What’s really happening with those microbes inside us? Are we really superorganisms or is it all hype? Dr Berenice Langdon reveals the truth about the microbiome.
Does ‘microbiome’ mean our friendly gut bacteria?
Yes, sort of. Many people are aware that the term ‘microbiome’ refers to ‘friendly gut bacteria’. But ‘microbiome’ also refers to all the microbes or germs inside us. These are mainly bacteria – but they also include fungi, viruses, and many others. The word ‘microbiome’ also refers to where these microbes are: the ‘biome’ part of the word. They couldbe in our gut, or on our skin but a microbiome can also refer to much bigger locations outside the body: the microbiome of a forest, even an ocean.
And going back to the human gut; are these microbes friendly? Well, some are and some aren’t. Like all best buddies, sometimes even the ‘friendly’ ones can be awkward sometimes.
Is it true that our microbiome helps protect us from infections?
We know that if we take antibiotics, they can reduce our gut microbiome, and we can get a diarrhoea infection moving into our gut. On the other hand, we know that the microbiome is mainly made up of bacteria, and bacteria often cause infections. So does our microbiome protect us from infections, or does it cause infections?
The answer is a little bit of both. Our gut microbiome is usually made up of benign bacteria, the sort that don’t cause us harm. These benign bacteria keep the ‘baddy bacteria’, the pathogens, out of the gut. They do this either by outcompeting the bad bacteria, or by making the gut a bit too acidic for the bad bacteria to grow. In this way we can see that the gut microbiome is helping us, just a bit, to avoid gastrointestinal infections.
On the other hand, if our ‘friendly’ gut bacteria happen to get out of our guts and into the wrong place—like our blood stream or our brain—even though these bacteria are generally benign and friendly, they can cause a very serious infection.
Is it true that probiotics are live microorganisms that improve our health?
We know that probiotics are live microorganisms. This is part of their definition, and the idea is that taking them is meant to improve our health in some way. It’s the ‘improve our health’ part that’s difficult to prove.
Scientists have been testing probiotics for decades to determine if they have an effect on our health. They’ve tested their effect on all sorts of medical conditions, including constipation, diarrhoea, ulcerative colitis, and irritable bowel syndrome, as well as other non-gut related conditions such as Parkinson’s and autism. So far, however, there’s no evidence to show that probiotics help any of these conditions. The American Gastroenterological Society mainly does not recommend taking probiotics except as part of a research trial.
Many probiotics currently on the market contain bacteria that are found in our food anyway (in yoghurt, for example), or in fact, are already inside us. Some probiotic packaging even says so itself: contains live microorganisms that naturally exist in the body.
If probiotics don’t do much, are they at least safe? The answer for most people is: yes, probably. The bacteria that make up probiotics are usually fairly benign and don’t usually try and attack us.
But for people who are very ill or in intensive care, probiotics are not recommended. Research shows that probiotics can translocate from the gut to the blood stream. Once in the wrong place—just like the microbes in our gut microbiome—probiotics can cause life threatening infections or even death.
Is it true that a microbiome is essential for survival?
Amazingly, the microbiome is not essential for survival for all sorts of animals including rats, mice, guinea pigs, chickens, flies, and even fish. All of these creatures have been successfully raised without a microbiome. Even more amazingly, this isn’t new. Scientists have been doing this for over a hundred years. It’s absolutely possible for certain animals to survive just fine without a microbiome, and even have babies. This is a fascinating field of research, and these animals are sometimes known as gnotobiotic animals or germ-free animals.
However, it is true that herbivores can’t survive without a microbiome. They are dependent on gut microbes to help them ferment grass or foliage and extract the necessary calories. Herbivores really couldn’t survive without a microbiome.
Is it true that fermented foods and drinks are healthy?
We know that not all fermented foods and drinks are healthy and interestingly, not all fermented foods and drinks have microbes in their final product. Alcohol is an obvious example of this; a fermented drink with known health risks and also one in which the final product contains no microbes whatsoever. Other popular fermented products such as soy sauce are full of salt and are also clearly not universally healthy, while the acid contained in the very popular fermented product cider vinegar can dissolve our teeth and is a known cause of oesophagitis.
However, we still love fermented foods. Fermentation often makes foods taste great and helps us preserve our food. So, while there are certain benefits to fermented food and drink in terms of food production and preservation, overall fermentation doesn’t automatically make foods healthy.
Is it true that we need to pay attention to our diets to improve our microbiomes?
We should of course pay attention to our diet, by not eating too much, having a varied diet and including plenty of fibre, as this is the route to good health. But from a microbiome point of view, the bacteria in our guts don’t need much help.
Our colon typically contains a quadrillion bacteria per ml or 1,000,000,000,000 – a mind-blowingly large number. We also have a wide variety of bacteria inside us, constantly changing minute by minute. We obtain these effortlessly from the bacteria that coat the outside of our foods – even those foods we think of as ‘clean’ like bread and fruit as well as the bacteria naturally found within certain fermented foods mentioned above.
A wide variety of bacteria in our gut is regarded by some as a mark of health and is easily achieved by eating a wide variety of foods and by daily contact with each other, with the outside world, and with nature.
Is it true that together with our microbiomes we are superorganisms?
No, this is not true. Together with our microbiomes we are not superorganisms. While microbes do help us a bit—helping us digest a little bit more food, avoiding certain infections—they also cause us a lot of work, as we have to protect ourselves from them and avoid infections. It is not a universally positive relationship.
But ultimately, we are not superorganisms simply because we do not evolve as one unit. Microbes evolve inside us at a vastly faster rate than we do. And we evolve slowly, evolving protective mechanisms against the microbes, but making use of them when we can.
Featured image by the National Institute of Allergy and Infectious Diseases via Unsplash.
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