You can feel it.
On sunny days with a crisp blue sky and a big bright sun, you might notice there’s more of a spring in your step. You just naturally feel happier. On cloudy, grey days, it’s much easier for your mood to match the weather.
How exactly are these things related?
At the most basic level, it’s simple. More sunshine equals more health and happiness. Then, it starts to get more complicated.
Sunshine Matters to Your Mental Health
Sunshine greatly impacts your mental health. One study looked at therapy distress measures across 19 weather/pollution variables for 16,452 adults over six years. When it comes to your mental and emotional health, the results showed that the amount of time between sunrise and sunset is the what makes the most difference.
Surprisingly, your day could include uncomfortably hot temperatures, thick air pollution, or even rainclouds, but that doesn’t necessarily affect your mood. If you’re getting enough sun, your emotions should remain relatively stable, the researchers found. But as the amount of sunlight in the day is reduced, levels of emotional distress can spike. This applies to the clinical population at large, not just those diagnosed with Seasonal Affective Disorder.
Seasonal Affective Disorder
Exposure to sunlight is a significant factor in a type of depression known as seasonal affective disorder (SAD). SAD comes and goes with the seasons, typically starting in late fall and early winter and easing during the spring and summer. Depressive episodes linked to the summer can occur also but are less common.
The causes of SAD are unknown, but research has found some biological clues:
- People with SAD may have trouble regulating one of the key neurotransmitters involved in mood, serotonin. One study found that people with SAD have 5 percent more serotonin transporter protein in winter months than summer months. Higher serotonin transporter protein leaves less serotonin available at the synapse because the function of the transporter is to recycle neurotransmitter back into the pre-synaptic neuron.
- People with SAD may overproduce the hormone melatonin. Darkness increases production of melatonin, which regulates sleep. As winter days become shorter, melatonin production increases, leaving people with SAD to feel sleepier and more lethargic, often with delayed circadian rhythms.
- People with SAD also may produce less Vitamin D. Vitamin D is believed to play a role in serotonin activity. Vitamin D insufficiency may be associated with clinically significant depressive symptoms.
Serotonin, Sunlight, and Depression
Research shows that your brain makes more of the feel-good neurotransmitter serotonin on sunny days than it does on darker days. Serotonin is a neurochemical that does so many different things in your body that it’s really tough to nail down its function precisely. Your brain’s prefrontal cortex, which primarily controls your personality and executive functioning, relies heavily on serotonin.
Your overall mood is greatly influenced by this neurochemical. Studies have connected low levels with physical and mental problems. Many studies have found higher levels of the neurochemical associated with positive moods and decreased levels correlated with lower moods. One theory, still widely believed, blames depression on too little serotonin. Unfortunately, it’s not that simple.
Research supports the idea that serotonin plays a role, not only in the treatment of depression but also in a person’s susceptibility to depression, but the connection isn’t fully understood. The ultraviolet rays in sunlight absorbed through your skin promote vitamin D and serotonin production. Research shows serotonin turnover increases with the amount of sunlight and even the brightness.
You can find more about serotonin’s role in depression and how to make more here.
Sunlight, Vitamin D, and Depression
Vitamin D can be obtained from food, but getting enough from your diet alone is difficult. Salmon, herring, sardines, cod liver oil, oysters, shrimp, egg yolks, and mushrooms are some of the best dietary sources of vitamin D. Various foods, like milk, orange juices, and cereals, are also fortified with it.
The way you get most of your vitamin D is by exposing your bare skin to sunlight. Vitamin D is produced from cholesterol in the skin using the energy from ultraviolet B (UVB) rays. This reaction can happen fairly quickly, particularly in the summer, and you don’t have to tan. You only need to expose your skin for around half the time it takes for your skin to burn. How much vitamin D is produced from sunlight depends on the time of day, where you live in the world and the color of your skin. The more skin you expose the more vitamin D is produced.
Vitamin D deficiencies were rare when the majority of people worked outside. However, today it’s estimated that up to 50 percent of the world’s population may not get enough sunlight. This is primarily because people spend more time indoors, wear sunblock when outside, and eat a diet low in sources of this vitamin.
You can also get vitamin D by taking supplements. This is a good option if you don’t get enough sunlight, or if you’re worried about exposing your skin to the sun. Vitamin D3 is easier for your body to absorb. To improve absorption, vitamin D should be taken with food that contains some fat, since it is fat soluble. You can find supplementation guidelines at the Vitamin D Council.
Vitamin D Health Benefits
Vitamin D has multiple roles in your body:
- Maintain the health of bones and teeth.
- Support the immune system, brain, and nervous system.
- Regulate insulin levels and aid diabetes management.
- Support lung function and cardiovascular health.
- Influence the expression of genes involved in cancer development.
Vitamin D’s best-known role is to keep bones healthy by increasing the intestinal absorption of calcium. More recently, vitamin D has been discovered to be an important factor that may have significant health benefits in the prevention and the treatment of many chronic illnesses, including depression and other mental health disorders.
Research examining the relationship of vitamin D to seasonal affective disorder (SAD), schizophrenia, and depression has proven increased exposure to sunlight to be a promising therapy to reduce symptoms. Several studies have shown light therapy to improve mood. Science found that vitamin D supplementation reduced the risk of developing schizophrenia.
Symptoms of Vitamin D Deficiency
Symptoms of vitamin D deficiency may include:
- Getting sick or infected more often.
- Painful bones and back.
- Depressed mood.
- Impaired wound healing.
- Hair loss.
- Muscle pain.
If Vitamin D deficiency continues for long periods of time it can result in:
- chronic fatigue syndrome
- neurodegenerative diseases, such as Alzheimer’s disease
Vitamin D deficiency may also contribute to the development of certain cancers, especially breast, prostate, and colon cancers.
Vitamin D sources
Sunlight is the most common and efficient way to get your vitamin D. Make an effort to get outside more. Go outdoors on your lunch hour, go for a walk, or (my personal favorite) take a nap in the sun. The richest dietary sources of vitamin D are fatty fish. Here are foods with good levels of vitamin D:
- cod liver oil, 1 tablespoon: 1,360 IU
- herring, fresh, raw, 4 ounces: 1,056 IU
- swordfish, cooked, 4 ounces: 941 IU
- raw maitake mushrooms, 1 cup: 786 IU
- salmon, sockeye, cooked, 4 ounces: 596 IU
- sardines, canned, 4 ounces: 336 IU
- fortified skim milk, 1 cup: 120 IU
- tuna, canned in water, drained, 3 ounces: 68 IU
- egg, chicken, whole large: 44 IU