Some 45,000 English and Scottish volunteers took part in the study, with a high proportion eating a vegetarian diet, and each answered questions on health, lifestyle, diet, exercise, and smoking and alcohol consumption.
Researchers from the University of Oxford also took blood samples and recorded blood pressure for almost 20,000 of the participants.
During the follow-up period of 11 years, scientists recorded the number of hospital admissions and deaths from heart disease.
Taking into account factors such as age, sex, exercise, smoking and alcohol consumption, the volunteers that led a vegetarian lifestyle reduced their risk of serious heart problems by 32 per cent.
Co-author Dr Francesca Crowe, whose report was published in the American Journal of Clinical Nutrition, wrote: "Most of the difference in risk is probably caused by effects on cholesterol and blood pressure, and shows the important role of diet in the prevention of heart disease."
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