Can Unprotected Sun Exposure Be Good for You?

Woman sitting on park bench outside
Michela Ravasio/Stocksy United

Most of us know to use sunscreen when we’re outside. After all, sunscreen minimizes the risk of skin cancer. However, constant use of sunscreen while outside prevents your skin from producing vitamin D. Although vitamin D is found in the foods that we eat, nearly one billion people worldwide are vitamin D deficient.

In addition to bone health, adequate levels of vitamin D may also mitigate the risk of various other diseases, such as diabetes, multiple sclerosis, and cancer.

Research suggests that spending several minutes a week in the midday sun sans sunscreen may help your body make the vitamin D that it needs and may currently be lacking.

Balancing Sunscreen Use and Adequate Sun Exposure

UV radiation from the sun is a cancer-causing agent (i.e., carcinogen) that is directly responsible for the majority of the 1.5 million skin cancer cases occurring in the United States each year. Moreover, ultraviolet radiation also is the major contributor to the 8000 deaths due to metastatic melanoma that occur each year. Metastatic melanoma is the worst type of skin cancer.

In addition to causing skin cancer, during a lifetime, the ultraviolet radiation in sunlight can lead to skin damage, cosmetic changes, and dryness.

Most of the time that you’re outside, you should definitely lather on a thick layer of sunscreen with an SPF of at least 15. Apply this sunscreen to any areas of your body exposed to the sun, including your face, arms, and legs.

Also, don’t forget to have a friend cover your back.

Even if it’s cloudy or cool outside, you should wear sunscreen. Sunscreen reflects, scatters, or absorbs ultraviolet radiation and protects you from its harmful effects. Make sure to avoid using sunscreen that’s expired.

You should also reapply sunscreen as needed.

For instance, after swimming, sweating, or toweling off, reapply sunscreen. You should also reapply sunscreen after being outside of the sun for two hours or more.

Although it’s a good idea to wear sunscreen with an SPF of 15 for most of the time that you’re outside, according to the NIH:

It has been suggested by some vitamin D researchers, for example, that approximately 5–30 minutes of sun exposure between 10 AM and 3 PM at least twice a week to the face, arms, legs, or back without sunscreen usually lead to sufficient vitamin D synthesis and that the moderate use of commercial tanning beds that emit 2%–6% UVB radiation is also effective. Individuals with limited sun exposure need to include good sources of vitamin D in their diet or take a supplement to achieve recommended levels of intake.

In other words, a couple times a week, you may want to go out in the sun for a brief walk without the protection of clothing or sunscreen. Please note that you don’t need to sunbathe per se—simply expose yourself to the warmth of the midday sun, since sunscreen does its job so well that much-needed vitamin D isn't getting through.

Vitamin D

Vitamin D is more akin to a hormone than a vitamin; vitamin D receptors are found on nearly every cell in the body.

In the body, vitamin D has many roles including the following:

  • bone metabolism
  • immune function
  • inflammation reduction
  • cell growth
  • nerve and muscle function

Of note, vitamin D helps with the absorption of calcium in the gut and maintains adequate concentrations of calcium and phosphate in the blood to mediate bone mineralization, bone growth, and bone remodeling.

In the body, vitamin D is first produced in the skin when the skin is exposed to the ultraviolet B (UV-B) radiation in sunlight. It’s then transported to the liver where it’s further metabolized. More than 90 percent of human vitamin D supply comes from sunlight.

Most people get at least some of their vitamin D from sunlight. Concentrations of vitamin D in the blood are the best indicators of potential deficiency.

During the past 20 years, vitamin D levels among American men but not American women have slightly declined. These declines in men are likely secondary to increased body weight, greater use of sun protection, and decreased consumption of milk.

Vitamin D is naturally found in just a few foods that we eat including the following:

  • egg yolks
  • fatty fish (e.g., salmon, tuna, sardines, trout, and mackerel)
  • cod liver oil
  • beef liver
  • portabella mushrooms

Vitamin D is also added to many (fortified) foods including the following:

  • milk
  • cheese
  • cereal
  • infant formula
  • orange juice

Dietary vitamin D is first absorbed in the small intestine then is further metabolized by the liver and kidney before making its way into the circulation.

