Science, in recent years, has never stopped extolling the virtues of vegetables, bringing continuous and conclusive evidence of how daily and abundant consumption of fruit and vegetables can truly improve people's general health. We asked Dr Franco Berrino, physician, epidemiologist and former director of the Department of Preventive and Predictive Medicine at the National Cancer Institute in Milan, to tell us what it is about vegetables that does us so much good and what we can do to make the most of them. Here is what he told us in Verona on the occasion of the fourth meeting of Campi da sapere, dedicated precisely to vegetables.

Vegetables: how important are they for health?
Epidemiological studies show that adding 200 grams of vegetables and/or fruit a day reduces mortality by 10 per cent, with maximum benefit at 700–800 grams.

Do fruit and vegetables hold the same importance in a daily diet? Or is one more protective than the other?
Vegetables, excluding potatoes, are generally slightly more protective than fruit, but what matters is a great variety of consumption: for the same quantity of fruit and vegetables, additional protection is observed through greater variety. Variety ensures that we lack nothing and that, conversely, we do not have too much of any one thing.

Why is it recommended to eat seasonal fruit and vegetables?
Because if for millions of years we have eaten only seasonal fruit, it is plausible that our bodies are programmed for this food.

What characteristics do vegetables grown (and eaten) "out of season" have? Are they less healthy? Can they be inadvisable?
Fruit is cooling, which is why the Eternal Father gave us an abundance of it in summer; eating a great deal of fruit in winter — necessarily imported from warm countries or produced under unnatural conditions — cools us down.

Are there vegetables that stand out more than others for their benefits and that should never be absent from our table?
Green vegetables for their richness in folates and beta-carotene, yellow-orange vegetables for their carotenoids, cruciferous vegetables for sulforaphane… but it is variety that guarantees us a thousand other substances that work together to promote health.

Are there vegetables that are always better eaten raw and others that are recommended cooked?
The ideal is to have both raw and cooked vegetables on the plate. When you eat a raw carrot, you absorb very few of the carotenoids it contains, because we cannot chew it thoroughly enough to break the plant cells; by sautéing it in a pan with a drizzle of extra virgin olive oil, the cell walls soften and the carotenoids become available. Cooking cruciferous vegetables (cabbages, broccoli, turnips…) deactivates the enzyme myrosinase, which releases sulforaphane from its matrix, so it is better to also add a raw broccoli floret to our plate of pasta and cooked broccoli.

Organic vegetables: why are they healthier?
Not only because they do not contain the chemical poisons that make farmers ill, but also because they are richer in various protective substances and, growing in living soil, they also bring us microbes that are beneficial to health.

Is it right to peel non-organic vegetables, or is it still preferable to leave the skin on so as not to lose the vitamins it contains?
A large part of the protective substances in fruit are found in the skin, but when organic fruit is not available it is prudent to peel it. In the case of non-organic vegetables, they will need to be washed very, very thoroughly.