However, more than '5 a day' appears to have no further effect, the researchers said.
These results conflict with a recent study suggesting that seven or more daily portions of fruits and vegetables were linked to lowest risk of death.
There is growing evidence that increasing fruit and vegetable consumption is related to a lower risk of death from cardiovascular disease and cancer. However, the results are not entirely consistent.
Researchers from Harvard School of Public Health and Shandong University in China examined the association between fruit and vegetable intake and risk of all-cause, cardiovascular, and cancer deaths.
They analysed the results of sixteen studies involving a total of 833,234 participants and 56,423 deaths. Differences in study design and quality were taken into account to minimise bias.
Higher consumption of fruit and vegetables was significantly associated with a lower risk of death from all causes, particularly from cardiovascular diseases.
Average risk of death from all causes was reduced by 5 per cent for each additional daily serving of fruit and vegetables, while risk of cardiovascular death was reduced by 4 per cent for each additional daily serving of fruit and vegetables.
But the researchers identified a threshold around five servings per day, after which the risk of death did not reduce further.
In contrast, higher consumption of fruit and vegetables was not appreciably associated with risk of death from cancer.
The researchers suggest that, as well as advice to eat adequate amounts of fruit and vegetables, the adverse effects of obesity, physical inactivity, smoking and high alcohol intake on cancer risk should be further emphasised.
The researchers say their study "provides further evidence that a higher consumption of fruits and vegetables is associated with a lower risk of mortality from all causes, particularly from cardiovascular diseases.
The results published in the British Medical Journal support current recommendations to increase consumption of fruits and vegetables to promote health and longevity.