Sunshine and Healthy Aging: Understanding UVA, UVB and Infrared

HealthyRetired — The Healthy Aging Project
Draft article • 6 October 2026

We spend plenty of time discussing what we eat. But our bodies also respond to the light around us. A morning outdoors can give the day a pleasant start, while sunlight on the skin helps us produce vitamin D. Understanding these benefits means looking beyond the simple idea that sunshine is either good or bad.

Living in Hua Hin, I enjoy swimming and spending time outside. I wear a cap when swimming or sunbathing. For healthy aging, my aim is to enjoy outdoor life while respecting the strength of the tropical sun.

Sunlight contains visible light, ultraviolet radiation and infrared radiation. Each affects us differently. Feeling warm tells us very little about how much ultraviolet radiation we are receiving.

Part of sunlight	Main effect relevant to health	Important limit
Visible light	Signals daytime to the body clock through the eyes	Looking directly at the sun can damage the eyes
UVA	Can release nitric oxide from stores in the skin	Also contributes to skin aging and skin cancer
UVB	Starts vitamin D production in the skin	Also causes sunburn and contributes to skin cancer
Infrared	Transfers energy that warms the skin and body	Excess exposure can cause overheating and thermal injury

Daylight: a daily signal for the body clock

Light reaching the eyes helps the brain coordinate our circadian rhythm: the daily cycle that influences sleep, hormone release, appetite and body temperature. The brain uses light information to regulate melatonin, a hormone involved in sleepiness. [1]

Getting outdoors in the morning is a practical way to give the day a clear light signal. An easy walk, some Tai Chi or breakfast on a shaded terrace can make this an enjoyable routine. This benefit comes from visible light; you do not need to expose bare skin to ultraviolet radiation or stare at the sun.

For retirees, a regular daylight routine also gives shape to a day that no longer follows a work schedule. Make outdoor time part of daily life, rather than treating sunshine as a medicine that requires a particular dose.

UVB: how sunshine helps make vitamin D

UVB starts a chemical process in the skin that produces vitamin D3. Vitamin D supports calcium absorption and normal bone and muscle function. Maintaining adequate levels matters as we age. [2]

However, sunshine is an unpredictable source. Production depends on skin pigmentation, age, season, time of day, clothing and other conditions. Older skin makes vitamin D less efficiently. Ordinary window glass blocks UVB, so sitting in sunshine behind a closed window does not produce vitamin D in the same way. [2]

There is no reliable rule that everyone should spend a fixed number of minutes in the sun. A routine suitable for one person may burn another. Living in a sunny country also does not guarantee adequate vitamin D.

Fortified foods and supplements can provide vitamin D without additional UV exposure. People eating a plant-based diet can choose vitamin D2 or vegan vitamin D3 sourced from lichen. If deficiency is suspected, discuss assessment and an appropriate dose with a clinician. [2]

UVA: an interesting connection with nitric oxide

UVA penetrates the skin more deeply than UVB. It does not provide the vitamin D benefit, but researchers have identified another effect: releasing nitric oxide from compounds already stored in the skin.

Nitric oxide helps blood vessels relax. In a controlled study involving 24 healthy volunteers, UVA exposure increased blood flow and lowered blood pressure temporarily. The effect was independent of vitamin D production. [3]

This is an interesting biological finding, not proof that deliberate UVA exposure prevents heart attacks or safely treats hypertension. A short experiment cannot establish the long-term balance between cardiovascular benefits and skin damage. UVA should not replace blood-pressure treatment, and tanning beds are not a health strategy.

Infrared: the warmth we feel

Infrared is invisible radiation beyond the red end of the visible spectrum. It includes near-, mid- and far-infrared wavelengths. Its effects depend on wavelength, intensity and exposure time. Absorbed infrared energy can warm our tissues. [4]

Gentle warmth can feel pleasant. But comfort is different from evidence that exposure heals organs, reverses aging or detoxifies the body. Those claims should not be assumed simply because infrared is part of natural sunlight.

Research involving controlled red-light or near-infrared treatment devices also cannot automatically be applied to sunbathing. A device delivers particular wavelengths and doses; sunshine delivers a changing mixture of light, UV and heat.

Excess infrared exposure can injure the skin or eyes, and whole-body heat exposure can cause heat stress. Humidity, air temperature and airflow affect that risk too. In Thailand, more warmth is not necessarily something the body needs. [4]

Enjoying sunshine sensibly

Both UVA and UVB contribute to skin cancer. UV exposure can also damage the eyes. Protection is recommended when the UV Index reaches 3 or above. Clouds and a cooling breeze do not reliably make exposure safe. [5]

A cap is a useful start, although a broad-brimmed hat covers more of the ears and neck. Combine shade, suitable clothing, UV-protective sunglasses and broad-spectrum sunscreen. When swimming, use water-resistant sunscreen and reapply according to its instructions, especially after swimming or towelling. [5]

Choose comfortable times for outdoor activity, take breaks in shade and drink water. If you feel dizzy or unwell in the heat, stop and cool down. Morning outdoor time can support a pleasant daily routine, but it should not be presented as a guaranteed vitamin D dose.

What does Dr Michael Greger say?

On NutritionFacts.org, Dr Michael Greger discusses the benefits and risks of sun exposure and points out that vitamin D can be obtained from supplements without deliberately exposing the skin to UV. He also cautions against interpreting observational findings about sun exposure and longevity as proof that sunbathing itself extends life. People who spend more time outdoors may also exercise more. [6]

That is a useful distinction for HealthyRetired. Outdoor life offers light, movement and enjoyment. We can value those experiences while remaining careful about claims that a particular type of radiation is an anti-aging treatment.

For me, vivere parvo fits here too: a simple morning outdoors costs little. Enjoy the daylight, move your body and give your skin protection when it needs it.

Sources and further reading

This article provides general information, not an individual sun-exposure or treatment prescription.