Tannins

A number of years ago I went to a Chinese restaurant with a friend, and at this particular restaurant the first thing they do after bringing you a menu is bring you a pot of hot Chinese black tea. I've always loved it, and before I got into tea I thought it had to be something radically different because none of the bagged teas (which are almost always Indian tea) I'd tried tasted as smooth and non-astringent as it. Now I realize it's a rather weak, flavorless cup of tea, but I digress.

Anyway, this friend did not drink tea. He was Mormon, so that was the reason why, but he attempted to justify it by this line of logic: tea has tannins, and tannins are used to tan leather, therefore tea must tan your insides. A lot of people have this misconception, or at least the part where tea contains tannic acid, the same substance used to tan leather.

It does not. Tea does contain tannins, which are a diverse group of polyphenols, but not tannic acid, which is extracted from oak leaves and has an entirely different chemical structure. Not all polyphenols are tannins, but all tannins are polyphenols, and as we all know, the best constituents of tea are polyphenols. Basically, a tannin is any polyphenol that shrink proteins or bind them together and cause water to evaporate off them. Any chemists or biologists reading this should correct me if I'm wrong—I got that last bit off Wikipedia earlier today.

Tannins are responsible for the astringency of low-quality or oversteeped teas, basically. Most fruits or veggies that causes your mouth to pucker up and feel like it's been dried out are high in tannins. This is why tisanes like rooibos or chamomile don't succumb to this effect when you steep them for a long time: no tannins. If teas didn't have tannins, it's very likely there wouldn't be concept of second and third steepings, because we'd just steep them as long as wBlogger: Tead Off: The Tea Blog - Create Poste wanted. White tea is the exception here, as it is relatively low in tannins, though lower quality varieties will get bitter if you steep them for too long, and most will become at least a little astringent if steeped for more than 5-8 minutes.


Tannins are good and bad for you. They are not poisonous like tannic acid, and there is absolutely no way you could ever tan leather using tannins from tea or any of the other foods and beverages we regularly ingest. First, the good, because that's what we all want to hear:

• Tannins cause the lining of the intestinal walls to constrict, making them a good remedy for diarrhea, in addition to a number of other inflammatory bowel conditions.
  
• They also help heal wounds by forming a protective layer around the abrasion and by helping stop bleeding.
• Tannins are anti-microbial, and have also shown antiviral and anticancer potential in tests.

And now the bad:

• Tannins inhibit the body's ability to absorb minerals such as iron. This can lead to anemia. If you eat a lot of red meat you probably don't have to worry as iron from animal sources absorbs very readily, though you should be worried about other things instead if you're a red meat freak...
• Some people may have gastro-intestinal troubles if they ingest a lot of tannins.
  
• Tannins have been linked to cancer, though tea has not been, so don't worry about this one unless you take a lot of astringent herbs

Basically, moderation is good. If you're worried about anemia or other mineral deficiencies, just don't drink tea while you eat (but if you've heard adding milk keeps the tannins at bay you've been lied to—milk does nothing and may even prevent your body from utilizing the tea's antioxidants). Or add some lemon juice or vitamin C to your tea.

In any case, the most compelling argument for tannins being either benign or benevolent is the fact that tea is the world's oldest beverage other than water, and that if it were actually harmful we'd probably know about it by now. So drink up.