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Can You Get Vitamin D Through A Window? The Answer May Surprise You

Do you need to step outside to reap sunshine's vitamin D benefits?

  • Posted on 24th Jun, 2022 00:35 AM
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Can You Get Vitamin D Through A Window? The Answer May Surprise You Image

Better known as the sunshine vitamin, vitamin D is often discussed as the answer to seasonal woes. During the short, gray days of winter, vitamin D comes up in conversations about the health effects of limited sun exposure. When spring and summer finally arrive, it’s credited for the way good weather brings on better moods and seemingly strengthened immune function. 

The truth is, the body can produce vitamin D on its own. However, regular and adequate exposure to ultraviolet rays (like those found in sunlight) are required to kickstart the process. With key roles in bone, thyroid, and immune health (to name just a few benefits), vitamin D seems to make the case for spending more time outdoors.* 

But for those who can’t get outside as often as they like, there’s a lot of curiosity around what exactly counts as sun exposure. Does putting your desk by a window count? Will taking a window seat on your daily commute give you a hit of vitamin D

We consulted experts in nutrition science to see exactly how the sunshine-to-vitamin-D pipeline works, plus how much sun exposure is needed to support sufficient vitamin D status.

Can you get vitamin D through a window?

While sitting near a sunny window might feel similar to getting outside, it’s no substitute for direct sun exposure. “Window glass absorbs all UVB radiation. You make no vitamin D [this way],” says professor of medicine, physiology and biophysics at Boston University medical center Michael Holick, M.D., Ph.D., who authored foundational research on vitamin d synthesis in the 1980s. 

But even direct sun exposure isn’t a foolproof way to produce vitamin D. According to Holick, sunscreen and shade (which are important for protection against other skin health concerns) will get in the way, and location, altitude, season, skin tone, and time of day have to be considered as well. 

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“For many people, sun exposure will simply not be enough to provide the vitamin D that your body needs,” says Victoria J. Drake, Ph.D., manager of the Micronutrient Information Center at the Linus Pauling Institute at Oregon State University. “Anyone who uses sunscreen to protect from the unwanted effects of sun exposure or spends a limited time outside, especially in the midday summer sun, may not be getting enough.”

She notes also that an SPF of just 15 can slash vitamin D production by over 90 percent.

Season and location can limit vitamin D production even more severely. “If you are in Boston in the wintertime and you go outside for 15 minutes, you make zero vitamin D. In fact, you make no vitamin D from about November until the following March,” Holick explains. “Unless you’re going to be a lifeguard or a hunter-gatherer, you’re not going to make very much vitamin D.”  

For people with darker skin tones, sunlight is an even less reliable source of vitamin D, as the presence of melanin reduces vitamin D production in the skin. While 29% of U.S. adults are deficient in vitamin D, Black Americans are 15 to 20 times more likely to be extremely deficient (i.e., have serum levels below 10 ng/ml). 

So, the answer is no—you can’t get vitamin D through a window. Ultimately, the question isn’t even that consequential, considering experts agree we shouldn’t be relying on sunlight as our sole source of vitamin D anyway. Unless, perhaps, you live close to the equator and spend most of your day in a bathing suit on the beach, you'll have to turn to other sources to reach sufficient vitamin D levels—and to reach truly optimal vitamin D status (i.e., over 50 ng/ml), supplementation is the way to go.*

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Other sources of vitamin D.

 When it comes to food, fortified milk and orange juice, as well as some kinds of mushroom and wild-caught fish contain small (as in, practically obsolete) amounts of vitamin D. In order to meet the recommended dietary allowance, (i.e., 600 IU for healthy adults, per the National Academies) one would have to drink more than six glasses of fortified milk a day, 12 whole eggs, or a 3.5-ounce serving of sockeye salmon, and experts agree—even that’s not enough to move the needle on vitamin D status and reach healthy levels.  

As mentioned earlier vitamin D deficiency rates among adults average 42% nationwide, with 82% of Black Americans and nearly 70% of Latino Americans experiencing deficiency. Other research shows that between 93 and 100% of the U.S. population fails to consume even 400 IUs of vitamin D per day (i.e., 200 IU below the recommended daily amount—which, for the record, is still far from sufficient to achieve and maintain healthy vitamin D status). 

