Sep 23 2008
Bacteria Are Your Friend
In the Robot series of science fiction books by Isaac Asimov, which take place in the far future, there are “Spacers”, who are those who live on colonies off earth. The Spacers live in a germ-free environment, since the planets that they colonized were initially sterile and access to those worlds includes the requirement of being treated to remove any bacteria or viruses. This created worlds free of infectious disease, but as a consequence the Spacers have impaired immune systems. Without the regular workout of fighting off germs, their immune systems are weak.
The Hygiene Hypothesis
Like many ideas Asimov cooked up, there is some legitimate science to this science-fiction. The modern industrialized world is obsessed with hygiene. There is undoubted benefit to this cleanliness (other than its putative divine propinquity) – crowding together in cities, airports, schools, and shopping malls creates a friendly playground for viruses and bacteria, and good hygiene is the best prevention against infection.
But perhaps we are heading toward having too much of a good thing. From watching TV commercials you would think that the goal of healthy living is to have a germ-free environment. Clean your hands regularly with anti-bacterial soap, wash all surfaces with germ-killing agents, keep your food vacuum packed, and don’t play in the dirt.
There are those who think this obsession has gone too far – that lack of exposure to germs is turning us into Asimov’s Spacers. In addition to having weakened immune systems it has been proposed that excess hygiene is leading to increased incidence of allergies, asthma, and other immune disorders, including type I diabetes. This is the so-called hygiene hypothesis (here is a good summary of the possible mechanisms).
Now new research in mice give support to the hygiene hypothesis (here is the technical paper in Nature, and here is a press discussion of the paper). Essentially what the researchers shows is that exposing a certain kind of mice to bacteria similar to the bacteria found in the human gut reduced their incidence of type I diabetes, presumably by reducing immune dysfunction.
What all this likely means is that there is a range of optimal exposure to germs: too much leads to excessive and possibly dangerous infections; too little and the immune system is out of whack. In practice this means that we should be clean but not sterile. A little dirt is a good thing.
Probiotics
The hygiene hypothesis is partly responsible for the probiotics movement. Probiotics is the use of friendly bacteria to promote bowel health or other health benefits. There is some logic to this – we need a healthy colony of friendly bacteria in our guts, so why not help is along by eating live bacteria in yogurt?
There is some evidence that giving Lactobacillus (a friendly GI bacteria) to infants reduces the incidence of asthma. While this question is far from settled, such strategies may play a role in reducing autoimmunity.
The evidence for probiotics and GI symptoms, however, is less clear. The problem is that the intestinal flora, as it is called, is comprised of many species of bacteria. It is a little ecosystem. Simply adding one or a few species does not seem to have a significant impact.
Studies looking at probiotics to restore intestinal flora after treatment with antibiotics generally show no effect. Mark Crislip (of QuackCast fame, and also a blogger over at Science-Based Medicine) likened this to cutting down a rainforest and then planting corn as a replacement. It doesn’t replace the lost ecosystem.
At present the science of probiotics is immature. This is a solid scientific approach, and I think will yield useful treatments for certain conditions, but at present the research is largely preliminary. This hasn’t stopped the marketing of probiotics for general health or a host of conditions for which there is little evidence of efficacy. At present such products are mostly hype.
The Future
If I were to wildly speculate about the future of friendly bacteria in health care the, then I would say that I think this technology will play an increasing, and possible very large role, in future medicine. Bacteria cells outnumber human cells in an average human by 10 to 1. Bacteria colonize all of our mucous membranes – mouth, nose, intestines, etc., and they serve vital functions for digestion and keeping out more harmful bacteria, fungus, parasites, and viruses. It seems that they also play an important role in the maturation of the immune system as well.
Therefore friendly bacteria present another method of altering our biological function. Perhaps we can develop a GI ecosystem of bacteria to replace lost bacteria from antibiotic use, for example.
We are already genetically engineering bacteria (have been for a long time) and are learning how to make them do interesting stuff. It is not difficult to imagine colonizing ourselves with dozens of specific engineered bacteria designed to serve specific functions – remove toxins from food, reduce absorption of too many calories or bad fat, actively fight off infections, aid digestion, reduce or perfume flatulence, improve overall immune function, prevent tooth decay, or infect and kill cancer cells.
Right now this is all science fiction, but as Asimov has demonstrated before, the plausible and well-reasoned science fiction of yesterday can be the science of tomorrow.
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18 Responses to “Bacteria Are Your Friend”
isn’t all yogurt by definition probiotic?
