Can You Get Vitamin D from the Sun Through a Window? Myths vs. Facts

Can you get vitamin D from the sun through a window? Discover the truth behind this common myth and how it affects your health.

On sunny days, many of us seek the outdoors to soak up the sun's warmth and boost our mood. But what if you don't have outdoor space? What if it's winter, and you're stuck indoors? What if you have limited mobility or a medical condition that makes it difficult to go outside? In these cases, staying inside might be your best option for a short time to avoid excess sun exposure.

But this raises an important question: "Can you get vitamin D from the sun through a window?" In this article, we'll explore the answer to this question and give you tips on how to meet your vitamin D needs safely.

To help you track your sun exposure, we created an easy-to-use daily sunlight exposure tracker. How to measure Sun exposure. This simple tool can help you safely meet your vitamin D needs without relying on misinformation about sun exposure.

Table of Content

How Long Do You Need to Sit In the Sun to Get Vitamin D?

sunlight coming from window - Can You Get Vitamin D from the Sun Through a Window?

When it comes to sun exposure, timing is everything. Mid-day sun exposure is the best for optimum levels of vitamin D production. This would be between 11 am and 2 pm. This is because the angle through the atmosphere affects how much UV-B radiation you get exposed to. The sun is highest at noon, and the transited atmospheric thickness is lowest. The sun must be above an angle of 50 degrees from the horizon in order for UV-B rays to penetrate the atmosphere.

However, you must also know that the atmosphere may also contain smog sometimes, which absorbs the UV radiation and reduces this effect, and you might not get enough vitamin D on a smoggy day, even if you get the sun at noon. Early morning or end-of-the-day (evening) exposure to the sun is not practical in getting enough vitamin D, as the sun has tiny UV-B rays during this time.

Factors That Affect Vitamin D Production

It is difficult to quantify how much sunlight you should receive for vitamin D without being affected by skin cancer due to the UV rays. The darker the skin, the more it is protected against skin cancer, but the less able it is to absorb the UV-B rays. The skin color also depends on how much skin is exposed to the sun and the time of the day. If you are fair-skinned, you must go outside for 10 minutes in the midday sun wearing shorts and a tank top with no sunscreen, as this will provide you enough radiation to produce about 10,000 international units of vitamin D.

However, dark-skinned individuals and elderly people produce less vitamin D, and many do not get enough nutrients from their dietary sources, such as fatty fish and fortified milk. So, if you are black-skinned, you require six times the sun exposure to make the same amount of vitamin D levels (from sunlight) as a very fair-skinned person would. In case you are of Hispanic origin or already tan, you may require 15 to 20 minutes to be in the sun to make enough vitamin D.

The Shadow Trick

This trick works great to get the most vitamin D from your daily sun exposure. You can sit in the sun when your shadow is shorter than your height. This means that in winter, with the sunlight at a slant, your optimal sunbathing time is narrowed considerably.

Can You Get Vitamin D from the Sun Through a Window?

Sunlight, Vitamin D, and You: Are You Getting Enough?

Are you getting enough sunlight? The data suggest maybe not. The Cleveland Clinic reports that vitamin D deficiency is a global problem: One billion people worldwide and approximately 35% of U.S. adults are deficient in this critical vitamin, which has many health benefits (including some that save lives!). If you don’t get enough regular exposure to sunlight, you can eat more vitamin D-rich foods or find the right vitamin D supplement based on your nutritional needs. You can also get vitamin D from the sun.

Harvard Health‘s Blog Explains

“The sun’s energy turns a chemical in your skin into vitamin D3, which is carried to your liver and then your kidneys to transform it to active vitamin D.”

Can You Get Vitamin D Through a Window?

Enjoying the sun’s warmth can be soothing—but can you get vitamin D through a window? Or do you have to be outside? “Ultraviolet B radiation (UVB) radiation is the type of radiation from the sun that triggers vitamin D production in the body and turns it into the active form of vitamin D,” explains Grant Radermacher, DC, a chiropractor in Wisconsin. However, as it turns out, UVB radiation is blocked mainly by ordinary window glass. So, no, you can’t get vitamin D through a window. There are actually two pieces of unfortunate news here:

First, you can’t get vitamin D through a window; second, you can get sun damage. Says Carly King, ND, a naturopath in Ontario, CA: “Since glass absorbs all UVB radiation, exposure of the skin to sunlight that passes through glass, plexiglass, and plastic will not result in any production of vitamin D in the skin. But glass doesn’t block UVA rays, so sun damage from window exposure is still a concern,” Dr. King says. (Just take car windows as an example: That may be a reason the area around the eyes is one of the body parts most at risk for skin cancer.)

