Why you can't absorb vitamin D through a sunny window
If you think you're getting a healthy dose of winter sun from sitting in front of a warm, sunny window — think again. The UV rays coming through a window can burn you but unfortunately they can't spark vitamin D production.
The health benefits of vitamin D are well documented. If we get a good amount of sun exposure year-round (but not so much that we burn or get skin damage), then our body can make vitamin D that helps strengthen bones and muscles, build immunity and, according to some studies, even reduce our risk of early death.
Our bodies make vitamin D after UVB light from the sun hits our skin.Most of us do pretty well at vitamin D production in summer because the UVB light is in abundance through the hottest parts of the day, and just a little bit will kick the internal vitamin D producers into gear.
But winter is a different story. Vitamin D expert Professor Rebecca Mason tells Coach that getting sunlight through a window won't do zip.
"UVB, which is the only part of sunlight that's got enough energy [for the body] to make vitamin D, doesn't go through window glass," explains Professor Mason, from the University of Sydney's Bosch Institute.
"You can still get sunburned and a tan because UVA sunlight, which is lower energy sunlight, gets through window glass but the [necessary] energetic UVB light doesn't."
Professor Mason says the best way to get adequate sun exposure — and therefore give yourself your best chance of having adequate vitamin D levels — is to go for a lunchtime winter walk with your sleeves rolled up.
"Exercise outdoors if you possibly can, because then you can take a couple of layers off your arms or your legs and get some of that energetic sunlight," she explains.
"Research shows the exercise itself may also be good for you in terms of hanging onto the vitamin D that you've got."
One of the biggest determinants of winter vitamin D levels is your vitamin D levels at the end of summer, so making sure you get safe sun exposure in the warmer months is also a good "long game".
"Vitamin D hangs around for some time in the body," Professor Mason explains.
"In summer, five or 10 minutes in the sun mid-morning or mid-afternoon with your arms and hands or the equivalent area of skin exposed is best for making vitamin D."
But it's certainly not a case of "the more sun the better" when it comes to vitamin D production.
"If you keep exposing your skin too long to sunlight, you start to break down the vitamin D that you've produced," Professor Mason points out.
"Short exposures are better for reducing the amount of damage you get, too."
Other studies have found that fish-eaters and people who get plenty of calcium from dairy, nuts and tahini also have better vitamin D levels.
"Vitamin D has effects in just about every tissue in the body," Professor Mason says.
"By exposing yourself to sunlight, you get the other beneficial effects of sunlight, including lifting your mood and reducing your blood pressure."
https://amp.nine.com.au/article/87a8f468-0044-402e-a7e3-b25f76125313#referrer=https%3A%2F%2Fwww.google.com&_tf=From%20%251%24s
The health benefits of vitamin D are well documented. If we get a good amount of sun exposure year-round (but not so much that we burn or get skin damage), then our body can make vitamin D that helps strengthen bones and muscles, build immunity and, according to some studies, even reduce our risk of early death.
Our bodies make vitamin D after UVB light from the sun hits our skin.Most of us do pretty well at vitamin D production in summer because the UVB light is in abundance through the hottest parts of the day, and just a little bit will kick the internal vitamin D producers into gear.
But winter is a different story. Vitamin D expert Professor Rebecca Mason tells Coach that getting sunlight through a window won't do zip.
"UVB, which is the only part of sunlight that's got enough energy [for the body] to make vitamin D, doesn't go through window glass," explains Professor Mason, from the University of Sydney's Bosch Institute.
"You can still get sunburned and a tan because UVA sunlight, which is lower energy sunlight, gets through window glass but the [necessary] energetic UVB light doesn't."
Professor Mason says the best way to get adequate sun exposure — and therefore give yourself your best chance of having adequate vitamin D levels — is to go for a lunchtime winter walk with your sleeves rolled up.
"Exercise outdoors if you possibly can, because then you can take a couple of layers off your arms or your legs and get some of that energetic sunlight," she explains.
"Research shows the exercise itself may also be good for you in terms of hanging onto the vitamin D that you've got."
One of the biggest determinants of winter vitamin D levels is your vitamin D levels at the end of summer, so making sure you get safe sun exposure in the warmer months is also a good "long game".
"Vitamin D hangs around for some time in the body," Professor Mason explains.
"In summer, five or 10 minutes in the sun mid-morning or mid-afternoon with your arms and hands or the equivalent area of skin exposed is best for making vitamin D."
But it's certainly not a case of "the more sun the better" when it comes to vitamin D production.
"If you keep exposing your skin too long to sunlight, you start to break down the vitamin D that you've produced," Professor Mason points out.
"Short exposures are better for reducing the amount of damage you get, too."
Other studies have found that fish-eaters and people who get plenty of calcium from dairy, nuts and tahini also have better vitamin D levels.
"Vitamin D has effects in just about every tissue in the body," Professor Mason says.
"By exposing yourself to sunlight, you get the other beneficial effects of sunlight, including lifting your mood and reducing your blood pressure."
https://amp.nine.com.au/article/87a8f468-0044-402e-a7e3-b25f76125313#referrer=https%3A%2F%2Fwww.google.com&_tf=From%20%251%24s