Sun as Medicine

It’s time to move away from the modern philosophy that sunlight is something to be feared or rigidly protected against. For most of human history, the sun was worshiped and revered.

Religions, temples, and deities were erected around sun veneration as a source of healing, energy, and life. Ancient cultures intuitively understood what science is now mirroring: sunlight is essential for health.

Emerging research is transforming the modern understanding of the sun’s impact on the human body. Sunlight is crucial to health. It’s an active participant in our physiology, influencing everything from immune function, mood, and metabolism to mitochondrial health.

The sun isn’t just a source of light. It’s a source of vitality and life…

Sunlight is a powerful and natural form of medicine. The sun isn’t just a source of light. It’s a source of vitality and life, one of the most easily accessible and potent forms of medicine we have. 

In functional medicine, we recognize that the body isn’t separate from its environment. For decades, public health messaging has drilled the message that UV exposure is hazardous. However, studies are showing strong and poignant evidence that the benefits of UV exposure outweigh the risks.

What You’ll Learn:

  • How sunlight triggers vitamin D production
  • Sunlight’s role in mood and mental health
  • Cardiovascular, gut, and immune benefits of sunlight
  • Sunlight’s impact on sleep, pain, and energy
  • Longevity and lower mortality as a result of sunlight
  • Perspective shift: sunlight as your health ally, not enemy 

Why We Need the Sun: Reconnecting to Our Light-Driven Biology

Let’s do a quick scientific overview of sunlight, the wavelengths that we experience here on Earth. Sunlight is made up of visible light, infrared radiation, and ultraviolet radiation.

Visible light is the portion of the electromagnetic spectrum we can see, the colors that make this world appear vibrant.  

Infrared radiation, also known as heat radiation, has longer wavelengths than visible light and contributes to warming the Earth.

Ultraviolet radiation, which has shorter wavelengths than visible light and is not detectable by the human eye, is divided into three main types: UVA, UVB, and UVC.

  • UVA has the longest wavelength and penetrates deeply into the skin, contributing to aging and long-term skin damage.
  • UVB, which has a medium wavelength, is essential for vitamin D production and is also responsible for sunburn.
  • UVC has the shortest wavelength and is absorbed by the Earth’s atmosphere, so it doesn’t reach the surface but is used in artificial sterilization.

Ultraviolet-B (UVB), in particular, is required for the epidermal (skin) formation of the precursor for vitamin D. When your skin is exposed to UVB rays from sunlight, a compound in your skin called 7-dehydrocholesterol absorbs the UV energy. This triggers a chemical reaction that converts 7-dehydrocholesterol into vitamin D3, the active form of vitamin D your body uses.

More than 90% of your vitamin D is produced this way, making sunlight the primary natural source of this essential nutrient.

More than 90% of your vitamin D is produced this way, making sunlight the primary natural source of this essential nutrient.

More than 50% of the world’s population is at risk for vitamin D deficiency. This deficiency is in part due to the inadequate nutrient levels of modern modified foods and the misconception that a healthy diet contains an adequate amount of vitamin D.

The Sunshine Vitamin: Vitamin D and Beyond

Vitamin D orchestrates functions across nearly every tissue in the body.

Vitamin D is more than just a vitamin; it acts as a hormone and plays a major role in physiological functions. Unlike other vitamins that rely solely on dietary intake, vitamin D is unique: it’s primarily synthesized directly in the skin during UVB exposure.

Over 1,000 genes are influenced by Vitamin D, making its reach both vast and vital. This vitamin is essential for bone and muscular health, immune system regulation, cardiovascular health, and neurological function.  Calcium and phosphate metabolism, foundational to the majority of organ system functions in the body, are also dependent on vitamin D.

But there’s a more prominent emergence of information regarding sunlight, research is showing that sunlight is also reducing the risk of disease development. 

It’s time to shift the perspective that sun exposure is only harmful to an appreciation for the many ways the sun supports the body, health, and longevity.

Sunlight and Serotonin

There’s a direct, measurable relationship between sunlight and serotonin, the brain chemical that stabilizes mood and promotes a sense of well-being. In one clinical study, researchers found that “the rate of production of serotonin by the brain was directly related to the prevailing duration of bright sunlight, and rose rapidly with increased luminosity.”

The more time you bask in the sun, the more serotonin you produce. 

Sunlight sets off a chain reaction that helps regulate mood, energy, and sleep. It’s why many people feel heavier, more sluggish, and more withdrawn during the darker winter months. And it’s why regular exposure to natural light is one of the most accessible tools we have to combat low mood, anxiety, and seasonal affective disorders.

