I just passed on some shu pu'er to a co-worker having stomach problems, and wanted to share some thoughts on the types of tea that might cause the most impact or are most gentle on your stomach. That's more relevant to people who already experience some type of stomach problems, which would vary in cause, since different people can tolerate different foods and eating related practices. It seems like the kind of thing everyone would already know about, about how different teas tend to cause stomach issues or else don't, but common knowledge would vary along with personal exposure.
a Moychay buds-heavy version of shu, that tastes like cocoa (from here)
this version is sold out; there seems to be an increase in demand for shu in the past year
To preface the context this won't be a research post (although I do mention a number of sources), and my own take is a hearsay account, drawn from personal experience. I don't have a sensitive stomach or stomach problems, so maybe that second part counts for less. But at the same time I've been drinking lots of tea for a half-dozen years, so on the other hand maybe I'm getting some things right.
About that co-worker's case: his doctor gave him the usual input, to avoid foods or drinks that can be hard on your stomach (coffee, tea, spicy foods, etc.), and to eat food with any drink that seems to pose some risk. A good prevention or resolution really depends on the specific cause for his own case, and I'm not sure what the cause is, and he seems not to know it. If he can't get it resolved by adjustments to diet that doctor will take a look in his stomach with a scope, which sounds like something I'd want to avoid.
He said that he's been drinking powdered green tea, which would usually go by the category name "matcha." If that relates to Thai versions maybe it's as well to just call it powdered green tea, even though the designation can be interpreted as not limited to tea from Japan, per some people's takes (with a generally good Thai producer source here). I personally don't find tea naming disputes as interesting as functional ideas.
At any rate that seems like one of the worst teas to drink if sensitivity is a problem, even if consumed along with food. An old Tea Chat discussion conveyed his experience isn't unique, titled "Matcha nausea?," but it doesn't shed much light on causes or likely extent related to other tea types. Most people there suggested eating some food along with drinking teas, especially first thing in the morning.
Onto what I think might cause stomach problems (related to tea, which may not be a primary cause in his case), and what types I think would be the least likely to, broken down by topic category.
Shu pu'er: this has a reputation as being easiest on the stomach, as tea types go. It can be hard to align that type of hearsay input to actual facts of the matter, and drawing on one's own experience might only be valid for one individual case. All the same it seems that way to me too. I'm not as convinced that it can help people with problems with digesting greasy food, a claim that does turn up, but maybe that works. It's probably better to just eat healthier food most of the time than to work around problems stemming from bad diet choices. Check out this related article, if it's of interest:
One serving of fried chicken a day linked to 13% higher risk of death, study finds
Matcha / powdered green tea: I've run out of the range of personal input here since I don't really drink matcha. In tea circles that's crazy; it would make more sense to tell people that you don't like black tea (which would seem crazy to me). I could easily pick up a preference for matcha if I drank it more regularly, since it doesn't seem bad to me. I've tried ceremonial grade versions, twice in actual Japanese tea ceremonies even, both prior to 10 years ago. So it's not that, more a matter of acclimation, at a guess.
Since I like green tea the least of all kinds it seems as well to just pass on intentionally picking up an interest in one variation of one. Of course I've tried cold matcha drinks and Starbucks' lattes, and they're ok, and love matcha soft-serve ice cream, so it's not as if I've never had any positive contact with it. Hojicha flavored ice cream can also be incredible; keep an eye out for that.
Green tea (also tied to the last topic, matcha): About the stomach concern green tea is said to the worst for your stomach, along with sheng pu'er, which is probably pretty close to green tea in terms of compounds present (although that isn't a given, and the main impact should be related to a very limited set of compounds found in tea anyway). I don't talk about sheng here (in this post--in the blog I do a lot), or point out that aged sheng is probably much easier on the stomach, since all that seems to apply more to people further through developing tea preferences.
this sheng was already two years old, reviewed here
a 12 year old sheng, if properly represented when sold (reviewed here)
Green tea is considered to be healthiest by many due to containing a lot of ECGC, which supposedly benefits your cardiovascular system health. I believe that it probably really does, but looking into the research gets confusing. Rats are taking tea extracts in a lot of related studies, which is only indirectly related in two different senses. On the whole it seems like there is evidence for such claims, but then separating back out research funded by tea interests is tricky.
