New research from Harvard Medical School found that subjects who drank two cups of hot cocoa a day had improved memory and blood flow to the brain, which may stave off Alzheimer's. However, benefits only came from antioxidant-rich types of chocolate, the researchers said.

The Harvard study found that cocoa consumption helps with memory and thinking and "neurovascular coupling," a type of blood flow change in the brain that is crucial in Alzheimer's and other conditions.

Dr. Gary Small, professor of psychiatry and aging, explained the benefits of antioxidants. "As the brain ages, it undergoes wear and tear in what's called oxidative stress," he notes. "And these antioxidants in our foods actually protect the brain from that kind of aging wear and tear."

Foods with antioxidants, however, may help slow this process, including chocolate.

"I think it is healthy in moderation, that's the key because if you drink too much cocoa or eat too many chocolate bars you're going to gain a lot of calories and that is not good for the brain," Small said. "In fact it's the dark chocolates that are particularly potent; milk chocolates have very little and white chocolate has almost none. So if you want the antioxidant boost, go for the dark chocolate."