Why you should eat 10 portions of fruit or vegetables a day
February 24, 2017
Eating 800 grams a day (about ten portions*) of fruit or vegetables could reduce your chance of heart attack, stroke, cancer, and early death, scientists from Imperial College London conclude from a meta-analysis of 95 studies on fruit and vegetable intake.
The study, published in an open-access paper in the International Journal of Epidemiology, included 2 million people worldwide and assessed up to 43,000 cases of heart disease, 47,000 cases of stroke, 81,000 cases of cardiovascular disease, 112,000 cancer cases and 94,000 deaths.
About 7.8 million premature deaths worldwide could be potentially prevented yearly if people followed this protocol, the researchers say.
Compared to not eating any fruits and vegetables, a daily intake of 200 grams (two and a half portions) was associated with a 16% reduced risk of heart disease, an 18% reduced risk of stroke, a 13% reduced risk of cardiovascular disease, a 4% reduced risk in cancer risk, and a 15% reduction in the risk of premature death.
However, a higher intake of fruits and vegetables of 800 grams a day was associated with 24% reduced risk of heart disease, a 33% reduced risk of stroke, a 28% reduced risk of cardiovascular disease, a 13% reduced risk of total cancer** and a 31% reduction in dying prematurely.***
The current UK guidelines suggest you eat at least five portions or 400 grams per day, but fewer than one in three UK adults are thought to even meet this target. The U.S. Health and Human Services/USDA guidelines use a different metric: “The recommended amount of vegetables in the Healthy U.S.-Style Eating Pattern at the 2,000-calorie level is 2½ cup-equivalents of vegetables per day and 2 cup-equivalents of fruit per day.
Foods that are best at disease prevention, according to the study
To prevent heart disease, stroke, cardiovascular disease, and early death: apples, pears, citrus fruits, salads, and green leafy vegetables such as spinach, lettuce and chicory, and cruciferous vegetables such as broccoli, cabbage and cauliflower.
To reduce cancer risk: green vegetables, such as spinach or green beans, yellow vegetables, such as peppers and carrots, and cruciferous vegetables.
Reasons for health benefits
So why do fruit and vegetables have such profound health benefits? According to Dagfinn Aune, PhD, lead author of the research, from the School of Public Health at Imperial: “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 also noted that compounds called glucosinolates in cruciferous vegetables, such as broccoli, activate enzymes that may help prevent cancer. And fruit and vegetables may also have a beneficial effect on the naturally-occurring bacteria in our gut.
Most beneficial compounds can’t be easily replicated in a pill, he said: “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.”
In the paper, the researchers qualify these statements, noting that they assume the observed associations are causal (there could be other causes of improved health). The team, however, took into account some other factors, such as a person’s weight, smoking, physical activity levels, and overall diet.
“We need further research into the effects of specific types of fruits and vegetables and preparation methods of fruit and vegetables,” Aune suggested. “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.”
This project was funded by Olav og Gerd Meidel Raagholt’s Stiftelse for Medisinsk Forskning, the Liaison Committee between the Central Norway Regional Health Authority (RHA) and the Norwegian University of Science and Technology (NTNU), and the Imperial College National Institute of Health Research (NIHR) Biomedical Research Centre (BRC).
* A portion (80 grams) of fruit equals approximately one small banana, apple, pear or large mandarin; three heaped tablespoons of cooked vegetables such as spinach, peas, broccoli or cauliflower count as one portion.
** For cancer, no further reductions in risk were observed above 600 grams per day.
*** The team was not able to investigate intakes greater than 800 g a day. The team also did not find significant differences between raw and cooked vegetables in relation to early death, and they noted that that other specific fruits and vegetables as well as preparation methods may also play a role.
Abstract of Fruit and vegetable intake and the risk of cardiovascular disease, total cancer and all-cause mortality–a systematic review and dose-response meta-analysis of prospective studies
Background: Questions remain about the strength and shape of the dose-response relationship between fruit and vegetable intake and risk of cardiovascular disease, cancer and mortality, and the effects of specific types of fruit and vegetables. We conducted a systematic review and meta-analysis to clarify these associations.
Methods: PubMed and Embase were searched up to 29 September 2016. Prospective studies of fruit and vegetable intake and cardiovascular disease, total cancer and all-cause mortality were included. Summary relative risks (RRs) were calculated using a random effects model, and the mortality burden globally was estimated; 95 studies (142 publications) were included.
Results: For fruits and vegetables combined, the summary RR per 200 g/day was 0.92 [95% confidence interval (CI): 0.90–0.94, I2 = 0%, n = 15] for coronary heart disease, 0.84 (95% CI: 0.76–0.92, I2 = 73%, n = 10) for stroke, 0.92 (95% CI: 0.90–0.95, I2 = 31%, n = 13) for cardiovascular disease, 0.97 (95% CI: 0.95–0.99, I2 = 49%, n = 12) for total cancer and 0.90 (95% CI: 0.87–0.93, I2 = 83%, n = 15) for all-cause mortality. Similar associations were observed for fruits and vegetables separately. Reductions in risk were observed up to 800 g/day for all outcomes except cancer (600 g/day). Inverse associations were observed between the intake of apples and pears, citrus fruits, green leafy vegetables, cruciferous vegetables, and salads and cardiovascular disease and all-cause mortality, and between the intake of green-yellow vegetables and cruciferous vegetables and total cancer risk. An estimated 5.6 and 7.8 million premature deaths worldwide in 2013 may be attributable to a fruit and vegetable intake below 500 and 800 g/day, respectively, if the observed associations are causal.
Conclusions: Fruit and vegetable intakes were associated with reduced risk of cardiovascular disease, cancer and all-cause mortality. These results support public health recommendations to increase fruit and vegetable intake for the prevention of cardiovascular disease, cancer, and premature mortality.
- Aune, D, Giovannucci, E, Boffetta, P et al. (7 more authors) (2016) Fruit and vegetable intake and the risk of cardiovascular disease, total cancer and all-cause mortality – a systematic review and dose-response meta-analysis of prospective studies. International Journal of Epidemiology. ISSN 0300-5771 (In Press)