FEATURE: Harness, don’t hide: The healing power of summer sun

Secciones de contenido

• ● Escuche el artículo
• ● What is photobiomodulation?
• ● Scientifically proven health benefits of non-burning sunlight exposure
• ●  Summary of benefits and supporting science 
• ● When to expose: timing matters
• ● Practical tips for safe and effective exposure
• ● Sunlight and the microbiome
• ● Toxic sunscreens
• ● Block the burn, not the sunlight: sun-friendly sunscreens
• ●  ‘Smart’ sunscreens
• ● Types of sunscreen that let the good light in
• ● The bigger picture
• ● Final words

Por Rob Verkerk PhD, director ejecutivo y científico

As the summer sun climbs ever higher in the sky, the dominant public health message urges us to protect ourselves from it. Some schools and nurseries forbid kids in their care to go outdoors without being slathered in sunscreen, rarely informing them or their parents or carers about their potential exposure to toxins.

Escuche el artículo

Emerging science is now reframing this narrative. While it is clearly evident that excessive ultraviolet (UV) exposure can damage the skin and increase skin cancers, moderate, non-burning exposure to natural sunlight confers a profound range of health benefits that go far beyond the production of the all-important vitamin D. In fact, sunlight acts as a powerful natural form of photobiomodulation (PBM), a term that’s commonly used to refer to low-level laser light therapy that uses wavelengths in the visible light spectrum which includes red light (RL, 620–700 nm) and near-infrared (NIR, 700–1440 nm).

By aligning our daily sun exposure with our biology, we can tap into one of nature’s most potent health-promoting forces. That’s assuming the solar geoengineers don’t get too successful in reflecting the energy from the planet’s key energy source back into space.

What is photobiomodulation?

Photobiomodulation is the process by which specific wavelengths of light influence biological systems, especially at the cellular and mitochondrial level. Red and near-infrared (NIR) light are particularly well-studied (see below), with effects that include enhanced ATP (energy) production, reduced oxidative stress, anti-inflammatory effects, improved wound healing, and better tissue repair. While many commercial PBM devices focus on red/NIR light, sunlight offers a free, full-spectrum source of biologically active wavelengths ranging from ultraviolet to infrared.

Sunlight: Nature’s multispectral PBM tool

Different components of solar radiation penetrate the skin to varying depths and interact with different biological pathways:

• UVB (280–315 nm): Primary driver of vitamin D synthesis and also stimulates beta-endorphin and serotonin production.
• UVA (315–400 nm): Triggers nitric oxide (NO) release from skin stores, promoting vasodilation and blood pressure reduction.
• Visible Light (400–700 nm): Especially blue light (450–495 nm), plays a central role in regulating circadian rhythms via melanopsin photoreceptors in the eye.
• Red and Near-Infrared (620–2500 nm): Penetrate deeply into tissues and stimulate mitochondrial respiration and cellular regeneration.

Scientifically proven health benefits of non-burning sunlight exposure

Below I summarise the scientifically-established benefits of sunlight exposure at levels that doesn’t cause the skin to burn (erythema). Below each point, you can dive into the hyperlinked references (click on “[view]”) that support these claimed effects.

1. Cardiovascular health via nitric oxide (UVA)

Heard about the benefits of producing nitric oxide in our arteries from high intensity interval training (HIIT) to improve blood circulation and health? Well, UVA exposure from sunlight prompts the release of nitric oxide from the skin, helping to lower blood pressure and improve vascular function independent of vitamin D. This effect has been shown to improve endothelial function, lower blood pressure, and therefore may reduce cardiovascular disease (especially high blood pressure [hypertension]) risk.

Key references

• Weller RB. Sunlight: Time for a Rethink? J Invest Dermatol. 2024 Aug;144(8):1724-1732 [view]
• Lindqvist PG, Landin-Olsson M, Olsson H. Low sun exposure habits is associated with a dose-dependent increased risk of hypertension: a report from the large MISS cohort. Photochem Photobiol Sci. 2021;20(2):285-292. [view]

1. Mood elevation and pain reduction (UVB)

UVB exposure increases beta-endorphins and serotonin, key neurotransmitters that help reduce pain and raise our mood. As Fell and colleagues found in 2014, beta-endorphin mediated by UVB exposure can actually cause us to develop a healthy addiction to sunlight (UV light)—that’s assuming we’re exposed to enough sunlight to develop the addiction in the first place! Sunlight (especially morning light) stimulates retinal photoreceptors that signal to the suprachiasmatic nucleus (SCN) in the brain so enhancing serotonin synthesis from tryptophan. This enhanced production of beta-endorphins and serotonin also explains the well-documented antidepressant effects of sunlight and its role in countering seasonal affective disorder (SAD).

