The current "five-a-day" recommendation for fruit and vegetable consumption is inadequate, according to a new report.
It proposes that certain drinks and tinned and processed fruit should not form part of the suggested intake, claiming they could decrease life expectancy.
Research from the influential Journal of Epidemiology and Community Health says eating seven or more portions of fresh fruit and veg will give people the best chance of staving off death and ill-health.
Vegetables are said to pack more of a protective punch than fruit, according to the analysis of lifestyle data from 65,000 adults.
They tracked recorded deaths from among the sample for an average of seven and a half years.
The authors say a diet rich in fruit and vegetables has been linked to good health, but many of the studies on which this association is based have largely been carried out on people who are already likely to be health-conscious.
And while plenty of fruit and vegetables in the diet are recommended to boost cardiovascular health, the evidence for its impact on warding off cancer has been less clear-cut.
The analysis revealed the higher the intake of fruit and vegetables, the greater the protective effects seemed to be.
Eating at least seven daily portions was linked to a 42% lower risk of death from all causes.
For cancer the risk was lowered by 25%, and for heart disease and strokes by 31%.
But while fresh and dried fruit seemed to strongly curb the risk of death, a portion of processed, frozen or tinned fruit seemed to increase it by 17%.
Lead investigator Dr Oyinlola Oyebode said: "What we found was that the most beneficial is fresh fruit, dried fruit, salad and vegetables.
"Canned and frozen fruit were not good for health. Nutritionists say they have just as many micro-nutrients and just as much fibre in them, so it's possible it is to do with canned fruit having a lot of sugar."
The authors believe current dietary guidance, which includes consumption of tinned fruit, smoothies and fruit juice as legitimate ways of reaching the "five-a-day" goal, might need to be revised.