The NHS currently recommends that we eat five different 80g portions of fruit and vegetables a day.
This suggested intake, based on Word Health Organisation guidance, can lower the risk of serious health problems such as heart disease, stroke, type 2 diabetes and obesity, according to NHS Choices.
But a new study suggests that eating seven or more helpings of fruit and veg a day can reduce a person's risk of dying of cancer by 25%.
Eating this many portions can also reduce a person's risk of dying of heart disease by 31%, the authors said.
The researchers from University College London (UCL) examined the eating habits of 65,000 people in England between 2001 and 2013.
They found that seven or more helpings a day can reduce a person's overall risk of death by 42% when compared to people who manage just one whole portion every day.
People who eat between five and seven a day have a 36% reduced risk of death, those who eat three to five portions have a 29% decreased risk and those who eat one to three helpings of fruit and veg have a 14% reduced risk of death.
The study, published in the Journal of Epidemiology and Community Health, showed that fresh vegetables had the strongest protective effect, followed by salad and then fruit.
The authors also found that canned and frozen fruit appeared to increase the risk of death, instead of decrease it. And no significant benefit of fruit juice was noted.
The authors said the findings lend support to the Australian government's advice of "two plus five" a day - encouraging people to eat two helpings of fruit and five portions of vegetables.
"We all know that eating fruit and vegetables is healthy, but the size of the effect is staggering," said lead author Dr Oyinlola Oyebode of UCL's Department of Epidemiology and Public Health.
"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.
"If you're happy to snack on carrots or other vegetables, then that is a great choice but if you fancy something sweeter, a banana or any fruit will also do you good.
"Our study shows that people following Australia's 'Go for 2 + 5' advice will reap huge health benefits. However, people shouldn't feel daunted by a big target like seven.
"Whatever your starting point, it is always worth eating more fruit and vegetables. In our study even those eating one to three portions had a significantly lower risk than those eating less than one."