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Tips for reading news about tea studies
As Dr. Oz is being thoroughly (and rightfully) shredded by the Senate Commerce, Science, and Transportation Committee for pimping weight-loss scams, we shouldn’t lose sight of the fact that (a) there are a lot of valid health benefits to tea, and (b) virtually every news story about tea and health manages to misrepresent or misinterpret the scientific study they’re describing.
As you read articles about tea and health, it’s important to keep in mind that the person writing the article is usually not the person (or people) who actually performed the study it references, and that the reporter/blogger may have read only the summary, not the whole study. Also, in larger news operations, the person writing the headline isn’t the same person who wrote the article, and if they’re operating on a deadline, the headline may not accurately sum up the story.
Tip 1: Beware of extreme claims
There’s an article on Authority Nutrition entitled,”How Green Tea Can Help You Lose Weight Naturally.” It’s worth reading. There are good explanations of the benefits of tea, and it cites dozens of actual scientific studies. But any article that begins with a statement like “green tea is the healthiest beverage on the planet” should set off alarm bells. No, there’s never been a study that tested every single beverage on the planet (there’s never been a study of every style of tea on the planet, for goodness’ sake). No, we don’t have a generally-accepted definition of “healthiest beverage.” An opening sentence like that one tells you you’re about to read something sensationalistic, and you should view everything they say with skepticism.
Any article that begins with a statement like “green tea is the healthiest beverage on the planet” should set off alarm bells.
Tip 2: They only studied what they studied
There’s an article on Byron J. Richards Wellness Resources entitled, “The Effects of Green Tea on Weight Management.” The author is a Board Certified Clinical Nutritionist, the studies cited all appear to be properly-conducted randomized controlled trials, and the conclusions all appear to be valid. So what’s the problem? Reading this may make you want to rush to your tea cabinet and throw away all of those white teas, oolong teas, yellow teas, and pu-erh teas. You need to replace those all with green tea, right. Wrong!
The studies looked at green tea. Specifically, they measured catechins and caffeine in green tea. They never compared green tea with white tea — or any other kind of tea. White tea may be even better for weight loss. So might oolong, pu-erh, or yellow. If green tea is measured against anything else in a study, it’s almost always black tea. What’s the difference between green and black tea? Black tea is oxidized, and that process converts a lot of the antioxidants into other compounds (catchins are a type of antioxidant). But white and yellow tea isn’t oxidized, and oolong is only partially oxidized. Shu pu-erh is oxidized and fermented, and sheng pu-erh is fermented without being oxidized first. Don’t draw conclusions about your oolong from a study that never even looked at oolong!
Tip 3: There’s more to tea than antioxidants
I think it’s pretty universally agreed that antioxidants are a good thing, but they aren’t the only source of health benefits in tea. When I got in a tiff with Fox News’ Chris Kilham about misrepresenting studies, it related to a study that showed coffee had some great health benefits. Reading the study showed that it looked at one thing: caffeine. All of the health benefits it listed for coffee would apply just as much to tea, guayusa, yerba maté, or Mountain Dew. If you like black tea, don’t let yourself get talked out of drinking it just because it doesn’t have the same antioxidant content as green tea.
Tip 4: All green tea is not created equal
It’s wonderful to see an article like the one titled, “Green Tea,” on the University of Maryland Medical Center page. It has tons of information, cites numerous studies, and explains potential drug interactions and side effects. But, like all of the other articles, it just references “green tea.” Did they test Japanese steamed green tea like sencha? Pan-fired Chinese green tea like longjing? Or was it roasted (hōjicha), powdered (matcha), shade-grown (gyokuro), scented (jasmine), or rolled (gunpowder)? The Kevin Gascoyne study I referenced in my 3-part series on caffeine found tea caffeine content ranging from 12mg to 126mg per cup. Yes, the most caffeinated tea had ten times as much caffeine as the least. He found a similar range of antioxidant contents. If you want to replicate the results of the study, you have to know what kind of tea they used.
Tip 5: Pay attention to who funded the study
If they had done a study that found that green tea gives people smelly feet, how much publicity do you think that would have gotten?
You can’t automatically discount a study because the funding group had something to gain from it. Tea companies are the ones most likely to fund tea studies, after all. But take a look at “Green Tea Promotes Weight Loss, New Research Finds,” an article on Medical News Today (well, actually, it’s a press release, but they don’t make that obvious until the end). It’s very clear in reading the article that Lipton did the research, and that Lipton is very excited about having done the research. It’s a big company, and their PR department did a good job of really spreading the news about that study.
If they had done a study that found that green tea gives people smelly feet, how much publicity do you think that would have gotten? I always tend to pay a little more attention to research coming from neutral parties, or research that’s been duplicated by neutral parties.
