New research on mice suggests that a compound found in dark chocolate and tea may protect against brain injury from a stroke.
You can read about the study led by Johns Hopkins University School of Medicine in Baltimore, Maryland, online in the 5 May issue of the Journal of Cerebral Blood Flow and Metabolism.
We already know from previous epidemiological studies that plant foods rich in polyphenols, such as flavanols (not to be confused with flavonols), can lower the risk of ischemic heart disease (disease that results from reduced blood supply to the heart), but how it does so is not clear.
In this study, Dr Sylvain Doré, associate professor of anesthesiology and critical care medicine and pharmacology and molecular sciences at the Johns Hopkins University School of Medicine, and colleagues, investigated whether epicatechin (EC), a flavanol found in in cocoa and tea, protected mice against brain damage from an ischemic stroke (where the blood supply to the brain is cut off).
For the study, they fed mice with 5, 15, or 30 mg/kg doses of EC and then 90 minutes later induced an ischemic stroke by essentially cutting off the blood supply to their brains (middle cerebral artery occlusion, MCAO).
They found that the treated mice had significantly less brain damage (infarcts) and reduction in brain function (“decreased neurologic deficit scores, NDS”) compared to mice that had not been fed with EC.
They also found that mice given 30 mg/kg of EC 3.5 hours after an induced stroke (MCAO) also had significantly less brain damage and NDS. However, when given 6 hours later, there was no protective effect.
(Usually with humans, treatments to prevent brain damage from strokes have to be given within a two- to three-hour window.)
Doré told the media these findings suggest that EC stimulates two already well researched pathways that shield brain cells from damage: these are the pathways used by the enzyme heme oxygenase 1 (HO1) and the transcriptional factor Nrf2.
When they did the same tests on mice bred to lack these pathways, they found that the protective effect of EC on the brain was mostly abolished, and the brain cells died after the induced stroke.
The researchers hope their findings will help us better understand how to research acute stroke damage, and how to protect against chronic brain-wasting diseases such as Alzheimer’s and other age-related cognitive disorders.
However, they were keen to point out this was not a clinical trial and this study should not be an excuse for us to go out and start eating masses of chocolate, which is also high in calories and fat. People should eat a diet high in a variety of fruits and vegetables, they said.
Research interest in epicatechin started in earnest with investigations of the eating habits of remote populations of Kuna Indians who live on islands off the coast of Panama.
These remote populations appeared to have low rates of heart disease, but when they moved away from their islands they were no longer protected from heart problems.
Genetic studies confirmed that the protection came from their environment rather than their genes, and scientists eventually settled on the likely cause being the very bitter epicatechin-rich cocoa drink they consumed when they lived on their island.
Doré believes the amounts of epicatechin needed to confer protective benefits might be quite small because their effect is indirect: they probably “jump-start” the protective pathways that are already there:
“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 Doré.
“Even a small amount may be sufficient,” he added.
He also cautioned that not all dark chocolates are the same: they contain differing amounts of bioactive epicatechin:
“The epicatechin found in dark chocolate is extremely sensitive to changes in heat and light,” said Doré, explaining that you have to make sure you don’t destroy the compound when you make the chocolate.
Source: Medical News Today