From what I understand, green tea has a very high fluoride content. Fluoride is notorius for causing esophageal and gastric pain. If you are making your tea with fluoridated city water, the combination of fluoridated water and the fluoride from the tea might meant that you are getting too much fluoride and it is causing you stomach pain and nausea.

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Maybe withdrawals from the coffee?

Could be the tannins in the green tea; they are most commonly associated with items like red wine and chocolate. While there's no doubt tannins can trigger migraines, the mechanism is pure theory at this time---while having anti-oxidant properties, they also act as anti-nutrients (like phytic acid), and can bind to nutrinets as well as to the GI tract itself. In the case of migraines, they are thought to interfere with the utilization of serotonin.

I'd suggest trying both black and white tea; white is less fermented than green; while the actual level of catechins will be higher than green, the fermentation/oxidation process may be creating compounds that are triggering your headache.

On the opposite end of the spectrum, also try black tea; it has less catechins than either white or green.

For me? Coffee fine. Black tea fine. Green tea? Massive dehydration and migraine hell. (a crying shame because I love the stuff with a good asian meal.)

NB: I keep my tea and coffee drinking to a minimum, and I drink it sporadically. I learned many years ago that caffeine addiction is no fun. I can go weeks without a caffeinated cuppa and suffer no withdrawals.

I must try this white tea you speak of...

Just found this blog after a long time of looking for others who suffer from green tea induced migraine. Its instant, the moment I swallow green tea I get a migraine aura, its something in green tea that isn't in black tea or coffee (or is at relatively lower levels) as I have experimented to make sure. Can't remember if it made me nauseated, the mind blowing migraine was enough. Need to be extremely careful when buying herbal teas or supplements to ensure green tea isn't in the ingredients list.

I drink green tea like a fiend - loose leaf, bagged, usually decaffeinated (naturally, by brewing for 30s, throwing out the tea and re-steeping), sometimes not - you name it. Also in an effort to drink less decaf black coffee which I wasn't particularly enjoying at the time.

My first thought mirrors others here, perhaps you're getting less caffeine and are thus experiencing some withdrawal symptoms.

Or perhaps you've gotten ahold of a bad batch of tea?

Interesting information above. For me, it doesn't have anything to do with coffee because I still have my morning cup and I never get headaches from it. I only notice it when I drink a cup of green tea. So I switched to white tea with a little black and I have gotten another headache, (no nausea). Totally bummed about this, but interestingly it does not happen to me when I drink a Starbucks iced green tea/with lemongrass with no sweetener.

I get nausea from drinking green tea no matter what. Not with black tea or white tea or herbal tea or coffee, just green tea. There is something specific about it that just give me nausea!! I simply cut it out. I don't know exactly what it is, if other kinds of tea don't cause problems and I'm fine with coffee, but it always happens to me.

Yes, I do get headaches, nausea, and sometimes stomach cramps. Can't drink the stuff. I have tried hundreds of different kinds and qualities of green tea, over several decades. I can drink black tea, but not green. I've tried using only purified water, distilled water, different water temperatures and steeping times, etc.

Perhaps it is partly the salicylates. I can't use coconut oil, for example. But, according to the list I've linked to, English Breakfast tea is higher in salicylates than green tea. I don't know if salicylates increase according to type of camellia sinensis, region, harvesting time of day, harvesting season, or other factors. That list seems insufficient, to me. I wish I had a more exhaustively researched list.

I have a camellia sinensis bush, and I notice that eating the tiny new leaves gives me a slight bit of the same reactions I get to green tea. The flower petals, too, but less so. The pollen, however, is the most amazing food. It is a wonderful pollen.

Here is some info on salicylate content of various foods:

http://failsafediet.wordpress.com/the-rpah-elimination-diet-failsafe/salicylate-content-of-foods/

Here is a post Emma wrote a few years ago about why some folks can't drink green tea:

Nasty antioxidants in green tea [The text following is Emma's. She has links in the blog post.]

There are a group of synthetic antioxidants that range from E310-E312 called the gallates, including propyl gallate, octyl gallate and dodecyl gallate. They’re on the “nasty antioxidants” list. They’re based around gallic acid, also known as 3,4,5-trihydroxybenzoic acid – that’s right, they’re closely related to benzoates.

