Background When equalized for alcohol content by volume, however, not all alcoholic beverages have the same effect on blood alcohol concentration (BAC) or neurotoxicity. The aim of this study was to investigate differences between metabolism of a natural wine and of a conventional wine. Methods Fifty-five healthy male volunteers were randomly administered the equivalent of 2 units of alcohol (24 g of ethanol) of a natural or of a conventional wine, and one week later received the same dose of the other wine. At each of the two sessions, a breathalyzer was used to estimate BAC levels before the intake of the wine and then every twenty-minute for 2 hours. The entire study was conducted in triple-blind conditions. Results The blood alcohol curves after consumption of the two different wines diverged significantly at the twenty-minute mark (T20) and then again at their peak values. In both cases, the BAC induced by the natural wine was lower than the one corresponding to the conventional wine (T20 0.44 vs. 0.49 [p<0.012], peak 0.56 vs. 0.60 [p<0.032]). Conclusions The results of the study suggest that natural and conventional wines have a different effect on BAC. The alcohol in the natural wine seems to be absorbed more slowly. Different techniques applied in the production chain likely lead to the development of different amino acids and different types and amounts of antioxidants in the two wines. These compounds, in turn, may affect the kinetics of alcohol absorption and metabolism. The presence or absence of residues of pesticides and other agrochemicals, differences in sugar and fiber content, and the use of either indigenous or selected yeasts, are additional factors that may contribute to the differences observed. If this hypothesis is confirmed, it could have important public health and policy implications.