If you drink wine, at one point or another you’ve probably heard someone refer to a wine’s tannins, but you may not know what they are or why they matter. While knowing what this term means is not a necessity for enjoying a glass of wine — really! — it can help you better understand the wine you’re drinking and even why some wines give you a headache.

You experience the effect of tannins any time you drink a wine that creates a drying sensation in your mouth.

Tannins are naturally occurring compounds that exist inside grape skins, seeds and stems. The scientific word for these compounds is polyphenols. Polyphenols release from the skins, seeds and stems when they soak in the grape juice just after the grapes have been pressed and are what give certain wines, such as Cabernet Sauvignon, their characteristic dryness or astringency. You experience the effect of tannins any time you drink a wine that creates a drying sensation in your mouth. Depending on how dry your mouth feels, you can determine whether a wine is high or low in tannins. We say a wine that is high in tannins is tannic.

If you want to try a trick that can help you recognize a tannin when you taste it, brew a cup of extra strong black tea. Tannins naturally occur in black tea and their characteristics emerge when the tea is brewed a few minutes longer than recommended. After brewing the tea, take a sip and you’ll immediately notice a slight bitterness in the middle of your tongue and a dryness in the front of your mouth — this is a tannin.

What makes a wine have strong or weak tannins depends on how long the juice sits with the grape skins, seeds and stems after the grapes have been pressed. The longer the skins, seeds and stems soak in the juice, the more tannin characteristics they will impart. This explains why red wines have stronger tannins than white wines. When producing a red wine, the winemaker wants the skins to impart more color, thereby adding more tannins to the juice. Further, by extracting the characteristics of tannins, they are able to add deeper complexity to the wine.

Winemakers also love tannins because they work as a natural antioxidant to protect the wine. This is actually a key reason why certain red wines, including Cabernet Sauvignon, can be so age-worthy. And, as we know, antioxidants aren’t just useful for helping us age wine; they also have great health benefits for humans! Now you can tell your nutritionist there’s no need to keep drinking that pomegranate juice; you’re just going to have a nice glass of red wine instead!

Black Tea Is Also High In TanninsDark chocolate and strong black tea also contain a lot of tannins.

The only downside to tannins is that they can give some people headaches. A good way to test if you’re susceptible to tannin headaches is to determine whether or not similar substances that are strong in tannins, such as dark chocolate and strong black tea, produce the same effect. Tannin headaches are rare, usually we just get a wine headache from consuming too much, but if you do realize you suffer from them, sticking to white wine, which is very low in tannins, would solve your tannin-triggered headaches!