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Sun exposure and health

Also sunlight health, sun avoidance mortality, UV exposure benefits.

Avoiding the sun entirely carries its own risk. Burning carries the melanoma risk.

Updated 18 Oct 20266 sources4 min read
Short answer

Sun exposure has benefits beyond vitamin D. In a Swedish cohort of nearly 30,000 women followed for 20 years, sun avoiders had higher all-cause mortality, mainly from cardiovascular and other non-cancer deaths, with a gap comparable to smoking. UVA light releases nitric oxide from the skin and lowers blood pressure in small studies. The trade-off is skin cancer: melanoma risk is tied mainly to intermittent intense exposure and sunburn. The evidence is observational, so causality is not settled.

Summary drafted from this entry’s sources; editorial review pending.

01Key questions

Do sun avoiders die earlier?

In the Swedish MISS cohort of 29,518 women, those who avoided the sun had about twice the all-cause mortality over 20 years of those with the most exposure (Lindqvist et al., 2014 and 2016). The data are observational.12

How could sunlight lower blood pressure?

UVA light releases nitric oxide stored in the skin, which widens blood vessels. In a small study, UVA exposure lowered blood pressure independent of vitamin D (Liu et al., J Invest Dermatol 2014). In 342,457 US dialysis patients, higher local UV was associated with lower systolic blood pressure (Weller et al., JAHA 2020).34

What about melanoma?

A meta-analysis found melanoma risk tied mainly to intermittent intense sun exposure and sunburn, while high continuous occupational exposure was, if anything, inversely associated (Gandini et al., 2005).6

Does daylight affect health in other ways?

In 88,905 UK Biobank participants who wore light sensors, brighter days and darker nights were each linked to lower mortality, largely through cardiometabolic deaths (Windred et al., PNAS 2024). The study measured light, not UV.5

Public-health advice on sunlight has focused almost entirely on one harm: skin cancer. That harm is real. But a body of cohort, mechanistic and light-sensor research suggests that regular, non-burning sun exposure has benefits that vitamin D pills do not reproduce, from lower blood pressure to lower all-cause mortality. This entry sets out both sides with the numbers, because sun advice that ignores either one is incomplete. For vitamin D specifically, see Vitamin D optimization.

02Sun avoidance and mortality: the Swedish cohort

The Melanoma in Southern Sweden (MISS) cohort followed 29,518 women aged 25 to 64 for 20 years. Women who avoided the sun had about twice the all-cause mortality of those with the most active sun-exposure habits (PMID 24697969). A follow-up competing-risk analysis found:

  • The survival gap came mainly from fewer cardiovascular and other non-cancer deaths among sun-seekers.
  • Because sun-seekers lived longer, cancer made up a larger share of their deaths.
  • Non-smokers who avoided the sun had a life expectancy similar to smokers with the most sun exposure; avoiders lost 0.6 to 2.1 years of life expectancy (PMID 26992108).

This is observational. Women who spend time in the sun may be healthier, more active or wealthier in ways a questionnaire cannot fully capture, and the cohort is Swedish women only, at a latitude where UV is weak much of the year.

03Mechanism: UVA, nitric oxide and blood pressure

Skin stores nitric oxide (NO) compounds. In 24 healthy volunteers, UVA exposure lowered blood pressure and raised circulating nitrite, and forearm blood flow increased independently of the NO-producing enzymes, pointing to release of pre-formed NO stores in the upper skin. This effect has nothing to do with vitamin D, which is made by UVB (PMID 24445737). At population scale, in 342,457 US dialysis patients, higher local UV was associated with lower systolic blood pressure even after adjusting for temperature (PMID 32106744).

04Light timing: bright days, dark nights

In 88,905 UK Biobank participants who wore light sensors for a week, brighter daytime light was linked to incrementally lower all-cause mortality over 8 years (adjusted HR as low as 0.66 to 0.83 in the brightest tenth), and brighter night-time light to higher mortality (HR up to 1.21 to 1.34), largely through cardiometabolic deaths (PMID 39405349). The study measured light, not UV or time outdoors, so it supports bright days and dark nights rather than sun exposure as such. See Sleep optimization for the circadian side.

05The melanoma trade-off

The pattern of exposure matters. A meta-analysis of 57 studies found that intermittent intense exposure and a history of sunburn are clear risk factors for melanoma, whereas high, continuous occupational exposure was, if anything, inversely associated with it (PMID 15617990). In the Swedish cohort, sun-seekers' longer lives came with a larger share of cancer deaths (PMID 26992108). The trade-off is real and depends on skin type, latitude and burning: the evidence for benefit is about regular exposure that does not burn, and none of it supports tanning beds or sunburn.

For people who have already had non-melanoma skin cancer, oral nicotinamide has phase 3 evidence for reducing new ones (see Nicotinamide for skin cancer and glaucoma).

06Where it sits on the Heretic scale

Promising. Consistent observational associations with lower mortality and blood pressure, a plausible vitamin-D-independent mechanism shown in a controlled human study, and a large objective light-sensor cohort. No randomized trial of sun exposure on hard outcomes exists, and the skin-cancer cost is established. What would move it: trials of controlled UV or daylight exposure on blood pressure and cardiometabolic outcomes. Related: Red light therapy, which uses the visible and near-infrared part of the spectrum without UV.

Further reading: detailed protocols

07Connections

Neighborhood · 4 linked entriesOpen full map →
Vitamin DCompound · 10 links→ Red light therapyTherapy · 14 links→ SleepGuide · 20 links→ Nicotinamide for skin cancer and glaucomaCompound · 2 links→

08Sources

  1. Lindqvist PG, et al. (2014). "Avoidance of sun exposure is a risk factor for all-cause mortality: results from the Melanoma in Southern Sweden cohort." J Intern Med 276(1):77-86. PMID 24697969 . DOI 10.1111/joim.12251PubMed 24697969 · DOI 10.1111/joim.12251
  2. Lindqvist PG, et al. (2016). "Avoidance of sun exposure as a risk factor for major causes of death: a competing risk analysis of the Melanoma in Southern Sweden cohort." J Intern Med 280(4):375-87. PMID 26992108 . DOI 10.1111/joim.12496PubMed 26992108 · DOI 10.1111/joim.12496
  3. Liu D, et al. (2014). "UVA irradiation of human skin vasodilates arterial vasculature and lowers blood pressure independently of nitric oxide synthase." J Invest Dermatol 134(7):1839-1846. PMID 24445737 . DOI 10.1038/jid.2014.27PubMed 24445737 · DOI 10.1038/jid.2014.27
  4. Weller RB, et al. (2020). "Does Incident Solar Ultraviolet Radiation Lower Blood Pressure?" J Am Heart Assoc 9(5):e013837. PMID 32106744 . DOI 10.1161/JAHA.119.013837PubMed 32106744 · DOI 10.1161/JAHA.119.013837
  5. Windred DP, et al. (2024). "Brighter nights and darker days predict higher mortality risk: A prospective analysis of personal light exposure in >88,000 individuals." Proc Natl Acad Sci U S A 121(43):e2405924121. PMID 39405349 . DOI 10.1073/pnas.2405924121PubMed 39405349 · DOI 10.1073/pnas.2405924121
  6. Gandini S, et al. (2005). "Meta-analysis of risk factors for cutaneous melanoma: II. Sun exposure." Eur J Cancer 41(1):45-60. PMID 15617990 . DOI 10.1016/j.ejca.2004.10.016PubMed 15617990 · DOI 10.1016/j.ejca.2004.10.016

09Entry history

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