Kombucha tea

I'm here, Lew. I'm supposed to be finishing up a bunch of slides, so I'll just give a short version without many references. First, the only good epidemiologic study on non-alcoholic liquids and kidney stones showed that all such liquids except grapefruit juice were roughly equally negatively associated with kidney stones. (Note that I say "negatively associated with" rather than "protective of" because this isn't a randomized study; it could be that drinking these liquids is not causal and is associated with something else truly protective - however, since they have an obvious physiologic basis I find these results believable). So drinking oxalate doesn't appear to cause oxalate kidney stones (unless there is some kind of odd sampling bias going on) anymore than eating cholesterol-rich eggs causes cholesterol buildup in arteries. But oxalate in tea can still cause harm, notably by chelating iron and preventing its absorption.

Now lots of fermentation products are bad for you. Evolutionary biologists opine that this is why yeast, etc. developed them - to keep us from eating the week-old carrion on which they were growing. Aflatoxin and peanuts have already been mentioned. But I think the issue is toxicity from _intentionally_ fermented substances. First, there is the famous link between drinking calvados brandy and esophageal cancer in Normandy. Blaming that on fermentation is tenuous because calvados is distilled and fermented, while the fermented-only substance (hard cider) doesn't seem to be dangerous. But maybe distillation just concentrates another substance besides ethanol which is already present in the cider. Temperature could also have something to do with it (calvados is drunk hot, cider cold). Temperature is also thought by some to be the etiologic agent in the few studies in which tea was associated with cancer (see

which, seems to refer to unfermented tea ["congou"] but, because it also calls it black tea, could also mean fermented.).

But lots of foods which are made by letting them lie around can kill or hurt you. Read the CDC's "Morbidity and Mortality Weekly Report" (nice beach reading, if you can get wifi at one) at

and you can see reports of salmonella, listeriosis, strep, and TB from cheese . Pasteurization sure doesn't prevent them, and Mexican cheeses seem to be the biggest culprits. Real tea doesn't appear in it, contaminated kombucha seems to have killed one woman and given her friend heart problems, and a whole lot of teenagers brew a whole lot of odd plants into tisanes and end up in emergency rooms.

Regarding cancer, except with extreme cases, it's very hard to say (smoking is such an extreme case because it is very common and multiplies the risk of lung cancer by roughly 14). But there is indirect evidence, e.g. the article in

548153 , in which Queens' University researchers note that vinyl carbamate, a metabolite of ethyl carbamate (also called urethane), causes cancer in susceptible mice. It appears to be found (see wikipedia article on it) in soy sauce and many alcoholic beverages.

On an only marginally related note, I just have to report that the bacteria which cause odor in limburger cheese have just been found to be from the same genus as those which cause foot odor (see Bart Knols, "On human odour, malaria mosquitoes, and Limburger cheese," The Lancet, vol. 348, issue 9037, p. 1322, for a report on research which won him the Ignobel prize). God's feet indeed.

Back to powerpoint.

Best,

------------------------------------------------------------------------------- Rick Chappell, Ph.D. Professor, Dept. of Statistics and of Biostatistics & Medical Informatics, University of Wisconsin Medical School

600 Highland Avenue, K6/430 Madison, WI 53792 USA