**Denver's Winter: Is Altitude Crashing Vitamin D Levels?**

Photograph of Franklin Everett ShawBy Franklin Everett Shaw
February 1, 2026

The sun feels different here. It’s not just a feeling; it’s a scientific reality. Denver, sitting a mile high, gets about 300 days of sunshine a year, but that doesn’t mean Denverites are swimming in Vitamin D. In fact, many are deficient, especially during the long winter months.

The Mile High City presents a unique challenge when it comes to Vitamin D. The thinner atmosphere filters less UVB radiation, the kind our skin uses to synthesize Vitamin D. This sounds like a good thing, but it’s deceptive.

Less atmosphere also means less time before you burn. Denverites are often slathered in sunscreen, blocking UVB rays and hindering Vitamin D production.

And then there’s winter. The sun hangs lower in the sky, and even on sunny days, the UVB rays are often too weak to stimulate Vitamin D synthesis.

Symptoms of Vitamin D deficiency can be subtle, especially in long-term residents who may have adapted to feeling “normal” with low levels. Fatigue is a big one. It’s easy to dismiss as just the winter blues or the result of a busy Denver lifestyle.

Muscle weakness and aches are also common. Think about struggling more than usual on those Red Rocks stairs.

Bone pain, particularly in the lower back, can also be a sign. This is especially concerning for older adults in Denver, who are already at higher risk for osteoporosis.

Mood changes, like increased irritability or sadness, are another red flag. The lack of sunlight already impacts serotonin levels, and a Vitamin D deficiency can exacerbate these mood swings.

So, what can a Denverite do? First, get tested. Ask your doctor for a Vitamin D blood test (25-hydroxyvitamin D). Aim for a level between 30-50 ng/mL.

Supplementation is often necessary, especially during the winter. But don’t just grab any bottle off the shelf at King Soopers.

Look for Vitamin D3 (cholecalciferol), which is more effective than Vitamin D2. The dosage will depend on your current levels, but many Denverites need at least 2,000-5,000 IU per day during the winter.

Consider a supplement that also includes Vitamin K2. Vitamin K2 helps direct calcium to your bones and teeth, preventing it from accumulating in your arteries. This is especially important if you’re taking high doses of Vitamin D.

Timing matters. Take your Vitamin D supplement with a meal that contains fat. Vitamin D is fat-soluble, so it’s absorbed better when taken with fat.

Light therapy is another powerful tool. A SAD (Seasonal Affective Disorder) lamp can mimic sunlight and stimulate Vitamin D production.

Look for a lamp that emits at least 10,000 lux. Position it about 12-24 inches from your face and use it for 20-30 minutes each morning.

Don’t stare directly at the light. Let it shine indirectly into your eyes.

Be consistent. Light therapy is most effective when used daily, especially during the darkest months of December and January.

Diet plays a role, but it’s difficult to get enough Vitamin D from food alone. Fatty fish like salmon and tuna are good sources, as are egg yolks and fortified foods like milk and cereal.

However, you’d have to eat a lot of salmon to meet your daily Vitamin D needs. Supplementation and light therapy are usually necessary to bridge the gap.

Monitor your progress. Get your Vitamin D levels retested after a few months of supplementation and light therapy. Adjust your dosage as needed.

Don’t assume you’re getting enough Vitamin D just because you live in a sunny state. Denver’s altitude and lifestyle factors create a unique challenge.

Be proactive. Get tested, supplement wisely, embrace light therapy, and enjoy the Colorado sunshine responsibly. Your body will thank you.

One common mistake is thinking that a multivitamin provides enough Vitamin D. Many multivitamins contain only 400 IU of Vitamin D, which is often not enough for Denverites.

Another pitfall is relying solely on sunscreen for sun protection. While sunscreen is essential for preventing skin cancer, it also blocks Vitamin D production.

Consider spending a few minutes in the sun without sunscreen each day, especially during the summer months. Just be careful not to burn.

Remember, even on cloudy days, you can still get some Vitamin D from the sun. The UVB rays can penetrate clouds, although not as effectively.

Don’t forget about the importance of Vitamin D for children. Vitamin D is crucial for bone development and immune function.

Talk to your pediatrician about Vitamin D supplementation for your children, especially during the winter months.

Consider the impact of altitude on Vitamin D absorption. Some studies suggest that altitude may affect the way the body processes Vitamin D.

More research is needed in this area, but it’s something to keep in mind if you’re struggling to raise your Vitamin D levels.

Be aware of potential drug interactions. Certain medications, such as steroids and some weight-loss drugs, can interfere with Vitamin D absorption.

Talk to your doctor or pharmacist about any potential drug interactions.

Don’t ignore the symptoms of Vitamin D deficiency. If you’re experiencing fatigue, muscle weakness, bone pain, or mood changes, get tested.

Early detection and treatment can prevent more serious health problems.

Think of Vitamin D as an investment in your long-term health. It’s not just about preventing rickets or osteoporosis.

Vitamin D plays a role in many aspects of health, including immune function, cardiovascular health, and mental well-being.

So, take charge of your Vitamin D levels and enjoy all that Denver has to offer, from hiking in the mountains to exploring the vibrant city scene. Just remember to protect your skin and optimize your Vitamin D intake.

Denver’s unique environment demands a proactive approach to Vitamin D. Don’t let the sunshine fool you; prioritize your health and thrive at 5,280 feet.

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