Feeling good is not just a nice side effect; it’s foundational to health. When mood lifts, people move more, sleep better, eat with more intention, and engage with life more fully. The body and mind are interdependent and intimately connected. 

Sun exposure is essential for your biochemical state of wellbeing, translating to your emotional state of wellbeing. 

Sunlight and Mortality

Sunlight exposure is not just about mood or vitamin D, it’s a powerful determinant of longevity. Multiple large-scale studies have shown that people who avoid sunlight have significantly higher all-cause mortality rates.

The association is strong: the less sun exposure, the greater the risk of dying from any cause.

Avoiding sunlight doubles the risk of mortality compared to those in the highest exposure groups. This pattern holds across various causes of death, but it’s especially pronounced with cardiovascular and cancer-related mortality. In one analysis, individuals who shunned sunlight had a 60% increased risk of dying from cardiovascular disease alone.

The overall cancer-related death rate is also higher in those with limited sun exposure. In women, low sun exposure was associated with a 40% greater risk of cancer-related death.

This underscores a broader reality: when sunlight is too tightly restricted, the protective benefits it offers against internal disease can be lost.

These effects scale globally. Populations living closer to the equator, with more consistent UV exposure, tend to have lower rates of cardiovascular disease and cancers like breast, colorectal, and prostate cancer.

One estimate suggests that between 50,000 and 63,000 premature deaths in the U.S. each year are attributable to inadequate sun exposure and vitamin D deficiency.

Regular, mindful sun exposure should be seen as a foundational health habit, not a risk factor.

Sunlight and Cardiovascular Health

Sunlight doesn’t just act on the skin; it acts on the heart.

UVA rays activate nitric oxide stores in the skin, which in turn cause vasodilation, a widening of the blood vessels. The result? Lower blood pressure.

This mechanism is not speculative; it’s been observed consistently: increased sunlight exposure is linked to a measurable reduction in the risk of hypertension.

High blood pressure is more than a symptom. It’s a signal, one that predicts cardiovascular disease, stroke, and early death. Globally, hypertension accounts for 18% of all deaths and remains the leading cause of disability-adjusted life years. 

Vitamin D levels tell a similar story.

Research shows that individuals with the highest vitamin D levels are half as likely to be diagnosed with hypertension as those with the lowest levels. But here’s the twist: oral vitamin D supplements don’t show the same effect. So something else is at work, something only sunlight delivers.

Epidemiological studies have observed lower rates of hypertension and cardiovascular mortality in populations with higher sun exposure. These findings suggest that moderate, regular sunlight exposure can be a simple yet effective strategy for cardiovascular disease prevention.

Sunlight, it turns out, isn’t just a mood-lifter or a vitamin source. It’s a cardiovascular ally, reducing risk at the root.

Sunlight and Gut Health

How the sun benefits gut healthVitamin D, triggered by UVB exposure, activates receptors in the gut lining that strengthen the intestinal wall. This barrier is the frontline, keeping toxins and harmful bacteria out of the bloodstream. When the intestinal wall breaks down, inflammation rises. When it holds, systems stabilize.

A clinical study found that repeated UVB exposure to the skin significantly altered gut microbiota composition. The study observed an increase in both the diversity and abundance of beneficial bacterial families after UVB exposure.

These changes occurred without any dietary modifications, indicating a direct effect of sunlight on the gut microbiome. No dietary changes. No supplementation. Just light—and a measurable shift toward microbial balance.

 

Sunlight as a Natural Immunomodulator

Sunlight and immune health

Sunlight directly activates the immune system through both surface-level and systemic pathways. When UVB rays reach the skin, they regulate immune responses right at the cellular level. 

When you receive sunlight and vitamin D is converted to its active form, the first responders of the immune system are stimulated. 

Sunlight increases powerful antiviral messengers that enhance immune surveillance across the body. T cells, crucial players in infection defense, show increasing mobility and response speed in response to sunlight.

Sunlight increases powerful antiviral messengers that enhance immune surveillance across the body.

Neuropeptides, a type of chemical messenger vital to immune function, are also released through sunlight exposure. These messengers help increase immune tolerance, reduce inflammation, and repair oxidative DNA damage. This mechanism may explain why sunlight benefits inflammatory skin conditions such as psoriasis.

Even though chronic inflammation, the immune system switching into overdrive, is incredibly prevalent today, sun exposure doesn’t tip the scales this far. 

Sunlight does sharpen the immune system, but studies have also shown UV exposure counteracts inflammation. A significant normalization of immune dysfunction markers occurred in studies conducted on UVs’ impact on the immune system. 

