Can you get vitamin d from sunlight through a window

Ten minutes or so of sun exposure to your face and arms is roughly equivalent to 200 IU of vitamin D supplement

Dear Dr. Roach: Does our skin make vitamin D from sun exposure through a car’s windshield? Sometimes I expose my stomach for about 10 minutes while driving or riding in a car, but I’m not sure if the skin responds the same way through glass as it does with direct sun exposure.

S.R.

Sunlight allows our skin to convert 7-dehydrocholesterol (made from cholesterol) to previtamin D3, which then becomes vitamin D3, the active form. The type of sunlight that is effective for this is in the ultraviolet spectrum, called UV-B. UV-B is effectively filtered out by windshields and ordinary glass, so you are NOT able to get vitamin D through the window: You need to go out into the sun. Ten minutes or so of exposure to your face and arms is roughly equivalent to 200 IU of vitamin D supplement. The exact amount depends on your skin type (lighter skin is much more efficient at using sunlight to convert vitamin D), your latitude, the season and the time of day.

UV-A light can get through most windows and light cloud cover, but not through UV-blocking window films that you can buy to block UV for your home and car windows. It does not help you make vitamin D. Unfortunately, it does penetrate deep into the skin, prematurely aging the skin and predisposing you to cancer. So, I wouldn’t recommend exposing your skin through a windshield, as it won’t cause health benefits and could cause health harms.

Dear Dr. Roach: I had my annual flu shot a week ago. I am eligible for the Pfizer booster shot now. How long should I wait to get the booster shot? I am 82 years old, and my second COVID-19 shot was in mid-March.

M.R.

Back in March, when you got the initial two doses, the Centers for Disease Control and Prevention and others recommended against getting any kind of vaccine within two weeks of getting the COVID-19 vaccine. That recommendation has been removed, and you can get the flu vaccine on the same day of your COVID-19 booster if you wish.

I do recommend the flu shot, which is available for all ages over 6 months. Last year, there was hardly any flu, because of the mask-wearing and social distancing protocols in place. These are still in place in many locations, so it’s possible we could have another light flu season. However, they are NOT in place in others, and because children are back at school in most parts of the North America, there is likely to be a lot more flu than last year. Further, because essentially nobody got the flu last year, there is much lower resistance in the population than normal, so experts are worried about a severe flu season.

The flu makes you feel terrible, and with COVID-19 still out there, a person with the flu might legitimately worry about having COVID, necessitating quarantine and testing. It’s far better to avoid this if you can by getting the flu shot and the COVID-19 booster if you meet the guidelines. It is certainly true that the flu vaccine isn’t perfect, but it remains the best way to prevent flu.

Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to [email protected]

Vitamin D is often referred to as the “sunshine vitamin” because it is produced naturally by the body when our skin is exposed to direct sunlight. It is an essential vitamin for maintaining many aspects of our health, yet a shocking 13% of the world’s population is considered deficient 1.

But why is this? And how can we ensure we get enough of it? Find out more in this article and learn the answer to the commonly asked question, “can you get vitamin D through a window?”

What Is Vitamin D and Why Do We Need It?

Vitamin D is a fat-soluble vitamin that has several important roles. One of the most vital is regulating calcium absorption and blood phosphorus levels to build and maintain strong bones and teeth 2. Without it, bones become brittle, thin and misshapen and bone conditions like rickets and osteoporosis may arise.

Another important role of vitamin D is supporting a healthy immune system to help protect against diseases. It works by enhancing the function of the body’s immune cells that kill invading pathogens and reducing inflammation associated with many chronic diseases.

Vitamin D is so important that scientists have found a link between vitamin D deficiency and an increased risk of infection, diseases, and immune-related disorders 3.

Additionally, vitamin D helps regulate our moods, protects against cardiovascular diseases, reduces the risk of breast cancer, supports healthy muscles, and is necessary for the growth and development of babies. Pretty important stuff!

Sources Of Vitamin D

One of the best sources of vitamin D comes from the sun. There are two types of UV rays: ultraviolet A (UVA), which causes skin aging, and ultraviolet B (UVB), which causes skin burning. Our skin naturally contains a precursor to vitamin D.

When the sun’s ultraviolet B rays hit the skin, they convert this precursor to vitamin D3. The liver and kidneys then convert this form of vitamin D into an active form called calcitriol, which the body can utilize.

Vitamin D is also obtained through food sources such as oily fish, egg yolks, red meat, and fortified foods, or it can be taken as a supplement.

The National Institutes of Health recommend that adults and children get 15 mcg of vitamin D daily through sunlight, diet, or a combination of the two.

Many people don’t get enough vitamin D and are deficient. This is especially common in people who live in countries with short winter daylight hours or that are far from the equator where the sun’s rays are much less intense.

