What’s the point in ‘active’ yoghurt? On the side of the pack it rambles on about how it helps to maintain your intestinal flora and fauna but surely any bacteria alive in the yoghurt when you eat it will be killed in the stomach long before they gey passed on to the gut.
Or am I wrong?
Possibly wrong. There are live bacteria in your intestines that assist in digestion.
Absolutely wrong. The live bacteria in yogurt produce lactase which helps digest the lactose contained in it, which is why yogurt is tolerated well even by people who are lactose intolerant.
And the cultures also colonize in the colon, shifting the balance of the bacteria that live there so that they will digest any undigested lactose that reach the colon, lessening symptoms.
Other health claims are also made for these cultures, although they are not as well supported in the medical literature.
In more general terms, bacteria of all sorts survive the trip through the intestines. That’s how the colon gets recolonized after a course of antibiotics kills the populations currently living there.
We add live bacteria to milk to make yoghurt right? If that bacteria all died out around the earth at the same time would we ever be able to make yoghurt again?
I think I may not have worded my question properly, so…
To get into the gut (or intestine - in UK English they both mean the same), the bacteria in the yoghurt have to pass through the stomach first. You all with me so far? 
The hydrochloric acid produced in the stomach kills bacteria. This being the case, surely by the time the yoghurt bacteria get into the gut (or intestine, if you prefer) they are dead. If they are dead, what good are they going to do?
Monty - you said that there are bacteria in the gut. Whilst this is correct you may not be aware that conditions in the intestine tend to be highly alkaline, rather that highly acidic (like in the stomach). Bacteria that live in one extreme cannot tolerate the other (generally speaking) so I find it highly unlikely that yoghurt bacteria that can tolerate the alkaline conditions of the intestine can survive in the acidic conditions of the stomach. Hence my question!
OK, JerzyBulowski if you do see that there are bacteria in the gut, where do you think they come from, if you reckon the HCl in the stomach kills them all?
You eat them, that’s how they get there.
Barring vomiting, the digestive tract is one way traffic, you know.
Some bacteria don’t die, but rather just shut down at pH extremes. Once they reach a pH level they can tolerate again, they will reactivate themselves, and continue to live as if nothing had happened (nothing phases a bacterium much!). The bacteria might simply become inactive in the stomach, and then reactivates in the intestine.
No it doesn’t. In fact, if you think about this for two seconds, you’d see that it can’t be true. If it were, then nobody would ever get food poisoning!
Bacteria of all types survive the trip through both the stomach and intestines extremely well. There is no question about this. You are simply wrong in your assumptions and your understanding of the intestines.
It seems logical that stomach acid kills anything alive in your food. But from my practical experience, it doesn’t seem so. I’ve had several, er… problems seemingly caused by improper intestinal flora disappear after my current yogurt regimine (acidipholus actually). Placebo effect? Maybe, but, hey, it works.
Nope, but mostly because we’d all be dead.
Though I wouldn’t want to overstate the case, it’s worth noting that the “acidophilus” in Lactobacter acidophilus means acid-loving. At the very least, it’s probably more acid-tolerant than most. Lactobacter refers to the fact that it is tolerant of, and even likes, lactic acid.
Various species of bacteria in geysers, hot springs, and other acid environments, thrive at pH levels like that of stomach acid - Helicobacter pylori actually lives in the stomach itself. (H. pylori, and not excess acid secretion, is responsible for most gastric ulcers. It irritates the stomach wall and breaks down the protective mucus layer. One standard test in diagnosis and treatment of ulcers is the hydrogen breath test (H pylori gives off hydrogen), if it’s positive, we may prescribe antibiotics for a cure.
BTW - not all food poisoning is caused directly by the bacteria itself. Many are pre-formed toxins. You can cook foods contaminated by such strains and kill the bacteria, but if the toxin is heat -stable, you’ll still get food-poisoning.
Other bacteria can survive stomach acid either by ‘shutting down’ or in the form of spores. Clostridia is a notorious spore former. (The most famous is botulinus, but botulism is a pre-formed toxin) Hospitals have serious problems with hand-to-mouth nosocomial spread of infections like Clostridium difficile, which set up shop in the colon.
Most importantly, the studies have actually been done on live culture yogurt. We’ve fed them to people, and observed the change in the microbial populations. We’ve even fed people labelled bacteria, so that we could confirm that they were not just the same species, but the very same bacteria that went in via their gut.
Common sense may tell you that nothing can survive a bath of strong acid, but *It just ain’t so. * Furthermore, the exposure that L acidophilus may not be all that strong. Yogurt is largely pre-digested (in terms of the physical and physiological markers your gut uses) so your stomach will start squirting it into your duodenum in little dribs almost as soon as you eat it. In the duodenum, pancreatic juices immediately neutralize the acid with bicarbonate (if this process failed, you’d get a duodenal ulcer, which is different from the gastric ulcers I mentioned above.) Yogurt is also modestly buffering, by itself.
If you have a cup of yogurt on an empty stomach, some of the bacteria will only get a small, brief, buffered-to-weakness dose of acid (which it isn’t particularly sensitive to, anyway) . In under a minute, “doses” of the bacteria are squirted to safety in the small intesting. It doesn’t take many of them to effect a change. They do multiply, after all, and you’re putting them in your gut along with a growth medium (the yogurt itself) that they favor, and which they were happily eating already. They are already in full-gear reproductive mode. The other bugs in your gut may be able to eat those same nutrients, but they’d have to change biochemical gears first.
I just e-mailed a yogurt/yoghurt company a few days ago to see if one of their products contained live or active cultures.
This is what the company wrote back:
The cultures used in our yogurt products are lactobacillus acidophilus,
lactobacillus bulgaricus and streptococcus thermophilus. Yogurt
cultures are added to the milk blend after pasteurization, and are part of the
fermentation process. This allows the cultures to remain alive to
provide important health benefits."
I read that different countries allow different strains of bacteria to be used in their yogurt. (Don’t have the book in front of me now.)
So it sounds like most yogurt products have to have bacteria in them to ferment from milk, although the bacteria may be destroyed if the yogurt is heated high enough later on…Correct?
And yes, I also read that lactobaculus acidophilus (sp) is a hardy little bacterium that can survive stomach/hydrochloric acid.
Excellent, KP; most kind!