It's the red-wine compound that can't seem to do anything wrong. Resveratrol, found in the skins of grapes and in red wine, is the focus of several newly published studies. All three find the polyphenol has positive health effects, but also raise critical questions about why it's helpful and how the body absorbs it.
A review of past studies on red-wine polyphenols, to be published in the September issue of Alcoholism: Clinical & Experimental Research, found that resveratrol stands tallest in providing potential health benefits. Red wine is a complex solution which contains a mixture of compounds such as flavonols, organic acids and pigment-producing anthocyanins. While all of these ingredients appear to produce health benefits when consumed responsibly, resveratrol is the most consistently linked to myriad benefits to one's overall health.
Another study, scheduled for publication in Cellular and Molecular Biology, finds that resveratrol may fight off the brain damaging effects of Parkinson's disease. A third review, available in the May issue of Heart and Circulatory Physiology, suggests that resveratrol optimizes the performance of individual cells in the body. All three studies share a common thread—resveratrol affects the body on a cellular level. While numerous studies have found that red wine can be beneficial, by improving circulation for example, this research is getting closer to understanding how wine does so on a cellular level.
In the first study, researchers at the University of Queensland analyzed recent research that focused primarily on resveratrol. They found the weight of evidence supported two main theories: Resveratrol tends to kill cancer cells and protects heart cells, and resveratrol aids in protection from brain ailments. The scientists looked at chemical compounds analyzed in research papers and found that some, such as curcumin, which is found in the curry ingredient turmeric, showed potential for health benefits, but that in recent years the number of studies on resveratrol have skyrocketed, from less than 500 in 2000 to more than 3,000 studies in 2009. The researchers combed the studies for commonalities in the data.
Lindsay Brown, an associate professor at the School of Biomedical Sciences at the University of Queensland and corresponding author, said in a statement that, "It sounds contradictory that a single compound can benefit the heart by preventing damage to cells, yet prevent cancer by causing cell death." The most likely explanation, according to Brown, is that low concentrations activate survival mechanisms of cells while high concentrations turn on the built-in death signals in these cells.
In the same release, Brown's colleague Stephen Taylor, a professor of pharmacology at the university, highlights a growing flaw in the current research extolling the abilities of resveratrol. "Resveratrol is largely inactivated by the gut or liver before it reaches the blood stream, where it exerts its effects, whatever they may be—good, bad or indifferent," he said. "Thus, most of the resveratrol in imbibed red wine does not reach the circulation."
But Taylor does not rule out that resveratrol may still be effectively absorbed in some other way that remains as yet unknown, say via the mucous membranes in the mouth. In which case, sipping slowly and allowing red wine to linger before swallowing may account for red-wine drinkers being generally healthier in epidemiological studies.
In an editorial in Heart and Circulatory Physiology titled, "A Glass of Red Wine to Improve Mitochondrial Biogenesis? Novel Mechanisms of Resveratrol," Gábor Szabó, a professor of cardiac surgery at the University of Heidelberg, Germany, echoes the Queensland study on many levels.
Szabó argued that all of the research on resveratrol points to a compound that works in a way new to science. Since the red-wine compound does so much, it cannot work only as an antioxidant, reducing oxidative damage to cells, he said. The likely explanation is that the polyphenol improves the performance of mitochondria, organelles that function as powerhouses inside cells. If this is true, the potential for resveratrol is seemingly limitless.
"The data about mitochondrial function as a missing puzzle [piece] complete the complex picture of the 'all-in-one' nature of this substance," wrote Szabó. "As intact mitochondrial function is a prerequisite of cellular integrity in any tissue, any drug which improves mitochondrial function may have large potential in the treatment of a wide variety of diseases."
The third body of research from Cellular and Molecular Biology takes a different approach. Researchers put resveratrol under the microscope, along with another red-wine polyphenol called quercetin.
The study by the department of biochemistry and neuroscience at the Université du Québec à Trois-Rivières found that both compounds helped prevent a Parkinson's disease-related neurotoxin from killing brain cells. But because the results were in the lab, the question remains whether resveratrol and quercetin in red wine can be metabolized by the body and used by the brain.
The study ultimately calls for more research, but notes the "powerful role of these dietary compounds," which seem to be becoming, "more and more important as alternative or complementary therapies," for humans with chronic illnesses.