"An onion can make people cry, but there has never been a vegetable invented to make them laugh," Will Rogers once said.

That may be true, but vegetables have an even more special talent: They keep the brain healthy and slash your risk for Alzheimer's disease, thanks to flavonols that are packed into almost every fruit and veggie, as well as tea. 

A recent study published in the journal Neurology tracked 921 adults with average age of 81 who didn't have Alzheimer's when the research started.

The participants filled out questionnaires about how frequently they ate certain foods as well as their other lifestyle habits such as fitness, education, and hobbies, which are known to boost memory and cognition.

After six years, 220 of the participants were diagnosed with Alzheimer's.

The researchers found that those who ate a diet that contained the largest amount (15.3 mg/day) of three types of flavonols — isorhamnetin, kaempferol, and myricetin — were 48% less likely to develop Alzheimer's than with those who took in the least (5.3 mg/day).

More research is needed to understand why flavonols in particular can help protect you from Alzheimer's. Still, you can do your body and brain a favor by making sure you get seven to nine servings daily of colorful fruits and vegetables that have the most flavonols and greatest Alzheimer's-fighting powers.

Kale (23.74 mg of flavonols in 3 ounces) and beans (31.32 mg in 3 ounces) lead the way, along with tea, spinach, and broccoli; also effective are pears, olive oil, wine (in moderation), tomatoes, tomato sauce, and oranges.