Let the Sunshine In

In 2017, Jeffrey C. Hall, Michael Rosbash, and Michael W. Young won the Nobel Prize for their discoveries of molecular mechanisms that control circadian rhythm. Cellular clocks, they showed, regulate critical biological functions such as behavior, hormone levels, sleep, body temperature, and metabolism.

But Hall, Young, and Robash were only identifying—some might say re-identifying—what humans have known for millennia: “Where the sun does not shine, goes the doctor,” in the words of a Czechoslovakian proverb. Or, in the slightly more poetic Persian one: “When you shut out the sun from coming through the window, the doctor comes at the door.”

Indeed, since antiquity, people spanning geographies and cultures have worshiped the sun as a divine healer: Ra in Egypt, Helios in Greece, Inti for the Incas, Surya in the Vedas. From Rome to India, Egypt to China, the sun has been seen as the creator, power, life force, and the central arbiter of good health. “Go with the flow of nature’s rhythms” is the fundamental principle of Ayurveda.

In 4700 BCE, Wong Tai described the relationship between mood disorders and light changes between seasons for the first recorded time. Hippocrates wrote extensively about the therapeutic benefits of sunlight on mood and mental health, which he termed “heliotherapy.” Posidonius, the Stoic, proposed the existence of a life force that emanates from the sun. And the Romans had “right-to-light” laws, according to which the home of every citizen, no matter how lowly, had to have access to direct sunlight.

And of course, there is the Bible. God’s first commandment, the very basis for all of creation, is “Let there be light.” A twist comes when we learn, sentences later, that it was not until the fourth day that the sun was created. For millennia, rabbis quarreled and debated this mysterious discrepancy. Kabbalistic consensus landed on the idea that the early light, from those first few days, refers to a healing, spiritual light, which God treasures for the righteous. Indeed, this light—Or, the force behind creation—drives the study of Kabbalah. Those who study Jewish mysticism are learning the rules and the ways a person can achieve its constant flow across all the realms of human life.

Now, as we move through the month of Kislev, the festival of Hanukkah reminds us how sacred light is. With its menorahs shining brightly, this month symbolizes the removal of darkness and the spread of holiness, goodness, and radiance.

Kindling light on Shabbat, on holidays, on Hanukkah, the Jewish tradition reflects the universal understanding of light as central to being human. It is both our North Star as well as a foundation of balance and footing.

The Jewish emphasis on light as a spiritual metaphor is meaningful in many ways, but what’s especially interesting is that the Jewish tradition recognizes the sun specifically as a source of health, healing, and abundance. In Genesis, Jacob, wounded and deceitful in his fight against Esau, finds that the sun shines for him, healing his injury, once he finally speaks the truth. And in the Talmud it is written that: “Sunshine on the Sabbath day is a boon for the poor” and “to you that fear my name [i.e., that keep the Sabbath, Rashi], the sun will shine as a boon for healing his wings.” (Taanith 8b). Though radiating only a fraction of the original divine light that created the world, the sun keeps us healthy, strong, and spiritually connected.

Sometime during the Industrial Revolution, we forgot about the sun’s medicinal power. As technology and scientific advancement progressed, an unfortunate effect occurred: Anything not provable in a lab was dismissed as superstition. In a short span, Western culture lost reams and reams of hard-won knowledge that had been passed along for thousands of years—what Norman Doidge calls our “lost wisdom.” With this, we began to take natural light for granted and buried ourselves, and our sick, indoors.

Post-Industrial Revolution, there have been steps to reclaim this wisdom, and brief pockets of progress, but shockingly little appreciation for the sun has been sustainably integrated back into public health practices, modern lifestyles, and medicine.

One advancement toward reclaiming the sunlight-health connection came in 1903, when Niels Finsen won the Nobel Prize in medicine and physiology for his work using concentrated light radiation to treat diseases, particularly lupus. His findings helped reestablish light’s healing power, but most people understood this to mean artificial light, making the broader implications for sunlight and medicine limited. Though few studies compare the effect of sunlight versus artificial light, those that have been conducted do demonstrate that better results come consistently from the sun.

