Key points from article :
In a UK study, nearly 400,000 people were enquired about their diet; health was tracked for 12 years.
On average, people ate 2 raw vegetables and 3 cooked vegetables.
Risk of dying from cardiovascular disease was around 15% lower for those eating the most vegetables, particularly raw veg.
No evidence of protective effect on how often heart and circulatory problems occurred.
Explained by other factors, including people's lifestyles, jobs, incomes and overall diet.
Cooking vegetables removes important nutrients; oils and fat used in cooking are known risk factors for heart problems.
What else we eat, how much exercise we do and where and how we live may have more of an impact.
Naveed Sattar, professor of metabolic medicine at the University of Glasgow, said the conclusions should not alter widespread advice to eat at least five portions of fruit and vegetables a day.
Study by Universities of Oxford and Bristol and the Chinese University of Hong Kong, led by Qi Feng, published in Frontiers in Nutrition.
