Colonizing the Colon

Over the recent Memorial Day weekend Mr. Scienticklish and I were lucky enough to participate in not one, not two, but THREE barbecues! There was a lot of corn, burgers and sweet treats to go around, but probably the most interesting food we consumed was Water Kefir, thanks to a new friend met at BBQ #2. While in conversation, this new friend was referred to as the "King of Fermentation" - a title that I'm sure only a small demographic is excited to have. Our new friendship resulted in him offering up various bacterial and yeast cultures, including a sourdough bread starter and Kefir grains. Similar in theory to the fermented Kombucha beverages, Water Kefir uses various bacteria strains (together called Kefir grains) to break down sugars. When you make Water Kefir yourself you add table sugar or fruit juice to feed the bacteria, which they use to produce CO2 and a small amount of ethanol, making the drink bubbly and about 0.5% alcoholic. In the end you get a fruity, carbonated drink that is very low in calories, high in active bacteria cultures and absent of the vinegar taste you find in Kombucha. The one we sampled the next day was so good in fact that we wondered why the producers chose to market the drink as a pro-biotic, fermented drink as opposed to a healthy alternative to soda? Anyway, if you can find some you should try it for the taste alone, if not for any health benefits you may get from the bacteria.

Don't be fooled by those good-for-nothing amateur biotics

Pro-biotic foods and beverages have been getting a lot of hoopla lately. I think it's pretty exciting stuff too. The more we learn about the functions of all of those bacteria living in our gut, the more we realize how integral they are for our own health. These colonies of bacteria exist mostly in the colon, some make it past the ileocecal valve into the small intestine, but when we think of the gut microflora generally we're thinking of the colon. So how did this bacteria get there? When you were a fetus you were sterile, it wasn't until you were born that mom passed on her bacteria to you as you traveled through her birth canal. As expected, babies that are born via cesarean section have a different composition of gut flora than those born vaginally. After delivery, it seems like almost everything, and then nothing, can change your gut flora. Some studies show that what the infant eats (breast fed versus formula fed for example), and whether the baby was born in a hospital or at home can affect what bacteria colonizes their gut. However when adults are given pro-biotic foods it's still not certain what the results are. For example, the live cultures in the yogurt you eat may be doing something beneficial while they're passing through your gut, but whether they hang around and make your colon their new home isn't really known yet.

The war in your colon?

A potential way to change what bacteria grow in your gut is to change what you feed them. For example, when comparing vegans vs vegetarians vs meat eaters you see different types of bacteria growing in the colon. Additionally, lean people and obese people also have a different world of bacteria taking up residency. To study the latter in more detail, researchers looked at the types of bacteria growing in the colons of obese and lean mice. They also looked at the contents of the fecal matter (taken from the caecum) and found differences in lengths of fatty acids between lean and obese mice (part a in the figure below). Next,they looked at differences in fecal material between lean and obese mice, finding that the obese mice had less energy (kcal) per gram of waste, perhaps showing that the obese mice were better able to absorb that energy into their blood stream as opposed to pooping it out (part b). Finally, in what I think is the coolest part of this experiment, the researchers did a "fecal transplant" into mice that were devoid of bacteria in their gut. This means that someone, a lowly grad student I'm sure, took poop from the lean and obese mice and fed it to the bacteria-free mice so that those bacteria would grow in the colons of the new mice. And now we know why people think scientists are crazy... BUT look at the cool results in part c below! The mice that got poop from lean mice (+/+) had less than half the percent increase in body fat compared to mice that got poop from obese mice (ob/ob). Keep in mind that these mice were on the same diet, and the mice that gained more weight didn't eat any more food than the mice that didn't gain the weight. Perhaps the bacteria from the obese mice helped breakdown the nutrients to make them more readily absorbed, thus permitting those mice to take in the energy and store the fat. So now we need to convince the world that the future of weight loss lies in fecal transplants.

I'm realizing that this is becoming quite a long blog post about poop and colons. I'm also realizing that I may have a strange fascination with these topics. I haven't even really got into what these little creatures may do for our health. Perhaps a future post about Jamie Lee Curtis and her empty promises with her Bifidus Regularis will be necessary. As for now I'm going to leave you all to digest this fecal-filled post, just like those poor mice.

Zimmer, J. et al. A vegan or vegetarian diet substantially alters the human colonic faecal microbiota. European Journal of Clinical Nutrition (2012)

Penders J. et al. Factors Influencing the Composition of the Intestinal Microbiota in Early Infancy. Pediatrics (2006)

Turnbaug, P.J., et al. An obesity-associated gut microbiome with increased capacity for energy harvest. Nature (2006)