Here's the ungarnished truth about tannins and tannin sensitivity. As you probably know, tannins are astringent polymers that naturally occur in coffee, tea, red wine and chocolate (among the most popular dietary sources).
Effects of Tannins:
Tannins may cause migraines, joint pain that mimics artheritis, tiredness, depression, bowel problems, problems with vision when focussing, digestion problems, thin brittle skin, perhaps hair loss and slow hair growth, and myriad other symptoms, both subtle and severe.
For years I suffered a series of symptoms that I had pinned on coffee, uncertain about tea, and pretty sure were tied to red wine - no problem with chocolate.
These symptoms were such diverse elements as - lethargy, tiredness, depression, joint pain in hips, shoulders and fingers, thin brittle skin, hair loss, slowed hair growth, slowed metabolism and even acid reflux and heartburn and diminished ability to focus closely, requiring reading glasses.
I tried experiments by going off all these items and found that in a few days the joint pains went away. In about a week my vision returned to normal, and in about a month my skin improved. So, I assumed that one of those drinks was the cause - perhaps some sort of allergy. I was sure it wasn't caffiene because even decafe coffee and tea caused the same problems.
After years of searching for information that would help me undestand the cause of all these maladies, I've finaly done an exhaustive intent research of everything from wikipedia to manufacturers, heralists and personal blogs and determined that the cause is tannins (as suggested it might be by my partner Teresa).
While there was no single source on the internet that really had a grip on the big picture, I was able to piece together a clear outline of tannin sensitivity from these many disparate sources.
Here's the results of my research on tannin sensitivity:
Tannins in Tea:
Tannins leach out of tea only after about two minutes of brewing. During the first two minutes, mostly caffiene leaches out. So, if you like tea and want to limit tannins, brew as quickly as possible.
Here's something I worked out on my own - just a theory, but sounds reasonable. Tannins are polymers. Polymers break down into different lenghts depending upon the temperature and the time. For example, when home-brewing beer, you actually cook the "wort" on the stove at different temperatures for different times to break down the polymers to the proper length for a porter, an ale, or a lager.
So, if you want fewer active tannins in your tea, brew at a lower heat for less time. Sun tea may be an exception since it doesn't get very hot. Perhaps even a long brew may not bring out the tannins.
Tannins in Coffee:
Apartently, in order to brew coffee beans, rather than tea leaves, it requires higher heat and longer exposure of the bean to the water. This makes it difficult to prevent tannins from getting in your drink.
I'm wondering if varying the grind from course to fine, or using paper or metal or French Press filtering has an affect. I'm not sure if decaffienating coffee changes the tannin level - no data on that I could find.
Tannins in Wine:
Red wine has lots, white wines not much. That's because red wines have the skins of the grapes included in the fermenting process and the skins and seeds of grapes are very high in tannins.
I have heard there are some wines that filter out the tannins, so I wonder if that could be applied to coffee and tea as well?
Tannins in Chocolate:
Chocolates are reasonably high in both caffiene and tannins. But I've never noted negative physical or mental effects from chocolate. I'm wondering if perhaps the low heat of preparing chocolate and that it is eaten usually and a lower temperature may prevent the tannins from being released or activated.
My Tannin Theory:
Overall, I get the sense that the tannin polymers just might be bound to other chemicals in the source. Brewing or fermenting breaks that bond and releases the tannins into the drink. Once free, the tannins are able to bond with chemicals in the body which has both physical and mental effects.
If so, then rather than filtering out or avoiding tannins, we might find a way to put an additive in drinks that would bond with the tannins and keep them from being free to bond in the body.
That way, coffee, tea and red wine might respond a lot more like choclate in the system.
Tannins - Both Good ANY Bad!
When reasearching tannin sensitivity I discovered there are two camps - those promoting the health benefits of tannins and those warning of tannins' detriments.
Here's how the Pros and Cons lines up:
Tannins act as antioxidents, which mop up free radicals in your system, thereby preventing cancer and preserving your DNA, hopefully slowing aging, but tannins are the stuff they use to tan leather (an astringent) and dries your skin and slows your metabolism.
Tannins inhibit tooth decay, but tea, coffee and wine stain your teeth.
Tannins leach nutriants from your system, especially iron, leading to anemia, but they aid in digestion. But, if you have tannin drinks between meals to avoid the leaching, tannins reduce your seratonin levels. This makes you more emotional because the dopamine remains normal, but also makes you more depressed because the dopamine wasn't raised, but seratonin was just lowered.
A final clue was that I don't particularly like cumin (a high source of tannins) but I DO like pomegranates (also high in tannins). This, I believe, supports my theory that the high temperatures of cooking when using cumin release the free tannins but the room temperature of pomegranates keeps the tannins bonded when they enter your system. In red wines it may be the fermenting process that unbinds the tannins.
Okay, so there you have it. It isn't a complete or scientific study of tannins, but it does provide an overall hyposthesis of how it all works and what might be done about it.