It's not as if everything published as a "peer reviewed" journal article was confirmed or well-received by peers, and it's the results of that review that matter, not that a paper made it to be published initially. Of course in the end people can just believe what they want to believe.
This interesting and helpful Specialty Tea Alliance article on tea compounds helps sort it all out:
In steeped tea, polyphenols are largely responsible for astringency... These compounds are plant metabolites produced as a defense against insects and other animals and are the most abundant compounds in tea comprising as much as 30-40% of both freshly plucked tea leaves and solids in tea liquor(1)...
There are an estimated 30,000 polyphenolic compounds in tea(4), flavonoids are arguably the most important group of polyphenols in tea and are the source of the many health claims surrounding tea, and specifically tea antioxidants...
Flavanols are also referred to as tannins, and during oxidation are converted to theaflavins and thearubigins—the compounds responsible for the dark color and robust flavors notably present in black teas. The major flavanols in tea are: catechin (C), epicatechin (EC), epicatechin gallate (ECG), gallocatechin (GC), epigallocatechin (EGC), and epigallocatechin gallate (EGCG). EGCG is the most active of these catechins and is often the subject of studies regarding tea antioxidants...
Reading the whole article is worthwhile; it's not that long, and only catching two thirds of what it means due to the compound types being unfamiliar doesn't diminish how interesting the rest is. This citation of a study of compounds found in teas shows how those levels map out:
an edited table of compound levels findings from this research article
A few things about that reference:
I had cited it in a Quora answer, to the question "I want to make it a habit of drinking green tea instead of coffee, but I do not like its taste as it is bitter; what should I do?"
The obvious answers are to brew the tea using cooler water (typical preparation for green teas), and to consider drinking other tea types, which is what my answer goes into.
The ECGC compounds--those said-to-be helpful ones--are shown in the last (right-most) column, in the form of levels of milligrams per gram of dry tea. There is more ECGC in green tea than black; those results show that clearly enough. Darjeeling black teas vary a lot due to oxidation level in those (shown in the results); that's kind of a long story to get into it here.
A bit of an aside about caffeine: CA in that table relates to measured caffeine levels; that may be very interesting to lots of people. It can be difficult to use it as an estimate for levels in tea since that's cited a mg / gram of dry tea, not as estimated mg / brewed cup. Let's pick an average value and see if we can convert that over.
20 mg / gram might work as an overall average (see the "CA" column). We can estimate 2 grams of tea are used to brew a single cup (although that's not a given; you could probably make a second cup with the same 2 grams you brew, but I'd use 3 grams or more if I wanted to make two good infusions). We can estimate an 85% extraction rate based on a four minute infusion time (that's a long story; check out where I got that here). 20*2*.85 = 34 milligrams of caffeine. A typical cup contains 30-50, per lots of sources, so it works out.
I also cited that tea-compounds article in that Quora answer, to work through reasons for why someone might drink green tea beyond the taste. If someone was really committed to getting to the bottom of things they could spend a day reading up on health-claims research, then another day reading about tea compounds present in different types of teas. Drinking sheng or light rolled oolongs might work as well, but someone trying sheng for the first time might be in for a long detour getting used to young sheng character (what it's usually like before aging), or sorting through types of it (differing regions, flavor profile ranges, preparation styles, sources and cost levels).
As a final aside that paper on tea compounds the table comes from was fascinating, just a dry read, even compared to the American Specialty Tea Alliance article on compounds (the organization formerly known as World of Tea). But don't let the title put you off; it is interesting and informative:
The Joint Use of Electronic Nose and Electronic Tongue for the Evaluation of the Sensorial Properties of Green and Black Tea Infusions as Related to Their Chemical Composition
black tea, oolong, compounds causing stomach problems: I never did really clearly pin down what compound was probably causing the stomach problems, did I? To be honest I don't know. Oolong and black tea seem to be more gentle on the stomach, but again that's hearsay input, not a research-finding evidence-based conclusion.
