When brain cells do their work, they produce byproducts called free radicals, which cause gradual damage to the cells.

The good news is that consuming fruits and vegetables — which contain substances called antioxidants — helps fight off this oxidative damage and protects your brain.

For this reason, the World Health Organization recommends eating at least five servings of fruits and vegetables each day.

In UCLA research conducted along with the Gallup Poll organization, we found that on average, older people consume more fruits and vegetables than middle-age people or young adults.

In a representative sample of more than 18,000 Americans, 64 percent of older adults reported eating the recommended amount on four or more days in the previous week. Compare that to 54 percent of middle-age people and 49 percent of young adults.

And those who ate more fruits and vegetables experienced significantly fewer memory problems.

Vibrantly colored fruits and vegetables such as blueberries, pomegranates, kale, and broccoli are filled with polyphenol antioxidants. Eating these and other fruits and vegetables is associated with a lower risk for developing Alzheimer’s disease and related forms of dementia.

A person who consumes 2,000 daily calories should eat approximately two cups of fruits and two and a half cups of vegetables each day.

A piece of fruit such as a banana or apple is equivalent to a cup, as is a half cup of dried fruit.

Along with antioxidants, fruits and vegetables also provide vitamins, minerals, and fiber that help protect the brain.

In addition, fruits and vegetables contain chemical compounds called phytonutrients that protect plants from germs and bugs. These compounds are what create the distinctive odors and pigments in plant-based foods, including the deep purple of blueberries and the strong smell of garlic.

Nuts, whole grains, beans, herbs and spices, and tea also contain important phytonutrients that help maintain normal body function and can even prevent some diseases.

The flavonoids in apples, berries, and onions contain strong antioxidants, and the phytonutrient lycopene — found in tomatoes, pink grapefruit, watermelon, and guava — has been shown to protect against some forms of neurodegeneration.