Another advancement came in the 1950s, when Sister Jean Ward, a nurse in Essex, discovered that sunlight could cure jaundice in babies. She had known this intuitively for years, but when she accidentally left a vial of blood from a jaundiced baby on a sunny windowsill and the levels normalized, her funny practice became scientifically justified. The light therapy now used in every hospital nursery for jaundiced babies comes straight from Ward’s discovery, though the sunny windowsill, too, has been replaced by artificial light.

But Florence Nightingale was really the first to see how critical hospital light and air quality could be to patient recovery in the modern world. She was meticulous in her observations. In Notes on Nursing, she writes, “It is the unqualified result of all my experience with the sick, that second only to their need of fresh air is their need of light … And that it is not only light but direct sun-light they want.” Like plants, her patients would turn their faces toward light, following the sun’s arc across the sky. She became obsessed with hospital design—advocating for wards with large windows for cross-ventilation and abundant natural light. For a moment her designs stuck, but when the artificial lightbulb was invented, they were largely lost to history.

Today’s hospitals show few signs of paying heed to Nightingale’s prescriptions. They tend to rely on the unrelenting glare of bright white fluorescent lighting, which, though efficient, notoriously disrupts circadian rhythms, deterring recovery. Hospitals nowadays do a great job of hiding sunlight, rather than amplifying its effects. Nonetheless, we know that hospital patients in rooms with daylight and views of the outdoors have quicker recovery times and need fewer painkillers. Natural light, scientists have observed, decreases heart rate, lowers blood pressure, jumpstarts critical chemical reactions in the body, and even treats depression faster than antidepressants. And just as Nightingale theorized, it can also decrease harmful bacteria and viruses.

But if the healing quality of sunlight—known for centuries, and reinforced in finding after finding—is so well established, why do we still treat sunlight as a health consideration that is, at best secondary, at worst fringe or even pseudoscientific? Possibly, it’s because although we know that sunlight heals, we still don’t know exactly why. That we accept artificial light as a tolerable substitute to sunlight in places of communal healing is a victory of scientific hubris that damages us more than we realize. And amid cultural obsession with health assessment—step counting, blood glucose monitoring, sleep tracking, and all sorts of other quantification exercises—is it not odd that we pay so little attention to the quality of the light in our lives?

Indeed, today, there is ever more reason to support the ancient insight that daylight and sun are critical determinants of health and wellness. In the style of the ancients, Martin Picard, a metabolic researcher at Columbia, cites the sun as the initiator of a life cycle—photosynthesis, glucose, oxygen, ATP—that has mitochondria as its linchpin. Health influencers in the vein of Andrew Huberman and Carnivore Aurelius are bringing new attention to the importance of light for wellness, too, backed up by newer science. Recent scientific attention has been given to what many have intuitively known, that metabolic dysfunction is the basis of almost all disease, particularly chronic disease. To researchers like Picard, an energetic view of medicine (metabolic health), rather than a static view (focused on genes and DNA), offers a more accurate and holistic representation of health. If the sun is the initiator of mitochondrial life and its energetic function, then that must also be the case for life, more broadly, beyond the cellular unit.

Maybe lives tucked away from sunlight are even contributing to making America sick. In the U.S., chronic disease, autoimmune disease, mental health disorders, obesity, and metabolic dysfunction are on the rise. We spend $3.7 trillion yearly on chronic treatments, and yet chronic disease still accounts for over 80% of deaths. Thirty percent of children are pre-diabetic, up from zero 50 years ago. Nearly half of all Americans live with at least one chronic condition, 1 in 10 Americans has diabetes, and roughly 2 out of 3 U.S. adults are overweight or obese. More than 1 in 5 Americans are diagnosed with psychiatric disease, and global cancer rates for people under 50 have risen nearly 80% in the last 30 years. Our health is suffering tremendously, and lack of sun exposure may contribute, if not to disease, then to difficulty healing.

When we do not feed healthy light to ourselves—to our cells and our souls—we suffer. Despite so many modern riches, we are so deeply impoverished in this way. Light is one of nature’s greatest gifts, greatest sources of healing and power, and a treasure for all life. We see this reflected in the Jewish tradition, and across medical and religious history. It is inseparable from our spiritual purpose and our physical well-being. Let’s bring back reverence for the life force that is most fundamental and universal to us all—the healing power of the sun. Of light, inner and out.