Many alcoholic beverages contain byproducts of the materials used in the fermenting process. These byproducts are called "congeners," complex organic molecules with toxic effects including acetone, acetaldehyde, fusel oil, tannins, and furfural. Bourbon has 37 times the amount of congeners that vodka has. A new study has found that while drinking a lot of bourbon can cause a worse hangover than drinking a lot of vodka, impairment in people's next-day task performance is about the same for both beverages.
Results will be published in the March 2010 issue of Alcoholism: Clinical & Experimental Research and are currently available at Early View.
"While the toxic chemicals called congeners could be poisonous in large amounts, they occur in very small amounts in alcoholic beverages," explained Damaris J. Rohsenow, professor of community health at the Center for Alcohol and Addiction Studies at Brown University. "There are far more of them in the darker distilled beverages and wines than in the lighter colored ones. While the alcohol alone is enough to make many people feel sick the next day, these toxic natural substances can add to the ill effects as our body reacts to them."
Rohsenow added that few studies have looked at the effects of high- versus low-congener beverages on next-day hangover or performance, and some of those early studies were not careful to wait until breath alcohol levels (BALs) were close to zero before measuring performance, so results may have included some of alcohol's direct effects.
"We wanted to investigate next-day effects of bourbon versus vodka while ensuring that BALs were zero or almost zero when we studied performance, and we used a variety of performance measures classified by their relevance to safety," said Rohsenow. "We wanted to use a new hangover questionnaire that included only the symptoms that had been found to be valid in laboratory studies of hangover. We wanted to find out if bourbon's effects the next day were due to different effects on sleep, so people's sleep patterns were recorded while they slept. Finally, we wanted to know if performance impairments the morning after drinking were associated with how hung-over the person felt."
Researchers recruited and paid 95 (58 women, 37 men) healthy, heavy drinkers to participate in one acclimatization night, followed by two drinking nights. The participants drank bourbon or vodka to an average of 0.11 g% BAL on one night, with a matched placebo on the other night, randomized for type and order. Polysomnography recordings were made overnight; self-report and neurocognitive measures were assessed the next morning.