Korte, niet-verbrandende blootstelling aan de zon helpt de meeste mensen, en de juiste hoeveelheid hangt af van je huid, je breedtegraad en het seizoen. Zonlicht maakt vitamine D aan, zet stikstofmonoxide vrij dat de bloeddruk iets omlaag brengt, stelt de biologische klok in en verbetert de stemming. In een groot cohort van vrouwen stierven degenen die de zon meden eerder, naar schatting 0.6 tot 2.1 jaar eerder, voornamelijk aan hartziekte.
Dat verband is verweven met roken en welvaart, dus het kan geen oorzaak bewijzen. Tegenover de voordelen staat dat afwisselend verbranden en zonnebanken het risico op melanoom duidelijk verhogen. De haalbare aanpak is regelmatige, korte blootstelling die nooit tot verbranding leidt, met extra voorzichtigheid bij een lichte huid en de middagzon in de zomer, en zonnebanken zijn een bewezen kankerverwekkende factor.
Findings & Outcomes
What It Is
Sunlight reaching your skin is a mix of two ultraviolet bands. Ultraviolet B is the shorter, higher-energy band. It does not travel deep, it makes vitamin D in the top layer of skin, and it causes most sunburn. Ultraviolet A is the longer band. It reaches deeper, drives most of the tanning and the long-term aging, and releases nitric oxide into the blood.
How much of this happens depends on you and on where you are:
- Skin type sets how fast you make vitamin D and how fast you burn. Fair skin that reddens easily makes vitamin D quickly; darker skin is more protected and needs longer sun for the same vitamin D.
- Latitude and season set how much ultraviolet B reaches the ground at all. A winter morning far from the equator delivers little of it; midday summer sun near the equator delivers a great deal.
- Time of day matters because ultraviolet B is strongest around midday.
What It Does
Sunlight acts through several pathways, and they point in opposite directions on very different evidence.
The benefits rest on weaker evidence. Three are mechanisms measured directly in skin and blood: vitamin D synthesis, a nitric oxide release that briefly lowers blood pressure, and the body-clock and mood signal of daylight. The fourth, longer life among people who get more sun, comes from following one large group of women for about 20 years. It shows a pattern, cannot prove cause, and travels with smoking, wealth, and baseline health. Together they support getting regular sun; none supports seeking more.
The harms rest on stronger evidence. Ultraviolet is a proven cause of melanoma and the common skin cancers.
The Research & Studies
Everything here is based on the research we have collected and checked, sorted into groups and ordered with the strongest evidence first. Click any claim to open the studies behind it.
Cancer Risk And Outcome
Burning and intermittent sun raised melanoma across 57 studies, steady outdoor sun did not
Across dozens of studies, sunburn history and occasional intense sun raised melanoma risk, while steady everyday outdoor sun did not. Burning is the part that matters.
Pooling 57 observational studies, intermittent sun exposure and a history of sunburn were associated with higher melanoma risk, while high steady occupational sun exposure was inversely associated. The pattern that raises melanoma is intermittent burning, not regular outdoor time. Measured in: 57 observational studies (case-control and cohort) of cutaneous melanoma and sun-exposure patterns, published before September 2002. The component studies rely on recalled sun exposure and sunburn, which is imperfect, and the estimates vary with latitude and skin type. It establishes association with a pattern of exposure, not a dose threshold.
The study · 1
Gandini et al., meta-analysis of risk factors for cutaneous melanoma: II. Sun exposure · Eur J Cancer 2005;41(1):45-60
Tanning beds raised melanoma about 20 percent, and 87 percent when started before age 35
People who had ever used a tanning bed had a higher chance of melanoma, and starting before age 35 nearly doubled it. More sessions meant more risk.
Across 27 studies, ever using a tanning bed was associated with about 20% higher melanoma risk, rising with the number of sessions, and first use before age 35 was associated with about 87% higher risk. Measured in: 27 observational studies of sunbed use and skin cancer, pooled in a systematic review and meta-analysis. The underlying studies are observational, so residual confounding by skin type and sun-seeking behavior is possible. The dose-response and the young-age signal are consistent across studies and point one direction.
The study · 1
Boniol et al., cutaneous melanoma attributable to sunbed use: systematic review and meta-analysis · BMJ 2012;345:e4757
Regular sunscreen halved melanoma over a decade in the one randomized trial
In the one randomized trial of the question, adults who used sunscreen daily had about half the melanoma over the next decade of those who used it as they pleased, and invasive melanomas fell more clearly still. The same trial had shown sunscreen prevents the common scaly skin cancer.
