Researchers say eating 10 portions of fruits and vegetables daily is best for preventing disease and premature death.
From an analysis of 95 studies assessing the health benefits of fruit and vegetable consumption, researchers found that eating 800 grams of fruits and vegetables daily - or around 10 portions of 80 grams - was associated with the lowest risk of disease and premature death.
Apples, pears, green leafy vegetables, and cruciferous vegetables were found to be among the most beneficial for health.
Lead author Dr. Dagfinn Aune, of the School of Public Health at Imperial College London in the United Kingdom, and colleagues recently reported their findings in the International Journal of Epidemiology.
Current guidelines recommend that adults should aim to eat around five cups of fruits and vegetables daily - two cups of fruits and three cups of vegetables - to help reduce the risk of heart disease, stroke, cancer, and other chronic diseases.
While consuming five portions of fruits and vegetables daily is beneficial, Dr. Aune and colleagues set out to determine how many fruits and vegetables need to be consumed for maximum protection against disease and early death.
To reach their findings, the researchers analyzed the data of 95 studies that looked at the health benefits of fruit and vegetable intake.
In total, the studies involved almost 2 million participants and around 43,000 cases of heart disease, 47,000 cases of stroke, 81,000 cases of cardiovascular disease (CVD), and 94,000 deaths.
The team analyzed the fruit and vegetable intake of each participant, looking specifically at how much they consumed daily and the specific fruits and vegetables consumed.
Up to 33 percent lower risk of disease and death with 10 portions daily
One portion of fruits of vegetables was defined as 80 grams - the equivalent to a small banana, pear, or apple, or three heaped tablespoons of cooked vegetables, such as peas, broccoli, or cauliflower.
The researchers then calculated the association between fruit and vegetable intake and the risks of heart disease, stroke, CVD, cancer, and premature death.
The team found that, compared with no fruit and vegetable consumption, participants who ate just 200 grams of fruits and vegetables a day - the equivalent to around 2.5 portions - saw health benefits. These included an 18 percent reduced risk of stroke, a 16 percent reduced risk of heart disease, a 13 percent lower risk of CVD, and a 4 percent reduced risk of cancer.
Eating 200 grams of fruits and vegetables daily was also associated with a 15 percent lower risk of premature death.
However, the researchers found that the more fruits and vegetables participants ate daily, the greater the benefits.
Compared with subjects who consumed no fruits and vegetables, those who ate up to 800 grams - or 10 portions - each day were found to have a 33 percent lower risk of stroke, a 28 percent reduced risk of CVD, a 24 percent lower risk of heart disease, and a 13 percent decrease in cancer risk.
A 31 percent reduction in premature death was also associated with a daily fruit and vegetable intake of up to 800 grams.
What is more, the researchers calculated that if everyone ate 10 portions of fruits and vegetables daily, then around 7.8 million premature deaths could be prevented across the globe annually.
Which fruits and vegetables are best?
The team found that apples, pears, citrus fruits, green leafy vegetables (such as chicory and spinach), and cruciferous vegetables (such as cabbage and broccoli) were best for reducing the risk of stroke, CVD, heart disease, and premature death.
The greatest reduction in cancer risk was associated with intake of green vegetables (such as green beans), yellow vegetables (such as peppers and carrots), and cruciferous vegetables.
Consumption of raw and cooked vegetables was associated with reduced risk of premature death, but the team did not have enough data to determine which specific fruits and vegetables reduced this risk.
While the study did not investigate the mechanisms behind high fruit and vegetable intake and reduced risk of disease and death, the team notes that fruits and vegetables have been linked to lower cholesterol and improved blood vessel and immune system function.
"This may be due to the complex network of nutrients they hold," notes Dr. Aune. "For instance, they contain many antioxidants, which may reduce DNA damage, and lead to a reduction in cancer risk."
Overall, the researchers believe their findings highlight the importance of fruits and vegetables as part of a healthful diet.
"We need further research into the effects of specific types of fruits and vegetables and preparation methods of fruit and vegetables. 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. Dagfinn Aune