04.10.08
a conservative review of tea research
posted by Sandy M. Bushberg | 8 comments
I recently read a review article by Jane Higdon, Ph.D. that I thought provided a good basic overview of some of the research into tea and health. Dr. Higdon is a research associate at the Linus Pauling Institute (LPI) which has done some very good research on tea. One of the principle researchers on white tea in this country, Dr. Roderick Dashwood, is a professor at LPI. If you are looking for some good overviews and specific research about tea, I would recommend perusing the LPI website. Just keep in mind that they present just one perspective on tea research. As we have shown numerous times, there is a vast amount of research out there, a fair amount of which tends to contradict previous research. This is not to say that one perspective or finding is right, and the other is wrong. It simply means that there are as many ways to set up a research study as there are researchers, which ultimately affects the outcome. What you will find in this review article are a smattering of studies deemed significant by the author. As we well know, it is by no means exhaustive of the myriad research studies that have been done, and continue to be performed, on a regular basis.
There are some inaccuracies included in Dr. Higdon’s article that you should be aware of. She uses the terms oxidation and fermentation interchangeably, which they are not. As I have clarified in previous posts, oxidation refers to the enzymatic breakdown of certain phytochemicals in the tea leaves through processing (like polyphenols,) while fermentation involves bacterial reactions that is only found in puerh. She also describes white and green tea as follows: “White teas are unfermented teas made from very young tea leaves or buds that are steamed immediately after harvest to inactivate polyphenol oxidase and then dried. Consequently, white teas usually contain higher concentrations of catechins than other teas. Tea leaves that are destined to become green teas are withered by air drying prior to heat inactivation of polyphenol oxidase. Although still rich in catechins, green teas may have slightly lower catechin concentrations than white teas.”
Most of that quoted material is inaccurate. White tea is not steamed to inactivate the enzymes. It is whithered, which creates minimal oxidation, and then air dried fully. Green tea is air dried briefly, not withered, before full heat drying and therefore is de-enzymed to prevent oxidation. As a result, although constituents of teas vary from farm to farm and even within the same farm, because white tea undergoes some slight oxidation and green tea doesn’t, it is more likely that green tea is higher in polyphenols than white tea.
Dr. Higdon makes a good point that although we continue to see promising results for tea’s myriad health benefits, there is still a lot to do. It would be very beneficial if standardization were established with the methodology, so that we can compare apples with apples. This is probably one of the key reasons why there is such variation in results. Each study uses different teas, quantities, steeping times and temperatures. It would also behoove tea researchers to enlist the aid of knowledgeable tea people who could provide them accurate information about the product they are studying. This same lack of standardization in research methodology can be observed with researchers studying medicinal herbs. If the researchers would just collaborate with the individuals who most use and are most knowledgeable about these products, they would wind up with more useful and consistent results.
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April 10th, 2008 at 4:23 pm
Hi Sandy,
yeah, I’ve read Jane Higdon’s article a long time ago and had similar thoughts. Actually, there’s a lot of information out there that describes the processing of white tea the way Dr. Higdon does. The fact that she describes green teas to be withered prior to the kill-green process indicates to me that she simply mixed up green and white tea processing. This shows you again, that the researchers often don’t know much about the steps the product goes through before they investigate its medical properties.
Anyone who is interested in the differences between oxidation and fermentation in tea should read your article on T-Ching and also the very good in-depth treatment by Robert J. Heiss in the last issue of The Leaf magazine. That should set the record straight.
BTW, I liked your contribution to The Leaf as well. When my partner Diane read it, she exclaimed that you must surely be an anthroposophist (she’s a trained Waldorf teacher).
April 10th, 2008 at 4:39 pm
Sandy,
I LOVE your technical prowess when it comes to tea (and even I just learned a few new things from this posting). Hopefully, we are all willing to continue learning and again hopefully the bottom line still is that tea is a drink with few known (if any, I’m not aware of them but anything taken in overdose form can’t be good) bad side effects, some probable good effects from the phyto nutrients and of course IT TASTES GOOD so please keep drinking the varieties of tea the you enjoy the most and let’s just be grateful for the existence of this long known wonderful little break in our daily lives, TEA!
