we would all like some quick and simple ways to improve our health but we're inundated with often conflicting advice so if you're going to try just one thing to improve your mental and physical wellbeing what should it be maybe a cup of tea to help your heart health or listening to music to open up your blood vessels how about a walk on a rainy day to improve your immune system I'm Dr Michael Mosley and this is just one thing where each episode we'll explore one thing you can start doing today to improve your health or life in ways you might not [Music] expect it's mid-afternoon on a dreary rainy day and I am just putting my boots on and I'm off to do something that should boost my mood and my immune system I'm going to embrace the Rain Go Terry Terry's my dog and she loves a good puddle stomp don't you Terry come on come on here in the UK we have an average 159 days with some form of precipitation every year there is no escaping the rain in this country many people find it tough to enjoy bad weather but I've been looking into it and it turns out new research is discovering good scientific reasons to change your mindset about a downpour because rain actually releases special compounds that can impact your brain and body in a good way rain also cleanses the air of harmful pollutants so going out when it's raining or shortly afterwards can deliver fresher air to your lungs you also get that gorgeous fresh rain smell so how about embracing the rain I'm speaking to Dennis a PhD student in Essex to find out if this is just one thing he'd like to try Hi D hi Michael do you manage to get outside much I'm pretty much at home most of the time because the nature of my job is remote work so I'm usually just glued on the computer are you a great one for the outdoors going for long walks and things like that not at the moment cuz it's quite cold it's a lot colder here than where I come from it feels like it's not the best time to go for a walk usually we would go out for a walk when it's sunny now I've got something that I'd like you to do I'm going to be asking you to go out when it's rainy how's that feel I'm quite aware that I really need to go out so I'm willing to give it a go brilliant and I'd like you to do that ideally two or three times in the next week I think there's a decent chance it'll rain on at least a couple of occasions it it is Britain and it's not so much going out in the rain but just after it's rained is that okay definitely okay right so the only thing that can stop you now is if the British weather lets you down and doesn't rain over the next week H yeah I think it's quite likely that it will rain sometime this week I'm Keen to see if Dennis changes his views about rainy days because they really do have an upside for starters a Harvard Business School study from 2012 found that people get more work done when it's raining mainly because they're not distracted by all the lovely things they'd rather be doing outside and if you're looking for fresh air there is no better time to go for a walk than on a rainy day a recent Japanese study found that rain improves air quality in fact there was a 20% reduction in the most harmful fine air particles that cause lung damage after rain and then there is that wonderful earthy smell that you sometimes get just after it has rained it's got a Wonderful Name petricor the main component of petricor is a chemical called josine which is made by bacteria and released into the air when rain water hits the Grand and there's evidence that inhaling geosmin can be good for us in a recent Korean study researchers asked 30 adults to either handle soil that contained geosmin or soil that didn't after just 5 minutes of exposure to geosmin the volunteers had higher levels of the mood boosting chemical serotonin in their blood and the Alpha Brain Wave activity increased a sign of relaxation they also had decreased levels of C reactive protein a marker for inflammation not only does rain improve air quality and release geosmin it also ionizes the air adding a negative charge to air molecules now there have long been claims about the health benefits of these negative ions which I've been skeptical of but there have been small scale scientific studies with some intriguing findings a small but interesting study from Austria for example showed that an hour a day breathing in ionized water particles improves people's immune response and surprising research shows that inhaling negative irons can even boost your mood and reduce depressive symptoms for me the idea that going for a walk on a rainy day can LIF your mood sounds deeply counterintuitive so I'll be talking to an expert about this in a moment but first let's check in with Dennis to see how he's getting on with his misly mission today it rained and I went for a walk it's the second time I've done this and today the scent was just amazing it was as if the Earth was giving off this sweet fragrance everything just feels so fresh and new the sound of the remaining raindrops hitting the ground and the cool temperature it's like a whole new world out there and it wasn't as cold or windy as yesterday which made the walk even more enjoyable I just feel refreshed and invigorated afterwards we'll catch up with Dennis again at the end of the week and see if embracing the rain is just one thing he'll keep up now let's speak to Dr Michael Turman from Columbia University in New York he is one of the Pioneers doing clinical trials into the mood lifting