Why being outdoors is good for our health
Being outdoors exposes us to natural, full spectrum light. Natural light benefits us in three important ways: it increases our production of serotonin, it regulates our circadian rhythms, and it improves our eyesight.
Serotonin is a neurotransmitter that plays a role in mood and social behavior, cognition and learning, appetite and digestion, sleep, memory, and sexual desire and function. The more full spectrum light we’re exposed to, the more serotonin we produce. Serotonin production is one of the reasons why bright light therapy (BLT) is now used to treat seasonal and non-seasonal depression. Serotonin is also a melatonin precursor; it gets converted to melatonin in darkness and helps to regulate our sleep-wake cycle.
Exposure to natural light each day regulates our circadian rhythms. Circadian rhythms are most often associated with our sleep-wake cycle, but they also affect hormone production, appetite, core body temperature, brain wave activity, cell regeneration, and other biological activities. If you’re looking to improve your sleep, research shows that getting outdoors in the morning is best. Being exposed to natural light or very bright artificial light in the morning advances our circadian clock, stimulating melatonin production earlier in the evening and making it easier to fall asleep at night. Daylight exposure later in the day has not been shown to have the same positive effects on circadian rhythms.
Exposure to natural light is protective against myopia (nearsightedness), while computer, phone, and TV screens and fluorescent light can cause eye strain. Researchers believe that the ways in which natural light affects vitamin D and dopamine production play a role in eyesight development, and that this is why too little natural light exposure during childhood can lead to nearsightedness .
Being exposed to sunlight makes our skin produce vitamin D. Getting enough vitamin D is essential for overall health. We need vitamin D so that we can absorb calcium, and so that calcium and phosphorus can be used to build our bones. Vitamin D also plays a role in protecting against and possibly helping to treat the following conditions:
Heart disease and high blood pressure
Diabetes
Infections and immune system disorders
Some types of cancer, such as colon, prostate and breast cancers
Multiple sclerosis
Fatigue
Bone pain
Muscle weakness, muscle aches, or muscle cramps
Mood changes, like depression
Being exposed to the sun for about 15-20 minutes three times per week is typically sufficient for our skin to produce the vitamin D that we need. But there are some important factors to keep mind. Vitamin D is produced when our skin is exposed to ultraviolet B (UV-B) radiation from the sun. Depending on where you live, UV-B light may not reach you during certain times of the year. UV-B light is typically most powerful between 10:00am and 3:00pm. Cloud cover and air pollution can decrease the amount of UV-B light that gets through. And the darker your skin, the more sun exposure is needed to produce sufficient vitamin D.
As we know, sun exposure is safest in moderation. You can refer to this chart, known as the Fitzpatrick scale, to see how much exposure is safe based on your skin type. Always wear sunblock if you’ll be exposed to the sun for a long period of time, and make sure to avoid getting sunburns.
Spending time in forests exposes us to phytoncides and enhances human natural killer (NK) cell activity. Natural killer (NK) cells are part of our immune system’s first line of defense, reacting rapidly to infected and dangerous cells, including cancer cells. And what are phytoncides, you ask? They’re antimicrobial compounds that are naturally emitted by trees and other plants. Scientists speculate that one reason forest bathing strengthens the immune system is because of exposure to phytoncides.
To test this theory, Dr. Qing Li put 12 healthy men in hotel rooms overnight for three nights. Phytoncides were produced in the rooms by vaporizing cypress stem oil with humidifiers, and the concentrations of phytoncides were measured. Phytoncide exposure significantly increased natural killer (NK) activity and levels of anti-cancer proteins, and decreased the concentrations of adrenaline and noradrenaline (stress hormones) in urine. This results of study and others that have tested the effects of forest bathing on immune system function indicate that phytoncide exposure and decreased stress hormone levels may partially contribute to increased NK cell activity.
Being near moving water exposes us to high levels of negative ions. If you don’t live near a body of water, you can expose yourself to naturally occurring negative ions by taking a shower or going outside right after it rains. As water breaks up into small droplets, electrons combine with oxygen molecules in the air to form negative-ion clusters.
Scientists have been speculating since the 1950s that negative ions stimulate the relaxation response of the parasympathetic nervous system. A 2005 study found that water-generated negative ions enhance NK cell activity, inhibit the initial formation of cancer, and suppress tumor growth in mice. Other studies have found positive effects of negative ion exposure in treating seasonal affective disorder and chronic depression. While there isn’t a great deal of consistent research on negative ions, it’s a topic that warrants exploration.
Ready for your nature prescription?
If you don’t currently spend much time outdoors, start by aiming for 20 minutes per day. This will get you to the threshold of 2 hours per week that has been found beneficial for overall health, and will likely provide you with enough vitamin D. The stress hormone cortisol also drops significantly after spending just 20 minutes outdoors in a natural environment.
The good news is you don’t need to plan a forest bathing trip to Japan to reap the benefits of going outside. A review of 143 studies found that living near or spending time in “greenspace” like parks was enough to improve health. The researchers found that stress, heart rate, blood pressure, cholesterol, type II diabetes, stroke, hypertension, asthma, heart disease, and cancer were all lower among people who were exposed to greenspace. A study of 345,143 people found that those who lived within 1 km of greenspace had lower rates of 15 of 24 disease clusters, most significantly anxiety and depression. And a study of 31,000 Toronto residents found that having an average of 11 more trees in a city block improved cardiovascular and metabolic health in ways comparable to an increase in annual personal income of $20,000.
Do you want to get outside more, but just can’t figure out how to fit it into your schedule? Start by thinking about ways that you can take your regular daily activities outside, like:
Eat meals outside
Take work breaks outside
Do your workouts outside
Walk or bike to work (if your work commute is too far, try walking to a local store or restaurant)
Play with your kids outside
Grab your laptop and do some work outside
Take phone or in-person meetings outside
Relax outside (read, talk with a friend, or even look at your phone!) instead of watching TV indoors
Before long, getting outside will be part of your regular routine. Once you start feeling the immediate boost in mood and energy you get from going outside, you’ll start to look forward to it and even crave it. A quick walk outside can take the place of a cup of coffee (seriously). See you out there!
