Many people swear that they feel especially tired after a glass of red, compared with white, and there’s some evidence of a scientific explanation. No study has actually been done to show it, but wine-lovers everywhere can attest that red wine has a powerful drowsiness quality. The flesh, skin and seeds of grapes, it turns out, contain melatonin in a form that’s very similar to the hormone we produce in the body to go to sleep at night. Something in the winemaking process, probably related to the yeast, seems to increase melatonin levels, giving wine a higher concentration than grapes or non-alcoholic grape juice. And since red wine is made with skin, while white wine is not, it stands to reason that there would be more in a merlot than a chardonnay. That said, it’s not a huge amount either way, and it’s hard to know what effect, if any, it’s really having.

Read More: Does Red Wine Make You Sleepier Than White Wine?