The Ten · Sunlight
Sunlight is medicine, and more than vitamin D.
We were made to live in the light, and modern life has moved us indoors, behind glass and screens. Getting back into the sun, sensibly, is one of the simplest ways to help the body.
Book a Consultation →What This Is
For generations people understood that sunshine and fresh air were part of getting well. Hospitals were built with sun porches for that reason. That wisdom was set aside for a time. The science is now catching up, and sunlight turns out to affect health in more ways than we knew.
What the research shows
Sun avoidance has a cost. The newest work explains part of why.
Length of life. Swedish researchers followed 29,518 women for twenty years. Those who avoided the sun died at about twice the rate of those with the most sun exposure, mainly from heart disease and from causes other than cancer. Nonsmokers who avoided the sun had the life expectancy of smokers who sought it, so sun avoidance was a risk factor on the order of smoking. This is observational work, so it shows a pattern and cannot prove cause, and it does not erase the skin cancer risk of burning (Lindqvist, J Intern Med 2016).
The body clock. Light is what sets it. When University of Colorado researchers sent people camping for a week with no electric light, their internal clocks shifted about two hours earlier and lined up with sunrise and sunset. Melatonin began rising at dusk, about two hours earlier than before. The change took a week (Wright, Current Biology 2013). Morning light is the simplest tool there is for poor sleep.
Beyond vitamin D. Vitamin D comes from ultraviolet light, a small slice of sunlight. More than half of the sun's energy reaching us is red and near-infrared light, which is invisible and passes deep into tissue. Much of the work on it has come from outside medicine. Scott Zimmerman, an optical engineer, and Russel Reiter, a melatonin researcher, proposed in 2019 that near-infrared light reaching the mitochondria stimulates them to make melatonin locally, as an antioxidant, in quantities far larger than the pineal gland makes at night (Zimmerman and Reiter, Melatonin Research 2019). That remains a hypothesis, still waiting to be tested.
In London, neuroscientist Glen Jeffery has worked with Robert Fosbury, an astronomer, on what these wavelengths do in people. In a small randomized trial, fifteen minutes of deep red light on the upper back, 45 minutes before a glucose drink, lowered the two-hour blood sugar rise by about 28% (Powner and Jeffery, J Biophotonics 2024). In 2025 the group measured near-infrared sunlight passing clean through the human chest, even through clothing, and showed that exposing the body alone, with the eyes covered, improved a measure of retinal function (Jeffery, Scientific Reports 2025). These are small studies with surrogate outcomes. They do not show that sunlight treats diabetes or eye disease. They do show that the invisible half of sunlight reaches the inside of the body and does something there.
Mood and immunity. Bright light treats seasonal and non-seasonal depression, and sunlight is the original bright light. The immune system is also tuned by light, through vitamin D and through other pathways still being worked out.
One practical detail: green plants reflect near-infrared light strongly. A walk among trees gives you more of it than a walk on pavement.
From the medical literature
Cases doctors have written up.
Behind every trial are real people. Here are a few whose doctors wrote up what happened.
Twenty-seven patients with plaque psoriasis spent four weeks at the Dead Sea, where the treatment is graded daily sun exposure with bathing. All of them finished. Their psoriasis severity scores fell by an average of 81.5%. Nearly half cleared completely and most of the rest improved markedly. For those who cleared, the skin stayed clear for an average of about three months before lesions began to return.
Journal of the American Academy of Dermatology, 2003 · Read the reportEighteen Danish patients with psoriasis were followed through four weeks of climate therapy at the Dead Sea, with sun exposure and bathing adjusted to each person. Severity scores fell by 88% and just over half of them cleared completely. Sun exposure has been shown in earlier work at the same site to be the main active ingredient, with the water adding something on top.
Frontiers in Medicine, 2020 · Read the reportA 30-year-old man in Korea developed bone pain and such difficulty walking that he was admitted to hospital. He had worked from home for six months, almost never going outdoors, on a strict vegetarian diet. His vitamin D was severely low and his bones had softened. He was treated with vitamin D and calcium and told to get outside in the sun every day; within a week he was walking better.
Journal of Bone Metabolism, 2013 · Read the reportHow I use it
Sunlight is powerful, so we use it sensibly: enough to help, well short of a burn. The right amount depends on your skin, your health, your climate, and the season. For most people, a modest amount of regular sun, especially in the morning, improves daytime energy and nighttime sleep. We find what fits your life and your body, balancing the good of the sun against protecting your skin. If you take a medication that makes your skin sensitive to light, or have a condition that does, we account for it.
What is possible
The newest science here is promising, and it confirms older wisdom: people need light, air, and time outdoors to do well. That much we can build on.
Where This Leads
Sunlight pairs well with fresh air and movement, and morning light is what sets up a good night's sleep. The next clear morning is a good time to start.