I told that co-worker that per my take (again, into hearsay, and personal judgement) it would be better to drink black tea made from more whole leaves, versus drinking tea prepared from ground leaf versions (CTC processed tea), or tea mixes in which the tea was powdered. That's more of a guess. Of course the flavor, mouth-feel, and compound range present vary, but I'm not certain that the advice works well as a generality. Brewed CTC (ground-up) black tea certainly doesn't taste as good, so at least it works on that level, if only that. Ground up tea or tea-bag tea is usually so astringent that it requires milk and sugar to be palatable, and those would help you stomach cope with the tea too.
broken leaf orthodox tea left, ground CTC produced tea right
Ceylon tea bag contents; tea so finely ground that it's more or less dust
a Laos version of black tea, on the more whole-leaf side of orthodox
what stomach problems?: According to a lot of people there are no problems; you can drink as much of any kind of tea as you want, on an empty stomach or with food, and it doesn't matter. Hearsay accounts vary though; stomach problems from drinking sheng pu'er on an empty stomach are so commonly encountered that there's a term for that: sheng gut. You don't want that; it refers to pain, not getting a six-pack / washboard stomach from fat-burning properties.
Researching potential links to stomach benefits and problems
WebMD has no take on this, so I'm at a loss for a standard go-to reference. There are lots of blogs that pass on hearsay knowledge based on minimal training and background input (like I'm doing here); here's one, the "Best Tea for Gut Health" post by the Cultured Guru:
Easing your stress and anxiety, decreasing inflammation, boosting natural detoxification processes of the body, restoring a healthy gut lining, and strengthening your immune system all help to keep the gut microbiome in a balanced state. Eating fermented vegetables with prebiotic rich foods, and drinking beneficial herbal teas is a great way to keep your gut health in tip-top shape...
There's no mention of which teas might actually cause a problem versus fixing one, and she only talked about drinking green tea and tisanes in that post, the first the main one I'm claiming might cause stomach problems in the first place. Related to that, let's check her credentials:
Kaitlynn is a Microbiologist specializing in gut health, microbiome health and vegetable fermentation.
That first part might not connect as directly with the second as it first seems. She mentioned resolving her own stomach issues through steps like taking pro-biotics but seems to have missed flagging green tea as a potential cause. At least she wasn't drinking matcha, a powdered green-tea version in which all of the compounds in the leaves go down the hatch, not just what infuses out.
There's a simple test for what those compounds would be like, although it doesn't extend to evaluating stomach impact (unless you try it and drink the tea on an empty stomach; then it might).
Brew a green tea tea-bag for 5 minutes, using relatively cool water (170 F / 70 C). That's essentially completely extracted, related to any normal brewing approach. Now brew it again using boiling point water for 5 minutes; that's what else you would take in if you drank that tea made as a powder, what you taste the second time. Do it again, for a third round. There is more astringency and bitterness left in that well-brewed-out tea bag, and in eating all the tea you'd be ingesting the compounds responsible for that flavor. Within the 20 minutes that experiment took you would have some insight into what the compounds in matcha are probably like related to effect on your stomach.
That blogger might have picked up on a hearsay-claim based link identifying shu (pre-fermented) pu'er as a potential pro-biotic input. I'm not claiming shu or aged sheng works in such a capacity but the idea gets mentioned, and for sure there are a broad range of fungus and bacteria responsible for that fermentation process, which are still present while the tea is stored and continues to ferment with age. This study measures them, with some examples cited here (among pages of measured discovered bacteria results):
As to whether any of those would help restore a healthy "gut biome" if ingested from brewed tea, how would I know? I wouldn't expect that most of the people typically making those "gut health" claims are all that familiar with what is present in kimchi, sauerkraut, or yogurt that may or may not serve such a purpose.
If you read this kind of reference it all seems clearly spelled out; different strains benefit you in different ways. Read this one instead and modern medicine is still sorting it all out. On the positive side there is this:
We have hundreds of randomized placebo-controlled trials in humans that have shown safety and efficacy of many different probiotic strains. So to just … outright, those media headlines saying “probiotics are useless,” they’ll maybe strip some probiotics, but there are certainly many probiotics that have been shown in randomized controlled trials to have beneficial effects...
But some common applications may not work out as previously thought:
...So now we’re getting into some of the really surprising perhaps parts of of the paper, which is that probiotics may slow recovery of the normal microbiome after antibiotics... So most interestingly they found that treating the gut with probiotics delayed the return of the normal microbiota for as long as five months after stopping probiotic treatment... Lactobacillus showed the strongest inhibition of the native human microbiome...
