The sweet spot for fruits and vegetables
When it comes to fruits and vegetables, 10 servings a day is the best target to aim for, according to a large meta-analysis and systematic review published in February 2017 in the International Journal of Epidemiology—though less is good, too.
It reviewed 95 studies that looked at the relationship between fruit and vegetable intake and risk of cardiovascular disease (including coronary heart disease and stroke), cancer, and all-cause mortality and found that for every 2½-serving increase a day, there was a steady reduction in these conditions, topping out at 10 servings a day for cardiovascular disease and premature death and 7½ servings a day for cancer. For instance, an intake of 10 servings a day was associated with a one-third reduction in all-cause mortality, compared to none.
Good news for produce-averse people: The biggest reduction in risk comes when you go from no fruits and veggies to just a few servings a day; additional servings provide smaller further benefit. And a “serving” is small—averaging 80 grams (about 3 ounces) in the study. A medium-size piece of fruit or a cup of cooked vegetables counts as 2 servings, by most definitions. A meal-size salad alone may count as 4 servings or more.
Assuming a causal relationship, the British researchers estimated that if everyone around the world ate 10 servings a day of fruits and vegetables, that would prevent 4 million deaths from cardiovascular disease, 660,000 deaths from cancer, and close to 8 million deaths from all causes a year. Eating 6 servings would avert more than 5 million premature deaths.
Fruits and vegetables contain an array of nutrients (such as vitamin C and potassium) and phytochemicals (including flavonoids and carotenoids), along with fiber, all of which “are likely to act synergistically through several biological mechanisms to reduce risk of chronic diseases and premature mortality,” the paper noted—and they may further help by displacing less-healthful foods in the diet.
It’s also possible that people who eat a lot of fruits and vegetables do other healthy things (like exercising, not smoking, not being overweight, and getting medical screenings) that may help account for the results, though studies usually adjust the data for the most obvious of these confounding factors.