There is no consensus across medical science as to whether or not there is a safe lower limit on alcohol consumption nor whether a small amount of alcohol is beneficial. The picture is complicated by the various congeners, such as polyphenols and other substances that are present in different concentrations in different types of alcoholic beverage, such as red and white wine, beers and ales, ciders, and spirits. Moreover, while, there has been a decisive classification of alcohol consumption as a cause of cancer, there is strong evidence that small quantities have a protective effect on the cardiovascular system.