Small amounts of flavanols occur in grapes, red wine, and apples, but abound only in green tea and natural cocoa.
Flavanols have been linked with a decreased risk of dementia, through epidemiological studies and preliminary clinical evidence (see our sidebar, “Cocoa in Brain Research”.)
They are believed to directly protect neurons (brain cells), improve metabolism, and maintain memory capacity.
Flavanols’ brain benefits happen indirectly, via their “nutrigenomic” influences on gene switches that stimulate the body’s antioxidant network, boost blood flow to the brain, and modulate immune-system signals beneficially.
Clinical trial finds brain and metabolic benefits from cocoa
The trial comes from a team of scientists at Italy’s University of L'Aquila, led by Giovambattista Desideri, M.D. (Desideri G et al. 2012)
They recruited 90 elderly participants with mild cognitive impairment, who were in generally good health without diagnosed cardiovascular disease.
The volunteers were randomly assigned to drink one of three drinks daily for eight weeks:
High-Flavanol Cocoa - 990 milligrams of flavanols.
Medium- Flavanol Cocoa - 520 milligrams of flavanols
Low- Flavanol Cocoa - 45 milligrams of flavanols
And their diets were restricted to eliminate other sources of flavanols.
Before and after the trial period, the researchers measured the participants’ executive (decision-making/judgment) functions, as well as their working memory, short-term memory, long-term episodic memory, mental processing speed, and “global cognition” (overall thinking ability).
The uncommon “antioxidants”
in raw cocoa and dark chocolate
There’s ample evidence that diets rich in berries or other foods rich in polyphenols help deter the oxidative cell damage and inflammation caused by free radicals.
It’s becoming clear that polyphenols generally do not exert direct antioxidant effects in the body… at least not to a very substantial extent.
Instead, polyphenols appear to reduce oxidation and inflammation via so-called “nutrigenomic” effects on gene switches (e.g. transcription factors) in our cells.
Polyphenols’ nutrigenomic effects tend to moderate inflammation and stimulate the body’s own antioxidant network … which includes enzymes, lipoic acid, CoQ10, melatonin, and vitamins C and E.
In terms of their amounts of polyphenols per ounce, the richest food sources of polyphenols include raw (non-alkalized / non-Dutched) cocoa, spices, herbs, berries, plums, prunes, tea, coffee, extra virgin olive oil, onions, beans, and whole grains.
The antioxidants in cocoa are called flavanols … a relatively rare group of polyphenols whose only members are the compounds called catechins and procyanidins.
Catechins only occur abundantly only in raw cocoa, dark chocolate, and green or white tea – with much smaller concentrations in other plant foods – while procyanidins abound in berries.
Comparison of the mental test scores showed positive changes among the people assigned to the high- and medium-flavanol cocoa groups:
Significantly higher overall cognitive scores.
Reduced insulin resistance, blood pressure, and oxidative stress.
Significantly improved ability to relate visual stimuli to motor responses.
Significantly improved working memory, task-switching, and verbal memory.
The researchers attributed about 40 percent of the composite scores for improvements in cognitive functioning to reductions in insulin resistance.
The reduction in insulin resistance meant that their cells could more easily absorb glucose from food … and the brain runs on glucose.
As Dr. Desideri said, “This study provides encouraging evidence that consuming cocoa flavanols, as a part of a calorie-controlled and nutritionally-balanced diet, could improve cognitive function. It is yet unclear whether these benefits in cognition are a direct consequence of cocoa flavanols or a secondary effect of general improvements in cardiovascular function.” (AHA 2012)
“Given the global rise in cognitive disorders, which have a true impact on an individual’s quality of life, the role of cocoa flavanols in preventing or slowing the progression of mild cognitive impairment to dementia warrants further research,” Desideri added (AHA 2012).
And he made a good point: “Larger studies are needed to validate the findings, figure out how long the positive effects will last and determine the levels of cocoa flavanols required for benefit.” (AHA 2012)
American Heart Association (AHA). Consuming flavanol-rich cocoa may enhance brain function. August 13, 2012. Accessed at http://newsroom.heart.org/pr/aha/consuming-flavanol-rich-cocoa-237327.aspx
Desideri G, Kwik-Uribe C, Grassi D, Necozione S, Ghiadoni L, Mastroiacovo D, Raffaele A, Ferri L, Bocale R, Lechiara MC, Marini C, Ferri C. Benefits in Cognitive Function, Blood Pressure, and Insulin Resistance Through Cocoa Flavanol Consumption in Elderly Subjects With Mild Cognitive Impairment: The Cocoa, Cognition, and Aging (CoCoA) Study. Hypertension. 2012 Sep;60(3):794-801. Epub 2012 Aug 14.
Field DT, Williams CM, Butler LT. Consumption of cocoa flavanols results in an acute improvement in visual and cognitive functions. Physiol Behav. 2011 Jun 1;103(3-4):255-60. Epub 2011 Feb 12.
Fisher ND, Sorond FA, Hollenberg NK. Cocoa flavanols and brain perfusion. J Cardiovasc Pharmacol. 2006;47 Suppl 2:S210-4.
Francis ST, Head K, Morris PG, Macdonald IA. The effect of flavanol-rich cocoa on the fMRI response to a cognitive task in healthy young people. J Cardiovasc Pharmacol. 2006;47 Suppl 2:S215-20.
Grassi D, Lippi C, Necozione S, Desideri G, Ferri C. Short-term administration of dark chocolate is followed by a significant increase in insulin sensitivity and a decrease in blood pressure in healthy persons. Am J Clin Nutr. 2005 Mar;81(3):611-4.
Patel AK, Rogers JT, Huang X. Flavanols, mild cognitive impairment, and Alzheimer's dementia. Int J Clin Exp Med. 2008;1(2):181-91. Epub 2008 Apr 15.
Scholey AB, French SJ, Morris PJ, Kennedy DO, Milne AL, Haskell CF. Consumption of cocoa flavanols results in acute improvements in mood and cognitive performance during sustained mental effort. J Psychopharmacol. 2010 Oct;24(10):1505-14. Epub 2009 Nov 26.