Some countries recommend eating 10 portions a day of fruit or veg
New research backs the five-a-day target for fruit and vegetables, but suggests eating more may have no added benefits.
An analysis of 16 worldwide studies suggested that for every portion of fruit and vegetables consumed, there was a lower risk of premature death.
But after five portions a day, there was no further impact, researchers report in The BMJ.
There have been calls to up the quota to seven-a-day, to prolong lives.
Current NHS guidance is to eat at least five portions of fruit and vegetables a day. Most people manage about four.The new analysis looked at 16 studies in the US, Asia and Europe involving more than 833,000 people, of whom about 56,000 died during the follow-up period.
Researchers in the US and China found eating more fruit and vegetables was linked with a lower risk of dying from any cause, particularly from cardiovascular disease.
The average risk of death fell by about 5% for every extra serving of fruit and vegetables, up to five servings a day, but not beyond.
"This analysis provides further evidence that a higher consumption of fruit and vegetables is associated with a lower risk of all-cause mortality, particularly cardiovascular mortality," said the team, led by Prof Frank Hu, of Harvard School of Public Health, in Boston, US.
"There was a threshold around five servings of fruit and vegetables a day, after which the risk of all cause mortality did not reduce further."
Eating even five portions of fruit and vegetables a day is a challenge for many.
There have been calls to increase the quota of fruit and vegetables beyond five.
A previous study in England found eating seven or more portions of fruit and vegetables a day was healthier than the minimum five currently recommended and could prolong lives.
But lead researcher Dr Oyinlola Oyebode, of University College London, said both studies showed eating more fruit and veg was associated with lower risk of early death.
"This study suggests not much additional effect over five portions, although there was possibly a greater effect in the groups eating five to seven, and seven plus portions in our study," she told the BBC.
"Most people do not eat five portions of fruit and veg a day, so the message for the public is still to eat more fruit and veg."
Five a day facts
The five-a-day message is based on advice from the World Health Organization
It highlights the health benefits of eating five 80g (3oz) portions of fruit and vegetables every day
The five portions should include a variety of fruit and vegetables
Most fruits and veg count towards five a day
The government says it can include fresh, frozen, canned, dried or pure juices
Potatoes and cassava don\'t count because they mainly contribute starch to the diet
Commenting on the study, Victoria Taylor, senior dietician at the British Heart Foundation, said: "Although our five-a-day message is well established, worryingly 70% of adults are still not meeting this target.
"Just remember that every extra portion you eat towards your five-a-day could help you keep your heart healthy."
Dr Alison Tedstone, chief nutritionist at Public Health England, said: "The majority of people in England are not eating enough fruit and vegetables with the latest National Diet and Nutrition Survey (NDNS) data from 2008 to 2012 showing that only 30% of adults and 41% of older adults met the five-a-day recommendation.
"Eating a healthy, balanced diet that is high in fruit, vegetables and fibre and low in saturated fat, sugar and salt, alongside being more active, will help you to maintain a healthy weight and lower your risk of developing heart disease, type 2 diabetes and some cancers."