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Red dry wine is often considered the safest and sometimes even a beneficial type of alcoholic beverage. However, numerous previous studies have indicated that there is simply no such thing as a safe alcohol dose. In some, the smallest amount of red wine can trigger a headache, while other beverages do not result the same. In a study conducted by scientists at the University of California, Davis, the reasons behind this occurrence have been elucidated.
The Culprit Behind Red Wine Headaches: Quercetin Flavanol
Quercetin is the compound found in the skin and seeds of grapes that gives red wine its distinctive color and taste. Overall, this antioxidant is considered beneficial and is even sold as a supplement. However, when combined with alcohol, problems arise.
After ethanol breaks down in the body, it transforms into acetaldehyde, a harmful toxin. The liver metabolizes alcohol into acetate through the enzyme ALDH2, also known as aldehyde dehydrogenase-2. However, at this stage, quercetin interferes with the process by blocking the ALDH2 enzyme.
When it gets in your bloodstream, your body converts it to a different form called quercetin glucuronide. In that form, it blocks the metabolism of alcohol.
Wine chemist and corresponding author Andrew Waterhouse, professor emeritus with the UC Davis Department of Viticulture and Enology
Elevated levels of acetaldehyde in the body can lead to facial flushing, headaches, and nausea. This can also occur due to excessive consumption, where the liver struggles to process toxins in a timely manner.
Conclusions and Future Steps of the Scientists
According to the researchers, not all wines contain the same amount of quercetin. For instance, white grapes have about ten times less quercetin than red ones. The cultivation process also plays a significant role, as quercetin production is responsive to sunlight. The level of quercetin can also vary depending on the winemaking process, such as skin contact during fermentation, clarification, and aging.
Therefore, the scientists plan to compare red wines with high quercetin content to those with very little quercetin in human trials. They also aim to understand why certain individuals are more susceptible to the “red wine headache,” regardless of lifestyle. Researchers are unsure whether the enzymes of individuals experiencing pain are suppressed by quercetin or if they lack them from birth. For example, approximately 40% of the population in Central Asia lacks the ALDH2 enzyme, making them almost unable to tolerate alcohol.
