After inducing an ischemic stroke in mice, John Hopkins scientists found that mice who had been fed a single modest dose of epicatechin suffered significantly less brain damage than the ones that had not been given the compound.
The study was recently published in the Journal of Cerebral Blood Flow and Metabolism.
While most treatments against stroke in humans have to be given within a two- to three-hour time window to be effective, epicatechin appeared to limit further neuronal damage when given to mice 3.5 hours after a stroke. Given six hours after a stroke, however, the compound offered no protection to brain cells.
Researchers say the study suggests that epicatechin stimulates two previously well-established pathways known to shield nerve cells in the brain from damage. When the stroke hits, the brain is ready to protect itself because these pathways — Nrf2 and heme oxygenase 1 — are activated. In mice that selectively lacked activity in those pathways, the study found, epicatechin had no significant protective effect and their brain cells died after a stroke.
The authors warn that people shouldn't get too excited about the results. The amount of dark chocolate people would need to consume to benefit from its protective effects remains unclear, since no clinical trials have been conducted. The study shouldn't be considered a free pass to consume large amounts of chocolate, which is high in calories and fat.
Scientists have been intrigued by the potential health benefits of epicatechin by studying the Kuna Indians, a remote population living on islands off the coast of Panama. The islands' residents had a low incidence of cardiovascular disease. Scientists who studied them found nothing striking in the genes and realized that when they moved away from Kuna, they were no longer protected from heart problems.
Researchers soon discovered the reason was likely environmental: The residents of Kuna regularly drank a very bitter cocoa drink, with a consistency like molasses, instead of coffee or soda. The drink was high in the compound epicatechin, which is a flavanol, a flavanoid-related compound.
The amount of epicatechin needed could end up being quite small because the suspected beneficial mechanism is indirect. "Epicatechin itself may not be shielding brain cells from free radical damage directly, but instead, epicatechin, and its metabolites, may be prompting the cells to defend themselves," said Sylvain Doré, associate professor at the Johns Hopkins University School of Medicine.
The epicatechin is needed to jump-start the protective pathway that is already present within the cells. "Even a small amount may be sufficient," Doré says.
Not all dark chocolates are created equally, he cautions. Some have more bioactive epicatechin than others.
"The epicatechin found in dark chocolate is extremely sensitive to changes in heat and light" he says. "In the process of making chocolate, you have to make sure you don't destroy it. Only few chocolates have the active ingredient. The fact that it says 'dark chocolate' is not sufficient."
Citation: Zahoor et al., 'The flavanol (−)-epicatechin prevents stroke damage through the Nrf2/HO1 pathway', Journal of Cerebral Blood Flow&Metabolism, 2010; doi: 10.1038/jcbfm.2010.53
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