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Please Pass the Science
by dr. scott berk

Simplistic, misleading, and somewhat condescending. . . but never boring!


Recently, with the advent of alterna-teen society, I have noticed an increase in body piercings and other "cool" stuff. My girlfriend (who is not a true alterna-teen) even got her tongue pierced. The neo-hippie-guy who poked the hole (hehe) gave her a list of what not to eat or drink until the wound healed. Among the obvious was spicy or salty foods. One that stuck out to me was beer. When I questioned beer's presence on the list of "no-no's", he said it could cause a yeast-infection.

Now have been a alcoholist for many years now, I wondered, were the yeast in beer still alive? And if they were alive, could they cause a yeast infection (given that they are in solution with alcohol)? For sure I thought they had lived our their little yeasty lives -- ultimately giving them up for a greater good (beer!)

Thank for your time!


[Dr. Berk redirected this question to Brewster Jen, a fellow scientist]

All righty...I'll give it a shot! (How can I resist...it ties together brewing AND medicine / bio! Oh, AND piercing! All of my favorite things!)

First...of the yeast population in beer, some is dead, and some is actually alive. The live yeast population is primarily dormant, though that depends somewhat on the age, type, storage & handling conditions of the beer, etc. etc. However, yeast are pretty tough little buggers...you probably remember a few years ago when some diving expedition found an intact bottle of beer in a shipwreck from 1825, and managed to rouse the yeast in the sediment. A commercial beer called Flag Porter was then made using the shipwrecked yeast.

It's the live yeast in beer that are exploited by homebrewers to carbonate their beer. Once the homebrew is done fermenting, a small amount of extra sugar is added just before bottling, which is enough for the yeast to go to work and produce enough CO2 over the next couple of weeks to make a nice 'pfffffft' when you open the bottle. If the yeast were all dead, nobody'd be throwing off any carbon dioxide, so no 'pfffft'. There is an upper limit to alcohol tolerance for yeasts, which varies from strain to strain (champagne yeasts being the ultimate champs in this regard, but they're not really beer yeasts, so I digress)

BUT...unless she likes to drink homebrew and/ or some types of imported beers (Hefeweizen anyone?), the yeast in beer ain't an issue. Nearly all of the breweries in this country filter their beer before bottling with the intention of removing all remaining yeast. In fact, most microbreweries and even little brewpubs (and even some homebrewers) do the same. This results in a 'prettier' product - clear and w/ no sediment, to appeal to the American drinkin' public. Another advantage is that by removing the yeast and artificially carbonating the beer, it's immediately ready for sale (no waiting two weeks for the yeast to carbonate the beer for you). The filter size used varies but ~0.5 -1 micron is pretty common. At 1 micron or less, nearly all of the yeast will be removed from the beer. And yes, a few cells probably do make it through, but most commercial breweries also pasteurize their beers, so fuggedaboudit.

I'm not even really going to touch on the yeast infection aspect. The prime culprit in yeast infections is generally Candida albicans, which is very different than brewer's yeast (Saccharomyces cerevesiae). I wonder if the piercing dude told her to stay away from her breadmaker too! I have to admit that I don't know if anyone has contracted an infection from Saccharomyces before...it's probably possible (especially in immune-compromised people and such). But I expect that the 'stay away from beer' warning was more a case of the average Joe mentality that yeast = yeast. You know, kind of like how all bacteria are harmful so everything we own has to have antimicrobial crap built into it these days (arrrrgh!!)

Okay...that was probably way more than you needed to know, but there you go. (I even have some references to back this up if you like!)

The brewster

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