Heart disease is the single largest cause of death in developed countries and is responsible for 65,000 deaths each year in the UK alone.
The latest analysis looked at 44,561 men and women living in England and Scotland who were enrolled during the 1990s in a separate Oxford study into links between cancer and nutrition.
The researchers say this database was used because of the unusually high proportion of vegetarians enlisted. 34% of those taking part ate neither mean nor fish at the time they volunteered.
All the participants were quizzed about their health and lifestyle when they joined. This included questions about diet and exercise, as well as other factors affecting health such as smoking and alcohol consumption. Almost 20,000 participants also had their blood pressures recorded, and gave blood samples for cholesterol testing.
The volunteers were tracked until 2009, during which time researchers recorded 169 deaths from heart disease and 1,066 hospital diagnoses.
The researchers found that vegetarians had a 32% lower risk of developing heart disease than those who eat fish or meat or both. They did not differentiate between red and white meat, nor did they track how much meat was eaten.
Blood pressure and cholesterol
Francesca Crowe, who led the study, tells BootsWebMD: "We didn't look at the specific components of the vegetarian diet that might contribute to the lower risk of heart disease in this study but because the vegetarians have lower blood cholesterol, it is probably because they have a lower intake of saturated fat and a higher intake of polyunsaturated fat.
"Other components of their diet such as a slightly higher intake of fruits and vegetables and a higher intake of dietary fibre might also contribute to the lower risk of heart disease in the vegetarians."
The authors say lower blood pressure among the vegetarians is likely to be an important factor.
Additionally, vegetarians typically had lower body mass indices ( BMI) and fewer cases of diabetes as a result of their diets, although these were not found to significantly affect the results. If the results are adjusted to exclude the effects of BMI, vegetarians remain 28% less likely to develop heart disease, they say.
The study appears in the journal of the American Journal of Clinical Nutrition.
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