The findings suggest that cranberries can aid recovery from stroke, particularly in its earliest stages, in which the most severe damage occurs, the researchers say. Their study, which they claim is the first to demonstrate a link between cranberries and protection from stroke, was described today at the 226th national meeting of the American Chemical Society, the world's largest scientific society.
"This study shows that cranberries have the potential to protect against brain cell damage that occurs during a stroke event," says Catherine Neto, Ph.D., an assistant professor at the University of Massachusetts-Dartmouth and a lead investigator in the study. "It may not stop a stroke from occurring initially, but it may reduce the severity of stroke," she says.
Neurons from the brains of several rats were collected for this study. After placing the neurons in tissue culture, millions of cells were grown and then divided into different treatment groups with varying concentrations of cranberry juice. Under simulated conditions of stroke, exposure to cranberry juice was found to have a statistically significant effect in reducing brain cell death, the researcher says.
Although animal and human studies are needed to confirm the findings, the study offers a compelling reason for recent stroke victims and those at risk for stroke to consume cranberries, Neto says.
Until those studies are done, nobody knows the amount of cranberries or cranberry juice people should eat or drink to have an optimal effect against stroke, she adds. Other studies have shown that cranberries are also effective in fighting urinary tract infection and may help combat cancer and heart disease. These health effects have been linked to the rich supply of antioxidants found in the tart berries.
In related studies using rats, researchers recently demonstrated that blueberries, which are closely related to cranberries and similarly rich in antioxidants, also appear to reduce brain damage associated with stroke. That blueberry study was led by Neto's collaborator in the current study, Marva Sweeney-Nixon, Ph.D., of the University of Prince Edward Island in Canada. Both researchers suspect that cranberries will have a similar effect in live rats, which they plan to test soon.
Stroke is the third leading cause of death in this country and the most common cause of disability in adults. It occurs when the blood supply to the brain is suddenly stopped, usually through a blood clot (ischemic stroke).
In the current study, Neto and her associates obtained brain cells from rats and exposed the cells to two specific conditions that commonly occur during stroke. In one condition, a group of cells was deprived of oxygen and glucose, which occurs during ischemic stroke as brain cells are starved of oxygen and die.
In the other condition, a separate group of brain cells was exposed to hydrogen peroxide, simulating the action that takes place following the stroke when oxygen again begins to flow to the brain. The process, called reperfusion, causes further damage and death to cells, as they are exposed to excess levels of highly reactive oxygen species. Like a second-wave of attacks, these "superoxides" can continue causing brain cell damage and cell death for days and weeks after the initial stroke.
Both groups of cells were then exposed to varying concentrations of cranberry extract, which was obtained from fresh, whole cranberries. Exposure to the highest concentration of extract, which was roughly equivalent to a half a cup of whole cranberries, caused a 50 percent reduction in brain cell death, as measured by chemical markers indicative of the death of neurons.
Like the blueberry studies, researchers still do not know the specific phytochemicals that appear to be responsible for the protective effect of cranberries. However, they believe that they may belong to a class of potent antioxidants called anthocyanins, which are common in both types of berries and are also responsible for giving the berries their characteristic dark color.
Further studies are now underway to isolate the active compounds, the researchers say. Once the active component is identified, researchers may be able to develop it into a stroke-fighting drug or nutraceutical.
There is a growing variety of cranberry products on the market. Besides juices and sauces, there are herbal teas, pills and dried whole cranberries. Fresh, whole cranberries are probably the healthiest, Neto says, since they are more likely to contain higher levels of antioxidants than processed versions of the fruit.
According to the National Institutes of Health, there are several proven steps that consumers can take to reduce their risk of stroke — lowering their blood pressure, quitting smoking, and keeping heart disease and diabetes in check.
Funding for this study was provided by the Cranberry Institute and the University of Massachusetts-Dartmouth.
The paper on this research, AGFD 54, will be presented at 9:20 a.m., Monday, Sept. 8, at the Javits Convention Center, Room 1A07, during the "Phenolics in Foods and Natural Health Products" symposium.
Catherine C. Neto, Ph.D., is an assistant professor in the Department of Chemistry and Biochemistry at the University of Massachusetts-Dartmouth in North Dartmouth, Mass.
— Mark T. Sampson