Many of us have heard that we should get out in nature more, whether from doctors, therapists, or just a concerned friend. This advice is almost always vague and given without any evidence based arguments. I decided to look into this a bit and I think that the reason there is rarely evidence given is not because there isn’t any evidence that nature is good for you, but rather that there is tons of very diverse evidence. It’s just too broad to get into in most conversations.
The Norwich Medical School did a meta-analysis of greenspace exposure and health outcomes. They found that greenspace exposure has been linked with decreased cortisol, heart rate, diastolic blood pressure, HDL cholesterol, low frequency heart rate variability, risk of preterm birth, small size for gestational age, cardiovascular mortality, type II diabetes, stroke, hypertension, dyslipidemia, asthma, coronary heart disease, and all cause mortality. There was also an increased incidence of good self-reported health.
That’s a long and very diverse list. Usually when something is claimed to be good for just about everything I assume it’s B.S., but in this case there really is evidence to back those things up. This would imply to me that being in nature has a more fundamental positive impact on our bodies.
An environmental and behavior researcher at the University of Illinois named Ming Kuo thinks that this fundamental effect could have to do with the immune system. Kuo reviewed studies on nature’s impact on health outcomes and identified 21 possible pathways by which this impact could happen. All but 2 of her possible pathways had to do with immune system response.
Being in nature provides an opportunity for increased physical activity but it also provides a number of other immune boosting factors including vitamin D producing sunlight, negative air ions, and a bacteria called mycobacterium vaccae (found in dirt) that’s been shown to increase serotonin in the brains of mice.
There is also a growing body of evidence suggesting that depression and our immune responses are linked. There is a two-way communication system between the brain and the immune system via the autonomic nervous system and the hypothalamic-pituitary-adrenal (HPA) axis. Basically if the immune system is hyped up the brain cannot work as well.
For instance, studies have shown that when the immune system kicks in to fight an infection there are behavioral changes inherent to the immune response that cause symptoms of depression. People will have changes in sleep patterns, are less interested in social interactions, and experience brain fog. From an evolutionary perspective this is to keep the person resting so they can heal faster, and to keep them isolated so they don’t spread the disease.
Also, in people without depression/anxiety there are receptors that, when exposed to cortisol (stress hormone) tell the body to stop producing cortisol. This is a self-regulating system that essentially gives you a burst of adrenaline to escape whatever danger you are facing and then calms itself down. In people with depression/anxiety these receptors don’t work. So we just get a continuing dose of cortisol leading to chronic stress.
Being in nature helps to regulate our immune system and also promotes feelings of awe and wellbeing. When we feel safe our bodies go into a state of “rest and digest” or parasympathetic nervous system activity. It is in the “rest and digest” state that our immune system works the best and our stress and cortisol levels are the lowest.
It seems that being out in nature in whatever capacity we can manage will be helpful for our physical and mental well being. Try to get out for a walk, if you’re in Pittsburgh consider a trip to Phipps. Bring plants into your house for a more mild version of these benefits. Go sledding when there’s snow or go ice skating. Have a bonfire if it’s a mild night. Whatever you can manage.
Sources:
Comments