Sunlight Is A Nutrient: Re-Evaluating Our Relationship with the Sun

For decades, we’ve been told to slather on sunscreen whenever we step outside to protect our skin from cancer-causing UV rays. At the same time, we’re warned about vitamin D deficiency and its health consequences.  Since the 1970s, we’ve seen rates of skin cancer continue to rise despite increased sunscreen use (1), increasing rates of vitamin D deficiency (2), and a drastic decline in public health. There’s an apparent contradiction here. This article examines the complex relationship between sunlight, vitamin D, skin health, sunscreen products, and how these influence our health.

Sunlight Creates Vitamin D in Your Skin

When sunlight touches your skin, UVB rays interact with a form of cholesterol in your skin called 7-dehydrocholesterol, converting it to previtamin D3. A heat-induced reorganization of this molecule, driven by the skin’s temperature, forms vitamin D3 (cholecalciferol) (4).

This sun-produced vitamin D3 is synthesized in a sulfated form, which research suggests plays a crucial role in maintaining vitamin D homeostasis in the body. The sulfate group makes the molecule more water-soluble, allowing it to act as a reservoir for vitamin D and regulate levels (5). It has also been shown to play a role in calcium balance (6).

This sun-derived vitamin D enters the bloodstream and travels to the liver, where it’s converted to 25-hydroxyvitamin D (calcidiol), then to the kidneys where it becomes 1,25-dihydroxyvitamin D (calcitriol)—the active form that regulates calcium absorption and bone health, supports immune function, and influences cell growth and neuromuscular activity (7).

 Radiation From the Sun: UVA, UVB, Red, and Infrared Light

We hear a lot about the potential dangers of ultraviolet (UV) light from the sun. But radiation comes in different forms, each affecting the skin differently, and some offering immense health benefits.

UV radiation comes in two forms, UVA and UVB rays:

UVA rays:

• Longer wavelength (320-400 nm)
• Penetrate deeper into the skin, reaching the dermis
• Present throughout daylight hours, all year round
• Can pass through glass
• Associated with skin aging, wrinkling, and photodamage
• Consistent intensity regardless of season or time of day

UVB rays:

• Shorter wavelength (290-320 nm)
• Primarily affects the outer layer of skin (epidermis)
• Intensity varies by season, location, and time of day (strongest midday)
• Blocked by glass
• Responsible for sunburn
• Synthesizes vitamin D in the skin

Both types of UV radiation affect cellular DNA and can contribute to skin changes, but they do so through different mechanisms and at varying depths within the skin.

Healing Radiation

Red and near-infrared light from the sun offers remarkable health benefits beyond vitamin D production. These longer wavelengths (600-1000nm) penetrate deeper into tissues than UV rays, triggering biological responses at the cellular level:

• Mitochondrial Enhancement – Red light stimulates mitochondria—your cells’ power plants—through photobiomodulation. When red light photons are absorbed by cytochrome c oxidase, it increases mitochondrial ATP production. This enhances cellular energy production, which in turn supports every internal cellular function (8).
• Boosts cellular melatonin production – you’re “sleep hormone” that also acts as a vital and potent antioxidant (9).
• Enhances immune function through several mechanisms (10):
  • Enhancing lymphocyte activity
  • Supporting natural killer cell function
  • Modulating cytokine production
  • Improving cellular energy needed for immune responses
• Healing and Tissue Repair – studies show red light therapy induces faster recovery from cuts, burns, surgical incisions, and other injuries with appropriate red light exposure by (11):
  • Increasing circulation to damaged tissues
  • Stimulating collagen production
  • Reducing inflammation
  • Enhancing cellular regeneration

Historical Heliotherapy for Tuberculosis

In the early 20th century, sunlight therapy (heliotherapy) was a standard treatment for tuberculosis before antibiotics became available. Dr. Auguste Rollier established sunlight clinics in the Swiss Alps around 1903, treating thousands of TB patients with progressive sun exposure.

Patients were gradually exposed to increasing durations of sunlight in open-air sanatoriums, with careful attention to preventing sunburn. They saw remarkable success rates, with many experiencing significant improvement or complete recovery.