Key references

• Mead MN. Benefits of sunlight: a bright spot for human health. Environ Health Perspect.2008;116(4):A160-7. [view]
• Fell GL, Robinson KC, Mao J, Woolf CJ, Fisher DE. Skin β-endorphin mediates addiction to UV light. 2014 Jun 19;157(7):1527-34. [view]
• Lambert GW, Reid C, Kaye DM, Jennings GL, Esler MD. Effect of sunlight and season on serotonin turnover in the brain. Lancet. 2002;360(9348):1840-2. [view]

1. Sleep and circadian rhythm regulation (visible blue light)

So you thought blue light was all bad? That might be the case when you’re constantly exposed to artificial blue light—especially late at night, just before bed, from digital devices and indoor lighting. But short-wavelength blue light from sunlight, which peaks from late morning to early afternoon when the sun is highest in the sky, isn’t just beneficial—it’s essential for health. It plays a vital role in synchronising our circadian rhythm, which in turn regulates sleep, metabolism, and hormonal balance. Sunlight-driven production of serotonin during the day is crucial, as serotonin is converted into melatonin in the pineal gland at night to support restful sleep. Disruption of this natural rhythm—known as poor circadian alignment—has been linked to increased risks of metabolic syndrome, cancer, and mental health disorders.

Key references

• Wright KP Jr, McHill AW, Birks BR, Griffin BR, Rusterholz T, Chinoy ED. Entrainment of the human circadian clock to the natural light-dark cycle. Curr Biol. 2013 Aug 19;23(16):1554-8. [view]
• Cajochen C, Münch M, Kobialka S, Kräuchi K, Steiner R, Oelhafen P, Orgül S, Wirz-Justice A. High sensitivity of human melatonin, alertness, thermoregulation, and heart rate to short wavelength light. J Clin Endocrinol Metab. 2005;90(3):1311-6. [view]

1. Photobiomodulation effects and mitochondrial stimulation

Red and NIR light is the sunlight you are bathed in early in the morning (after dawn) and late in the day (before dusk). Think about how good it feels when you sit and watch the sun rise or the sun set. These wavelengths have profound effects on the body, stimulating mitochondrial cytochrome c oxidase, boosting ATP production and reducing inflammation, persistent low-grade inflammation being the process that underlies all chronic diseases. These wavelengths support tissue repair, muscle recovery, and skin regeneration, offering natural alternatives to artificial red light/NIR (PBM) devices.

Key references

• Chung H, Dai T, Sharma SK, Huang YY, Carroll JD, Hamblin MR. The nuts and bolts of low-level laser (light) therapy. Ann Biomed Eng. 2012;40(2):516-33. [view]
• Hamblin MR. Mechanisms and applications of the anti-inflammatory effects of photobiomodulation. AIMS Biophys. 2017;4(3):337-361. doi: 10.3934/biophy.2017.3.337. [view]

1. Immunomodulation and autoimmune disease mitigation (UVB/UVA)

Autoimmune diseases are spiralling globally and there are many reasons for this including bad diets, loss of gut (and sometimes blood/brain) barrier function, as well as environmental, chemical and psychological trauma or stress. But we need to add lack of sunlight to the list. UV radiation from sunlight, and UVB in particular, modulates immune responses, reducing excessive inflammation and increasing regulatory T cell activity. This may help reduce the incidence or severity of autoimmune diseases, including rheumatoid arthritis (RA), multiple sclerosis (MS), Crohn’s disease, ulcerative colitis and type 1 diabetes.

Key references

• Ponsonby AL, McMichael A, van der Mei I. Ultraviolet radiation and autoimmune disease: insights from epidemiological research. Toxicology. 2002 Dec 27;181-182:71-8. [view]
• Hart PH, Gorman S, Finlay-Jones JJ. Modulation of the immune system by UV radiation: more than just the effects of vitamin D? Nat Rev Immunol. 2011;11(9):584-96. [view]

1. Antimicrobial and anticancer effects (UVA/UVB)

The sun’s out so slap on that sunscreen to protect yourself from skin cancer, right? That’s what we’ve heard from public health authorities for years. Well, non-burning sunlight has been shown not only to reduce the risk of a whole range of internal cancers, probably linked to elevated natural vitamin D production. But UV exposure also stimulates the production of antimicrobial peptides such as cathelicidins and photoproducts like lumisterol3 and suprasterols. These compounds exhibit antiproliferative properties and appear to reduce the risk of some skin cancers.

