Flavanols in cocoa and extra-dark chocolate may enhance brain blood flow, improve cognitive health; flavanols in tea and berries may discourage kidney cancer
by Craig Weatherby
Raw, un-“Dutched” cocoa and extra dark chocolates are rich in polyphenol antioxidants called flavanols, some of which also occur in tea.
New findings suggest that these compounds may foster healthy brain function and help prevent cognitive decline and dementia, and may help curb the risk of kidney cancer.
The brain-health news comes from scientists who presented new data at the annual meeting of the American Association for the Advancement of Science (AAAS), while the cancer findings hail from Italy.
Cocoa enhances blood flow to brain
During the AAAS session entitled “The Neurobiology of Chocolate: A Mind-Altering Experience?,” a panel of scientists presented evidence from several recent studies that demonstrated the enhanced brain blood flow after study participants consumed a specially formulated flavanol-rich cocoa beverage that was supplied by a major candy maker.
One study, conducted by Ian A. Macdonald, PhD, from the University of Nottingham Medical School in the United Kingdom, found that the consumption of this cocoa resulted in regional changes in blood flow in study participants, suggesting that cocoa flavanols may have therapeutic potential for the treatment of vascular impairments within the brain itself.
Healthy young women underwent a test of cognitive function (distinguishing between vowels and consonants and between odd and even numbers) while inside an MRI machine, to assess the brain regions activated after drinking cocoa drinks containing either a low or a high level of cocoa flavanols.
The drink containing a high level of cocoa flavanols produced increased activation of the prefrontal, parietal cortex and anterior cingulated cortex, and subsequent tests showed that consumption of cocoa flavanols increased grey matter blood flow for 2-3 hours.
As the presentation abstract said, “The demonstration of an effect of cocoa flavanols on cerebral blood flow raises the possibility that food ingredients may be beneficial in increasing brain blood flow and enhancing brain function in situations where individuals are cognitively impaired such as fatigue, sleep deprivation, or possibly ageing” (Macdonald IA 2007).
Indian study yields more evidence of cardiac benefit from cocoa
At the AAAS meeting, Norman K. Hollenberg, MD, PhD, of Harvard Medical School presented new findings based on his ongoing work with the Kuna Indians of Panama, who are heavy consumers of cocoa (Bayard V et al 2007).
The indigenous population still living on the Islands near Panama consume a type of cocoa rich in flavanols on a daily basis and enjoy very low rates of hypertension and cardiovascular disease.
Dr. Hollenberg used death certificates to compare cause-specific deaths of island-dwelling Kuna to those who live on mainland Panama—who do not drink the flavanol-rich cocoa that is so prominent on the islands.
He and colleagues found that Kuna Indians living on the islands had significantly lower rates of heart disease and cancer compared to those on the mainland. The relative risk of death from heart disease on the Panama mainland was 1,280 percent higher than on the islands and death from cancer was 630 percent higher.
In his AAAS meeting presentation, Hollenberg suggested that the same mechanism resulting in improved blood vessel function that he and others have observed following consumption of cocoa could also be responsible for the enhanced brain blood flow he and Professor Macdonald reported independently in previously published research.
Dr. Hollenberg and others have observed that improvements in blood vessel function following consumption of flavanol-rich cocoa are paralleled by an increase in the circulating pool of nitric oxide, a molecule that helps dilate blood vessels and keep them pliable.
In a study presented at the AAAs meeting, Hollenberg fed flavanol-rich cocoa to 20 healthy volunteers who were over age 50, and reported a marked blood flow response that evolved over several weeks. But this enhancement only occurred in volunteers given a flavanol-rich cocoa drink, not in those given a flavanol-poor but otherwise identical beverage (Hollenberg NK 2007).
As he said in a press release, “…[this result] raises hope that the brain blood flow response [flavanol-rich cocoa] stimulates can result in maintenance of healthy brain function and cognition, which is an issue that unfortunately plagues many older adults today” (Weber Shandwick Worldwide 2007).
Flavonoids may curb kidney cancer
Flavonoids is a term that encompasses most of the polyphenol-type antioxidants in plant foods, including those in tea and cocoa.
Flavonoids garnered more evidence of anti-cancer benefit from an Italian study that assessed the dietary intakes of 767 kidney cell cancer patients (494 men and 273 women) and 1,534 controls (988 men and 546 women) using a food frequency questionnaire.
Researchers led by Cristina Bosetti of Milan’s Institute for Pharmacological Research analyzed the food-intake surveys to calculate the participants’ consumption of six major classes of flavonoids—isoflavones, anthocyanidins, flavanols, flavanones, flavones, and flavonols—from the participant’s food and beverage intake (Bosetti C et al 2007).