The practice was so effective that by the 1920s, there were over 165 heliotherapy centers in Switzerland alone (12). While initially thought to work primarily through vitamin D, we now understand that multiple mechanisms were likely involved, including UV’s antimicrobial effects, red light’s tissue-healing properties, and the overall immune enhancement from balanced sun exposure.

Before the antibiotic era, this sunlight therapy represented one of the most effective treatments available for tuberculosis and other respiratory infections. The success of heliotherapy provides historical evidence for sunlight’s therapeutic potential beyond what we typically recognize today.

Our Evolutionary Relationship with Sunlight

Human beings evolved under the sun. For hundreds of thousands of years, our ancestors lived outdoors with significant sun exposure. Our biology developed complex mechanisms to both benefit from and protect against solar radiation.

Skin pigmentation itself evolved as a balancing mechanism—darker skin provides protection in high-UV environments near the equator. Alternatively, lighter skin allows for adequate vitamin D production in lower-UV environments at higher latitudes (13). This evolutionary adaptation underscores the importance of both sun protection and sun exposure for human health.

Sunlight plays another crucial role beyond vitamin D production—it regulates our circadian rhythm. Light entering our eyes stimulates the suprachiasmatic nucleus in the brain, which controls our internal 24-hour clock. This system regulates (14):

• Sleep-wake cycles
• Hormone production (including melatonin, cortisol, thyroid, and sex hormones)
• Body temperature
• Metabolism and hunger patterns
• Cellular repair processes

Research shows that regular exposure to natural light, particularly morning sunlight, improves sleep quality, mood, and overall health (15). Modern indoor lifestyles with artificial lighting have disrupted these ancient biological systems, contributing to sleep disorders, seasonal affective disorder, and potentially other health issues.

Importantly, for proper circadian entrainment, sunlight needs to enter the eyes unfiltered. Wearing sunglasses, especially in the morning, can block this crucial light signal to the brain. Similarly, staying completely covered or remaining indoors during daylight hours prevents the brain from receiving proper light cues, which are essential for regulating the body’s internal clock. Even brief exposure to morning sunlight without sunglasses can significantly improve circadian rhythm alignment, enhancing sleep quality and daytime alertness.

Sunlight and Skin Cancer:

The relationship between sun exposure and skin cancer is more complex than often portrayed. While excessive UV exposure and sunburn increase the risk of skin cancer, moderate sun exposure may actually provide protective effects against some cancers.

1. Sunburn vs. regular exposure: Research indicates that intermittent intense sun exposure and sunburn are more strongly associated with melanoma than regular, moderate sun exposure. People who experience regular sun exposure, such as outdoor workers, often have lower melanoma rates than indoor workers who get occasional intense exposure (16).
2. Genetic factors: Genetic predisposition plays a significant role in skin cancer development. Family history, skin type, and specific genetic mutations are strong determinants of risk. Some individuals are genetically more vulnerable to UV damage than others (17).
3. Types of skin cancer: Non-melanoma skin cancers (basal cell and squamous cell carcinomas) are more clearly linked to cumulative sun exposure. While common, these are typically slow-growing and rarely metastasize. They’re usually treatable with simple removal procedures (18).
4. Melanoma complexity: Melanoma, the most dangerous form of skin cancer, shows a more complex relationship with sun exposure. While UV radiation is a risk factor, melanoma can also occur on areas of skin that are not exposed. Research suggests factors beyond simple UV exposure are involved, including genetic predisposition and immune function (17).
5. Protective tanning: Gradual tanning without burning illustrates the skin’s natural defense mechanism. The pigment melanin provides some UV protection, acting as the body’s built-in sunscreen. This process, when allowed to develop gradually, may provide some protection against DNA damage (19).

Multiple epidemiological studies have found correlations between moderate sun exposure and reduced rates of certain internal cancers, suggesting potential protective effects beyond vitamin D production. This doesn’t negate the risks of excessive exposure but highlights the need for a balanced approach (20).

