and of vitamin B12.
Fracture risk may be high in vegans and other individuals with low intakes of calcium due to low or zero intakes of dairy products. The risk for joint replacement for osteoarthritis may be low in vegetarians, due to low intakes of animal protein.
The risk of several disorders of the digestive system may be low in vegetarians, primarily due to high intakes of dietary fibre and absence of meat.

Health of vegetarians: technical summary
EPIC-Oxford is a population cohort of 65,500 men and women recruited throughout the UK in 1993-2000. The cohort comprises 34,000 meat-eaters, 10,000 people who eat fish but not meat, 19,000 lacto-vegetarians and 2,500 vegans. Participants completed a questionnaire on diet and lifestyle and gave written consent for follow-up through medical records. 20,000 participants gave a blood sample at recruitment, and 1,000 gave a second blood sample 5 years later. Follow-up questionnaires were completed 5, 10 and 15 years after recruitment. Participants are followed through record linkage to NHS data for all hospital episodes, cancers and deaths. The main dietary exposures examined will be vegetarian and vegan diets, and consumption of meat, fish, dairy products, animal protein, dairy protein, saturated fat, n-6 polyunsaturated fatty acids, n-3 fatty acids, fibre, vitamin B12 and calcium.
The main disease endpoints will be: cardiovascular disease including ischaemic heart disease and stroke, skeletal health including fractures and joint replacement for osteoarthritis, and gastrointestinal disorders. The data will be analysed by standard methods for cohort studies. Repeat measures of diet and other factors will be included, and adjustments made for smoking and other relevant confounding factors.
In addition to these specific research objectives, a further important part of the work proposed is to make the data from EPIC-Oxford accessible to other medical researchers, thus maximising the scientific output from the study. This will include the incorporation of the EPIC-Oxford databases into the Richard Doll Centenary Data Archive, as well as linkage to the MRC Gateway and other communications with external medical researchers.

Health of vegetarians: impact summary
The research will benefit vegetarians and the general public in the UK and elsewhere. Individuals will gain information on both potential benefits and risks of following a vegetarian diet. This type of information could not only lead to long-term health improvements for many people, but also more directly help to avoid deficiencies, such as vitamin B12 deficiency.
For scientists, the research will provide direct information on the health of vegetarians, and also help give insight into the health effects of related factors such as intake of animal protein and saturated fat.
For the private sector, food companies and caterers will gain information on dietary patterns which can be followed by ordinary people and on their associations with health.
For the NHS, the research will provide information to inform their advice, e.g. as on their website: http://www.nhs.uk/Livewell/Vegetarianhealth/Pages/Goingvegetarian.aspx
For Defra, the research will inform evaluation of the likely impacts on health of any moves towards lower meat consumption to reduce greenhouse gas emissions, which would be expected to increase the number of vegetarians (for example http://sd.defra.gov.uk/2011/01/food-climate-change-and-land-use/)
For other policy makers, the research will provide essential information on the long-term health of vegetarians and related dietary patters. This may contribute, for example, to the evaluation of guidelines for food providers in schools, hospitals and prisons.
In the third sector, charities such as the Vegetarian Society, the Vegan Society, Viva and the Jewish Vegetarian Society will gain information to communicate to their members.