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Probiotics eat our food for us and help us digest. Gross? Or amazing?? Hank explains why we need bacteria and how cool it is.

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So fermented foods have been around for pretty much forever, but they seem to be even more in fashion now: the rainbow-colored selection of kombucha tea, the fridges full of miso and kefir and tempeh and sauerkraut - you can't toss a gluten-free cookie without hitting a 'live and active cultures' label.

Those 'live and active cultures' are actually a thriving community of probiotic bacteria living in the container. 'Probiotic bacteria' literally just means 'good germs'. By definition micro-organisms that instead of giving you strep throat or gonorrhea or something worse, are beneficial, and maybe even make your life possible. These bacteria help balance out the microfloral foam party going on in your intestines and keep pH levels in check. They block bad bacteria from latching onto your intestinal walls, help you produce digestive enzymes so you don't get all bloated after that third burrito, and increase your nutrient uptake. And they do it, basically, by eating our food for us.

Essentially, the food that these micro-organisms feast on and the food that we buy them in, undergo a chemical transformation that's basically controlled rotting. So if you prefer, you could think of probiotic foods as being partially rotten. Or pre-digested. You probably don't prefer that. Like it or not, though, they're what turn milk into yogurt, soy into tempeh, and cabbage into sauerkraut, a special kind of fermentation.

Fermentation is a type of anaerobic respiration, where microorganisms feed on organic compounds, often sugars, to get the energy they need, but they do it in the absence of oxygen. Most of us are familiar with the fermentation that turns hoppy water into beer or grape juice into wine. Those kinds of cultures are usually yeasts, and they produce alcohol as a byproduct. The cultures in probiotic foods, by contrast, are usually bacteria, and they break down sugars to make lactic acid. This is known as lacto-fermentation, and the star of the show here and by 'here' I mean your intestines, is Lactobacillus acidophilus. It's a bacterium that lives naturally in your gut, but its numbers can dwindle if you've been taking antibiotics, had a nasty gastro-intestinal bug, or if your innards are just generally bad bacteria farmers.

What's particularly excellent about Lactobacilli is that they're salt-tolerant, whereas various bad bacteria, like the kinds that spoil our food and make us sick, are not. So by, say, submerging cucumbers in salty water for a few days, we can keep out the bad germs that would rot our cukes while still courting the good bacteria which partially digest those vegetables, converting lactose and other sugars into lactic acid, and turning the cucumbers into pickles.

But remember, fermenting is not the same thing as pickling. Non-refrigerated food stuffs your find in the market, like those jars of pickles and sauerkraut getting dusty on the shelf, were just dumped into vinegar and never fermented.

Fermented foods, many of which have that 'live and active cultures' label, are a lot easier to digest, precisely because they've been partially digested for us, and in a manner much cleaner than, say, a mama bird regurgitating a mouthful of worm mush to her babies. So in addition to eating that semi-decomposed cucumber, you're also ingesting the friendly bacteria that so helpfully started the digestion process. That's the double benefit of lacto-fermentation.

We spend a lot of time and effort trying to limit our exposure to bacteria, but the fact is, we would die without them. Your body, glorious shrine to hygiene that it may be, contains about 100 trillion bacteria. That's more than ten times the number of your own cells that you have in your body. Which sorta means that you're more bacteria than you are you!

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