In this study, 90 elderly participants with mild cognitive impairment were randomized to drink daily either 990mg (high), 520mg (intermediate) or 45mg (low) of a dairy-based cocoa flavanol drink for eight weeks.

The diet was restricted to eliminate other sources of flavanols from foods and beverages other than the dairy-based cocoa drink. Cognitive function was examined by neuro-psychological tests of executive function, working memory, short-term memory, long-term episodic memory, processing speed and global cognition.

The research showed that scores significantly improved in the ability to relate visual stimuli to motor responses, working memory, task-switching and verbal memory for those drinking the high and intermediate flavanol drinks.

Participants drinking daily higher levels of flavanol drinks had significantly higher overall cognitive scores than those participants drinking lower-levels; insulin resistance, blood pressure and oxidative stress also decreased in those drinking high and intermediate levels of flavanols daily.

"This study provides encouraging evidence that consuming cocoa flavanols, as part of a calorie-controlled and nutritionally- balanced diet, could improve cognitive function," said Giovambattista Desideri, study lead author and a professor at University of L'Aquila in Italy.

Flavanols can be found in tea, grapes, red wine, apples and cocoa products and have been associated with a decreased risk of dementia. They may act on the brain structure and function directly by protecting neurons from injury, improving metabolism and their interaction with the molecular structure responsible for memory. Indirectly, flavanols may help by improving brain blood flow, researchers said.