Sunlight supports immune system homeostasis, helping to maintain a balanced and well regulated immune response. In a world where chronic inflammation is increasingly common, daily sun exposure can be a simple yet powerful tool for restoring balance.

Sunlight and pain

Another interesting fact about sunlight is UVB exposure stimulates the production of beta-endorphins, natural opioids that alleviate pain and induce feelings of pleasure. This analgesic effect underscores sunlight’s potential as a complementary approach to pain management.

Sunlight and Sleep 

Morning sunlight is especially powerful. It signals the body to suppress melatonin, the hormone that promotes sleepiness, and initiates a cascade of wakefulness.

That exposure early in the day doesn’t just boost alertness—it shifts your entire cycle forward, helping you feel naturally tired at night and energized in the morning. Just thirty minutes of morning light can anchor your rhythm.

Throughout the day, continued light exposure supports mental clarity and emotional regulation. Bright sunlight during waking hours strengthens the overall stability of the circadian rhythm, making it more resistant to disruption from artificial light, late-night screen time, or inconsistent schedules.

By contrast, darkness at night tells your body it’s time to wind down. But without sufficient daylight, especially morning light, your body loses that contrast, and melatonin production becomes delayed or irregular. That’s when sleep becomes shallow, fragmented, or hard to initiate.

Supporting your circadian rhythm is easier than you might think. It all starts with light. Getting outside for some morning sunlight helps your body wake up, reset, and stay in sync throughout the day.

Sunlight and Mitochondrial Vitality: Energizing the Cellular Powerhouses

Mitochondria, the energy-producing organelles within our cells, are also influenced by sunlight exposure. Light stimulates the activity of a key enzyme in the mitochondrial electron transport chain, enhancing ATP production, the energy currency of the cell.

Improved mitochondrial function translates to increased energy levels, better metabolic health, and enhanced resilience against oxidative stress. Sunlight, therefore, can play a pivotal role in maintaining your cellular vitality.

Sunlight and Cancer Prevention

While sunlight is often associated with skin cancer, it also offers protective benefits against certain internal cancers. Research has linked regular sun exposure to a reduced risk of cancers such as colon, breast, and prostate. This effect is likely due in part to vitamin D, which supports healthy cell regulation, encourages the natural elimination of abnormal cells, and helps inhibit tumor growth.

Epidemiological (disease) studies have observed lower cancer incidence and mortality rates in regions with higher sun exposure, emphasizing the importance of balanced sunlight exposure in cancer prevention strategies.

New research is also showing that the melanoma and UV causation may not be as cut and dry as we originally thought. It’s clear that moderate sun exposure is drastically more beneficial than low sun exposure or sun avoidance.

Although there is not enough research yet to make a clear, definitive, concise shift in our understanding of melanoma, researchers who are finding the benefits of UV with other cancer outcomes are asking new questions. We’ll have to see what this research unveils.

Sunscreen

Sunscreen reduces or blocks the above effects. However, when in the sun for prolonged periods of time, where you could be subjected to burns, choosing a non-toxic sunscreen is important. The integument (skin) is incredibly sensitive to chemical absorption. Many ingredients in popular sunscreens may prevent harm from burns, but initiate a different harmful response further inside the body. 

Ingredients like oxybenzone and octinoxate have been shown to disrupt hormone function and may have other systemic effects when absorbed through the skin. These chemicals are now being scrutinized for their potential role in endocrine disruption and environmental toxicity. 

Consider using mineral-based sunscreens that contain simple, non-toxic ingredients like zinc oxide or titanium dioxide. These sit on the surface of the skin and block UV rays without being absorbed into the body.

Takeaway: Embracing the Sun

Sun exposure has been widely associated with an increased risk of skin cancer when it leads to repeated sunburns. Understandably, this fear has led many people to avoid the sun. But widespread sun avoidance cascades not only into missed health opportunities, but also the elimination of essential health benefits that only the sun can provide.

Sunlight is a multifaceted healer, influencing our physiology from the molecular to the systemic level. It’s a natural, accessible, and cost-free ally in promoting health and preventing disease.

Regular, moderate exposure to natural sunlight, without sunscreen, may be one of the most powerful and natural tools you have for supporting immune health, reducing inflammation, and lowering long-term disease risk.

Regular, moderate exposure to natural sunlight, without sunscreen, may be one of the most powerful and natural tools you have for supporting immune health, reducing inflammation, and lowering long-term disease risk.

By understanding and harnessing the therapeutic potential of sunlight, we can illuminate a path toward holistic well-being.

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