Taking advantage of the improved weather, I spent an enjoyable few hours in the veg patch this week, getting some beds ready for the sowing of early potatoes.
While I hoed and raked the soil (happy to be out in the fresh air with the sun on my back), my seven-year-old son Nicky mooched around – helping occasionally, but mainly exploring and indulging in the favourite pastime of young boys everywhere: getting dirty and asking lot of questions.
When we headed in to the house as it started to get dark, I turned around and it was as if the fictional Tom Sawyer had leapt off the pages of the book and come to life right there in front of my eyes. He had soil all over his face and caked in his hair, his clothes were filthy, his hands were manky. I also noticed that he was beaming from ear to ear, and I reckon the two things – dirt and smiles – are somehow connected.
Don't get me wrong, I'm all for a good scrub and a clean child, but I also think that our kids are living in a world that is just far too clean and sanitised. There is some science behind the idea that getting dirty is good for their mental and physical health.
So effective is soil in making us happy that recent research studies prompted scientists to ask whether dirt could be the new Prozac. The studies found that treatment with a specific soil bacterium, mycobacterium vaccae, can alleviate the symptoms of depression.
Scientists set up an experiment whereby mice were put in a beaker of water and watched to see how long they would keep swimming and looking for an exit before giving up. The mice that were treated with the bacteria kept swimming for longer than the control mice, leading the scientists to conclude that they had a more active "coping mechanism". Leaving aside the all-round oddness of the experiment, you have to admit that's pretty interesting.
A related study by the Sage Colleges in New York found that soil bacteria can also accelerate learning. More long-suffering mice were fed myco-bacterium vaccae and were subseq-uently able to navigate a maze twice as fast as the control mice. In yet another study, scientists found that human cancer patients who were injected with mycobacterium vaccae reported better quality of life and less nausea and pain. It's no wonder GIYers are such a happy bunch – it turns out we're all jacked up on mycobacterium vaccae!
So, how does it work? The researchers believe that the key to it is the 'happy chemical' serotonin, which is produced in the brain and acts as a natural anti-depressant. The mycobacterium vaccae bacteria cause an immune system response in the body, causing serotonin-releasing neurons to fire in the pre-frontal cortex of the brain – the part of our brain known to be involved in mood regulation. It is these same nerves that are targeted by the anti-depressants such as Prozac.
The benefits of regular contact with soil extend beyond mood improvement and mental agility – it can also improve our immune system function. In 2012, researchers at Harvard Medical School published a study showing the health benefits of contact with dirt. They studied two groups of mice – one that had been exposed to microbes and one that had been raised in germ-free environments – they found that the group with early-life microbe exposure had significantly lower numbers of inflammatory immune cells in the lungs and colon, giving them a better chance at avoiding asthma and inflammatory bowel diseases later in life.
We live in a 'germaphobic' society where everything is kept spotlessly clean and germs are considered the enemy. We use antibacterial soaps each time we wash our hands and blitz surfaces with antibacterial wipes. Vegetables are cleaned before being put on the supermarket shelves, in case we might consider them too dirty to buy. Sit through the standard ad break when you're watching television and you quickly arrive at the conclusion that all dirt is bad, and bacteria and germs should be obliterated with the strongest chemicals you can find. Undoubtedly, improved hygiene has reduced disease in the last century, but have we gone too far?
The 'hygiene hypothesis' posits that routine exposure to harmless microorganisms in the environment is actually good for us, boosting our immune systems by training it to ignore harmless molecules. People that do occasional 'immunological exercise' like this, get less asthma, fewer allergies, less skin irritations and so on.
This might explain why kids like Nicky love to get so dirty. An article in the 'New York Times' claimed that when children eat soil, they might be acting out an evolutionary behaviour – that the human body has evolved to need the millions of bacteria and fungi that are soil for the development of a healthy immune system.
For now, the last word goes to Dr Mary Ruebush, immunologist and author of 'Why Dirt is Good' who has taught immunology, infectious disease, and pathology in medical school settings for over 30 years. She says that encouraging our children to play in the dirt is so healthy that "if your child isn't coming in dirty every day, then they're not doing their job."
Michael Kelly is author of 'Trading Paces' and 'Tales from the Home Farm',
and founder of GIY.