With this in mind, Holick recommends all his patients take a vitamin D supplement daily, no matter the season. Drake agrees, stating the Linus Pauling Institute recommends generally healthy adults take 2,000 IU of supplemental vitamin D every day, but noting that reaching ideal blood levels of vitamin D (i.e., that coveted 50 ng/ml or above) may require an even higher dosage of supplementation. 

mbg's vice president of scientific affairs, Ashley Jordan Ferira, Ph.D., RDN, breaks down exactly how much vitamin D we need to achieve healthy serum levels: "Pharmacokinetic research shows that it takes 100 IU of vitamin D to increase a normal-weight adult's serum D levels by about 10 ng/ml. So, that means that in order to achieve 50 ng/ml, you need 5,000 IU of vitamin D per day."

If you're trying to do some quick mental calculations to determine how many servings of milk, eggs, or fish you'd need to eat to consume 5,000 IU of vitamin D daily, we'll save you the trouble—it's a lot. Too much, one would be fair to argue. Simply put, daily vitamin D supplementation is the most effective way to reach sufficient vitamin D levels and maintain whole-body health.*

(Looking for a comprehensive supplement that will help you achieve sufficient vitamin D status? Check out our vitamin D supplement roundup.) 

Why is vitamin D important?

Now that we’ve reviewed where you can get your vitamin D and how much you need to optimize your health and well-being, let’s discuss the many benefits you can look forward to upon achieving healthy D status.* 

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Bone health benefits. 

Vitamin D is perhaps most well-known for its role in maintaining bone health because the body needs it to absorb calcium and maintain healthy phosphorus levels.* It’s long been a go-to for supporting bone mineral density, particularly as we age.* More recently, it’s also been linked to supporting musculoskeletal health and even improving muscle strength.* 

Heart health benefits.

Evidence suggests that vitamin D plays an important role in bolstering cardiovascular integrity and promoting overall heart health.* As demonstrated in a 2019 Biology scientific review, this cardiovascular support can be attributed, in part, to vitamin D’s role in antioxidant and anti-inflammatory actions throughout the body, which help combat oxidative stress.* 

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Immune health benefits.

As far as the immune system is concerned, vitamin D has been shown to support white blood cell function and mediate immune cells’ response.* The science is clear: Vitamin D is a key regulator of healthy immune function and an important tool for maintaining whole-body health throughout the year.* 

Longevity benefits.

Thanks to its many important roles in maintaining overall health—including DNA protection and promoting antioxidant activity—vitamin D is a huge factor when it comes to supporting longevity outcomes.* In fact, a 2014 meta-analysis exploring vitamin D levels and health span found that those with higher levels of vitamin D were significantly more likely to live longer, healthier lives.* 

More recently, a study conducted in Germany found vitamin D supplementation to literally add years to the life and health span of individuals aged 60-85 that were deficient in the essential vitamin.*

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Mood support. 

Vitamin D supplementation gets a lot of hype in the gray days of winter, when the mood-boosting benefits of sunshine are inaccessible—and for good reason. A 2020 review of 61 studies published in the Indian Journal of Psychological Medicine found that people with mood concerns often have lower levels of vitamin D than their happier counterparts.* 

In another study from the Journal of Internal Medicine, the potential mood-supporting effects of vitamin D supplements was tested against a placebo in over 300 Norwegian adults. After one year, those in the supplement group showed significantly elevated moods, while those in the placebo group showed no significant changes.* 

The takeaway.

Despite the slew of health benefits associated with optimal vitamin D levels, most people fail to get enough vitamin D from sun exposure or food sources alone. And if you thought sitting by a sunny window would help, well, sorry you’re out of luck. 

Experts recommend turning to vitamin D supplements to meet sufficiency levels, and we’re partial to mindbodygreen’s own vitamin D3 potency+.* Sourced from organic algal oil and paired with an organic trio of flax, avocado, and olive oil to support optimal absorption, our vitamin D3 is hard to beat.*

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