If you live in Idaho or anywhere in the Pacific Northwest, there's a good chance your body is running low on one of the nutrients your skin, bones, and immune system depend on most: vitamin D. It's often called the "sunshine vitamin" because your skin produces it when exposed to sunlight — and that's exactly the problem for those of us living at northern latitudes.
The Latitude Problem
Boise sits at roughly the 43rd parallel, and much of the Pacific Northwest stretches even farther north. From about October through March, the sun sits too low in the sky for UVB rays — the specific wavelength your skin needs to synthesize vitamin D — to reach us in meaningful amounts. Even on a bright, crisp January day, you can stand outside for an hour and produce almost no vitamin D at all.
Add in our long stretches of cloud cover, cold-weather layers that keep skin covered, and the indoor lifestyles most of us lead during winter, and it's easy to see why vitamin D deficiency is so common in our region.
Why Your Skin (and the Rest of You) Cares
Vitamin D isn't just about strong bones, though that's its most famous job. It plays a role in:
Skin health and repair. Vitamin D supports the skin barrier, helps regulate skin cell growth and turnover, and plays a part in wound healing. Research has linked low vitamin D levels to flare-ups of conditions like eczema and psoriasis.
Immune function. Your immune system relies on vitamin D to function well, which may be one reason winter — when our levels drop — coincides with cold and flu season.
Mood and energy. Low vitamin D has been associated with fatigue and low mood, symptoms many Northwesterners chalk up to "winter blues."
Bone strength. Without adequate vitamin D, your body can't absorb calcium efficiently, which matters at every age.
The Sunscreen Question
Here's where things get interesting for a skin-focused practice like ours: sunscreen, which we recommend wearing daily to protect against skin cancer and premature aging, also reduces vitamin D production. Some people take this as a reason to skip SPF — but that's the wrong takeaway.
The smarter approach is to protect your skin from UV damage and get your vitamin D from other sources. Sun exposure is an unreliable and risky way to maintain vitamin D levels, especially in a region where the sun can't do the job for half the year anyway. Supplements let you have it both ways: protected skin and healthy vitamin D levels.
How Much Do You Need?
General guidelines suggest 600–800 IU of vitamin D daily for most adults, though many people in northern climates benefit from more, particularly during the winter months. Individual needs vary based on age, skin tone (melanin reduces vitamin D synthesis, so people with deeper skin tones often need more), body weight, and how much time you spend outdoors.
The only way to know your actual status is a simple blood test — a 25-hydroxyvitamin D level — which your primary care provider can order. If you're deficient, your provider may recommend a higher dose for a period of time before settling into a maintenance level.
A few practical tips:
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Look for vitamin D3 (cholecalciferol), which is generally more effective at raising blood levels than D2.
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Take it with a meal that contains some fat — vitamin D is fat-soluble and absorbs better that way.
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Don't megadose on your own. More isn't always better, and very high levels can cause problems. Work with your provider to find your right dose.
The Vitamin D and K2 Partnership
If you've shopped for vitamin D lately, you've probably noticed supplements that pair D3 with vitamin K2 — and there's a reason these two are often bundled together.
Vitamin D's job is to help your body absorb calcium. Vitamin K2's job is to help direct that calcium to the right places — namely, your bones and teeth — and keep it away from where you don't want it, like your arteries and soft tissues. K2 does this by activating specific proteins (osteocalcin and matrix Gla protein) that act like traffic controllers for calcium in the body.
In other words, vitamin D gets calcium into your bloodstream, and K2 helps make sure it ends up where it belongs. Some researchers believe that supplementing with vitamin D long-term without adequate K2 may be less than ideal, which is why combination formulas have become popular.
K2 is also harder to get from a typical American diet than you might expect. Its best food sources — natto (fermented soybeans), certain aged cheeses, and organ meats — don't show up on most Idaho dinner tables very often. If you're taking vitamin D regularly, it's worth asking your provider whether a D3 + K2 combination makes sense for you.
A note on form: look for K2 as MK-7 (menaquinone-7), which stays active in the body longer than other forms. And if you take blood-thinning medication like warfarin, talk to your doctor before adding any vitamin K supplement, since it can interfere with how those medications work.
Food Helps, But Only So Much
Fatty fish like salmon, fortified milk and cereals, and egg yolks contain vitamin D, but it's difficult to reach optimal levels through diet alone. For most people in our region, a daily supplement is the most reliable strategy from fall through spring — and for many, year-round.
The Bottom Line
Living in the Pacific Northwest comes with incredible perks — mountains, rivers, four real seasons. Abundant year-round vitamin D isn't one of them. A daily supplement is one of the simplest, most affordable things you can do to support your skin, your immune system, and your overall health, all while continuing to protect your skin with daily SPF.
If you have questions about how vitamin D fits into your skin health routine, we're happy to talk about it at your next visit.
Ready to Give Your Skin What It Needs?
Your skin works hard through every Idaho winter — let's make sure it has the support it deserves. At Skin Sanctuary, we look at skin health from every angle, from what you put on your skin to what you put in your body. Whether you're dealing with winter dryness, an eczema flare-up, or just want a skincare plan built for our unique Northwest climate, we'd love to help.
Book your appoiontment today or give us a call to schedule a consultation. Your skin (and the rest of you) will thank you
This post is for general educational purposes and isn't a substitute for personalized medical advice. Talk with your healthcare provider before starting any new supplement, especially if you take medications or have underlying health conditions.
Juanita Layne, FNP-C
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