Tip 6: Check to see if the methodology was realistic
WebMD has an article entitled, “Green Tea Fights Fat,” which does appear to actually compare weight loss effects of green tea with oolong tea. But read this sentence from the article carefully: “For three months, the first group drank a bottle of oolong tea fortified with green tea extract containing 690 milligrams of catechins, and the other group drank a bottle of oolong tea with 22 milligrams of catechins.”
First, they aren’t comparing green tea with oolong. Both groups drank oolong tea. In one group, they added green tea extract, and in the other, they didn’t. So this study actually compares drinking oolong with drinking oolong plus green.
Second, the average cup of green tea has 50-100mg of catechins. That means the “extract” they fortified the bottle of oolong with made it equivalent to 7-14 cups of green tea. That’s a lot of tea!
If you have specific reasons for controlling your intake of caffeine, L-theanine, catechins, and other components, then there’s plenty of research to plunge into. Focus on people who actually study tea rather than folks like Dr. Oz or Oprah. Look at the paper and see what they actually studied. If it doesn’t apply to you, move on to the next one. If it does, take it at face value without trying to overgeneralize.
But if you’re just looking for a healthy drink that tastes good, stop worrying and buy more of what you like the most. You’re likely to drink a lot more of a beverage you love than one you don’t. If you like to experiment, all the better! If you drink a wide variety of tea, you’ll get a wide variety of nutritional benefits, and you can enjoy yourself as you do it.
Tea and theanine
I mentioned theanine (C7H14N2O3) in the first post of my caffeine trilogy, but I haven’t really gone into any detail about it. I suppose now is as good a time as any.
Theanine (or more precisely, L-theanine) is an amino acid found in tea, guayusa, and certain mushrooms. It acts as a relaxant, helps to improve concentration, and adds a savory (umami) flavor to whatever it’s added to. Most importantly — at least when we’re talking about tea — is what it does when combined with caffeine.
At the 2012 World Tea Expo, I attended a session entitled “Tea, Nutrition and Health: Myths and Truths for the Layman,” presented by Kyle Stewart and Neva Cochrane. They discussed the relaxation and alertness affect of tea, and also noted that a “2012 study found tea was associated with increased work performance and reduced tiredness, especially when consumed without milk or sugar.”
This caught my attention not only because of the increased work performance, but because it validated my personal preference for tea without sweetener or milk.
Stewart and Cochrane attributed the increased work performance to the combination of caffeine, theanine, theophylline, and theobromine. There have been some excellent articles on theanine, including Tony Gebely’s “Theanine: a 4000 Year Old Mind-Hack” and RateTea’s “L-Theanine and Tea.”
Both of them agree with the conclusion that theanine coupled with caffeine produces a seemingly-contradictory combination of relaxation and alertness. This isn’t news to tea aficionados, of course. People have been relaxing and focusing themselves with tea for millennia. Many of the health benefits of tea come from the caffeine, and those obviously apply to theanine-free drinks like coffee, cola, and cocoa.
Caffeine by itself doesn’t work quite the same way, however.
The “spike & crash” affect of caffeine is well known to any coffee drinker. You’re droopy and tired, you have your morning cup, and you swiftly find yourself wide awake and full of energy. A while later, bam! You’re back where you started, and possibly in a pissier mood than when you started. Yes, I said “pissier.” It’s a technical term. When drinking tea, thanks in large part to the theanine content, the effects take longer to kick in, and also take longer to wear off. Mixing a relaxant (theanine) with a stimulant (caffeine) works quite well in this case.
Wikipedia summarizes a half-dozen studies with this statement:
“Theanine has been studied for its potential ability to reduce mental and physical stress, improve cognition, and boost mood and cognitive performance in a synergistic manner with caffeine.”
“Boost mood,” eh? As I wrote last week, there has been at least one study that indicates tea improves mood. That study, however, defined a good mood as decreased fatigue. It appears that there may be more to the mood-enhancing effects of tea than my previous post indicated!
Tea and caffeine part I: What is caffeine?
The most popular drug?
This article is the first of a three-part series.
Part I: What is caffeine?
Part II: Exploding the myths
Part III: Decaf and low-caf alternatives
In his excellent book, A History of the World in 6 Glasses, Tom Standage selected the six beverages that he felt had the greatest influence on the development of human civilization. Three of the six contain alcohol; three contain caffeine. Tea was one of the six.
Is it the caffeine that has made tea one of the most popular beverages in the world? The flavor? Its relaxing effects? I think that without caffeine, Camellia sinensis would be just another of the hundreds of plant species that taste good when you make an infusion or tisane out of it. Perhaps yerba maté would be the drink that challenged coffee for supremacy in the non-alcoholic beverage world.