Key references

• Holick MF. Cancer, sunlight and vitamin D. J Clin Transl Endocrinol. 2014;1(4):179-186. [view]
• Bolerazska B, Rabajdova M, Spakova I, Marekova M. Current knowledge on the active form of Vitamin D synthesized in the skin and its effects on malignant melanoma. Neoplasma. 2017;64(1):1-12. [view]
• Felton S, Navid F, Schwarz A, Schwarz T, Gläser R, Rhodes LE. Ultraviolet radiation-induced upregulation of antimicrobial proteins in health and disease. Photochem Photobiol Sci. 2013 Jan;12(1):29-36. [view]

1. Serotonin and cognitive health (UVB/Visible Light)

Do you feel like your mind is clearer after you’ve had a holiday in the sun? Turns out it wasn’t just the break from your normal routine that helped. Exposure to sunlight influences tryptophan metabolism, particularly increasing the conversion to serotonin—a precursor to melatonin. Higher serotonin turnover is associated with improved mood, cognition, and sleep regulation. So get out there and clear your head! Just don’t get yourself burned!

Key references

• Kent ST, McClure LA, Crosson WL, Arnett DK, Wadley VG, Sathiakumar N. Effect of sunlight exposure on cognitive function among depressed and non-depressed participants: a REGARDS cross-sectional study. Environ Health. 2009 Jul 28;8:34. [view]
• Lambert GW, Reid C, Kaye DM, Jennings GL, Esler MD. Effect of sunlight and season on serotonin turnover in the brain. Lancet. 2002;360(9348):1840-2. [view]

1. Skin health

Sunlight creates wrinkles and ages the skin, right? Wrong! Too much UV light in the middle of the day can do that, but red light, particularly in the visible red spectrum (around 620–750 nm) that you get exposed to early in the morning and late in the afternoon does the exact opposite! It has been shown to benefit skin health by stimulating fibroblast activity, leading to increased collagen and elastin production, while also stimulating tissue repair and reducing inflammation. This enhances skin elasticity, reduces fine lines and wrinkles, and improves overall skin texture and tone. This has led to non-invasive, rejuvenation treatments with artificial red light, but you can do it in nature while enjoying what many regard to be the most beautiful times of the day: dawn and dusk.

Key references

1. Avci P, Gupta A, Sadasivam M, Vecchio D, Pam Z, Pam N, Hamblin MR. Low-level laser (light) therapy (LLLT) in skin: stimulating, healing, restoring. Semin Cutan Med Surg. 2013;32(1):41-52. [view]
2. Barolet D, Boucher A. Prophylactic low-level light therapy for the treatment of hypertrophic scars and keloids: a case series. Lasers Surg Med. 2010 Aug;42(6):597-601. [view]

 Summary of benefits and supporting science 

When to expose: timing matters

As you’ve been gathering, different times of day expose us to different wavelengths of sunlight. Harnessing the benefits of sunlight depends on aligning exposure with natural light cycles. Dividing the day into three sections is helpful, as follows:

• Morning (Sunrise–10 AM): Rich in blue light. Best for circadian rhythm regulation and mood improvement.
• Midday (10 AM–2 PM): UVB is most abundant. Ideal for vitamin D, nitric oxide, and beta-endorphin production. Exposure must be short to avoid burning.
• Late Afternoon (2 PM–Sunset): Red and NIR light dominate. Best for tissue recovery, anti-inflammatory benefits, and preparing for melatonin production.

Practical tips for safe and effective exposure

Let me stress this again: avoid getting burned by the sun, and that’s highly dependent on your skin colour, skin type and the amount of recent exposure you’ve had. Some tanning oils can accelerate tanning and can therefore increase your risk of burning your skin – so be careful.  