The Concerns with Chemical Sunscreens

Many commercial sunscreens contain chemical filters that may pose health concerns. These chemicals enter the bloodstream in measurable amounts and may disrupt various biological processes:

Potentially problematic ingredients (21):

• Oxybenzone: Detected in blood after application, may disrupt hormone function, and has been linked to skin allergies
• Octinoxate: May affect estrogen levels and thyroid function
• Homosalate: A potential endocrine disruptor affecting hormones
• Octocrylene: May promote the generation of reactive oxygen species when exposed to UV light
• Avobenzone: Can break down in sunlight, forming free radicals
• Parabens: Preservatives that mimic estrogen in the body and disruption to reproductive organs in women (22)
• Phthalates: Often found in fragrance mixtures, linked to significant hormonal disruption in males and females starting during gestation (23)

Research published in the Journal of the American Medical Association in 2019 and 2020 demonstrated that several common sunscreen chemicals exceed FDA safety thresholds in bloodstream levels after just one day of use (24). These chemicals can remain in the body for extended periods, raising questions about long-term safety.

Environmental Impact of Sunscreen Chemicals

Beyond human health concerns, chemical sunscreens pose serious environmental threats (25):

1. Coral reef damage: Oxybenzone and octinoxate have been linked to coral bleaching, prompting bans in places like Hawaii and parts of Australia
2. Marine toxicity: These chemicals can damage marine organisms’ reproductive systems, affect growth, and increase mortality
3. Bioaccumulation: Sunscreen chemicals accumulate in aquatic ecosystems, potentially affecting the entire food chain
4. Water contamination: Chemical filters wash off swimmers and enter waterways through wastewater systems, even in inland areas

A single drop of oxybenzone in an Olympic-sized swimming pool may be sufficient to damage coral organisms, highlighting the potency of these compounds in aquatic environments (26).

Safer Alternatives and Balanced Approaches

It’s important to protect yourself from sunburn. Rather than avoiding sun protection entirely, consider these more natural alternatives:

Non-Toxic and Reef-Safe Sunscreen (21):

• Zinc oxide (non-nano): Creates a physical barrier that reflects and scatters UV radiation. Unlike chemical filters, it doesn’t penetrate the skin significantly.
• Titanium dioxide (non-nano): Another mineral-based option that stays on the skin’s surface.
• *IMPORTANT NOTE* Apply these as rub-on sunscreen and avoid spray-on versions. Both of these mineral-based sunscreens disturb the lungs and are possibly carcinogenic when inhaled (21).

Natural oils with mild sun protection properties:

• Coconut oil: Contains natural SPF of approximately 4-6
• Olive oil: Offers mild protection with an SPF of around 2-3
• Red raspberry seed oil: Contains antioxidants and offers modest UV protection
• Shea butter: Traditionally used in Africa, it provides minimal SPF protection while moisturizing

Traditional approaches:

• Tallow (animal fat): Used historically in various cultures for skin protection
• Carrot seed oil: Contains antioxidants that may help reduce UV damage

Behavioral approaches:

1. Gradual exposure: Start with short sun sessions of 10-20min and gradually increase duration to build melanin without burning
2. Timing: Avoid peak UV hours (10am-2pm) for extended exposure
3. Clothing: Use lightweight, breathable fabrics for physical protection (only to avoid initial burning for extended periods or during peak UV time)
4. Seek shade: Use natural shade while still enjoying outdoor benefits
5. Morning light: Get unfiltered morning sunlight (without sunglasses and preferably outside rather than through a window) to support circadian health while UV is lower

Finding Your Personal Balance

Just as with everything in functional wellness, finding your personal balance is key. This will be based on:

• Your skin type and genetic background
• Geographic location and season
• Personal health history and risk factors
• Lifestyle and outdoor activity levels

By understanding the science, listening to your body’s signals, and simply doing what humans have done for melenia, you can develop a relationship with the sun that supports optimal vitamin D levels, circadian health, immune function, mood enhancement, and overall wellbeing while minimizing damage and long-term risks.

How to safely bask in all of the healing powers the sun has to offer you:

• Start slow and work your way up to at least 30 min per day of natural, unfiltered light exposure.
• Avoid adding additional chemical exposuring and biological disrutors
• Get sunlight in your eyes when you first wake up, and at night when the sun is setting and the infrared waves are strongest
• Protect your skin of needed when UV rays are at their peak and over prolonged periods
• *Pro tip: go ahead and take your shoes off while you’re out there for the grounding benefits.*

Remember that individual needs vary significantly—what works perfectly for one person may not be ideal for another. Consider consulting healthcare providers knowledgeable about both the risks and benefits of sun exposure and vitamin D optimization to develop a personalized plan.