After adjusting the results to eliminate possible confounding factors, the researchers calculated that the highest intake of total flavonoids was associated with a 20 per cent reduction in the risk of kidney cell cancer, compared to the lowest intake of all flavonoids.
And amongst the various kinds of flavonoids, the biggest protective effect was associated with high intake of flavones (32 per cent risk reduction) and flavonols (31 per cent risk reduction; not to be confused with flavanols).
The only rich food sources of flavones are parsley and celery.
Good food sources of flavonols include curly kale, leeks, tomatoes, broccoli, red cabbage, yellow onions, blueberries,
|The autumnal antioxidant|
Proanthocyanidins are colorless chemicals that become anthocyanins and turn leaves red in the fall.Anthocyanins are also found in red wine, certain varieties of cereals, and certain leafy and root vegetables (eggplant, cabbage, beans, onions, radishes), but they are most abundant in fruit.
Cyanidin is the most common anthocyanidin in foods, and the content in foods corresponds generally to color intensity, with blackcurrants or blackberries being the richest sources. Anthocyanins are found mainly in the skin, except for cherries and strawberries, in which they also occur in the flesh (Manach C et al 2004).
black currants, apricots, apples, green beans, red grapes, tomatoes, black and green tea, and red wine.
Increased intake of the other classes of flavonoids was associated with lesser risk reductions than those produced by flavones and flavonols: 24 per cent for isoflavones (soy, red clover), 23 percent for flavanols (tea, cocoa, grape seed extract, wine), 10 per cent for flavanones (fruits and vegetables), and six per cent for anthocyanidins (berries, grapes).
Good food sources of flavanols include the food sources of flavonols listed above, plus raw cocoa, extra-dark chocolate, and peaches.
Dr. Jack Masquelier, who discovered flavan-3-ols while experimenting with peanut skins, believes that they should not be categorized as flavonoids at all, because their properties and structure differ greatly from flavonoids.
Flavanols exist in two forms, and always consist of one or more flavan-3-ol molecules:
This study offers more evidence that fruits and vegetables, tea, and chocolate have the makings of powerful anti-cancer allies.
- Monomer flavanols are also called catechins, and are most abundant in chocolate, apricots, and tea.
- Oligomeric proanthocyanidins (OPCs or pycnogenol) are pairs and triplets of flavanols, and they occur most abundantly in peanut skins and grape seeds. OPCs and longer chains of flavanols (condensed tannins) are responsible for the bitter notes in very dark chocolate and the astringent character of some fruits (e.g., grapes, peaches, apples, pears, berries) wine, and tea.
- Bayard V, Chamorro F, Motta J, Hollenberg NK. Does flavanol intake influence mortality from nitric oxide-dependent processes? Ischemic heart disease, stroke, diabetes mellitus, and cancer in Panama. International Journal of Medical Sciences. 2007;4:53-58.
- Bosetti C, Rossi M, McLaughlin JK, Negri E, Talamini R, Lagiou P, Montella M, Ramazzotti V, Franceschi S, LaVecchia C. Flavonoids and the risk of renal cell carcinoma. Cancer Epidemiol Biomarkers Prev. 2007 Jan;16(1):98-101.
- Hollenberg NK. Aging and Brain Blood Flow Response to Flavanol-Rich Cocoa. Within session “The Neurobiology of Chocolate: A Mind-Altering Experience? AAAS Annual Meeting, San Francisco, Feb 18, 2007.
- MacDonald IA. Effect of Flavanol-Rich Cocoa on the fMRI Response to a Cognitive Task in Healthy Young People. Within session “The Neurobiology of Chocolate: A Mind-Altering Experience? AAAS Annual Meeting, San Francisco, Feb 18, 2007.
- Manach C, Scalbert A, Morand C, Remesy C, Jimenez L. Polyphenols: food sources and bioavailability. Am J Clin Nutr. 2004 May;79(5):727-47. Review.
- Schroeter H. Cocoa as a Source of Bioactive Natural Products. Within session “The Neurobiology of Chocolate: A Mind-Altering Experience? AAAS Annual Meeting, San Francisco, Feb 18, 2007.
- Van Praag H. Can Cocoa Influence Learning and Memory? Within session “The Neurobiology of Chocolate: A Mind-Altering Experience? AAAS Annual Meeting, San Francisco, Feb 18, 2007.
- Weber Shandwick Worldwide. Flavanols in cocoa may offer benefits to the brain. February 18, 2007.