Peace
Fr. Patrick
April 10th, 2008 at 5:54 pm
A properly conducted and documented research study should be able to be replicated. For that reason alone, it makes perfect sense that researchers studying the beneficial effects of say, milk thistle, would consult with milk thistle users and prescribers, right? To make assumptions about products and report those assumptions as gospel (forgive me, Patrick) compromises the validity of the research itself! How can you form a reasonable thesis if you don’t know the first thing about what you are studying?
Any research that is cloaked in secrecy or verbiage violates the beauty of research . . . which ought to be the systematic adherence to research paradigms. Researchers who fear inquiry into their research methodology must have something to hide. . . which is contrary to good science.
April 10th, 2008 at 7:03 pm
Regena,
No forgiveness needed! In my mind, you are CORRECT. The very nature of scientific study is that you can make assumptions but then you call it a hypothesis, NOT scientific fact. It may sound like being nit picky, then so be it. As you so eloquently stated, there should be some “systematic adherence to research paradigms”, otherwise you might as well call it some sort of for lack of a better word voodoo medicine and NOT good science.
Peace,
Fr. Patrick
Just keep drinking the good stuff and ENJOY IT !!
April 10th, 2008 at 7:21 pm
Jo - Tell Diane she is sort of right. As a jew, we believe that there is no higher purpose than to learn and grow and to be of service to others, even above God. Before moving out to the pacific northwest, I had been an active member of a traditional Cherokee spiritual community. The Cherokee spiritual traditions are also rich with mysticism and the importance of personal growth. They believe that we are not born human, only 2 legged animals, and that it is up to each individual to grow into a full human based on his/her actions throughout his/her lifetimes. The quality of your actions will also determine whether you grow your spirit or shrink it through your lifetimes. The best way to grow to a full human and grow your spirit is through service to others. You have 7 lifetimes to get it right. How ever you left it each time you die is what you get to start with in the next lifetime. If after the 7th lifetime you have succeeded in becoming a full human, your spirit goes on to the Sun Land. If not, your spirit get broken up into its component parts.
Thanks Patrick. I agree with you completely. When I think about how little I know about tea it makes my mouth dry (and in need of another cup of tea). Always important to keep learning. There is sooooo much to learn.
April 11th, 2008 at 10:15 am
Sandy,
Right back at you. The day we think we stop learning is the day I’ll know that I’m dead and in my view, I’ll still be “learning” even after that inevitable event, just in a different way. HMMM, love that mysticism too but this probably isn’t the correct forum right now for that so as usual, just keep drinking the good stuff! Blessings, peace and CHEERS
Fr. Patrick
P.S. I LOVE THE LAST SHIPMENT I RECEIVED FROM YOU!!! (especially the bird’s tongue) I hope that many of your bloggers have had the chance to at least try one of the sample packs from your online shop. You have a nice small selection but ALL the teas in that selection are of what I would consider superior quality items. One thing, Sandy I realize that there are MANY different puehr’s out there (and most of us can’t even agree on exactly how to spell it much less choose one or two to represent the whole class of tea) would you consider adding one or two of them so others may enjoy them? I realize that they aren’t everybody’s (and excuse the terrible line but it fits) “cup of tea” (GROAN/MOAN or whatever else you see fit to do
)but I’m sure that some of the bloggers would like to experience this until recently pretty much unheard of specialty tea from China (and a lot of it comes from Yunnan Province). THANKS!
April 11th, 2008 at 12:39 pm
I am pleased that you are enjoying your purchases from the store so much, Patrick. Your assessment of the quality of teas is very accurate. We only choose superior quality teas for the store. As far as offering puerh, that is something I am working on, in addition to some other selections. I will notify you when I’ve added them.
April 11th, 2008 at 1:21 pm
Sandy,
GREAT, can’t wait till it comes about. There are many different teas available to try but as we both know they aren’t all “created” equally. Thanks again for your kind consideration. I happen to like several of these varietals but I tend to favor the “ripe” styles usually in full cake form which I break apart myself but there are also some good loose forms as well as ones considered “green” as well. I’m sure that you already know this Sandy but some of the other bloggers may not. While I don’t consider myself an expert on them, they do hold a certain fascination as one of the few teas that actually can grow in value (which isn’t usually the reason I buy them, I just like the taste) with age.
Cheers
Fr. Patrick