benefits of negative irons hello there greetings so negative irons how are they created they can be created artificially or or through various acts of nature the intense rainfall creates a physical disturbance that releases free electrons into the atmosphere and they attach to oxygen molecules that's a negative ion how interesting how did you come to do your first clinical trial and what did it involve we were studying light therapy for winter depression we were searching for a sibo control for light therapy light therapy now is the international standard for the treatment of winter depression these are serious major depressive disorders but it was always speculated from the start that it was just a placebo effect so I needed a placebo control we knew that there was a long folk history about negative air ions being mood lifters so we assigned randomized groups to bright light therapy or negative air ion therapy fully believing that that was a placebo and would prove the effectiveness of light we went one step further ion flow out of a conventional air purifier is very low so we souped up the ionization in one group this gives us now three groups bright light therapy high density negative air ionization and low density the subjects couldn't tell the difference between high and low density ion we thought both of those would be placebos turned out otherwise okay that's the great thing about science isn't it you never know what's going to happen yes the ones who received the room air puf method showed a slight Improvement and that's what we would call a placebo effect a belief that this would work but not enough to call it a remission the research subjects who received the high density ions gradually improved over about 3 weeks time right so a lower dose wasn't really doing it and when you use the higher density how effective was it compared for example to a standard anti-depressant the level of improvement was comparable to what you would see either with bright light or with an active anti-depressant after six weeks with negative air ions we saw a gradual improvement over 3 weeks and it is side effects free so this was with people who suffered from wind to Blu Seasonal effective disorder does it work just as well in people who have other forms of depression or indeed who aren't actually depressed the short answer is yes and yes we screamed patients who had what we call chronic depression this is a very serious syndrome where there's virtually no relief from depressed mood for years at a time it is very hard to treat with medication or Psychotherapy and yet we were able to get statistically a lifting of mood in these various serious cases it works for the average person as well a student of mine conducted a controlled experiment with college students who were not screened for depression some had Bluer moods than others within half an hour of exposure to the high density air ionization they were feeling better so it works for the average person as well that is impressive what do you think is the mechanism why would negative ions help mood there's been very little research done here yet I have my pet hypothesis I like to hypothesize that when we respond to negative arons you could call it something like what you might experience in intense aerobics a hyper oxygenation of the blood which is mood l right so you would hypothesize that it's something to do with the fact that when you are inhaling negative ions you're super oxygenating the blood if you like that's correct interesting now you're obviously using souped up air purifiers to produce a big stream of negative ANS do you think you can get a comparable dose going out soon after a heavy rainfall yes the dose is very similar so here in the UK obviously we're blessed with lots of Rin and the moral of the story is get out in it shortly after it's finished that may be a mood booster I think that's a safe bet it's fascinating to think that the rain that falls so abundantly from our British Skies really could improve our mood if we just got out and breathed it in let's check in with Dennis one final time to see if he has been singing in the rain I've been walking after it's rained for a week now and I've not that I feel more present and chill this activity made me realize that I don't have to walk when it's sunny and I might as well make good use of the rainy weather it improved my productivity it makes me more focused and more motivated you just feel that everything is clean everything is fresh definitely I will be taking more walks in the rainy day it rains a lot in the country so I'll be walking lot I'm in my garden and it just sto raining oo just smell that geosmin I'm delighted to hear that Dennis is seeing rainy weather in a different light now I too have been making a conscious effort to go out more when it's wet outside and I do think it's worth it knowing that something beneficial about rain itself has made rainy days more welcome in my book so why not give it a go you could improve your mood benefit your brain and even give your immune system a boost as for me I'm just going to breathe in as many negative irons as [Music] again so that's it it's just one thing you can incorporate into your daily routine which really could benefit your body and life if you want to hear more of the series why not subscribe on BBC sounds on the next episode of just one thing how a daily dose of laughter can keep your heart healthy 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