Marks Daily Apple
Serving up health and fitness insights (daily, of course) with a side of irreverence.
16 Jan

Let the Sun Shine In

sun1It’s the absolute dead of winter, and many of you are subsisting in ruthlessly frigid weather. The local meteorologist cheerfully announces that, since December, you now have 19 more minutes of daylight! Yippee. It’s 4:30, and the sun hasn’t completely sunk below the icy horizon. That’s all the news from Lake Tundra!

As tempting as it is to hibernate in the comfort of our warm living room, the fact remains that, while we’re well within our rights to curse the cold, we need the sunlight.

Yes, in summer, it’s simple. Just get off your duff and walk outside. In January, well, it’s The Christmas Story scene when Ralphie’s mom bundles up his little brother in preparation for the walk to school: “I can’t put my arms down!”

And, oh, we know what you’re thinking. The happy lights, while we love them and agree that they definitely help, aren’t as efficient as the real deal at inducing vitamin D3 production in the body. (Remember, I’m just the messenger.) Anyway, the dog needs his walk, and you could use the fresh air.

We at MDA talk quite a bit about sunlight starvation and the benefits of moderate sun exposure. Continuing research further bolsters proof that soaking up the rays (again, in moderation) is essential for good health. Recommended daily exposure times vary considerably, from 3-15 minutes for lighter skinned people to as much as an hour for darker skinned people. Opt for at least 15 minutes a day, depending on your skin tone and sun intensity.

Need more motivation? Let’s review.

Sunlight and Cancer

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Research studies and analysis of global incidence data (GLOBOCAN) consistently find that sun exposure is a protective factor against the following cancers: lung, kidney, breast, endometrial, ovarian, prostate, colon and skin cancer. And the list keeps growing.

Whoa! Wait a minute – protective against skin cancer?? Yes, Watson, research out of Stanford University shows that moderate sun exposure causes dendritic cells (immune cells in the skin) to convert inactive vitamin D3 to the active form. The active vitamin D3 then allows the immune system’s soldier T-cells to transfer to the outer layers of the skin, where they do their otherwise usual duty of overthrowing damaged cells and fighting infections.

So, let’s go back, you say. Cancer-sunlight. How does this all work? Vitamin D, research shows, prevents cancerous cells from dividing as well as advances the death of cancer cells themselves. On top of it all, vitamin D enhances the activity of certain genes, including those that manage cell cycle. Is that a cool hat-trick or what?

Sunlight and Heart Health

Studies have also supported vitamin D’s role in promoting heart health. Vitamin D apparently enhances the heart’s pumping ability as well as the integrity of heart cell structure. It can also help lower blood pressure and inflammation and aids in reducing insulin resistance. And it keeps getting better….

Sunlight and Osteoporosis
The vitamin D sunlight produces in the body is essential to bone density. Yes, we know what Big Moo tells you. That milk moustache isn’t just overplayed; it’s an oversimplification. There are plenty of population groups around the world that consume little to no dairy, and their osteoporosis rates are miniscule compared to ours. In addition to well balanced nutrition and smart supplementation as well as regular weight bearing exercise, the vitamin D we get from sunlight is crucial to maintaining bone density. Need more still?

Sunlight and Mental Health

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Research has found that vitamin D is essential for those suffering from SAD (Seasonal Affective Disorder). The vitamin has also been a successful therapy for many people suffering from depression. The trick: vitamin D boosts serotonin levels (a feel good chemical) in the brain, which is substantially lower in those suffering from depression-of the seasonal variety or not.

Feel good. Hmm. Not such a bad idea for run-of-the-mill winter crankiness either. We could probably all use that about now.

jurvetson, RonAlmog, OiMax Flickr Photo (CC)

Further Reading:

10 Ways to Stay Active in the Cold Winter Months

Sunscreen May Not Be Your Friend

Laurel on Health Food: Vitamin D Study Shows Cancer Reduction

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You want comments? We got comments:

Imagine you’re George Clooney. Take a moment to admire your grooming and wit. Okay, now imagine someone walks up to you and asks, “What’s your name?” You say, “I’m George Clooney.” Or maybe you say, “I’m the Clooninator!” You don’t say “I’m George of George Clooney Sells Movies Blog” and you certainly don’t say, “I’m Clooney Weight Loss Plan”. So while spam is technically meat, it ain’t anywhere near Primal. Please nickname yourself something your friends would call you.

  1. I heard rumors about “sun” saunas, and winter depression clinics in Alaska due to the lack of sunlight. Anyone out there from Alaska? Is it true?

    Squid Pocket wrote on January 16th, 2008
  2. You must not forget about sleep. Bright light/sun light is essential for regulating our circadian ryhthms. If one forgoes sunlight exposure early in the day and then compounds the problem by sitting under bright, artificial lighting at night, you are encouraging sleep problems.

