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Miranda Popen, hormone nutritionist, answers common vitamin D questions
Published Feb 13, 2026 • 4 minute read
How much vitamin D do Canadians really need? A nutritionist explains. Photo by Getty ImagesArticle content
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Winter in Canada means cold temperatures, snowy weather and reduced daylight hours. The season also often brings an increase in common illnesses like the cold, flu and other respiratory issues that can affect our overall health.
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Maintaining a balanced diet and an active lifestyle can help boost your immune system and mood throughout winter, but even those with the best diets can be afflicted by vitamin deficiencies. As Canadians, we’re especially susceptible to lower levels of vitamin D, which is only produced when skin is exposed to sunlight.
Miranda Popen, a nutritionist who specializes in hormone health, describes Canadians as “basically running on airplane mode for half the year” due to the lower levels of sunlight we receive.
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“From October to April, the sun sits so low in the sky that even if you’re outside, your skin can’t produce meaningful vitamin D,” she notes. This can lead to a whole host of potential issues that affect our day-to-day life, including fatigue, brain fog and frequent illness.
All is not lost, however. Supplementing vitamin D is an easy and inexpensive way to protect our health as winter drags on. Below, Popen shares more of her expertise on how much Vitamin D Canadians really need, plus what to look for when shopping for an effective, high-quality supplement.
Miranda Popen, hormone nutritionist. Photo by Miranda PopenWhat to know about vitamin D, according to Miranda Popen, hormone nutritionistQ: What is Vitamin D and its main function?
A: Vitamin D acts like a master light switch for the body. When it’s low, things don’t turn on properly. The thyroid slows down, energy drops, the immune system weakens and hormones stop communicating clearly. You can be eating well and sleeping enough, but your body still feels like it’s moving through mud. When vitamin D is where it should be, systems run smoothly. When it’s not, everything becomes less efficient.
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Q: Why is vitamin D so important, especially for Canadians?
A: Your body makes Vitamin D when UVB rays hit your skin, but during Canadian winters, those rays barely show up. It’s like your body is waiting for a text that never gets delivered.
Over time, your internal reserves slowly drain, and because vitamin D acts more like a system regulator than a simple nutrient [and] everything starts to feel less efficient. Energy drops, mood flattens, immune system becomes less sharp, hormones lose their rhythm, the thyroid slows and recovery takes longer. It’s one of the most common deficiencies I see, and one of the quiet drivers behind fatigue, depression, hormone disruption, including hypothyroidism, fertility challenges, endometriosis and that feeling of never fully “bouncing back.”
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What are the symptoms of low vitamin D?
People often notice fatigue that sleep doesn’t fix, as well as:
Low mood, especially in winterFrequent illnessMuscle weakness Slow recovery from workoutsHair sheddingBrain fogHormonal symptoms like PMS, irregular cycles or fertility challenges Q: How much vitamin D is recommended daily?
A: General recommendations exist, but they’re often based on preventing severe deficiency, not optimizing function. Most adults do well between 1,000–4,000 IU daily, depending on body size, sun exposure, skin tone and blood levels. Children typically require less, but still benefit from consistent intake, especially in low-sun regions. The most important factor is testing. Your blood level tells you exactly where you stand and removes guesswork.
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Factors like sun exposure, skin tone, body composition and how well your gut absorbs nutrients all play a role. Older adults often need more because their skin becomes less efficient at producing vitamin D from sunlight. People with darker skin tones also need more sun exposure to produce the same amount. For women, Vitamin D is especially important because it directly supports hormone communication, including thyroid function, ovulation and overall cycle regulation.
Q: Do we need more vitamin D supplements at different times of the year?
A: Yes. Your body naturally produces more vitamin D in summer and less in winter. Think of it like filling a reservoir in warm months and slowly draining it in cold months. Supplementation helps stabilize levels so your immune system, mood and hormones don’t fluctuate dramatically with the seasons. Without support, many people enter winter already depleted and continue declining until spring.
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Q: Are there any dietary ways to consume more vitamin D?
A: Some foods contain vitamin D like salmon, sardines, egg yolks and liver, which are the richest sources. Realistically, food alone rarely provides enough to fully support optimal levels, especially in northern climates. Sun exposure is the most efficient natural source, and supplementation helps fill the gap when sunlight isn’t sufficient.
Q: What should you look for in a vitamin D supplement?
A: Look for vitamin D3 specifically. It’s the form your body naturally produces and should be paired with vitamin K2 and magnesium, which helps with the direct absorption of calcium into bones and away from soft tissues. Oil-based forms absorb better than dry tablets because vitamin D is fat-soluble. Third-party testing is important to ensure purity and accurate dosing. I prioritize supplements that are clean, well-absorbed and properly dosed rather than excessively high or poorly regulated. Some of my favourite trusted brands include Thorne, Pure Encapsulations and Can Prev.
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