So there's that.
That initial blog-post source reminded me of other findings in trying to look up some wisdom about stomach problems on Web MD, which didn't work. This Web MD article came up in a search, on When Opioids Become Tough to Stomach:
If you have severe pain, your doctor may prescribe opioids to treat it. These drugs can cause stomach problems like nausea, vomiting or constipation, which can make you feel worse instead of better. Some of these problems go away quickly. Others can be managed easily.
Nausea and vomiting often go away after a few days, but constipation caused by opioids tends to last longer because the medicine causes food to move slower through your system. This gives your body more time to absorb the water from your stool, which makes it harder to pass.
Depending on the type of trouble you’re having, your plan for relief may be different...
Guess what the article never even mentions? Getting off opioids as an option.
I just saw an interview with Dr. Phil (conducted by Joe Rogan, with that topic excerpt here), and he mentioned that short-term use of opiods for pain management is fine, but in the long term there has to be other solutions because opioid addiction causes as many problems as it solves. Which includes death in a lot of cases; Americans more likely to die from opioid overdose today than car accidents. Really; unfortunately that's not just more dodgy, poorly supported media content.
That's pretty bad when Dr. Phil has to be the well-grounded voice of reason, and Web MD overlooks that a "cure" has become a leading cause of death in America. He wasn't saying that opioids shouldn't be used for pain relief, or anti-depressants shouldn't be used to treat that other range of disorders, but was saying that using both types of drugs for long-term management of such issues can be very problematic. Here's one reason why so many people are dying.
comparing lethal dose quantities of heroin and fentanyl (credit)
more of my take, and common sense: I mostly only ever drink tea with some food, or eat prior to drinking tea, because that offsets the potential for stomach problems. The idea comes up that tea impairs adsorption of iron, and that's surely true to some extent. I don't drink tea with every meal, or more than half of them, and take multivitamins (sometimes), so I'm probably still ok.
This next part is so deep into common sense the meaning and implications might not be obvious at first: eating a varied diet is a good idea, and as part of that I also drink different kinds of tea.
That co-worker (and stomach guru blogger) drank mostly one kind of tea, and that's a formula for the negative side-effects from that one kind to add up. The dose makes the poison, and drinking or eating a lot of any one thing increases exposure risk from whatever might not work out well from what's in that food or beverage. If you drink enough tea taking in too much caffeine would be a problem, or maybe even fluoride. If you drink one type of tea all sourced from the same place any contaminant or trace element in that tea could add up to causing you problems, and simply varying range offsets the relatively low risk of that occurring.
To be fair (and slightly repetitive) the effects of tea or causes of any stomach issues would vary a lot by person. To me it works best as a precaution to eat some food with tea (that includes either a starch or dairy component; just fruit doesn't seem to help), but if someone had no stomach issues it may not be necessary.
Given that my co-worker faces recurring problems even if tea isn't a primary cause, or tied to a cause sequence (eg. he may have a stomach-valve problem, or a pro-biotics related stomach biome issue, etc.) he could reasonably still be careful about even potential stomach issue triggers. He should lay off drinking a lot of coffee and tea, spicy foods, alcohol, avoid overeating, or eating a lot of greasy foods, heavily processed and preserved foods like fast-food, etc. No harm would be done if none of those were actually causes; he would be slightly healthier for avoiding all of that.
If one of those seemed critical to him, even if it was that high-risk fried chicken, he could always try removing it from his diet and going back to it to check on a potential related effect. It would seem to work best to vary only one factor at a time, otherwise you wouldn't know which change had helped. A friend living in Indonesia (at that time) had a skin condition he couldn't connect to any known source, and worked through changes in environment and diet until he finally figured out that a flavored jasmine black tea was causing it. Who knows why, but he stopped drinking that tea and stopped having that problem.
Even if the two shu I gave him don't relate to resolving drinking matcha as a cause of stomach problems they were really interesting and pleasant teas. I can't cite a review of the buds-intensive cocoa-aspect flavored shu version that I mentioned, but I did review the other Lao Man E origin huang pian shu here, along with two other versions of shu pu'er, and all those were really nice.
some of the producers develop cool tea-cake label graphics now too (Moychay versions)