With such little sunlight, a huge amount of vitamin D-rich food would need to be consumed, which can be difficult. Plus, even if it’s sunny in the winter, sometimes it’s just too cold to stay outside for long!

This begs the question, “can you get vitamin D through a glass window?”

Why Direct Sunlight Is Necessary

Unfortunately, as nice as it is to sun yourself in front of a window during the winter, you can’t get your daily vitamin D dose this way. This is because glass blocks those all-important UVB rays needed to trigger vitamin D synthesis.

In fact, sitting in the sun through a window means you are getting no vitamin D benefits but are exposing your skin to harmful UVA rays, which penetrate through glass and contribute to skin aging and cancer.

With that cleared up, here are some top tips to help ensure you are getting all the vitamin D you need!

Tips For Getting Your Daily Dose of Vitamin D

Get outside around midday

The most efficient time for vitamin D production from sunlight is around midday, when the sun is at its highest point, and UVB rays are the most intense. This means you need to spend less time in the sun to get your fill of vitamin D. Spending too long in the afternoon sun can cause burning, skin damage, skin aging, and skin cancer.

One study found that people in the UK need just 13 minutes of midday sunlight during the summer, three times a week, to achieve healthy vitamin D levels 3. We would need much more in the winter as the sun is less intense.

It’s important to note that SPF sunscreens work by blocking UV rays, so they will also block vitamin D production. While protecting yourself from the sun is vital, it takes very little unprotected sun exposure for your body to produce vitamin D.

People with darker skin will need to spend longer in the sun than people with lighter skin to produce the same amount of vitamin D. This is because darker skin typically has more melanin, a pigment that helps protect the skin from sun damage by absorbing UV rays and acting as a natural sunscreen.

However, darker-skinned people have a higher risk of vitamin D deficiency as more UVB rays are blocked. According to research, people with dark skin may need 30 minutes to three hours longer of sunlight to get enough vitamin D 4.

Eat vitamin D-rich foods

Fatty fish and seafood are one of the best food sources of vitamin D. These include tuna, mackerel, sardines, shrimp, and salmon. One study found that one serving of wild salmon can provide your full recommended daily amount of vitamin D, just in one meal! 5

If you’re not a fish eater, mushrooms are the only vegetarian source of vitamin D. Interestingly, mushrooms make their own vitamin D like we do - through exposure to sunlight. Vitamin D content depends on the type of mushroom variety and whether they are wild, which have more or farmed.

Egg yolks provide another great source of vitamin D. Always look for free-range eggs as chickens who don’t have access to the outdoors don’t produce eggs containing much vitamin D. Plus, they have a much nicer life.

As so few foods are naturally high in vitamin D, and most are animal products, many foods are fortified with vitamin D. These include plant-based milks, fruit juices, cereals, yogurts, and tofu.

Take a supplement

A vitamin D supplement is often the best way to ensure you meet your daily requirement. These are especially beneficial during the winter or for those living far from the equator.

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Can you get vitamin d from sunlight through a window

Get a UV lamp

If you struggle to get enough sunlight in the winter, try investing in a UV lamp. These emit UVB rays to mimic the action of the sun and trigger vitamin D production. UV lamps also provide other benefits to skin health and are often used to treat a number of skin conditions 6.

Conclusion

Vitamin D is an essential vitamin that is produced by the skin in response to the sun’s UVB rays or is consumed through the diet. It serves a number of important functions, primarily maintaining strong, healthy bones and teeth and supporting an efficient immune system.

Unfortunately, vitamin D cannot be obtained through sunlight through a glass window. The best ways to ensure you are getting enough vitamin D for good health is to spend some time in direct sunlight around midday, eat a diet full of vitamin D-rich foods, take a vitamin D supplement, or use an artificial lamp to stimulate vitamin D production.

References

  1. Shaker, Joseph L., and Leonard Deftos. "Calcium and phosphate homeostasis." Endotext (Internet) (2018).
  2. Aranow, Cynthia. "Vitamin D and the immune system." Journal of investigative medicine 59.6 (2011): 881-886.
  3. Rhodes, Lesley E., et al. "Recommended summer sunlight exposure levels can produce sufficient (≥ 20 ng ml− 1) but not the proposed optimal (≥ 32 ng ml− 1) 25 (OH) D levels at UK latitudes." Journal of Investigative Dermatology 130.5 (2010): 1411-1418.
  4. Feldman, David, Peter J. Malloy, and Coleman Gross. "Vitamin D: biology, action, and clinical implications." Osteoporosis. Academic Press, 2001. 257-303.
  5. Jakobsen, Jette, et al. "Vitamin D in wild and farmed Atlantic salmon (Salmo Salar)—what do we know?."