In the only randomized trial of sunscreen and melanoma, adults assigned to daily sunscreen for about 4.5 years had about half the melanoma rate of those using it at their discretion over the following decade (11 versus 22 cases; hazard ratio 0.50, 95% CI 0.24 to 1.02, P = 0.051), and invasive melanomas fell more clearly (3 versus 11 cases; hazard ratio 0.27, 95% CI 0.08 to 0.97). The same trial had earlier shown regular sunscreen use prevents squamous cell carcinoma. Measured in: 1,621 adults aged 25 to 75 in Nambour, Queensland, Australia, randomized to daily versus discretionary sunscreen from 1992 to 1996 and then followed to 2006 (the Nambour Skin Cancer Prevention Trial). The overall melanoma reduction did not quite reach statistical significance (P = 0.051); the clearer signal was for invasive melanoma, on modest case numbers. This is a single trial in a high-ultraviolet, fair-skinned setting, so the size of the melanoma benefit rests on few events.
Who this may not transfer to:Conducted with fair-skinned adults in a high-ultraviolet Australian setting where melanoma stakes are unusually high. The protective direction should carry to other fair-skinned populations, though the absolute benefit depends on local ultraviolet and skin type.
The study · 1
Green et al., reduced melanoma after regular sunscreen use: randomized trial follow-up (Nambour Skin Cancer Prevention Trial) · J Clin Oncol 2011;29(3):257-263
How it works
Ultraviolet B makes vitamin D3 in the skin, the main natural source for most people
Your skin makes vitamin D when ultraviolet B light hits it, and this is where most people get most of theirs. Darker skin, winter, high latitude, sunscreen and age all lower how much you make.
Ultraviolet B light converts a cholesterol precursor in the skin into vitamin D3, the main natural source for most people. How much is made falls with darker skin, higher latitude, winter, sunscreen and age. That the skin makes vitamin D from sun is settled, but the vitamin D page shows that adding more to a person who already has enough did not deliver the wider disease prevention once hoped for; the value is in correcting a shortfall that exists.
The study · 1
Holick, vitamin D deficiency (review of cutaneous synthesis and determinants) · N Engl J Med 2007;357(3):266-281
Heart And Vascular
Ultraviolet A released skin nitric oxide and briefly lowered blood pressure in 24 volunteers
When researchers shone ultraviolet light on people's skin, it released a chemical that widened blood vessels and briefly lowered blood pressure, separate from vitamin D. It is an early clue, not a treatment.
In a small human experiment, exposing skin to ultraviolet A released nitric oxide stored in the skin into the circulation and briefly lowered blood pressure, independent of vitamin D. It offers a mechanism for why blood pressure tracks with season and latitude. Measured in: 24 healthy volunteers exposed acutely to two standard erythemal doses of ultraviolet A. This was 24 volunteers measured acutely, not a trial of health outcomes. It shows the pathway exists; it does not establish that everyday sun meaningfully lowers blood pressure over time, and the same ultraviolet carries a skin cost.
The study · 1
Liu et al. (Weller, Feelisch), UVA irradiation of human skin vasodilates arterial vasculature and lowers blood pressure independently of nitric oxide synthase · J Invest Dermatol 2014;134(7):1839-1846
Longevity And Mortality
Sun avoidance tracked with 0.6 to 2.1 fewer years of life, a confounded association
In een grote groep Zweedse vrouwen overleden degenen die de zon meden gemiddeld eerder dan degenen die de meeste zon kregen, geschat op een half jaar tot twee jaar eerder. De extra sterfgevallen waren vooral hartgerelateerd, niet huidkanker.
Over about 20 years, women who avoided the sun had higher all-cause mortality than women with the most sun exposure, an estimated 0.6 to 2.1 years of shorter life expectancy. The excess deaths were cardiovascular and other non-cancer causes, not skin cancer. Measured in: 29,518 Swedish women aged 25 to 64 at enrollment, followed roughly 20 years (the Melanoma in Southern Sweden cohort). What could explain it instead: Sun avoidance is associated with things that shorten life: it correlates with smoking, poorer baseline health and less physical and outdoor activity, and people already unwell stay indoors more, so reverse causation is plausible. The analysis adjusted for several of these but cannot remove them all.. Sun habits were self-reported at a single baseline and this is one regional cohort. The authors describe the effect size as comparable to smoking, and the same caution applies: exposure was observed, not assigned, so the number cannot be read as a treatment effect.
