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Even a Dietitian Can Be Low in Vitamin D — Here's What I Learned

A stressful year, no sun, a multivitamin I trusted — and a blood result that surprised me.


There are certain things you tell your clients constantly. Eat your vegetables. Stay hydrated. Get your vitamin D checked. And then life gets busy — really busy — and you realize those messages need to be louder for caregivers (including health care providers).


Last year was one of the harder ones. I was managing more than I want to get into here, but the short version is: a lot of stress, no vacation to somewhere warm, and a long stretch of what felt like perpetual indoor winter. I was taking my multivitamin every day, doing what I was supposed to be doing. So when my blood work came back showing low vitamin D, I'll be honest — I was a little surprised. Then I thought about my year, and I really wasn't.


Even my mug from my last trip to a sunny destination during the winter wasn't enough to remind me. I wasn't getting my Vitamin "Sea" which is actually Vitamin D
Even my mug from my last trip to a sunny destination during the winter wasn't enough to remind me. I wasn't getting my Vitamin "Sea" which is actually Vitamin D

I want to be honest about something else too. The reason I was getting my blood work done in the first place wasn't only vitamin D. My health wasn't optimal and I was doing many things to feel better yet things seemed more difficult than I would have expected with sleep, general nutrition and stress reduction.


My great-grandmother died of pernicious anemia — a condition where the body can't absorb vitamin B12 properly — and the neurological effects of that were significant. B vitamins, and B12 in particular, are something I keep a close eye on because of that family history. (The good news: my B vitamins came back fine. But it's a good reminder that family history is always worth paying attention to when you're thinking about what to test.)

The vitamin D result was the surprise. And looking back, it shouldn't have been.


Why Canada Is Especially Challenging for Vitamin D


Vitamin D is often called the "sunshine vitamin" because our skin can produce it when exposed to UV-B rays from the sun. The catch? In Canada, between October and March, those UV-B rays are too weak to trigger meaningful vitamin D production — and that's basically half the year.


In Canada, reduced daylight and limited skin exposure between October and March make it hard to produce vitamin D. And beyond seasonality, there are other factors quietly reducing what your skin can make: age, skin colour, sunscreen use, and the season all affect how much vitamin D your body produces.


For me, it wasn't just the winter months. I had skipped my usual sun-filled break, spent far more time indoors than normal, and was under significant stress — which, as we'll get to, matters too. My multivitamin provided some vitamin D, but clearly not enough to compensate for everything my body wasn't getting.

"My multivitamin had some vitamin D in it. But it turns out 'some' isn't always enough — especially when you're running on empty and spending all your time inside."

The Difference Between Deficiency and Insufficiency — and Why It Matters


One of the things that gets lost in the average health conversation is that vitamin D isn't binary. You're not just either "fine" or "deficient." There's a spectrum, and a lot of people fall into a middle zone — insufficiency — where they feel off without ever being flagged as having a problem.


In Canada, we measure vitamin D as 25-hydroxyvitamin D in the blood, and the units are nmol/L (you'll sometimes see ng/mL used in American research — they're different, so always note which unit your lab is using). According to the Endocrine Society guidelines, vitamin D sufficiency is defined as a serum 25-hydroxyvitamin D level greater than 30 ng/mL (approximately 75 nmol/L), while insufficiency falls between 12 and 30 ng/mL, and deficiency is below 12 ng/mL (30 nmol/L).

Status

Level (nmol/L — Canadian labs)

Level (ng/mL — US ref)

Deficient

Below 30 nmol/L

Below 12 ng/mL

Insufficient

30–75 nmol/L

12–30 ng/mL

Sufficient

Above 75 nmol/L

Above 30 ng/mL

If you get your blood tested in Ontario (through LifeLabs or a similar lab), the cost ranges from around $54 with a healthcare provider's requisition to $79–$89 if you order it yourself. It's one of the most accessible and actionable tests you can run. (It could also be free through your HCP if you are at risk due to a history or other condition.)


The Symptoms That People Miss


Here's where things get interesting — and where my own story really clicked into place. When most people, or at least dietitians, hear "vitamin D deficiency," they think rickets in children, or severe bone disease. Those are real outcomes from prolonged, severe deficiency. But they're not what most adults experience.


In adults, signs of vitamin D deficiency are not always obvious and can include fatigue, bone pain, muscle weakness, muscle aches or cramps, and mood changes like depression. You might have no symptoms at all — or you might have symptoms that look like a hundred other things.


The subtler presentation — the one I recognized in myself — can include things like persistent tiredness that doesn't improve with sleep, muscles that ache in a diffuse, hard-to-locate way, a low mood that doesn't have a clear cause, and a sense of just being "off."


When vitamin D has been low for a long time, your body starts pulling calcium from your bones to compensate, and that's when you can start noticing bone pain, joint aches, muscle twitching, and deeper fatigue.



