How many servings of fruit and vegetables a day to protect our health? Does the type of fruit and vegetables matter? These long-debated questions are finally answered by a very recent research published in the American Heart Association's journal Circulation thanks to the work of a team from the Harvard T. H. Chan School of Public Health (Wang et al, Circulation, Mar 2021).
The American researchers drew on data from two very large studies, the Nurses' Health Study and the Health Professionals Follow-Up Study, which involved more than 100,000 adults following them for a period of thirty years. The aim of the scientists was to understand any protective action given by the diet and, in particular, by the frequency with which fruits and vegetables were eaten. What emerged is that the consumption of 5 portions of fruit and vegetables guarantees the greatest protection, with a 12% reduction in death from heart disease, 10% from cancer and 35% from respiratory diseases compared to the intake of two servings of fruit and vegetable a day. However, eating more than 5 portions of fruit and vegetables did not bring more benefits, probably due to the fact that the healthful substances provided by fruits and vegetables, such as vitamin C, carotenoids and polyphenols, are limited in terms of absorption, transport, use and accumulation in the body. It has also been observed that, in order to ensure maximum longevity, the optimal combination is given by 2 daily servings of fruit and 3 servings of vegetables.
However, not all fruits and vegetables have shown the same beneficial properties. For example, starchy fruits and vegetables, such as pears, corn and potatoes, but also fruit juices are not associated with a reduced risk of mortality. This is probably due to the fact that this type of food causes a notable increase in blood sugar, in addition to the fact that, especially corn, which is mainly sold canned, and industrial juices, being highly processed, have lost many of their properties. Green leafy vegetables, such as kale, spinach and lettuce, but also carrots, berries and citrus fruits are, on the contrary, particularly beneficial.