Who this may not transfer to:Measured only in women. The vitamin D, nitric oxide and circadian pathways proposed behind the signal are not sex-specific, but no men were in this cohort, so the size of the association is not established for them.
The study · 1
Lindqvist et al., avoidance of sun exposure as a risk factor for major causes of death (Melanoma in Southern Sweden cohort) · J Intern Med 2016;280(4):375-387
How It Works
Anatomy of the Practice
1Ultraviolet B makes vitamin D
The shorter ultraviolet B band turns a cholesterol precursor at the surface of the skin into vitamin D3, the main natural source for most people. Production climbs fast, then plateaus well before the skin reddens. Past that point you add skin damage without adding vitamin D. How much you make drops with darker skin, higher latitude, winter, sunscreen, and age.
2Ultraviolet A releases nitric oxide
The longer ultraviolet A band reaches deeper and frees a store of nitric oxide from the skin into the blood. In a small experiment that release relaxed blood vessels and briefly lowered blood pressure, separate from vitamin D. It may be one reason blood pressure runs higher in winter and at higher latitudes. It is still an early finding.
3Light sets the body clock
Light striking a specialized set of retinal cells sets the master clock in the brain. Morning light pulls that clock earlier; late light pushes it later. This is the pathway behind daylight sharpening morning alertness, bringing sleep on sooner, and lifting mood. It is why sun taken toward morning does the most.
4Ultraviolet damages skin DNA
The same ultraviolet that does all this also damages the DNA in skin cells. The body repairs most of it, but not all, so damage builds over a lifetime and occasionally becomes a mutation that grows. Burning doses cause the most damage. Melanoma tracks episodes of burning and past sunburns; steady outdoor work carries less of this risk.
A real vitamin D shortfall is worth correcting; adding more to someone already sufficient did little in the large vitamin D trials. Morning light in the day and darkness at night pull the body clock the same direction.
Getting the Balance Right
Ways to Do It
Almost nothing here costs money. The core is a little regular sun without burning and learning your own skin, both free. The one paid item is sunscreen, for days spent long in the sun. Start at the top.
Short, regular time outdoors with some skin uncovered lets the body make vitamin D and set the clock. Taken in the morning, it does the most for sleep and mood. Aim for warmth on the skin and stop before any pinkness. On a strong-sun day a short spell suits lighter skin; darker skin and higher latitudes need longer.
Fair skin needs less sun and reddens fast; darker skin tolerates more and needs a longer dose. Season and latitude move the same dial: high summer near the equator is far stronger than a winter morning up north. Learn how fast your own skin begins to redden, and treat that as your ceiling.
The vitamin D forms early, while the skin-cancer risk builds with the hours. So for a long day outside, the free move is a hat, a shirt, and shade. Shade around midday, roughly late morning to mid-afternoon in summer, cuts the strongest ultraviolet and leaves the gentler morning and evening sun. Clothing is the most reliable sun protection there is.
For time outdoors beyond a short sensible dose, a broad-spectrum sunscreen of SPF 30 or higher lowers burning and cumulative damage. Reapplied every couple of hours and after swimming, it holds that protection. In the one randomized trial that tested it, regular use also lowered melanoma over the following decade. Most people apply too little; a generous layer is what reaches the labeled SPF.
A tanning bed gives ultraviolet with none of daylight's benefits, and it is a proven cause of melanoma.
In a sunless winter, or for someone who cannot get outdoors, sun alone will not cover vitamin D. Oily fish and fortified foods carry some, and a daily [vitamin D3](/go/integrative/practice/vitamin-d) supplement replaces the rest with no ultraviolet.
Protect against burning; you do not need to avoid daylight to be safe from skin cancer.
Some people should lean toward less sun and more cover:
- very fair skin, or many or unusual moles
- a personal or family history of skin cancer
- a suppressed immune system
- a sunny, high-ultraviolet latitude
Darker skin at a high latitude in winter leans the other way, toward getting sufficient sun.
Go Deeper
- Vitamin D: what the sun-made vitamin does in the body, a sensible dose, and where the large trials found its limits.
- Morning light: the circadian half of the benefit, and how to get the body-clock return without seeking a tan.
- Nitric oxide and the endothelium: the blood-vessel lining and the nitric oxide pathway the skin feeds into.
