How do fruit and vegetables influence mental health?

The main benefit is that fruit and veggies contain water-soluble vitamins which are readily absorbed by the body and are available for immediate use. These include minerals such as potassium, and vitamins like folic acid, and other B vitamins, which have an impact on serotonin levels in the brain, which is known to relieve depression and anxiety.

Water soluble vitamins are beneficial with a current, or very recent, intake. Fat soluble vitamins need the presence of fat to dissolve and be absorbed by the body, and are stored in the tissues until needed.

They cannot therefore give you the quick boost or lift that water-soluble vitamins can offer.

Here is a list of foods that can improve your mental health for good:

Leafy greens such as spinach, turnips, lentils, beets, and mustard greens are high in folic acid and B vitamins. Deficiencies in folate and B vitamins have been linked with high rates of depression and fatigue.
In addition to the B vitamins, broccoli also contains traces of selenium, which helps to keep depression, anxiety, and fatigue at bay.
Legumes like beans, peas, and lentils contain chemicals and protein which provides the mood-enhancer, serotonin, to the brain, promoting feel-good feelings.
Potatoes are also rich in water-soluble vitamins for that instant lift.
Citrus fruit like oranges, lemons, limes, grapefruit, and clementine are all extraordinary high in vitamin C, another water-soluble vitamin for a great boost of energy and vitality.
Berries, blueberries, or blackberries are also noted as water-soluble fruits that provide an instant mood-lifter.
According to the US Department of Agriculture, adults should aim to eat about two cups of fruit, and two or three cups of veggies per day. Note that one cup of fruit is more or less the equivalent of a half grapefruit or one large orange. While one cup of vegetables is about equal to one serving of squash, or a medium to large baked potato. Otherwise, you can measure it out as you prefer in a cup of peas or beans, etc.