People who ate about 600 milligrams (0.02 ounces) of flavonoids per day had a 20% lower risk of cognitive decline than those who ate only 150 milligrams (0.005 ounces) per day, according to the study published Wednesday in the American Academy of Neurology journal.

A 100-gram (3.5-ounce) serving of strawberries has about 180 milligrams (0.006 ounces) of flavonoids, while an apple has about 113 milligrams (0.003 ounces), the study said.

Flavonoids are a series of compounds with strong antioxidant abilities that are commonly found in many fruits and vegetables, said study author Dr.

Eating foods high in flavonoids could make the downward slope less steep, he added.

After tracking the participants' diets over 20 years, researchers had them answer a questionnaire multiple times over a four-year period to determine cognitive decline, Willett said.