Can You Get Vitamin D Through a Window?

Quick Health Scoop

• Vitamin D, also known as the sunshine vitamin, is a fat-soluble vitamin that supports bone health, muscle function, immune system function, and heart health.^†
• Your body can make Vitamin D when the skin is exposed to sunlight, but there are a lot of variables that can affect this process.
• You can’t get Vitamin D through a window and most people don’t spend enough time outdoors to meet their needs.
• The best way to increase Vitamin D levels is through a combination of sunlight exposure, diet, and supplementation.

Sunlight stimulates your body to make Vitamin D, a fat soluble vitamin that plays a big role in health and quality of life. If you don’t get outside much, you may be wondering: can you get Vitamin D through a window? Do hours spent working near a sunny window or driving help you make enough of the sunshine vitamin?

The short answer is: no, the rays you receive through a window aren't the same as being directly outdoors under sunlight. The glass between you and the sun acts as a buffer, absorbing the ultraviolet rays that send the start signal to your body’s Vitamin D production. [1] [2]

In fact, you may not be getting as much Vitamin D from sunshine as you think. Your body becomes less efficient at making Vitamin D with age and the process depends on a lot of factors, including geographic location, season, and skin tone. A three-pronged approach that includes time outdoors, nutrition, and supplementation is your best bet for increasing your Vitamin D level.

Read More: Everything You Need to Know About Vitamin D

How Much Vitamin D Comes Through a Window?

You’ll get zero Vitamin D sitting in a sunny window seat, whether it’s in your house, car, or another form of transportation. Glass absorbs 100% of the sun’s ultraviolet B (UVB) rays, which signal your body to make Vitamin D. [1] [2]

To make Vitamin D the old-fashioned way, your skin needs exposure to direct sunlight. It may not be enough to just get outdoors, though. Clothing, sunscreen use, age, and skin tone can also impact Vitamin D synthesis. Individuals with darker skin tones make less Vitamin D from sunlight than those with fair skin tones. [1] [2]

To maximize your time in the sun and improve Vitamin D levels:

• Get outdoors between 10AM and 3PM, which is when sunlight is strongest.
• Wear a short-sleeved shirt and/or shorts when temperatures allow you to maximize skin exposure.
• Aim for 15 minutes of unprotected sun exposure before applying sunscreen or moving to shade, since sun protective measures block Vitamin D production.

The strength of the sun changes with the season, time of day, and geographic location. It’s harder to make Vitamin D from the sun during winter and in high latitude locations due to the position of the sun. Air pollution and overcast days also interfere with how much sunlight can reach your skin. [1] [2]

Read More: How Much Vitamin D Do You Really Get From The Sun?

Other Ways to Get Vitamin D

Since sunlight varies, food and supplements can help you meet your Vitamin D needs year-round.

Eating Foods with Vitamin D

If you don’t get outside much, you may be wondering what foods have Vitamin D.  There aren't many foods that naturally contain vitamin D. Some foods are fortified with vitamin D to contribute to vitamin D intake.  Some fortified foods contain vitamin D2, which is not as effective at raising levels as the D3 form. [3]

The best food sources of Vitamin D include: [2]

• Fatty fish, such as salmon, mackerel, tuna, and sardines
• Egg yolks
• Mushrooms
• Fortified cow’s milk and plant-based milk alternatives, such as soy and almond milk
• Fortified orange juice
• Fortified breakfast cereals

Vitamin D is included on the Nutrition Facts label as a percent Daily Value, meaning what percent of your day’s needs are met by one serving of a food or beverage.

Taking Vitamin D Supplements

It can be hard to get enough Vitamin D from food since it’s natural for everyone’s food intake to vary from day to day. A dietary supplement that contains Vitamin D can help fill in gaps in your diet, as well as to help ensure you’re getting the Vitamin D you need during the shorter, darker days of winter when there are fewer hours of sunshine.^†

A supplement is an especially good idea if you live in a smoggy city or have been advised by a healthcare provider to avoid unprotected sun exposure for skin health.