- Evening light and screens: the other end of the daily light signal, protecting the dark so the daytime sun holds.
- Circadian entrainment: how light sets the master clock, the mechanism underneath the timing advice.
Cautions For This Practice
Extra restraintEverything to be aware of is here, in one place. This practice suits most healthy people; a few situations call for real care.
Never burn, and protect children especially
A sunburn is skin damage, and a history of sunburn is one of the clearest melanoma risk factors, with childhood and adolescent burns carrying particular weight. Keep children out of burning sun with shade, clothing, and sunscreen. Protect against burning; you do not need to avoid daylight to be safe from skin cancer. Cumulative ultraviolet over a lifetime also ages the skin and adds to skin-cancer risk.
Tanning beds raise melanoma risk, most when started young
A tanning bed is pure ultraviolet with none of the daylight that comes with time outside. Ever using one raises melanoma risk, and starting before age 35 nearly doubles it. The risk climbs with each session. The tan it produces is accumulated DNA damage that protects against almost no later burning, and self-tanning lotions add the same color with no ultraviolet.
Watch changing moles and spots
Have a doctor check any mole or spot that changes over time. The ABCDE signs are the guide: an uneven, Asymmetric shape; an irregular Border; more than one Color; a Diameter wider than a pencil eraser; or Evolving size, shape, or color. Also check anything that bleeds, itches, or will not heal. Caught early, melanoma and the common skin cancers are usually very treatable, so a changing spot is worth a prompt appointment.
A past skin cancer or family melanoma means much less sun
A personal history of melanoma or another skin cancer, or a close relative with melanoma, shifts the balance hard toward protection. The safe amount of sun, and how often to have your skin checked, are best set with a dermatologist who knows your history.
Some medications and conditions make skin far more sun-sensitive
Certain drugs make the skin burn much faster. They include some antibiotics such as doxycycline, some diuretics, retinoids, and St John's wort, and conditions like lupus do the same. If a medication you take lists photosensitivity, treat your usual sun tolerance as much lower and cover up or use sunscreen sooner.
A suppressed immune system raises skin cancer risk sharply
Organ-transplant recipients and others on long-term immune-suppressing treatment have a much higher rate of skin cancer. This group needs strict, consistent sun protection and regular skin checks.
Skin type changes how much sun is safe
At high latitudes, darker skin is the most likely to fall short of vitamin D, because it makes the vitamin slowly while the available ultraviolet is already low. Very fair skin has the opposite problem: it burns before it has had much sun, so it needs the most cover. Set the dose to your own skin.
Protect the eyes
Ultraviolet harms the eyes over time, adding to cataracts and other damage, and staring at the sun can injure the retina. Sunglasses that block ultraviolet are worth wearing in bright conditions. Getting morning light means facing the open sky, with your eyes off the sun itself.
Start slow, be smart, read the research, and consult a professional if you have any concerns. This is here to inform your choice, not make it for you.
Common Questions
How much sun do I actually need for vitamin D?
Less than most people picture. For lighter skin under strong summer sun, uncovering the forearms and lower legs for a short spell a few times a week is plenty. Darker skin and northern latitudes need appreciably longer for the same amount.
Is the sun or a supplement the better way to get vitamin D?
For anyone with reliable daylight, brief non-burning sun is the natural source of vitamin D. It also delivers a body-clock and mood signal a capsule cannot. Where daylight is scarce (through a dark winter, on night shifts, or for someone housebound) a small daily D3 pill restores the vitamin and nothing else.
Does sunscreen block vitamin D?
In theory it filters the ultraviolet B that starts vitamin D. In practice people spread a fraction of the tested amount and reapply rarely, so the real-world drop is small. Studies of regular sunscreen users have generally not found them deficient. Since the vitamin is made early in a session, the short daily dose that gives the benefit is largely done before a long-exposure sunscreen matters.
Explore Related
Other pages this one connects to, by the evidence they share, the outcomes they touch, and the ground they cover.
All 6 sources on this page independently checked and cross-referenced.
Thomas Dehli, Founder & Editor, Sacred Lotus
Sacred Lotus has published Chinese medicine reference material since 2001. Integrative pages are held to the same standard as the herb and formula library: cite the source, grade the claim at its real strength, and say where the research has not looked. This page is educational and it is not medical advice. Last reviewed and updated August 9, 2026.
Evidence strength
How confidently the research supports a claim. Strength describes the evidence, not our endorsement.