“Caffeine is the world’s most popular drug”
The above quote opens a paper entitled Caffeine Content of Brewed Teas (PDF version here) by Jenna Chin and four others from the University of Florida College of Medicine. I’ll be citing that paper again in Part II of this series. Richard Lovett, in a 2005 New Scientist article, said that 90% of adults in North America consume caffeine on a daily basis.
But yes, caffeine is a drug. It is known as a stimulant, but its effects are more varied (and sometimes more subtle) than that. It can reduce fatigue, increase focus, speed up though processes, and increase coordination. It can also interact with other xanthines to produce different effects in different drinks, which is one reason coffee, tea, and chocolate all affect us differently.
Tea, for example, contains a compound called L-theanine, which can smooth out the “spike & crash” effect of caffeine in coffee and increase the caffeine’s effect on alertness. In other words, with L-theanine present, less caffeine can have a greater effect. See a great article from RateTea about L-theanine here.
Even though Part II of this series is the one that dispels myths, I really need to address a common misconception right now. First, I’m going to make sure to define my terms: for purposes of this series, “tea” refers to beverages made from the Camellia sinensis plant (the tea bush) only. I’ll refer to all other infused-leaf products as “tisanes.” Okay, now that we have that out of the way:
“All tea contains caffeine”
Yes, I said ALL tea. The study I mentioned a couple of paragraphs ago measured and compared the caffeine content of fifteen regular black, white, and green teas with three “decaffeinated” teas and two herbal teas (tisanes). With a five-minute steep time, the regular teas ranged from 25 to 61 mg of caffeine per six-ounce cups. The decaf teas ranged from 1.8 to 10 mg per six ounce cup.
That’s right. The lowest caffeine “regular” tea they tested (Twinings English Breakfast) had only 2-1/2 times the caffeine of the most potent “decaffeinated” tea (Stash Premium Green Decaf).
There are two popular ways to remove caffeine from tea. In one, the so-called “direct method,” the leaves are steamed and then rinsed in a solvent (either dichloromethane or ethyl acetate). Then they drain off the solvent and re-steam the leaves to make sure to rinse away any leftover solvent. The other process, known as the CO2 method, involves rinsing the leaves with liquid carbon dioxide at very high pressure. Both of these methods leave behind some residual caffeine.
(As a side note: I’m not a fan of either process. When I don’t want caffeine, I’d much rather drink rooibos than a decaf tea. I only have one decaf tea out of over 80 teas and 20 tisanes at my tea bar, and I’m discontinuing that one.)
This is why tea professionals need to make a strong distinction between the terms “decaffeinated” (tea that has had most of its caffeine removed) and “naturally caffeine-free” (tisanes that naturally contain no caffeine such as rooibos, honeybush, and chamomile).
“Coffee has more caffeine than tea”
Almost everyone will agree with the statement. For the most part, it is true, assuming you add some qualifiers: The average cup of fresh-brewed loose-leaf tea contains less than half the caffeine of the average cup of fresh-brewed coffee. In the seminar, Tea, Nutrition, and Health: Myths and Truths for the Layman, at World Tea Expo 2012, the studies Kyle Stewart and Neva Cochran quoted showed the plain cup of fresh-brewed coffee at 17 mg of caffeine per ounce versus the plain cup of fresh-brewed tea at 7 mg per ounce (that’s 42 mg per six-ounce cup, which agrees nicely with the numbers from the caffeine content study I quoted above).
Interestingly, though, a pound of tea leaves contains more caffeine than a pound of coffee beans. How can that be? Because you use more coffee (by weight) than tea to make a single cup, and caffeine is extracted more efficiently from ground-up beans than from chunks of tea leaf. Tea is usually not brewed as strong as coffee, either.
At another 2012 World Tea Expo seminar, A Step Toward Caffeine and Antioxidant Clarity, Kevin Gascoyne presented research he had done comparing caffeine levels in dozens of different teas (plus a tisane or two). The difference between Kevin’s work and every other study I’ve seen is that he prepared each tea as people would actually drink it. For example, the Bai Mu Dan white tea was steeped 6 minutes in 176-degree water, while the Tie Guan Yin (Iron Goddess of Mercy) oolong was steeped 1.5 minutes in 203-degree water. Matcha powder was not steeped per se, but stirred into the water and tested without filtering.
The results? Caffeine content ranged from 12mg to 58mg for the leaf teas, and 126mg for the matcha — which is higher than some coffees.
In our next installment, I’ll look at the myths regarding caffeine in tea, including what kinds of tea have the most caffeine and how you can remove the caffeine at home all by yourself — or can you?
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