In the latest issue of the American Journal of Clinical Nutrition, researchers from Northumbria and Newcastle Universities in England report the results of a double-blinded, crossover study which found a benefit for oral resveratrol consumption on cerebral blood flow.
Following an initial study confirming the bioavailability of orally administered resveratrol in 9 volunteers, 22 healthy adults were randomized to receive two capsules containing a placebo, 250 milligrams trans-resveratrol or 500 milligrams trans-resveratrol in a specific order over three clinic visits subsequent to an initial screening visit. Fifty minutes after ingesting the capsules, the subjects were asked to complete a selection of cognitive tasks that had been previously demonstrated to activate the brain's prefrontal cortex. Near-infrared spectroscopy assessed frontal cortex changes in oxygenated and deoxygenated hemoglobin in order to evaluate blood flow and hemodynamics during the 36 minutes of task performance.
Resveratrol was found to dose-dependently increase blood flow during task performance, as demonstrated by increased total hemoglobin concentrations. Deoxygenated hemoglobin also increased following both doses of resveratrol, suggesting increases in oxygen extraction and utilization. No significant differences in cognitive function were observed.
The authors remark that similar findings had been observed in relation to vinpocetine, a compound that increases cerebral blood flow through several mechanisms. They suggest that the increase in total hemoglobin observed in the current research could be due to an effect of resveratrol on nitric oxide, which helps improve blood flow by relaxing the blood vessels, although other factors may be involved.
"These results showed that single doses of orally administered resveratrol can modulate cerebral blood flow variables," the authors conclude. "Natural aging is associated with impaired nitric oxide-mediated vasodilation and reduced cerebral blood flow (CBF), and the etiologies of many neurologic disorders, such as Alzheimer's disease, vascular dementia, and stroke, include deficits in CBF. The results of the current study provide the first indication in humans that resveratrol may be able to modulate CBF variables. Thus, it seems reasonable to suggest that the potential effects of this molecule on brain function deserve a great deal more research attention with a clear focus on both healthy humans and pathologic groups."
Multiple studies have found that a diet high in fruits and vegetables lowers risk of cerebrovascular disease and both ischemic and hemorrhagic stroke (Gariballa SE 2000; Sauvaget C et al 2003). Two major reviews recommended that public health policy promote increased dietary intake of antioxidant vitamin C, beta-carotene, vitamin E, B vitamins (including folate), potassium, calcium, magnesium, vitamin D, fiber, and omega-3 fatty acids to reduce risk of stroke (Gariballa SE 2000; Johnsen SP 2004). These vital nutrients can also be obtained through dietary supplements in conjunction with a healthy diet.
Vinpocetine has been widely studied for its ability to restore blood flow to the brains of stroke victims. It appears to have multiple effects that interfere with the ischemic cascade. Studies have shown that it reduces the depletion of adenosine triphosphate, which is the main cellular energy source, and functions as an antioxidant (Hadjiev D 2003; Vas A et al 2002). Recently, researchers have found that high-dose, intravenous vinpocetine (at doses up to 70 mg daily) is able to restore blood flow to the brain and reduce the size of ischemic stroke lesions, leading several researchers to identify vinpocetine as a potential therapy for the acute treatment of ischemic stroke (Szilagyi G et al 2005; Szapary L et al 2003; Dezsi L et al 2002). The protective effects are most pronounced in areas of the brain with the highest uptake (Szilagyi G et al 2005). These studies build on previous work showing that oral vinpocetine is also effective in enhancing cerebral blood flow (Dezsi L et al 2002).
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