    Sleep disruption then leads to the munchies. The munchies then lead to chronic conditions.

    primalman08 wrote on January 16th, 2008
  3. Exposure to sunlight is beneficial for maintaining circadian rhythms, as primalman08 noted; however, for those of us living north of the 35th Parallel, the sun is too far south right now to send us UVB rays needed to stimulate vitamin D production. I read somewhere that Boston, at 42 N, is without UVB rays two months of the year. I didn’t notice anywhere in today’s post, although maybe it was mentioned in an earlier entry, that time of day matters very much if you’re aiming for healthy sun exposure. UVB rays are shorter than UVA rays, so they penetrate our atmosphere only at higher angles found during the middle of the day and from spring to fall in more extreme latitudes. Early morning sun is great for resetting your inner clock, but it won’t do anything for your vitamin D stores. the body does store fat-soluble vitamin D, but I don’t know how long.

    Sonagi wrote on January 16th, 2008
  4. Oh geez. SAD seriously sucks–and I’m sure I’m not the one who has it worst. No need to say that as soon as there’s a ray of sun in wintere, I’m out there, trying to suck it up as much as possible. Maybe that’s also why I love biking to work at 8 am these days; it wakes me up way better than any cup of coffee.

    Still, I can’t wait for spring to be here again.

    Kery wrote on January 17th, 2008
  5. Here’s a question – I wear SPF 15 moisturizer on my face. In winter, when my face is pretty much the only place getting sunlight, is this stopping me from getting the benefits?

    Also, since plants can get what they need from the sun through windows, can we get some of the benefits that way, too? We have a big sunny kitchen at work, but at street level (NYC) there isn’t much that makes it through the tall buildings.

    surplusj wrote on January 17th, 2008
  6. I love the sun, even in winter i do get out in the sun when it does come out, and it makes me feel great, just got to bundle up in layers, get out there and walk. And with my dog, that is, the dog don’t mind, she’s got her own fur coat!!!!

    Donna wrote on January 17th, 2008
  7. I wear SPF 15 moisturizer on my face. In winter, when my face is pretty much the only place getting sunlight, is this stopping me from getting the benefits?

    YES. UVA rays promote melanin production that gives our skin that tanned look. UVB rays stimulate vitamin D production, but too much exposure burns the skin. Virtually all sunscreens block UVB (SPF rating reflects UVB protection), friend of vitamin D, and full-spectrum sunscreens also block UVA.

    Sonagi wrote on January 17th, 2008
  8. “Virtually all sunscreens block UVB (SPF rating reflects UVB protection), friend of vitamin D, and full-spectrum sunscreens also block UVA.”

    So what do I do if I want vitamin D, but also want to protect my pale, pale skin from the skin cancer that two of my grandparents have developed (and, okay, also from wrinkles)?

    surplusj wrote on January 17th, 2008
  9. I’m with you Kery – I get SAD something terrible. This winter is worse than usual for me. *sigh* BRING ON THE SPRING!

    charlotte wrote on January 17th, 2008
  10. I take about a teaspoon of Radiant Life cod liver oil once every three or four days in the winter (when I remember, basically), and I find it helps greatly with the winter blues. The label recommends a daily dose of 1/2 teaspoon. Other brands typically recommend 1 teaspoon, so perhaps the Radiant Life brand is more potent for some reason. Vitamin D is fat soluble, so your body can store some, but I don’t know the extent to which it can be stored.

    Mark – also worth mentioning is that cholesterol is a precursor to vitamin D production, which is another reason that the demonization of cholesterol is misguided.

    surplusj: I would ditch the SPF 15 in winter unless you live on the equator or something. I don’t think you need it. (Good luck finding sunscreen-free moisturizer, though. I gave up makeup, except for special occasions, because they all have sunscreen.) I’m hesitant to comment further on sunlight and skin cancer, though. And I remember learning from my high school earth science classes twenty years ago that UV rays do not pass through glass, which is why you can’t get a sunburn from sitting in a sunny window. Plants don’t use UV rays; they use, IIRC, red and blue wavelengths, which do pass through glass.

    Migraineur wrote on January 18th, 2008
  11. An anthropologist gives alternative view of sunbathing and vitamin D. Mad dogs and ….

    Ken wrote on June 16th, 2009
  12. A great post, and one that really opened my eyes to vitamin D deficiency. I’m now taking 5000 IU per day and looking forward to spring so I can work on my tan.

    BTW, you can get a home testing kit for vitamin D from the Vitamin D Council, a non-profit organization formed to promote greater knowledge of this important vitamin. It’s the only source for this kind of home testing kit that I know of. I think the cost is around $70 but I saw one article that said you might get a discount if you participated in a scientific study. I’ll try to find the link for another comment.

    Dirk Fetherstonhaugh wrote on January 26th, 2010

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