Dr. Paul Mason - 'Sunlight and health - from Vitamin D to Fish oil'
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Dr Paul Mason obtained his medical degree with honours from the University of Sydney, and also holds degrees in Physiotherapy and Occupational Health. He is ...

Paul Mason argues that sunlight’s health effects are not primarily explained by vitamin D, but by broader ultraviolet-light biology, especially UVA-driven nitric oxide release that may lower blood pressure and improve metabolic markers. He links sun exposure with lower mortality in cohort data, while distinguishing timed, lower-UVB exposure from sunburn-heavy exposure that raises skin-cancer risk. He also argues that nicotinamide, omega-3 intake, and lowering omega-6-rich seed oils may reduce ultraviolet-related skin-cancer risk while preserving sunlight’s systemic benefits.

summerizer

Sunlight, mortality, and ultraviolet light

  • Sunshine has health value, and the benefit is not mostly about vitamin D.
  • Death rates peak in winter in both hemispheres, with lower seasonal variation near the equator.
  • A Swedish cohort of more than 38,000 women linked sunbathing vacations with lower mortality over follow-up.
  • The same Swedish data linked no sunburn history with higher death rates than some sunburn-history groups.
  • The Melanoma in Southern Sweden cohort linked active sun avoidance with the highest mortality over 20 years.
  • In that cohort, smokers with high sun exposure had mortality similar to nonsmokers with low sun exposure.
  • Skin cancer risk rises with ultraviolet exposure, but the mortality pattern is more complex than skin cancer alone.
  • A Danish whole-population study of adults over 40 found little lifespan difference with melanoma and longer survival with non-melanoma skin cancer.
  • That pattern does not make skin cancer harmless; it indicates sun exposure can have benefits even when skin cancer occurs.

UVA, UVB, vitamin D, and nitric oxide

  • UVA reaches the ground readily, UVB is reduced more by ozone and atmospheric path length, and UVC does not reach the ground.
  • UVB is the major driver of sunburn and a major driver of skin cancer, while also making vitamin D in skin.
  • UVA has less skin-cancer involvement than UVB, contributes to skin aging, and releases nitric oxide from skin.
  • Nitric oxide is the key mechanism for the mortality benefit because it relaxes blood vessels and lowers blood pressure.
  • Vitamin D tracks sunlight exposure and therefore tracks mortality, but it is mostly a marker for sunlight biology here.
  • Vitamin D remains important for bone health; deficiency can cause rickets and remains a public health issue.
  • Diet supplies only a small share of daily vitamin D needs, with fatty fish, liver, eggs, and fortified margarine as sources.

Vitamin D observations versus supplementation

  • A 32-study meta-analysis linked low vitamin D levels with nearly double the mortality risk of high vitamin D levels.
  • A German ESTHER cohort of 9,578 adults aged 50 to 74 linked lower vitamin D with higher mortality over 9.5 years.
  • A randomized vitamin D trial of more than 2,600 people found no clear mortality difference after about five years.
  • Two systematic reviews found large observational benefits but no significant mortality benefit from vitamin D tablets.
  • These results make vitamin D supplementation a poor explanation for the large lifespan differences tied to sunshine.

Nitric oxide, blood pressure, and blood glucose

  • Real UVA exposure lowered blood pressure more than sham exposure in a human experiment.
  • Seasonal blood pressure falls in summer and aligns closely with UVA exposure.
  • High blood pressure is a major risk factor for heart attack, stroke, and vascular disease, with heart attacks peaking in winter.
  • Nitric oxide also improves insulin sensitivity, and sodium nitroprusside increased insulin-mediated glucose removal.
  • HbA1c is lower in summer than winter in northern-hemisphere data, matching the nitric-oxide pathway.

Safer sun timing

  • Lower sun gives proportionally more UVA and less UVB, making morning and late-day sunlight more favorable.
  • The UV index mainly reflects sunburn potential from shortwave UVB; a higher value burns faster on a linear scale.
  • At UV index 2 or lower, most people have little sunburn risk; at 3 or 4, many can spend about an hour unprotected.
  • Skin type and sun-sensitizing medications change the risk, so fixed timing rules are not universal.
  • Shadow length is a practical guide: a shadow at least as tall as the body usually means lower UVB exposure.
  • Heat is a poor guide to UV exposure because temperature can peak when UV radiation is already low.

Reducing skin-cancer risk

  • Diabetes raises skin-cancer risk, while higher lifetime metformin use was linked with lower skin-cancer risk.
  • In a Sydney trial, nicotinamide at 500 mg twice daily for 12 months reduced non-melanoma skin cancers, mainly squamous cell carcinomas.
  • High-dose fish oil in 15 volunteers more than doubled the UVB dose needed to cause sunburn after six months.
  • The fish-oil benefit wore off after stopping, so ongoing intake was needed for the sunburn-resistance effect.
  • UV radiation suppresses skin immunity, and immune suppression raises skin-cancer risk.
  • In 79 females, omega-3 intake reduced solar-simulated UV immune suppression after three months.
  • A review and meta-analysis of 11 studies linked high omega-3 intake with a 48% lower melanoma risk.

Omega-6, omega-3, and diet

  • Vegetable and seed oils are rich in omega-6 and low in omega-3, pushing the fat balance away from omega-3.
  • Omega-6 fats drive series 2 prostaglandins, inflammation, and carcinogenic activity after ultraviolet exposure.
  • Omega-3 fats drive series 3 prostaglandins that inhibit those processes.
  • A 12-week low-omega-6 diet raised red-blood-cell EPA by 21 percent and lowered omega-6 markers by about 21 to 26 percent.
  • A low-omega-6 plus high-omega-3 diet raised omega-3 by 271 percent and lowered omega-6 by 50 percent without supplements.
  • The practical target is appropriate sun exposure: more UVA, less UVB, adequate vitamin D, and a better omega-6 to omega-3 balance.
  • Very high sunlight avoidance probably causes more harm than benefit, while timed exposure and diet can make sunlight safer.

References