Global guidelines recommend eating at least 400g of fruit, vegetables or legumes per day, the equivalent of five average servings.
But the new findings from a major international study show that in terms of life expectancy, there is no extra benefit to be gained from increasing fruit and vegetable consumption from four to five a day.
Lead researcher Victoria Miller, from McMaster University in Canada, said: "Current dietary guidelines may not be achievable globally since fruits and vegetables have been shown to be unaffordable in many low and lower-middle income countries.
"Our findings suggest an approach that is likely to be more affordable in lower and middle-income countries - that three to four servings of fruit, vegetables and legumes per day show a similar benefit against reducing the risk of death to 'five-a-day' guidance."
The Pure (Prospective Urban and Rural Epidemiological) study included more than 135,000 people aged 35 to 70 from 18 low, middle and high-income countries whose progress was followed for 7.4 years.
During the follow-up period, scientists recorded a total of 5,796 deaths and 4784 major cardiovascular events such as heart attacks and strokes.
Eating three to four servings of fruit, vegetables and legumes per day reduced the risk of death by 22 per cent, compared with lower consumption levels.
Higher intakes did not reduce death rates any further, the study found.
Compared with eating cooked vegetables, consumption of raw vegetables tended to lower the risk of both heart disease and death.