If you paint your skin with benzoates, you will get an instant rash. They’re thought to cause angioedema and urticaria by triggering not histamine but serotonin release.

Gallates reportedly cause the same effects as benzoates. These chemicals are notorious; they cause the full range of health problems like asthma, eczema, and the ADHD behaviour we’re familiar with in food chemical intolerant kids. Failsafe parents describe their children as having screaming fits when they are exposed to unlabelled antioxidants.

I had a small epiphany last night after reading something about green tea that had been posted on FailsafeNT. The chemical name of green tea extract had never struck me before.

Green tea extract is basically catechins, which make up as much as 25% of the dry weight of the tea. I once tried to lose weight on green tea extract, and I felt really run down, irritable and awful the whole time, and I kept recycling the same 2lbs on the scale.

The names of the catechins are: epicatechin, epigallocatechin, and EGCG (epigallocatechin gallate), the most abundant polyphenol of all. That’s right. Green tea is made of gallates. Green tea extract has been portrayed as a source of “wonderful” antioxidants. In actual fact green tea appears to be made up of the richest natural source of nasty antioxidants. Go look at the drawings of EGCG and gallic acid on wikipedia if you don’t believe me. EGCG is just a couple of gallic acid molecules tied together via another molecule, all arms protruding.

EGCG is even marketed as a “fountain of youth” for skin cells because it smoothes out wrinkles. Is this because, like other dodgy anti-wrinkle cosmetics, it’s causing angioedema? It’s marketed as an anti-inflammatory. Is this because it is acting like aspirin to block the all-important arachidonic acid pathway? Obviously if this is the case, it will cause asthmatic and pseudo-allergic reactions.

It’s really no wonder I had such horrible reactions to green tea extract, and in more recent trials, awful arthritis pains when I drink green tea.

Now I don’t care how many times EGCG helps me to recycle the antioxidant value of vitamin E, if it makes run around like a mental case until I fall over and burst into tears, I don’t want it in my body.

No nausea here. Green Tea has substantially less caffeine than coffee though. Does this happen with regular tea as well?

This used to always happen to me when I drank either black or green tea on an empty stomach. I've gotten used to it and it's also more tolerable now (maybe because of healed gut flora?), but I hated and avoided tea for years because of this.

I have the same reaction to green tea. I used to drink it occasionally, but upped the quantity when I started working in a cold office. This is when I noticed the pattern. This does not happen to me when drinking black tea. I have only had white tea once and did not enjoy the taste, so I can't say really what that does.

I have switched to herbal teas: most are caffeine free, there are a multitude of flavors, and I haven't had any headaches or nausea. I know a lot of people say herbal teas aren't really tea, but I mostly just drink it to have a hot drink that's not coffee or hot chocolate. They keep it cold in my office! 8)

Per tannins, I haven't noticed any reaction when eating chocolate, but I do get nauseous after drinking just about any type of wine. No headache, but it roils my stomach even more so than green tea.

This topic came up in one of Robb Wolf's podcasts, and it seems that some people have negative reactions to green teas, even though they do fine for white and/or black teas. Try some other varieties and see if the problem persists.

Happens to me, too...BUT...only in the morning! And coffee makes me feel awful only in the afternoon. Weird!

So, I have a couple of cups of coffee in the morning (cut with heavy cream, of course) and a cup of green or oolong tea in the afternoon/evening.

There are so many varieties of green tea; if you find a specialty tea shop, you can go to a tasting, or ask to sample. That being said, I have experienced this with certain green teas, specifically the nausea. On an empty stomach, certain green teas seem too acidic or something. With matcha or sencha, I don't find this to be the case, though. I do make sure that the water is well below boiling and the steeping time (for the sencha) is very short.
Best wishes and happy sipping,

from my own personal experience i guess that the point is, as you wrote, "I recently decided to incorporate it into my intermittent fasts" - green tea indeed feels nauseating on an empty stomach, though not so after a meal

It could easily be the tannins which give some people stomach upset and headaches. Having milk to the tea (because of the protein) or gelatin would offset the effect somewhat if it was that. I don't find that just eating meat with tannin-containing food helps much, presumably because it's a solid.