Vitamin D Deficiency

Common causes of vitamin D deficiency include not enough exposure to sunlight, inadequate dietary intake, and problems with absorption. Because vitamin D is fat soluble, people with conditions that interfere with fat absorption, such as inflammatory bowel disease and gastric bypass, are at greater risk for deficiency.

The amount of UV-B radiation exposure that your skin receives depends on various factors including the following:

  • season
  • time of day
  • latitude
  • age
  • skin pigmentation
  • clothing
  • sunscreen use

People living in New England, the Midwest, and the Pacific Northwest don’t receive enough UV-B to produce vitamin D during winter months. Furthermore, proper application of sunscreen with a sun protective factor (SPF) of 15 or more prevents 99 percent of vitamin D synthesis in the skin. In fact, sunscreen with an SPF of 8 or above blocks vitamin D synthesis in the skin. Moreover, veils, headscarves, and other protective clothing prevent exposure to UV-B radiation and production of vitamin D in the skin.

Cloud cover reduces exposure to UV-B radiation by 50 percent, and shade—including that caused by pollution—reduces exposure by 60 percent. UV-B radiation doesn’t pass through glass; thus, sitting indoors in the sun won’t result in vitamin D production in the skin.

In adults, vitamin D deficiency presents as pain and muscle weakness. Pain in the hip, ribs, thigh, foot, and pelvis is typical of deficiency. Muscle weakness affects the limbs and back and can be confused with either fibromyalgia or depression.

Without adequate amounts of vitamin D, bones can become brittle, thin, and misshapen. Vitamin D deficiency results in rickets in children and osteomalacia in adults. In elderly people, vitamin D along with calcium protects against osteoporosis.

Some debate exists as to whether ample amounts of vitamin D can curb the risk of nonskeletal disease. Researchers are currently investigating the role of vitamin D in autoimmune disorders, heart disease, respiratory disease, cancer, infections, and fractures.

The recommended dietary allowance of vitamin D for all people between 1 and 70 years old is 600 IU (15 mcg). People older than 70 require 800 IU (20 mcg).

Vitamin D Supplements

People at risk for vitamin D deficiency should be screened by their primary care physicians. At-risk individuals include elderly people, those who receive limited sun exposure, those with darker skin, and those with certain illnesses (e.g., Crohn’s disease, celiac disease, and kidney disease).

In addition to limited unprotected sun exposure, people who are vitamin D deficient can take supplements. Vitamin D should also be give with calcium so as to promote bone health. Supplements can contain two iterations of vitamin D: vitamin D3 and vitamin D2. Vitamin D3 may be more beneficial than vitamin D2. Specifically although at nutritional doses, vitamin D2 and vitamin D3 may be equally beneficial, at higher doses, vitamin D2 is less potent. And people taking vitamin D supplements take high doses (i.e., 6000 IU daily).

A Word From Verywell

Most of the time, when you’re outside, you should don protective clothing and sunscreen with an SPF of 15 or greater. Protecting yourself from the sun’s ultraviolet radiation limits your risk of skin cancer. For between 5 and 30 minutes a couple times a week, it may be a good idea to enjoy the midday sun without the benefit of sunscreen or protective clothing—especially during the spring, summer, and fall months in northern latitudes. You don’t need to sunbathe, a brief walk will do. Getting some sunshine will help your body make necessary vitamin D.

Sources

Pearce, SHS, and Cheetham, TD. BMJ. 2010; 340:142-147.

Pfotenhauer, KM, and Shubrook, JH. Vitamin D Deficiency, Its Role in Health and Disease, and Current Supplementation Recommendations. The Journal of the American Osteopathic Association. 2017; 117(5):301-305.

Sunscreen. PubMed Health. www.ncbi.nlm.nih.gov.

Vitamin D: Fact Sheet for Health Professionals. NIH. www.nih.gov.

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