What accompanies some fun and exhaustion after a night out may, unfortunately, be a headache. The causal relationship between alcohol consumption and headache has been well elucidated. After having a few drinks, your body processes the ethanol by converting it into ethanal, also known as formaldehyde. However, given the toxic nature of formaldehyde, your body converts it into ethanoic acid with the help of aldehyde dehydrogenase (ALDH). When the ALDH is dysfunctional, the formaldehyde accumulates and causes discomfort, including headaches.

The richness of flavours in red wine can be attributed to its spectrum of aromatic compounds, of which flavonols are the most studied. Quercetin, one of the flavonols, exists in the form of glycosides or aglycone. Quercetin glucuronide with an IC50 of 9.62 µM is a strong inhibitor of ALDH2. One standard drink of wine with 5µM of quercetin-3-glucuronide would lead to 37% ALDH2 inhibition. The resultant combination of the formaldehyde generation and its hindered clearance may contribute to a bad hangover. Of course, quercetin levels in wines vary with different grape species, sun exposure, wine-making techniques, stabilisation procedures and ageing methods, so not all wines give you the same headache.