• Start small: Regarding midday, intense sun, think about short periods of exposure around 5 to 20 minutes in duration depending on skin type, building up gradually. You can use protective oils like coconut oil, jojoba, macadamia, olive, or almond oil. If your skin starts to feel prickly or sensitive, you’ve had too much, but those who very fair, may have learned from experience that there’s no sensation till it’s too late. Timing is your best friend here. Start slow and low and work up.
• Avoid burning: Stop before skin reddens or just time 5-10 mins in the beginning. Use natural shade or clothing (SPF-assured for those most sensitive) if exposure is prolonged.
• Be consistent: Regular daily exposure is more effective than infrequent longer bouts.
• Consider sunscreen choice: Non-nano zinc oxide sunscreens without tints allow NIR and visible light through while blocking harmful UVB/UVA.

Sunlight and the microbiome

Ultraviolet (UV) radiation from sunlight significantly influences the microbiome—the diverse community of microorganisms residing on our skin and in our gut—affecting our health in various ways. The interactions are complex and as yet not well understood, with evidence of both beneficial and adverse affects on the skin’s microbiota that may reduce or increase skin diseases, including some skin cancer, like melanoma (that represents only about 1% of skin cancers). 

Some, but not all, of the positive effects are mediated through the skin’s production of vitamin D, which has well-documented immunomodulatory effects, including helping to maintain a balanced skin immune response and support microbial homeostasis.

But sunlight can also enhances host defense peptides (e.g. cathelicidins and defensins) that control the overgrowth of pathogenic microbes and support a healthy skin microbial balance, while promoting tolerance toward beneficial commensals like Staphylococcus epidermidis. Interestingly, S. epidermis produces compounds like 6-HAP that can inhibit the growth of cancer cells, suggesting a potential protective role against UV-induced skin damage.

However, high-dose or prolonged UV exposure (especially UVA and UVB) can damage the skin barrier and lead to inflammation, oxidative stress, and antimicrobial peptide dysregulation. These changes negatively impact the composition and stability of the skin microbiome.

But UV exposure doesn’t only affect the skin; it can also influence the gut microbiome. Research indicates that UVB light exposure can lead to changes in the gut microbiota, including an increase in bacterial diversity and shifts in the abundance of specific bacterial families, including an increase in the relative abundance of Firmicutes and Proteobacteria (associated with overweight phenotypes) and a decrease in the relative abundance of Bacteroidetes (associated with leaner phenotypes). These changes are thought to be related to the production of vitamin D, which is stimulated by UVB light and plays a role in immune function and microbial balance.

The take-home is this: While moderate sun exposure can have beneficial effects on the microbiome, it’s essential to balance this with the risk of skin damage. Excessive UV exposure can lead to skin damage and increase the risk of skin cancer. Therefore, it’s advisable to protect the skin from prolonged sun exposure while maintaining a healthy lifestyle that supports both skin and gut health. More than that, we should recognise that the skin and the gut are much more closely connected than previously recognised; so we must now appreciate not only the gut-brain axis, but also the gut-skin axis, or even the gut-brain-skin axis!

Toxic sunscreens

While sunscreens are widely promoted as essential tools for protecting the skin from sunburn and skin cancer, many conventional formulations contain chemical ingredients that raise serious health and environmental concerns. Some of the most commonly used UV filters—such as oxybenzone, octinoxate, octisalate, homosalate, octocrylene, and avobenzone—have been linked to a range of adverse effects. These include endocrine disruption, reproductive toxicity, allergic reactions, and cellular oxidative stress. A study in the Revista de la Asociación Médica Americana (JAMA) found that several of these compounds, especially oxybenzone and octinoxate, are readily absorbed through the skin, with residues found in blood, urine, breast milk, and even amniotic fluid. Oxybenzone and octinoxate have also been identified as contributors to coral reef bleaching, prompting bans in Hawaii and Palau.

Beyond UV filters, additional sunscreen ingredients such as synthetic fragrances, parabens, and nano-sized particles may pose further risks. Fragrance mixtures often contain undisclosed chemicals that can cause allergic reactions or disrupt hormonal function, while parabens have been associated with estrogenic activity and possible links to breast cancer. Some mineral sunscreens use nano titanium dioxide or zinc oxide, which may penetrate the skin or pose inhalation risks when sprayed. That’s where mineral-based sunscreens containing non-nano zinc oxide or titanium dioxide, free from synthetic fragrances and preservatives come in (see below).

Block the burn, not the sunlight: sun-friendly sunscreens

Sunlight is a powerful force—both nourishing and potentially damaging. The growing appreciation of sunlight’s health benefits beyond vitamin D has led many of us to question: Can we protect ourselves from the harm of UV rays while still enjoying the benefits of beneficial solar wavelengths like red and near-infrared light? The answer, thankfully, is yes—with the right approach.

