How Much Sunlight do I Need to get Vitamin D?

How Much Sunlight do I Need to get Vitamin D?


Who doesn’t love the sunshine? When absence makes the heart grow fonder of it in the dead of winter, or on a shady day, we miss and love the sunshine that much more.

Sunlight exposure is the most natural way to absorb vitamin D, which is produced when the sun’s ultraviolet B (UVB) rays reach cholesterol in the skin cells, setting off vitamin D synthesis.   

Vitamin D helps prevent bone loss, depression, diabetes, multiple sclerosis, and hypertension, among other health benefits. People deficient in “the sunshine vitamin” may experience muscle weakness and bone pain.    

The Skin Cancer Foundation states that people severely deficient in vitamin D may experience slower growth, bone softening and weakened bone structure.

But the line between safe and dangerous levels of sunlight is unfortunately very thin.

Midday sun is good for vitamin D

The sun is at its highest point in the middle of the day, making that the most efficient time of day to soak up sunlight.   

Some Vitamin D researchers suggest that approximately 5 to 30 minutes of sun exposure – particularly between 10 a.m. and 4 p.m. – either daily or at least twice a week to the face, arms, hands, and legs without sunscreen, usually leads to sufficient vitamin D synthesis.

This level of sun exposure produces vitamin D in the skin that may last twice as long in the blood compared with ingested vitamin D, according to a Journal of Clinical Investigation study on the process of an individual’s vitamin D intake.

But simply strolling along the sidewalk for a half hour each afternoon isn’t a cut-and-dried solution for just everyone.

Season, time of day, length of day, cloud cover, smog, skin melanin content and the topical application of sunscreen are among the factors that affect UV radiation exposure and vitamin D synthesis.

Can too much sun be dangerous?

That thin line between safe and dangerous levels of sunlight can manifest itself if you are out in the sun for too long. Anyone who’s ever endured a sunburn – which, is pretty much everyone – can attest to that.

But there are other dangers of too much sunlight, including:

Eye damage

The development of moles, freckles, and other changes to the skin

Aging skin

Heat stroke

Skin cancer

Understanding the ultraviolet index and getting adequate sun in the winter

During the winter, vitamin D deficiency can be more prevalent because there is less sunlight available.

When the Ultraviolent (UV) Index is low, taking in enough sunlight needed to produce vitamin D becomes more challenging.

The UV Index provides a daily forecast of the expected intensity of the UV radiation from the sun. By entering your zip code or city name into the UV Index page on the Environmental Protection Agency’s (EPA) website, you can read the UV Index levels on a given day.

When the UV Index sits below 3, like it regularly does in the fall and winter, you might want to bundle up in your warmest winter clothes, fight the elements, and spend a little time walking through your neighborhood or a local park.

Here is a full reading of the UV Index, according to the EPA:

Low (0-2): No protection needed. You can safely stay outside using minimal sun protection.   

Moderate to high (3-7): Protection needed. Seek shade during late morning through mid-afternoon. When outside, generously apply broad-spectrum SPF-15 or higher sunscreen on exposed skin, and wear protective clothing, a wide-brimmed hat, and sunglasses.

Very high to extreme (8-10): Extra protection is needed. Be careful outside, especially during late morning through mid-afternoon. If your shadow is shorter than you, seek shade and wear protective clothing, a wide-brimmed hat, and sunglasses, and generously apply a minimum of SPF-15, broad-spectrum sunscreen on exposed skin.

Read on:

Cold Weather Clothing Tips: Gear to Wear and How to Layer

How Cold is too Cold for your Pet?

Steps to take for a Safe Return to the Gym

We hope you enjoyed this blog from Blue Cross Blue Shield's A Healthier Michigan

Our mission is to help everyone in Michigan get healthier from the inside out. This means everything from giving you resources to help you make better decisions about diet and exercise, as well as information on creating and sustaining nurturing communities and successful businesses — everything you need to help create a healthier Michigan. Read more at www.ahealthiermichigan.org.

Photo credit: Getty Images

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