No – not all yogurt uses a live culture. In order to be probiotic you need live bacteria.
I wonder what a germophobes reaction would be to the claim that 10 times more bacteria than human cells in a body. Would it be an effective way to combat the phobia, or would it just aggravate the phobia? (I suspect the latter.)
Steve,
Which “toxins” are in our food supply? One of the claims often charged by alt. med. parishioners is that our bodies are overloaded with “toxins”, and the “unnatural” food we eat is often provided as one of the reasons for the abundance of “toxins”. I was under the impression that a toxin is a specific type of poison that is biologically produced (presumably for defense). I was also under the impression that the claim our food contains toxins was a load of rubbish. Overall, I’m just curious what the bacteria would remove from the food that is dangerous to our bodies.
I think this hypothesis is really interesting. Since I first heard about it around six or seven months ago, I’ve been trying to pay attention to the people around me more. It seems, to me, that the people I know or see around that are more germaphobic seem to be sick more often. I know that’s anecdotal and doesn’t mean anything, but it seems like a good hypothesis. I’ll be interested to see how this turns out.
MK – I was thinking more in terms of neutralizing botulinum toxin or similar common causes of food-borne illness.
Dan, if you were sick all the time, you’d be afraid of germs, too!
Thanks. I thought I might have been overly critical of some “detox” diets and the claims surrounding them. =D
It is unfortunate that essentially only the gut has been looked at as a site for commensal bacteria and then only for heterotrophic bacteria. The external skin is the site for the bacteria I am working with (the ammonia oxidizing bacteria) and which I think are the agent for the hygiene hypothesis. They set the basal NO level by metabolizing ammonia in sweat into NO/NOx which is absorbed into the skin. They suppress the heterotrophic bacteria that can cause infections (and body odor).
NO inhibits NFkB, reduces the sensitivity of mast cells to degranulation, and is an important tonal regulator of the immune system. Local inflammation destroys NO, and removes that inhibition. With a low basal NO level the “gain” on the immune system is set too high.
There are important commensal bacteria on the tongue that reduce salivary nitrate to nitrite. That nitrite has important antimicrobial effects on pathogens in the gut and also can have systemic NO/NOx effects including lowering blood pressure and reducing platelet adhesion. There is considerable thought that the health effects of green leafy vegetables is due to the nitrate they contain (a few tenths of a percent) when concentrated in saliva (~10x) and reduced to nitrite on the tongue (where levels can reach 2 mM/L).
The NEJM article talks about bacteria suppressing Crohn’s disease. There are other organisms can suppress that, intestinal parasitic helminthes do a pretty good job.
http://gut.bmj.com/cgi/content/full/54/1/87
Of course this was an open label study, so we can’t be sure that eating worms is actually good for you.
A “generic” control paradigm that physiology uses in a lot of cases is to turn a pathway on until there is “enough”, and then turn it off until there is not enough and then turn it back on. The process of stochastic resonance causes a measurement system to achieve better results by adding “noise” to it. The “noise” keeps the regulatory pathways turning on and off more frequently, so they don’t get into a bad state so much or for as long. A control system designed (or evolved) to work in a high noise environment isn’t going to work as well in a low noise environment. A control system that expects a lot of noise may turn up the gain until it activates whether there is a real signal there or not.
[...] Cleanliness is far from godliness – A little dirt is a good thing [...]
Hello Dr. Novella. Just wanted to say all the hyped fear of bacteria seems silly too me. The TV commercials that urge everyone to disinfect toilet bowl water to protect family health seem a particularly extreme example of playing on peoples unreasoning fears in order to make a profit.
I think Jessica Sach’s book, Good Germs, Bad Germs: Health and Survival in a Bacterial World, is a great overview of the subject and very accessible for the non-medical person. I’ve been touting it to many of my friends who are germophobically inclined to give them a more balanced perspective.
http://jessicasachs.com/books/
Hee, the title of this post reminded me of growing up reading the Jimmy Microbe books. He was a human-friendly Lactobacillus, and he had a little friend whom he adventured with who was illustrated as a smaller organism, maybe a coccus of some kind? They were firsthand microbe witnesses to such human adventures as the nurse leaving the baby’s bottle unrefrigerated!!! To Jenny’s towel being used by Johnny to wipe his germy hands all over!!! And to mom not cooking all the harmful germs out of a can of vegetables, until– oh joy!– a phone call inadvertantly leads to her leaving the veggies on the stove until the critical temperature is achieved!!!
