Researchers from University College London also found that fresh vegetables may be slightly more protective than fresh fruit, and canned fruit actually appears to increase the risk of death.
The study analysed information from more than 65,000 people in England ages 35 and older who answered questions about their eating habits.
Researchers found that the more fruit and vegetables people ate, the less likely they were to die at any age.
Eating seven or more portions of fruit and vegetables a day reduced the specific risks of death by cancer and heart disease by 25 per cent and 31 per cent respectively.
Compared to eating less than one portion of fruit and vegetables, the risk of death by any cause is reduced by 14 per cent by eating one to three portions, 29 per cent for
three to five portions, 36 per cent for five to seven portions and 42 per cent for seven or more.
The study, published in the Journal of Epidemiology & Community Health, found that fresh vegetables had the strongest protective effect, with each daily portion reducing overall risk of death by 16 per cent.
Salad contributed to a 13 per cent risk reduction per portion, and each portion of fresh fruit was associated with a smaller but still significant 4 per cent reduction.
"We all know that eating fruit and vegetables is healthy, but the size of the effect is staggering," said Dr Oyinlola Oyebode of UCL's Department of Epidemiology & Public Health, lead author of the study.
"The clear message here is that the more fruit and vegetables you eat, the less likely you are to die at any age. Vegetables have a larger effect than fruit, but fruit still makes a real difference," Oyebode said.
The researchers found no evidence of significant benefit from fruit juice, and canned and frozen fruit appeared to increase risk of death by 17 per cent per portion.
The survey did not distinguish between canned and frozen fruit so this finding is difficult to interpret, researchers said.
"Most canned fruit contains high sugar levels and cheaper varieties are packed in syrup rather than fruit juice," said Oyebode.
"The negative health impacts of the sugar may well outweigh any benefits. Another possibility is that there are confounding factors that we could not control for, such as poor access to fresh groceries among people who have pre-existing health conditions, hectic lifestyles or who live in deprived areas," Oyebode said.