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
- Infections and immune system disorders
- Some types of cancer, such as colon, prostate and breast cancers
- Multiple sclerosis
- 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.