Posts tagged: gut

Micro links 2: what’s in grandpa’s gut and mom’s nose?

Some more quickies:

Healthy old people have healthy gut bacteria – Makes sense, right? But the logic behind it is very chicken-and-egg. The authors say that when somebody goes into a nursing home, they start eating institutional food, their diet affects their gut bacteria, and their gut bacteria affects their health. I find this theory appealing, especially if it convinces the institutions to provide better food: “Mashed potato and porridge were the only staples in this diet type that were consumed daily,” says one of the authors.

But it could be the other way around: they get sick, then enter the nursing home, where the diet changes their gut flora. Or, they get sick, which changes the gut flora, and also leads to their move to the home. The title of the actual paper sticks to the bare facts: Gut microbiota composition correlates with diet and health in the elderly – which is exactly what they found. Causation TBD.

Parents are resistant to cold and flu viruses – and the effect lasts even after their kids have long since left home. This seems only fair, since children are little disease vectors, ferrying germs to and from school (or, in my case, day care). The funny thing is, the study found that parents have the same levels of antibodies to the viruses as non-parents, but are still less likely to get sick when a researcher shoves viruses up their nose.

Their theory: parents are happier and less stressed (haha). My thought: there’s a lot more to the immune system than antibodies, so maybe one of those other aspects of immunity gets strengthened by frequent exposure.

Twitter chat about germs today (Thurs) at 1:00pm EST. Follow #germchat. It’ll be like sitting at the cool kids’ lunch table, except the table is, um, full of germs.

Swabbing your nooks and crannies for science

navel gazingI learned about this one through a tweet announcing that “[well-respected science writer] Carl Zimmer has weird belly button fluff.”

Don’t we all? I thought. But the story was a good one: the belly button microbiome is now being studied, and Zimmer has some unusual species in his. The project comes from the lab of Rob Dunn; you may recall that Dunn and Zimmer were two of the three authors whose books I mini-reviewed last week.1

Dunn’s area is the ecology of species surrounding people, including but not limited to microbes, and the idea behind the belly button project was to find an area of skin that should be roughly comparable between people, and not washed too often. Preliminary results, reported by Jason “Germ Guy” Tetro, suggest that we accumulate belly-button bacteria from all the places we have lived, making it “a museum of lifetime experiences.”

My belly button pops inside-out when I’m pregnant. Have I just washed off all my lifetime experiences?

This is where you come in

Cotton SwabsSixty volunteers had their navels swabbed and cultured for the project, which is now listed as “sampling complete,” but if you missed out, don’t worry – the next phase of research is about to begin: Armpit-pa-looza.

Dunn has plenty to say about armpit stink and why it’s valuable to humans, but perhaps the most astounding is that our bodies seem to deliberately cultivate stinky bacteria there (and in our crotches, sorry, genitoanal region) – feeding the critters with secretions from our apocrine sweat glands, and providing a hairy trellis for the resulting bacterial garden.

If armpits aren’t enough, you can also donate your poop to science – I mean, the website doesn’t mention poop, but what else could it be? – through the American Gut project. They are looking for diversity in their subjects, especially dietary diversity, which I think is an excellent question:

The government’s Human Microbiome Project effort sampled only healthy adults, mostly medical students! While it was an amazing project, did it really capture the American Gut? We are not sure, so we decided to find out. We are calling on athletes, couch potatoes, vegans, diabetics, Paleo dieters, centenarians etc – we need your help. If you have IBD, diabetes, autism or some other ailment – we need you too.

You know what to do. Go forth and swab thyself.

1 Obviously I foresaw this, rather than just choosing my library’s three least boring books on microbiology that weren’t checked out already. Expect Idan Ben-Barak to join the story in some further, bizarre way.

Do artificial sweeteners affect a glucose test?

Lucky me, I get to do a 3-hour glucose tolerance test today. (That’s 8 hours of fasting, 1 bottle of the world’s worst kool-aid, 3 hours of daytime TV in the waiting room, and 4 blood draws).

So, when you’re fasting for a glucose test, it’s OK to drink water, but I was told “nothing with calories.” The diet coke addict in me wonders: would artificial sweeteners affect the test?

Hopelessly AddictedHere’s a study on just that, except they used Diet Rite (sweetened with sucralose and acesulfame; compare to Coke Zero with aspartame and acesulfame, and Diet Coke with just aspartame. All are sweeteners with no calories that trick your taste buds into thinking you’re eating sugar.

The graph below shows a 3-hour glucose tolerance test (with 75g of glucose) – the soda was given 10 minutes after the glucose. Results: no effect on glucose (graph A), no effect on insulin (B), but the soda/glucose combo (C) increased GLP-1,  which increases insulin secretion and is supposed to help get glucose out of the bloodstream. (Why didn’t it affect glucose in this study? I don’t know, but I wonder if caffeine from the cola was a factor – acute doses are known to impair glucose tolerance.)

(Glucose/insulin refresher: When you eat carbs, glucose (a sugar) goes into your bloodstream. The pancreas makes insulin in response, which tells body cells (fat, muscle, etc) to soak up the glucose, thus removing it from your blood. Diabetes is what we call it when there’s more glucose in the blood than there should be, either because the pancreas isn’t making enough insulin (Type 1) or the cells don’t listen to the message (Type 2).)

Glucose response after Diet Rite cola

The neat-o thing about the GLP-1 result is that it seems to come from the intestines, because – yes – we have taste receptors in our gut.  (Here’s a separate study showing that these receptors cause the release of GLP-1). We’re lucky this tasting is under our radar, dispatching hormones without notifying our conscious brain: if we experienced tasting intestinal contents the same as tastes in our mouth, well, it would all taste like poop, wouldn’t it?

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