Fruit and veg should make up over ⅓ of the diet, according to the NHS Eatwell Guide. This is because they are great sources of vitamins, minerals and fibre. Eating 5 portions of fruit or vegetables each day is recommended, which most people don’t reach.
Important vitamins found in fruits and vegetables are:

Vitamin C, which helps to protect cells, bones, cartilage and blood vessels. Good sources of vitamin C are found in oranges, green and red peppers, as well as broccoli.
Vitamin B1 (thiamin), which aids the nervous system and helps to release energy from food. Thiamin can be found in food sources like peas, as well as fresh and dried fruits.
Vitamin B6 (pyridoxine), which allows the body to use and store energy from proteins and carbohydrates, as well as forming haemoglobin, which is vital for the transport of oxygen around the body. Vitamin B6 is found in most vegetables, as well as lots of other food sources.
Vitamin B9 (folate), which helps the body make new red blood cells. This can be found in foods like broccoli, brussel sprouts (everyone’s favourites!), leafy greens and peas.
Vitamin K, which allows wounds to heal properly due to its role in blood clotting. Vitamin K can be found in green leafy vegetables, such as broccoli and spinach.

The high amounts of dietary fibre in fruits and vegetables helps to maintain a healthy gut, preventing constipation and other digestive problems. Fibre is the name given to a range of substances found in the cell walls of fruits, vegetables, pulses and cereal grains, and helps you feel full, meaning you are less likely to eat too much. By eating plenty of fibre, this also decreases the risks of bowel cancer. The fibre found in fruit and vegetables, like apples, carrots and potatoes, can help to reduce the amount of cholesterol in the blood.