Are All Windows the Same?

Not all types of glass are created equal, though. “While ordinary glass blocks most UVB rays, specialized glass, such as low-E glass, allows more UVB rays to pass through,” Dr. Radermacher says. Still, you shouldn’t expect to synthesize much vitamin D from sunlight exposure through a window.

How Your Body Gets Vitamin D From the Sun

It’s important to note that we don’t actually “get” vitamin D from the sun in the same way that we get it through supplements or from eating foods like tuna, salmon, or eggs. What happens is that the body produces vitamin D when exposed to UVB rays, which triggers vitamin D synthesis.

Says BreAnna Guan, ND, a Boston-based naturopathic physician. “Most of the UVB radiation (290 to 320) nm [nanometer] is absorbed by the ozone layer,” Dr. Guan says, “and is most abundant when the sun is overhead in summer months between the hours of 10 a.m. and 2 p.m.” You don’t need to spend much time out there (Guan suggests 10 to 15 minutes, max).

Also, apply sunblock. You’ll still get the exposure your body needs to make vitamin D.

What Is a Safe Way to Get Enough Sun to Meet Our Vitamin D Needs?

sunlight - Can You Get Vitamin D from the Sun Through a Window?

How to Safely Get Vitamin D From Sun Exposure

To get Vitamin D safely from the sun, try getting direct sunlight early in the morning or late afternoon when UVB rays are lower, and you have the least chance of harming your skin. Any part of your body can get Vitamin D, so consider having your legs or arms in the sun rather than your face, head, and neck, which may get more sun exposure naturally throughout your lifetime. Wear a hat and sunglasses to protect your face, head, and eyes while exposing other body parts. Since the head is a small part of the body, it will only produce a small amount of Vitamin D anyway.

How Skin Type and Geography Impact Vitamin D Production

The amount of Vitamin D your skin produces depends on several factors, including the time of day, season, latitude, and skin pigmentation. People with darker skin typically have more pigment called melanin than people with lighter skin, which naturally helps protect their skin against sun damage.

But then this means that darker-skinned people need to spend longer in the sun than lighter-skinned people to produce the same amount of Vitamin D – a significant reason why darker-skinned people have a higher risk of deficiency. Also, depending on where you live and how much sunlight your area gets, you may only get very little or almost no Vitamin D during the winter.

Other Sources of Vitamin D

Vitamin D can also be found in foods like fatty fish such as salmon, sardines, and mackerel. However, because it is not naturally found in many foods, look for it in fortified milk, cereals, and yogurt. Packaging for these foods should list if they are fortified with Vitamin D, and you can check the nutrition label for the exact amount per serving. Overall, the amount of Vitamin D adults get from their diets is often less than recommended. Especially in northern Indiana, where we don’t get much sunlight during the winter, the result can be low Vitamin D levels or seasonal affective disorder.

How to Address Seasonal Mood Disorders Related to Low Vitamin D Levels

Talk with your doctor about the use of a lightbox to address seasonal mood disorder. But remember that the sun’s UVB rays cannot penetrate through windows and don’t come from artificial lights, so if you sit or work next to sunny windows or electric lights, you are not getting Vitamin D and can still be prone to a deficiency. Many older adults do not get regular exposure to sunlight (especially in the winter) and may also have trouble absorbing Vitamin D.

A simple and regular blood check by your doctor’s office can monitor your Vitamin D level. Your doctor may recommend a daily multivitamin or Vitamin D supplement like cod liver oil to help with your bone health or to help with symptoms of fatigue or mood, especially in the winter.

The Dangers of Too Much Vitamin D

But don’t overdo it. Too high levels of Vitamin D have not been shown to provide more benefits, and too much has been linked to other health problems like constipation, confusion or kidney stones. Always talk with your doctor about what’s right for you.

Download Our App to Track your Daily Sunlight Exposure Today

Sun Exposure App - Can You Get Vitamin D from the Sun Through a Window?

SunSeek helps you optimize your daily sunlight exposure by tracking and providing personalized recommendations based on your location, skin type, and health goals. The app combines real-time UV monitoring with guided outdoor activities to help you improve sleep, boost energy levels, and maintain optimal vitamin D levels throughout the year.

By aligning your daily routine with natural light cycles, SunSeek makes equipped sunlight's health benefits easy while ensuring safe exposure through personalized timing recommendations and cloud coverage forecasts. Download our app now to track your daily sunlight exposure.