How much sunlight you really need to get enough vitamin D
- Vitamin D can be obtained from the sun, certain foods, or through supplements.
- How much sunlight you need to get enough vitamin D depends on altitude, latitude, and skin color.
- In general, to get enough vitamin D from sunlight you only need about 10 to 15 minutes outside.
The sun is our most common source of vitamin D since it's rarely found in foods. In fact, when exposed to ultraviolet B (UVB) rays, our skin produces vitamin D naturally.
Yet, about 35% of adults in America have a vitamin D deficiency.
Important: Adults need about 15 micrograms of vitamin D daily to meet nutrient requirements.
And that's a problem since vitamin D is important for strengthening and maintaining bones, supporting a healthy immune system, and breaking down glucose in the body, says David J. Leffell, MD, chief of Yale Medicine Dermatologic Surgery and professor of dermatology at Yale School of Medicine.
Here's how to make sure you're getting enough of it from the sun.
How to get vitamin D from the sun
"It does not take excessive amounts of sun to get a healthy dose of vitamin D. It would be possible to get adequate vitamin D with limited exposure to your arms and legs for 10 to 15 minutes two to three times a week," says Susan Massick, MD, a dermatologist at The Ohio State University Wexner Medical Center and associate professor of dermatology in the Ohio State College of Medicine.
Several factors affect UVB exposure and vitamin D production, including:
- Time of day: The best time for sun exposure is noon since the sun is most intense, meaning you don't have to stay out as long to get an adequate amount of vitamin D.
- Skin color: Individuals with darker skin tones have more melanin, a natural pigment in the body that protects the skin from UV damage, so they tend to produce less vitamin D through sun exposure.
- Geographic location: People living in countries further from the equator usually get less vitamin D because more of the UVB rays are absorbed by the ozone layer.
- Altitude: People living at higher altitudes can produce more vitamin D because the UVB rays travel a shorter distance to the skin. In fact, a 2009 study found that there is a four-fold increase in vitamin D production at the Mount Everest base camp, which is approximately 5,350 meters (17,500 feet) above sea level compared to Agra, a city in India which is 169 meters (554 feet) above sea level.
However, you should avoid prolonged sun exposure, which is about 10 to 30 minutes for fair skin, because UVB rays also cause sunburns and photodamage, increasing the risk of skin cancer, says Massick.
Therefore, protect your skin by always using sunscreen or wearing protective clothing when outside - even in the winter. However, sunscreen does not block UVB rays perfectly, says Leffell. Therefore, it can prevent sunburn without compromising the body's vitamin D production.
When to take a vitamin D supplement
Vitamin D supplements are generally recommended for the following cases:
- Vitamin D deficiency
- Health conditions such as Crohn's disease or celiac disease, which impairs vitamin D absorption.
- Lactose intolerance or milk allergies, which increase the risk of vitamin D deficiency since people with these conditions are less likely to consume dairy products fortified with vitamin D.
- Darker skin tones, since their skin produces less vitamin D.
- Breastfed infants, because breast milk doesn't provide adequate amounts of vitamin D.
Talk to your primary care provider before taking any supplements to discuss the recommended amount of supplementation.
Important: Vitamin D is a fat-soluble vitamin, so it's best to take supplements with some fat from food to maximize absorption.
Insider's takeaway
You can generally get an adequate amount of vitamin D by spending time in the sun for about 15 minutes several times a week. However, skin color, geographic location, altitude, and time of day affect your UVB exposure and vitamin D production.
If you have a darker skin tone, vitamin D deficiency, or certain health conditions that affect your absorption or production of vitamin D, you can take supplements to meet the daily recommended allowance for your age.
"You certainly do not need prolonged and frequent sun exposure for the sake of vitamin D," Massick says. "When in doubt, get additional vitamin D through your diet rather than increasing your time in the sun," since the increased risk of skin cancer isn't worth the minimal extra amount of vitamin D you may gain.