Shifting our diet towards more plant-based foods (especially whole and minimally processed ones) is one of the most solid and “wide-ranging” choices we can make for our health: it helps prevent many chronic diseases, improves several cardiometabolic parameters and, at the same time, reduces the environmental impact of our diet.
National and international recommendations set a minimum target of at least 5 portions of vegetables and fruit per day, often with a practical ratio of 3:2 (3 portions of vegetables and 2 of fruit). This simple target is associated with a lower risk of numerous chronic diseases, as it increases intake of fibre, micronutrients and phytocompounds.
What is a “standard portion” according to the Italian Society of Human Nutrition?
- Vegetables: 200 g raw, which can be eaten cooked or raw
- Leafy salads: 80 g
For fruit:
- Fresh fruit: 150 g, with one medium fruit or two small fruits as a practical portion
- Dried fruit / shelled nuts: 30 g
These are “minimum” portions useful as a guide: in practice, the more vegetables on the plate, the more fibre, vitamins, minerals and phytocompounds (polyphenols, sulphur compounds, carotenoids, plant sterols) are gained.
What makes fruit and vegetables such valuable allies for our health?
1) Fibre: the ally of the microbiota, blood sugar and satiety
Fibre cannot be digested by human enzymes; for this reason, during intestinal transit it is not absorbed like other nutrients and reaches the colon, where it is fermented by the microbiota (the collection of all the individual microorganisms that inhabit the gut). This fermentation produces useful compounds, in particular short-chain fatty acids, which are associated with benefits for colon cells and the entire body. For this reason, fibre is often also described as a prebiotic substance, essential for the growth and development of the intestinal microbiota.
What else does fibre do:
- increases the feeling of fullness
- slows gastric emptying
- lowers the glycaemic load of the meal
- improves intestinal function
- by reducing transit time, it limits contact with potentially harmful substances
It is therefore no surprise that the preventive role of fibre is extensively studied in relation to diabetes, cardiovascular disease, hypercholesterolaemia and colon cancer.
How much fibre should we consume?
For adults, SINU guidelines report adequate intake levels in relation to calories and, as a prevention target, at least 25 g per day even when energy intake is below 2000 kcal. International bodies such as the World Cancer Research Fund set a target of at least 30 g/day from food sources.
2) Fruit and vegetables are an excellent source of vitamins and minerals, for example, vitamin A, B5, folic acid, C, E, K, calcium, iron, magnesium, manganese and potassium. The amounts and types of nutrients vary across different types of fruit and vegetables. Fruit and vegetables are also rich in water, making up 75 to 90% of their weight. This explains their low energy density.
3) Fruit and vegetables also contain several thousand phytochemical compounds with numerous benefits. Among these, the glucosinolates found in cruciferous vegetables (broccoli, cabbage, etc.) give rise to sulforaphane, a compound widely studied for its anti-tumour properties, thanks to its ability to activate detoxification enzymes, reduce oxidative stress and modulate inflammation and cell proliferation.
Diet, metabolic health and cancer risk
In recent decades, scientific evidence has made it increasingly clear that diet quality is one of the most powerful modifiable determinants of health. Dietary patterns rich in whole plant foods are associated with:
- better lipid profile (in particular lower LDL)
- better blood sugar and insulin control
- on average a more favourable body weight
- lower systemic inflammation
Extensive evidence from large prospective studies and meta-analyses indicates that vegetarian and vegan diets are associated with a lower risk of cancer and, in some cases, with more marked reductions for tumours at specific sites, particularly in the gastrointestinal tract.
Consistent data also emerge from the Adventist Health Study-2, one of the largest and best-characterised cohorts from a dietary standpoint, in which vegetarians and vegans showed a lower risk of several cancers compared to non-vegetarians. Furthermore, the Global Burden of Disease attributes a significant share of cancer mortality to modifiable dietary factors, in particular low fibre intake and high consumption of red and processed meats. In 2019, according to GBD data, approximately 6% of cancer deaths and 5.5% of disability-adjusted life years (DALYs) were overall linked to diet.
Diet and healthy ageing
Several longitudinal studies indicate that dietary patterns rich in plant foods and low in ultra-processed foods are associated with a greater likelihood of reaching old age while maintaining good physical, cognitive and metabolic function. From this perspective, the most useful approach is not a “perfect” diet that is the same for everyone, but a flexible dietary model centred on vegetables, whole grains, legumes and healthy fats, which represents a solid strategy for promoting longevity and quality of life in the long term.
In this regard, it is worth mentioning an analysis published in 2025 in Nature Medicine on over 100,000 individuals followed for more than 30 years, which showed that adherence to dietary patterns characterised by a high proportion of fruit, vegetables, whole grains, legumes and unsaturated fats is associated with a greater likelihood of reaching the age of 70 free from major chronic diseases and without cognitive or functional decline.
Similar results also emerge from analyses based on European and UK cohorts, which highlight how predominantly plant-based diets are associated with a reduced risk of multimorbidity and a slowing of biological ageing.
The planet: why “more plant-based” is also good for the environment
A decisive step towards a greener diet is linking individual health with the health of the planet. The study by Scarborough and colleagues, conducted on tens of thousands of people in the United Kingdom, compared the environmental impact of different diets (vegan, vegetarian, pescatarian and various categories of omnivores based on meat consumption), linking food consumption to indicators such as greenhouse gas emissions, land use, water use, water pollution and biodiversity loss. The result is consistent and hard to ignore: vegan diets have the lowest environmental footprint, and the impact increases progressively as meat and dairy consumption rises. In other words, steering our food choices towards a greater presence of plant-based foods and reduced meat consumption, particularly beef and dairy products, can significantly decrease the overall impact of our diet, offering a dual benefit for both human health and the health of our planet.
