Are You Getting Enough Vitamin D?
It's no secret that the PNW doesn't get much sunlight during the winter months. That's also when people tend to get sick more often, feel more fatigued, and struggle with motivation and mood.
Vitamin D plays a bigger role in that pattern than most people realize - and it's one of the most common deficiencies among people living in northern states, including Washington.
This post covers why it matters, how to know if you're deficient, and what to do about it.
How common is vitamin D deficiency?
Vitamin D insufficiency is one of the most widespread micronutrient deficiencies in the US - and it's more common in northern states like Washington, where limited sun exposure for several months of the year makes it difficult to maintain adequate levels through sunlight alone. People who work indoors, train in the early morning or evening, or spend most of their time away from direct sunlight are particularly likely to be deficient without knowing it. The best way to confirm your levels is a simple blood test through your doctor.
Why vitamin D matters for health and training
Vitamin D affects a wider range of body functions than most people expect. Beyond immune health - which is the most commonly discussed benefit - vitamin D plays a direct role in muscle function and muscle mass maintenance, bone density, mood regulation and energy, cardiovascular health, and how your body manages inflammation.
For people training regularly, two of those matter most. Vitamin D supports muscle function and helps maintain muscle mass, which becomes increasingly important as you get older. It also plays a role in bone density - relevant for anyone doing weight-bearing exercise and particularly important for women over 40.
Low vitamin D levels don't always produce obvious symptoms. Fatigue, low energy, more frequent illness, and low mood - especially during fall and winter - are common signs worth investigating.
How your body gets vitamin D
Despite being classified as a vitamin, your body can actually produce vitamin D on its own when skin is exposed to direct sunlight. The catch is that several common factors block this process:
Sunlight through glass (windows, car windows) doesn't work - the UV wavelengths needed are filtered out
Sunscreen blocks vitamin D production
During winter months in Washington and other northern states, the sun's angle is too low to trigger meaningful production even with outdoor exposure
People with darker skin tones require more sun exposure to produce the same amount of vitamin D
Most foods contain very little naturally occurring vitamin D. Fortified foods (milk, some cereals, some orange juices) add it, and fatty fish like salmon provides a meaningful amount - but for most people in the PNW, food and sun alone are unlikely to maintain optimal levels through the winter.
How to optimize your vitamin D levels
Get tested first. If you're frequently getting sick, feeling fatigued, or experiencing low mood - particularly in fall and winter - ask your doctor for a vitamin D blood test. Supplementing without knowing your baseline isn't harmful for most people at standard doses, but knowing your actual level helps determine how much you need.
Spend time outside when you can. Even in winter, outdoor daylight has benefits for mood and circadian rhythm even when sun angle is too low for significant vitamin D production. During warmer months with more direct sun, 15-30 minutes of midday exposure on arms and legs produces meaningful vitamin D for most people.
Consider supplementation. For most people in the PNW, supplementing with vitamin D through fall and winter is a reasonable and commonly recommended approach. Standard supplementation doses are widely considered safe for most healthy adults. Your doctor can provide personalized guidance based on your blood levels and health history.
What this means for bStrong members
Vitamin D is one of the micronutrients that comes up most often in the context of strength training and recovery - particularly for members at our Bellevue and Redmond locations dealing with the PNW's limited winter sun.
If you're training consistently but still feeling fatigued, getting sick frequently, or noticing your mood and motivation dropping through the winter months, it's worth asking your doctor about vitamin D levels. It's a quick test and one of the more actionable things you can address when results come back low.
Vitamin D isn't a substitute for training, nutrition, and sleep - but it's one of the foundational micronutrients that makes those things work better. For more on how nutrition supports your training, read our nutrition for strength and recovery guide.
Frequently asked questions
How do I know if I'm vitamin D deficient?
The most reliable way is a blood test ordered by your doctor. Common signs that may suggest low vitamin D include frequent illness, persistent fatigue, low mood particularly in winter months, and bone or muscle discomfort. These symptoms overlap with many other conditions, so testing is the only way to confirm.
How much vitamin D should I take?
This depends on your blood levels and individual health factors - which is why testing before supplementing is recommended. Standard over-the-counter doses are widely considered safe for most healthy adults, but your doctor can give you a specific recommendation based on your results. Don't guess on the high end - very high doses over time can cause issues even though standard doses are generally safe.
Can I get enough vitamin D from food?
For most people, food alone isn't enough to maintain optimal levels - especially in the PNW through fall and winter. Fatty fish like salmon provides meaningful amounts, and fortified foods (milk, some cereals) add some. But diet typically covers only a fraction of what direct sun exposure or supplementation provides.
Does vitamin D affect strength training specifically?
Yes. Vitamin D supports muscle function and helps maintain muscle mass - particularly relevant as you get older when muscle maintenance becomes a more active concern. It also supports bone density, which is directly relevant for anyone doing weight-bearing exercise regularly. Low vitamin D doesn't automatically mean your training suffers, but optimizing levels is one of the foundational things that supports training and recovery over the long term.
If you want training that's built around long-term health and not just short-term effort - our 3-week trial is a practical place to start. A consultation call, an Intro / Ramp Up session, 6 coached small group personal training workouts, an InBody scan, and practical nutrition resources - all for $99 at our Bellevue and Redmond locations.