You can find Vitamin D in multivitamins and as stand-alone supplements. Vitamin D3 supplements tend to contain higher doses than those found in multivitamins. For example, Nature Made® men’s and women’s multivitamins contain 1,000 IU (25 mcg) of Vitamin D3, or 125% of daily needs, per serving. We also have a full line of Vitamin D3 supplements that range from 1,000 to 10,000 IU (25 to 250 mcg) per serving.

Your healthcare provider can help you determine where your current Vitamin D levels fall, how much you need to take per day, and which supplement is best for your needs.

Why Should I Care About Vitamin D?

Vitamin D is an essential nutrient that plays a role in supporting healthy bones, muscles, immune system function, and more.^† [2]

Vitamin D supports bone health by enhancing calcium absorption, so calcium is available to support strong bones. ^† [2]

Normal muscle function, including contraction and relaxation, relies on the presence of Vitamin D in the body.^† [5]

A number of studies have found Vitamin D supports normal immune system function. Research also suggests adequate Vitamin D supports heart health. More research is needed to understand the connection between Vitamin D, immune, and heart health.^† [6] [7]

Read More: What Is Vitamin D Deficiency? Symptoms, Causes, and Treatment Options

Bottom Line

Your body makes Vitamin D from sunlight, but can you get Vitamin D through a window? Sitting beside a sunny window doesn’t help you meet your Vitamin D needs, since glass absorbs all of the ultraviolet B rays that stimulate Vitamin D production.

Most people don’t spend enough time outdoors to make enough Vitamin D and for some, like those located in northern latitudes, the sun’s rays aren’t consistent enough to support Vitamin D synthesis for much of the year.

That means to support adequate levels of Vitamin D year-round, most people can benefit from including both food and supplement sources of Vitamin D. If you have questions about your Vitamin D intake or want to have your levels checked, speak with your healthcare provider.

Learn More About Vitamin D:

• How Much Vitamin D Do You Need Per Day?
• What Helps Vitamin D Absorption?
• Vitamin D Immune System Benefits: How Does It Help?

Follow @NatureMadeVitamins on Instagram for new product news, healthy tips, and more.

† These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease.

References

1. Wacker M, Holick MF. Sunlight and Vitamin D: A global perspective for health. Dermatoendocrinol. 2013;5(1):51-108. doi:10.4161/derm.24494

2. National Institutes of Health. Vitamin D Fact Sheet for Consumers. November 2022. Available at: https://ods.od.nih.gov/factsheets/VitaminD-Consumer/

3. Shieh A, Chun RF, Ma C, et al. Effects of High-Dose Vitamin D2 Versus D3 on Total and Free 25-HydroxyVitamin D and Markers of Calcium Balance. J Clin Endocrinol Metab. 2016;101(8):3070-3078. doi:10.1210/jc.2016-1871

4. U.S. Department of Health and Human Services and U.S. Department of Agriculture. 2015 – 2020 Dietary Guidelines for Americans. 8th Edition. December 2015. Available at http://health.gov/dietaryguidelines/2015/guidelines/

5. Latham CM, Brightwell CR, Keeble AR, et al. Vitamin D Promotes Skeletal Muscle Regeneration and Mitochondrial Health. Front Physiol. 2021;12:660498. Published 2021 Apr 14. doi:10.3389/fphys.2021.660498

6. Martens PJ, Gysemans C, Verstuyf A, Mathieu AC. Vitamin D's Effect on Immune Function. Nutrients. 2020;12(5):1248. Published 2020 Apr 28. doi:10.3390/nu12051248
   
   
7. de la Guía-Galipienso F, Martínez-Ferran M, Vallecillo N, Lavie CJ, Sanchis-Gomar F, Pareja-Galeano H. Vitamin D and cardiovascular health. Clin Nutr. 2021;40(5):2946-2957. doi:10.1016/j.clnu.2020.12.025