Almost eight million premature deaths could be avoided worldwide if people consumed more fruit and vegetables, new research has found.

According to the findings, eating 800g of fruit and vegetables every day - that is around 10 portions - could prevent 7.8 million premature deaths globally.

UK researchers analysed 95 studies on fruit and vegetable intake, which involved some two million people.

The researchers found that while eating the recommended five-a-day reduced the risk of heart attack, stroke, cancer and premature death, the greatest benefit came from eating 800g per day, which is around 10 portions.

One portion is defined as 80g. This is equivalent to a small banana, apple or pear, a large mandarin or three heaped tablespoons of cooked vegetables such as broccoli, cauliflower or peas.

"We wanted to investigate how much fruit and vegetables you need to eat to gain the maximum protection against disease and premature death. Our results suggest that although five portions of fruit and vegetables is good, 10 a day is even better," commented the research's lead author, Dr Dagfinn Aune, of Imperial College London.

Eating up to 800g per day was linked with a 24% reduced risk of heart disease, a 28% reduced risk of cardiovascular disease, a 33% reduced risk of stroke, a 13% reduced risk of cancer and a 31% reduced risk of premature death.

This risk was calculated in comparison to not consuming any fruit and vegetables.

However, the researchers did find that consuming even 200g per day was linked with a 16% reduced risk of heart disease, a 13% reduced risk of cardiovascular disease and an 18% reduced risk of stroke.

Meanwhile, the researchers also looked at which fruit and vegetables appeared to offer the greatest protection against disease. They found that when it came to reducing heart disease, cardiovascular disease, stroke and early death, the best fruit and vegetables to choose from included apples, pears, citrus fruits, green leafy vegetables such as spinach and cruciferous vegetables such as broccoli and cabbage.

The best for reducing cancer risk included green vegetables such as spinach, yellow vegetables such as carrots and peppers, and cruciferous vegetables such as brocolli.

Dr Aune pointed out that there may be a number of reasons for these findings.

"Fruit and vegetables have been shown to reduce cholesterol levels, blood pressure, and to boost the health of our blood vessels and immune system. This may be due to the complex network of nutrients they hold. For instance, they contain many antioxidants, which may reduce DNA damage, and lead to a reduction in cancer risk," he explained.

He also noted that that compounds called glucosinolates, which are found in cruciferous vegetables such as broccoli, activate enzymes that may help prevent cancer. Furthermore, fruit and vegetables may also have a beneficial effect on naturally-occurring bacteria in the gut.

"Most likely it is the whole package of beneficial nutrients you obtain by eating fruits and vegetables that is crucial is health. This is why it is important to eat whole plant foods to get the benefit, instead of taking antioxidant or vitamin supplements (which have not been shown to reduce disease risk).

"We need further research into the effects of specific types of fruits and vegetables and preparation methods. We also need more research on the relationship between fruit and vegetable intake with causes of death other than cancer and cardiovascular disease. However, it is clear from this work that a high intake of fruit and vegetables hold tremendous health benefits, and we should try to increase their intake in our diet," Dr Aune added.

Details of these findings are published in the Journal of Epidemiology.