The cocoa bean is naturally high in flavanols– plant chemicals thought to protect from oxidative stress and other types of damage. While studies have found that these compounds can help improve cardiovascular health, large controlled studies have not found a direct benefit for brain health, cognition, or dementia. On the plus side, safety concerns are minor and generally limited to caffeine and theobromine content, as well as the number of calories.
Several meta-analyses and systematic reviews exist, along with a large randomized controlled trial that studied the effects of cocoa flavanols on cognitive function in elderly people. Our search found:
In a large clinical trial of over 2,000 elderly people, cocoa flavanol treatment (500 mg daily) for three years failed to improve cognitive function compared to the placebo group [1]. However, a related study found that people with low baseline levels of flavanols showed improvements in certain kinds of memory tasks if they were supplemented with cocoa flavanols [2]. A few smaller clinical trials have also suggested that while cocoa and cocoa flavanols might slightly improve cognitive function, most aspects of cognition are unaffected [3; 4; 5; 6]. Cocoa may therefore offer only small or specific cognitive benefits in select people.
Observational research has also found mixed results. In one observational study, people who ate chocolate or cocoa regularly were just as likely to experience cognitive decline over five years [7], although another study reported that they tended to have better cognitive abilities [8]. Another observational study found that compared to no chocolate, moderate consumption of chocolate was associated with fewer dementia deaths [9]. Potential benefits of cocoa or cocoa flavanols have also been reported for cardiovascular diseases and diabetes [10; 11; 12; 13; 14], which may also affect the risk of cognitive decline and dementia [15; 16].
Cocoa or its flavanols may increase blood flow to the brain [6], which often decreases with aging [17] and in neurodegenerative diseases such as Alzheimer's [18]. Cocoa flavanols may also have anti-inflammatory or antioxidant roles and may directly affect brain health as well [19].
There is no rigorous human research on the possible benefits of cocoa or related flavanols for dementia patients. A few small clinical trials have investigated whether cocoa flavanols improve cognitive function in people with early stages of dementia, but results have been mixed [5; 20]. Larger, rigorously designed clinical trials are needed to determine the efficacy of cocoa in dementia patients.
Chocolate, cocoa, and flavanol-enriched cocoa extracts have few known safety issues. The only side effect reported in many trials is gastrointestinal upset or nausea, and taking cocoa flavanols with food can help decrease the chance of nausea. There are concerns, however, related to the caffeine, theobromine, sugars, saturated fat, and additional calories found in most chocolate products. Moderation is essential since chocolate often has very high caloric content, which could contribute to weight gain.
There have been concerns about the high levels of lead and/or cadmium in some brands of cocoa products, including cocoa powder and chocolate. This is particularly important for children and pregnant people to avoid, but it can be good for anyone to check their cocoa source for heavy metal contamination.
NOTE: This is not a comprehensive safety evaluation or complete list of potentially harmful drug interactions. It is important to discuss safety issues with your physician before taking any new supplement or medication.
Clinical studies have used daily doses of flavanol ranging from 500 to 990 mg. Dietary intake of flavanols is often much lower, particularly for cocoa-related flavanols. If flavanols are the critical ingredients for possible health benefits, then the chocolate or cocoa commonly found in the diet may not be a good source, depending on ingredients, sourcing, and processing method. Milk chocolate contains less cocoa powder by weight than dark chocolate and, therefore, has a lower flavanol content. "Dutch" processing or alkalization lowers the amount of flavanols by 60 to 90 percent [21].
The flavanols in cocoa are also found in other food products such as tea, apples, pears, and berries. Tea has particularly high levels of flavanols.
Full scientific report (PDF) on Cognitive Vitality Reports