Sunburn, or erythema, is mainly caused by UVB radiation (wavelengths 280–315 nm), which triggers direct DNA damage and inflammatory responses in the skin. UVB is highly “erythemogenic”—a scientific term for its sunburn-inducing power.

But what about the rest of the solar spectrum?

• UVA (315–400 nm) doesn’t typically cause sunburn, but it penetrates deeper into the skin, contributing to oxidative stress (ageing), immune suppression, and long-term photoaging. It also plays a co-carcinogenic role in skin cancer.
• Visible light (400–700 nm) and near-infrared (NIR, ~700–1400 nm) don’t cause burning, but they interact with skin in other important ways—modulating pigmentation, circadian rhythms, and mitochondrial energy production.

Can you block the harmful rays without blocking the helpful ones?

Yes—partially, with the right product. Most broad-spectrum sunscreens are designed to block UVB and UVA while allowing visible and NIR light through. However, very few are explicitly engineered to block only UV and leave the rest untouched. Still, with care, you can select products that do just that.

 ‘Smart’ sunscreens

There’s an ever greater array of sun-friendly, so-called ‘smart’ sunscreens coming onto the market. Some are natural, others not—we always suggest gravitating to the natural simply because the ingredients are almost certainly going to have a better-known safety profile. The following table helps you discern what different ingredients are aiming to achieve.

Types of sunscreen that let the good light in

1. Transparent zinc oxide-based mineral sunscreens (non-nano)
   • Benefits: Block UVB and UVA, while allowing red, yellow, green, and NIR light through.
2. “Vitamin D optimised” sunscreens
   • These niche formulations aim to allow some UVB exposure to support vitamin D synthesis while still offering UVA protection.
3. Phototherapy-compatible sunscreens
   • Specialised products used in clinical settings to allow red and NIR light penetration for therapeutic purposes. These are uncommon in mainstream markets.

 Avoid:

• Tinted sunscreens or BB creams — these often contain iron oxides, which block blue and green light.
• Infrared-blocking formulas — some advanced sunscreens marketed for “infrared protection” may filter out beneficial NIR.
• Suncreens containing

To block or not to block: summary

If you’re looking to protect your skin without missing out on the health-promoting benefits of natural light, the ideal sunscreen, in our view, is:

• Mineral-based, using non-nano zinc oxide
• Free from tints, iron oxides, and added infrared-blocking agents
• Broad-spectrum for UV, but transparent to visible and near-infrared light

This kind of product allows you to enjoy the sun safely and strategically, supporting your circadian rhythms, mitochondrial function, and even mental and cardiovascular health—without the burn.

The bigger picture

Modern lifestyles that keep us indoors, along with excessive sun-avoidance messaging and routine use of potentially toxic sunscreens, may be inadvertently depriving people of essential and beneficial sunlight exposure. This not only contributes to widespread vitamin D deficiency, but also disrupts circadian rhythms and is an often-forgotten contributor to the rising rates of chronic illness that’s now threatening to collapse health systems. Reframing sunlight as a natural PBM tool encourages responsible, intentional exposure as part of a broader, nature-connected lifestyle.

Final words

Sunlight, the ultimate source of nearly all the energy used by living organisms, humans and all associated technology included, when harnessed wisely, offers far more than vitamin D. It acts as a multifaceted, full-spectrum natural PBM therapy—modulating inflammation, energising cells, regulating sleep, and elevating mood. It is only with an awareness of the incredibly broad benefits of sunlight exposure that we can begin to appreciate how our species’ progression towards indoor, artificially illuminated lives is a major—and often ignored—contributor to the escalating chronic disease epidemic that has now afflicted all industrialised societies.

By embracing regular, non-burning sunlight exposure aligned with natural light cycles, we can reclaim one of the most ancient and effective tools for human health and vitality.

Enjoy the summer – care-fully and chemical free!

>>> Previous ANH articles on sunlight and vitamin D:

EU continues to tighten noose on vitamin and mineral limits (12 Jun 2023)

Vitamin D — an evolutionary tale for application (02 Nov 2022)

Sunday Times late-winter attack on high dose vitamin D [26 Feb 2020]

Let’s beat the vitamin D pandemic before it beats us! [28 Aug 2019]

Are you rea’D’y for Winter? [22 Nov 2018]

Vitamin D – Prevention rather than cure [16 Aug 2017]

UK government stays in the shade with no changes in vitamin D recommendations [12 Aug 2015]

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