Do as kids do and get outside to expose yourself to microbes. Photo / Getty Images
Exposure to microbes in early life can help set up our immune systems for success.
If you’re the kind of person who carries hand sanitiser at all times and thinks cleaning the kitchen means blasting every surface with antibacterial spray, you may want to put down that bottle of Dettol.
According to experts, since we’ve become a nation of “germaphobes” we’re actually making ourselves sicker. In fact, there are many health benefits to be gained by getting a bit, well, mucky.
“Most infectious diseases - putting aside Covid - are far less common in the modern world than they were historically, whereas rates of chronic inflammatory disorders such as asthma and Crohn’s disease are rapidly increasing,” says Dr Neil McCarthy, a senior lecturer in immunology at Queen Mary University of London. “This is happening too quickly to be explained by genetics alone, so there must be other factors involved.”
Exposure to microbes (minute organisms such as bacteria, that can’t be seen by the naked eye) is needed in early life to set up our immune system correctly, explains McCarthy.
“Otherwise our immune system struggles to tell the difference between the dangerous stuff and the harmless things in your environment. It’s possible that some important microbial signals are missing in today’s modern world, which may help explain some of the health problems we experience.”
Here’s how you can increase your exposure to dirt to bolster your health.
Pounding the gym treadmill may burn the same calories as an outdoor run, but being outside will expose us to more of the good stuff.
A healthy, resilient gut involves having a high microbial diversity, i.e. a high number of different species that are evenly spread across your gut microbiome. These various species of gut bacteria serve several important functions such as aiding in digestion, helping with the absorption and production of essential nutrients, and regulating our immune, metabolic and nervous systems.
In essence, the more diverse your gut bacteria are, the more potential they have to support all these functions. “Plenty of research shows that wild animals have more diverse microbial communities living on skin and inside their bodies, compared with animals kept in clean indoor environments,” says McCarthy. “Their immune systems work very differently, and more effectively, as a result of that.”
He suggests that spending more time in nature could have similar benefits for humans, although it’s not clear exactly which microbes are most helpful or how our immune cells might be reacting to them, he admits.
When you drop food do you employ the so-called “five-second rule”, giving you licence to pick it up and eat it anyway? Top marks if so.
“Kids are constantly putting dirty stuff in their mouths and that may not be an entirely bad thing,” says McCarthy. “Early life is a critical time for our immune system to learn which microbes are living in the world around us and how best to recognise them. This is about getting the balance right; living in filthy conditions is obviously not sensible but it’s also a bad idea to keep children totally ‘bug free’.”
Researchers have found that the likelihood of asthma was reduced in children exposed to endotoxin, a major building block in many bacterial cell walls (i.e. their protective outer coat). These common ‘bits of bugs’ can build up in household dust (the microbes don’t have to be alive as our immune systems can still detect stuff they leave behind in the environment).
“Even some unpleasant infections such as measles and chickenpox (or vaccines against them) which make kids feel sick for a while, actually reduce their risk of nasty diseases including certain cancer types as adults,” says Dr McCarthy.
A lower diversity in our guts is associated with various diseases such as inflammatory bowel disease, Type 1 diabetes, obesity and other health concerns.
Plants live in soil which is rich in diverse microbial species, so any form of interaction with plants is likely to increase your microbial biodiversity.
“You won’t get much exposure to different microbes by buying carefully washed vegetables from supermarkets,” says McCarthy. “It’s useful to encounter some of the microbes in garden bugs and the chemicals they produce so that your immune system can get a proper look at them and build up good defences.”
In one study, the guts of non-gardeners contained fewer or no soil bacteria, and their gut microbes stayed monotonous all year.
If you don’t want to maintain your own garden vegetable patch or don’t have the room, why not grow your own herbs instead, suggests Emily English, a nutritionist and the founder of gut supplement Epetóme.
“Having a herb plant in your kitchen is low maintenance, gets your hands in the soil, and then eating the herbs also benefits the gut as they contain certain polyphenols, which are natural compounds found in many plants, and have antioxidant and anti-inflammatory properties and also act as “food” for the good bacteria in your gut,” she says. “After all, the gut microbiome is inextricably linked to the digestive system, the brain (via the vagus nerve), our skin health, our immune system and hormones.”
However, it would be unwise to encourage any play in an actual compost heap, especially for people with weakened immune systems. “They can be ideal homes for sporulating fungi, including species that can be pathogenic to people,” says Dr Kieran Bates, a lecturer in microbiome science at London’s Blizard Institute. “A recent study found that many of the fungal isolates collected from compost were resistant to multiple frontline antifungal drugs used in hospitals.”
While some dirt is good for us, Bates insists it’s wise to retain some caution.
You don’t need to go as far as milking a cow, but walking in fields where there are grazing animals is a good start.
“We have evolved throughout human history to co-exist with a diverse range of micro-organisms both in and among us, yet our modern lifestyles, spent largely indoors in relatively sterile environments, are a stark contrast to those of our ancestors, " says Dr Louisa James, a senior lecturer in immunology at the Blizard Institute. “It makes sense that activities which increase our exposures to the rich diversity of the microbial world can have an overall beneficial effect on our immune health.”
Research done on more than 6000 randomly selected animal farmers has suggested that people who grow up on farms have lower rates of Crohn’s disease, asthma and allergies.
“Rural environments - especially farms - are naturally more biodiverse than cities, which explains this reduced rates of allergies,” says James. “In terms of asthma, pollution and a lack of exercise are also important contributing factors for lung health.”
A paper in 2017 compared microbes in the guts of 18 populations in 16 countries. Their study showed a clear distinction between the microbes in people living in industrialised societies and those living in what the investigators called “more traditional” societies.
These studies, explains McCarthy, looked at isolated populations in the United States who still use old-fashioned farming methods, like the Amish. “They were found to have much lower rates of allergies and asthma compared to the general public. This might be linked with the different types of microbes found in their homes.”
During the pandemic, many of us adopted germophobic levels of cleanliness. But curbing the instinct to reach for the disinfectant might be wise.
“It’s quite likely that less clean households contain lots of ‘microbial friends’ that produce chemicals our immune cells can detect,” explains McCarthy. “This causes different immune genes to be switched ‘on’ and ‘off’ in useful ways, though scientists are still trying to figure out exactly how this works.”
No one likes to imagine the bugs lurking as you sleep, but having high levels of microbial junk in your mattress has been linked with a lower risk of hay fever, says McCarthy. “Having a big family with lots of older brothers and sisters can reduce your chances of getting hay fever.”
It’s not a green light to stop cleaning altogether though. “While excessive cleanliness does reduce the microbial diversity in our environment, hygiene is absolutely necessary to prevent communicable diseases,” says James. “Raw meat, for example, can contain disease-causing pathogens, so cleaning kitchen surfaces after food preparation is sensible.
“It is really a balance regarding cleaning products; bleach-based or anti-bacterial cleaning products used moderately, as part of good hygiene practices, are important to minimise transmission of disease. But we certainly shouldn’t be creating sterile indoor environments.
“In addition, the detergents in cleaning products can damage the barriers of our lungs or skin. This can trigger inflammation, which in turn can increase the risk of eczema and asthma.”
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