I’m sure the books are out of print now, but it was my very first exposure to the concept of beneficial vs. harmful bacteria and how they interact with humans. Sure wish I could find some updated kidbooks on the same topic!
So, I have been pondering something for awhile, actually.
I have never been the type to buy antibacterial products, to use them, or to worry so much about the sterility of things. For example, I sterilized my sons’ baby bottles only until they were six months old, my kids have ‘the five-second rule’ for dropped consumables, I don’t wash my hands every five seconds or use anti-bacterial hand sanitizer, and I don’t use many fancy germ-eradicating cleaners in my house.
I have never even tasted soy milk or probiotic yogurts. I don’t eat articifical sweeteners like Splenda or Equal.
It seems that these things have been growing in popularity in the past twenty years. Who is to say that primary autoimmune disorders, among other things, like GI problems are not the consequence? We are ‘wussifying’ ourselves to natural survival and coping mechanisms that develop as a consequence to germ exposure, and in the process, creating more resistant and nasty germs as a result. We are self-regulating our gastrointestinal tracts as if the products know just how much we need. We drink soy milk not because it tastes good, but because we are told it is a better alternative. The people who consume it probably do to excess because more must be better for us, in fact.
I wonder, then, if the proliferaton of allegedly healthy foods and drinks along with the use of anti-bacterial products in the past twenty years could be related to autoimmune-based autistic disorders. It seems that many of the kids who are diagnosed somewhere on the spectrum have GI problems and autoimmunodeficiencies.
If a pregnant woman is using these products regularly, or even excessively, could this not then harm an developing child in the womb? It’s almost analogous to trying to bake a cake and leaving an ingredient out, except in this case, one of the ingredients is vastly inhibitied – the immune system of the mother. It is diminished by the chronic usage of these products.
Along with all of the other rules of pregnancy – avoiding certain foods like peanut products, quelling digestive problems inherent in pregnancy with probiotic foods, the massive consumption of incompletely processed soy products like soy ‘milk,’ I have to wonder to myself if the very things that are being marketed as being ‘good for us’ are actually making our children susceptible to disease/malformation in the womb.
I ate a TON of peanut butter with both pregnancies. Neither of my kids have peanut allergies. The thing that makes no sense to me is that if I go to an allergist and am found to have reactions to anything, they pump me full of those same allergens in order to develop a resistance. Would it not follow then that to consume a potential food allergen (like peanuts) during pregnancy help the fetus build a resistance to any potential allergic reaction in the future?
Perhaps we should all just go back to drinking from the hose, eating real butter, sugar and milk, and move on with our lives. It’s all just fear-based marketing anyway with the commericals of the unrealisitically creepy, oversized germs on the counter that the incredibly cute kid is about to put their hands on, until Mom swoops in with the anti-bacterial Lysol product to save the day.
Darwinism will sort the rest out. Let your kids eat mud.
Tracy – it’s important to realise that not all allergies are the same. While allergic reactions to pollen and pollution have a strong environmental factor, there is evidence that nut allergies, for example, have a genetic basis.
It’s also important to realise that reactions to allergens vary and can dictate whether treatments are safe or not. If it’s hayfever and the worst side effects you get will be sneezing and runny eyes, immunotherapy may be a good choice. If side-effects are severe anaphylaxis and potentially death, the risks outweigh the benefits. The oft-forgotten response to “That which does not kill us only makes us stronger” is “And that which does kill us makes us dead!”
Regarding soy milk… are you sure you’re not mixing cause and effect? The only people I know who drink soy milk are those who are already lactose intolerant and made the switch because cow milk made them sick (yes, yes, anecdotal evidence I know). I don’t know anyone who drinks soy milk by choice because it’s (in my opinion) not very nice. Almond milk, on the other hand…
I realise this has been a pretty critical comment so I should say that I agree with most of what you’re saying. I’m well on my way to my bushel of dirt (I think I got about halfway there before the age of 18 months) and the five-second-rule is in full effect in my household. As a certain detergent company is fond of saying, dirt is good.
Thanks for the clarification. I do maintain, however, that we are being pushed upon products that are too ‘good for us’ to be true.
I’ll meet you at the bushel of dirt. lol
So Steve, seeing as you read Crislip, can you lick your fingers when you leave the examining room? It crosses the “ewwww” line for me.
[...] few months ago I blogged about so-called “good” bacteria. We are colonized by friendly bacteria that do not cause infections or harm, and in fact serve [...]