Why Sunshine Doesn’t Always Give You Vitamin D

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Why you can't always make Vitamin D from the sun | ourheritageofhealth.com

I used to think that any time I was out in the sunshine, my body was making Vitamin D. Unfortunately, though, I was wrong about that.

It turns out that, depending on where you live, there are only certain times of the day when you are able to get Vitamin D from the sun, and there are some days of the year when you actually can’t make any Vitamin D at all.

No UVB Means No Vitamin D

Basically, you need to be able to get both the UVA and UBA rays of sunshine to be able to make Vitamin D (source).

If you’re only getting the UVA without the UVB, then your body can’t make Vitamin D and you’re actually more likely to suffer damaging effects from the sun exposure like wrinkles and skin cancer.

The problem with the UVB rays is that they are only present when the sun is 50 degrees or more above the horizon. Depending on where you live, that might only be possible for half of the year. It also only happens at certain times of the day, usually in the middle part when the sun is at its highest in the sky.

Kind of ironic, isn’t it, that everyone tells you to avoid the sun when it’s at it’s peak in the sky even though that’s usually the only time you can get the benefits of the Vitamin D!

How to Know if You Can Get Vitamin D

Thankfully, there’s a really easy way to figure out if the sun is at the right angle above the horizon for the UVB rays to be present – one that doesn’t require any science or math skills (which is great because I’m pretty sure I would have no idea how to figure it out myself!)

The United States Naval Observatory website has a nifty little table you can use to calculate the degree of the sun for the town where you live. All you have to do is type in the month and day and the state and town where you live, and the website will give you a table that shows the degree of the sun every ten minutes throughout the day. Anything 50 or above is good to go as far as Vitamin D is concerned. You can find the table by following this link here.

For the area where I live in Massachusetts, I can only get Vitamin D from the sun from March 27th until September 15th. That means I have less than a month left to be able to Vitamin D from the sun, so I guess I’d better make the best of these sunny days while they’re still here!

There’s also a much smaller window of time now where the sun is above 50 degrees. For tomorrow, I can only make Vitamin D from the sunshine if I’m out in the sun between 10:00 am and 1:30 pm. For anyone who lives in a sunnier climate or closer to the equator, though, you might still have a couple of months left to enjoy good Vitamin D-producing sunshine.

If There’s No UVB, Don’t Bother Sunbathing

Back when I was first learning about the benefits of Vitamin D and before I realized that you can only get Vitamin D from sunshine at certain times, I used to also think that sitting by a sunny window would be a great way to get some extra Vitamin D during the winter time when it was cold and icy outside.

Well… unfortunately, I was wrong again. For one thing, the sun never gets more than 50 degrees above the horizon in New England during the winter months, but, even it if had, UVB rays don’t penetrate well through windows, so you only get the damaging UVA rays.

There were some winter days last year when I even tried to get more Vitamin D exposure by walking outside without wearing a hat or the hood on my coat because I thought that maybe I’d be able to get a little bit of D if every inch of my body wasn’t all bundled up. It turns out, though, that I was just freezing cold for nothing because I couldn’t possibly have made any Vitamin D anyways.

Even when the weather starts to get warmer in the spring time, though, there’s no point to going outside to sunbathe if the sun isn’t at least 50 degrees above the horizon. This past spring, we had some unusually warm days in New England, so I went outside to soak up what I thought was Vitamin D. The problem, though, was that most of the time I was spending outside was in the late afternoon when the sun’s rays were too low on the horizon for the UVB rays to penetrate. So all I was doing was potentially damaging my skin by sitting out in the sunshine!

Plan Your Sun Exposure, If Possible

Now that I know that there are only certain times that I can get Vitamin D from the sun, I’m going to try to get most of my sun exposure during those times.

Does that mean I’m going to avoid the sun like the plague during the times when I can’t get Vitamin D? No, I’m not going to go crazy about it. Sometimes it’s just not possible or practical to stay out of the sun during the times when it’s less than 50 degrees above the horizon.

I also think there’s something to be said for just the feeling of warmth and light you get when you’re out in the sun, even if you’re not getting any beneficial Vitamin D from it. It does mean, though, that I’m not going to purposely sit outside with the intent of sunbathing unless I’ve checked first to make sure that it’s even possible for me to get any Vitamin D at all.

What to Do about Vitamin D in the Winter?

Since I can’t get any vitamin D in the wintertime (or for a good part of the fall and spring) from the sunshine, I make sure I’m getting plenty of D from food sources like old-fashioned cod liver oil, and eggs yolks from pastured chickens. I also take a natural D3 supplement in the months when it’s too cold to be out in the sun. (You can find the one I take here).

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The information in this post is not to be taken as medical advice and is not intended to diagnose or treat any disease.

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11 thoughts on “Why Sunshine Doesn’t Always Give You Vitamin D

  1. Because not everyone receives adequate sunlight exposure, it’s important to take a look at other sources of vitamin D. Vitamin D supplements are very essential if you live in areas that don’t receive much sunlight. Studies suggest that vitamin D toxicity is rare, but it’s still advisable to ask your doctor how much intake you need before buying supplements.

    • So far, in all that I’ve never read, I’ve never seen an exact number. It depends too on the individual person because people with lighter skin make Vitamin D much faster than people with darker skin do. It seems like the general consensus is between 10-30 minutes of midday sun. If it seems like your skin is getting a bit pink and you’re feeling a little over-warm, it’s probably time to head back inside, but if you’re perfectly comfortable, than a few more minutes is probably ok. That’s how I usually do it anyways. I never actually keep track of the exact time, especially if I’m reading a good book and lose track of time 🙂

  2. This is so fascinating!!! I do have a question though. I have found that coconut oil has been a good sunscreen, and I tend to not burn. I’m sure I read somewhere that coconut oil protects from the bad guys but lets the good guys in. From which after reading that I deduce it protects from the UVA rays, but lets the UVB rays in. Do you know if this is correct?

  3. So following on from that, would it be wise to use coconut oil all the time as a sunscreen no matter whether the UVB rays are there or not? During the sunbathing time, is it better to go out without any sunscreen/coconut oil at all to ensure you absorb the D3? Thanks

    • Hi Jane,

      Good questions! You know, I’ve never actually done any research about whether coconut oil protects from the UVA rays while letting the UVB ones in, but that would be really interesting to find out. It seems like it would make a lot of sense. I’ve found, too, that coconut oil has been a good sunscreen replacement for me that that I don’t burn during everyday activities when I’m out in the sun. (If I’m planning to be out in the sun for several hours in a row, like at the beach, though, I usually use a natural zinc oxide sunscreen.)

      The article by Dr. Mercola that I referenced above with the information about needing both the UVA and UVB rays to get vitamin D has a paragraph about sunscreen and vitamin D, and it lists coconut oil as being a good moisturizer to use if you still want to benefit from vitamin D. (You can find the entire article here: http://articles.mercola.com/sites/articles/archive/2012/03/26/maximizing-vitamin-d-exposure.aspx)

      Based on what that article was saying, it seems like using coconut oil wouldn’t inhibit vitamin D absorption, so I don’t see any reason to avoid using it before sun exposure. And, yes, it seems like using coconut oil on a regular basis would be a wise idea as a natural sunscreen and skin protector, and also because it does such a good job of moisturizing the skin even if you’re not going to be out in the sun.

  4. Thanks for this information. The only other thing I would recommend is that people combine Vitamin K2 when taking a Vitamin D3 supplement, and make sure magnesium levels are up (or include a magnesium rich diet/supplementation). This recommendation comes from several sources including Dr. Mercola and Dr. Carolyn Dean.

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