Less-known symptoms to watch for:

  • Persistent, unexplained fatigue — even after adequate sleep

  • Diffuse muscle aches — especially in the back, legs, or hips

  • Low mood or increased anxiety — vitamin D receptors exist in the brain

  • Frequent illness — vitamin D plays a key role in immune regulation

  • Bone pain — particularly in the spine, ribs, or pelvis

  • Muscle cramps or twitching

  • Hair thinning — less commonly discussed, but noted clinically


None of these symptoms alone confirm deficiency, but if several feel familiar, it's worth asking your healthcare provider about a blood test.


Why Multivitamins May Not Be Enough


I want to be careful here, because multivitamins aren't the problem — they're genuinely useful as part of a broader nutrition strategy. But they're designed as a safety net, not a solution to significant depletion.


Most multivitamins contain some vitamin D, but if you take a multivitamin, you should check the label to see how much it contains and ensure your total daily intake stays within the recommended range. Many common multivitamins contain 400–600 IU of vitamin D — which meets the basic RDA under ideal conditions. But those conditions are rarely all present simultaneously, especially in Canada in winter, especially for someone working long indoor hours, especially when under stress.


About 20 minutes of sunshine daily, with over 40% of skin exposed, is estimated to be needed to prevent vitamin D deficiency from sun alone. For most Canadians in most seasons, that simply doesn't happen — making dietary and supplemental sources do the heavier lifting.


What the Science Says About Why It's So Important


Vitamin D is fat-soluble, which means the body stores it in fat tissue rather than excreting it daily like water-soluble vitamins. That's genuinely useful — it means you don't have to stress about getting a perfect dose every single day, because your reserves can buffer short-term gaps.


But it also means that toxicity is theoretically possible with very high-dose supplementation over time. Unlike getting too much sun (which doesn't cause toxicity), taking very large amounts of vitamin D in supplement form can lead to too much calcium in the blood — which causes symptoms like nausea, confusion, excessive thirst, and weakness. This is why getting tested before dramatically increasing your dose — and working with a healthcare provider — matters.


Here's the plain-language version of what vitamin D is actually doing in the body: it acts like a key that unlocks your gut's ability to absorb calcium. Without enough vitamin D, even if you're eating plenty of calcium-rich foods, your body can't absorb it properly. Over time, that means your bones may start to weaken — because your body has no choice but to pull calcium from them to keep blood levels stable. That's why this nutrient matters well beyond just taking a supplement and moving on.


The Emerging Connection with Blood Sugar


As a dietitian who works closely with blood sugar regulation — it's woven through so many of my Health Pathway programs — the vitamin D and glycemic health connection is one I find particularly compelling.


Research is showing an inverse relationship between vitamin D status and blood glucose: when vitamin D is lower, blood sugar tends to run higher. Studies have also found associations between insufficient vitamin D and increased risk of prediabetes progression. While supplementation alone isn't a treatment for diabetes, this connection reinforces why optimizing vitamin D status is part of a holistic approach to metabolic health — not a side note.


Key research areas where vitamin D plays a role

  • Bone health — the most well-established link; supports calcium absorption and bone density

  • Immune function — vitamin D receptors are found throughout immune tissue

  • Muscle function and fall prevention — particularly relevant as we age

  • Mood and mental health — vitamin D receptors exist in the brain; low levels linked to depression

  • Blood sugar regulation — emerging evidence of an inverse relationship with glucose levels (it still in debate is it more biology vs behaviour, but biochemistry research is showing possible reasons)

  • Cardiovascular markers — observational associations, though causality is still being studied (so far nothing that is consistent results)


Food Sources: Better Than Most People Think — But Still Limited


Only a few foods contain vitamin D naturally, including egg yolk and fatty fish such as salmon, sardines, and trout. In Canada, vitamin D must be added to cow's milk and margarine by law, and other foods such as yogurt, fortified plant-based beverages, and some cheeses may also have vitamin D added.


Sockeye or Pink Salmon 75g → ~400–550 IU


Tuna (bluefin) 75g → ~219 IU vs Tuna (canned, light) 75g → ~36 IU


Cow's Milk 250mL → ~200 IU


Fortified Plant Milk 250mL → 84–200 IU


Egg Yolk 1 egg → ~32 IU


Mushrooms (exposed to sunlight minimum of 15 minutes) 100g → ~ 400 IU


A note on units, because this trips people up: when you see food labels, vitamin D is listed in micrograms (μg). Supplements use International Units (IU). They're different expressions of the same thing: 1 μg = 40 IU. So if your supplement says 25 μg, that's 1,000 IU.


One of my favourite food tips — and one that came up on a mushroom farm tour I went on a couple of years ago — is that mushrooms exposed to UV light can produce meaningful amounts of vitamin D. Just set them gill-side up on a sunny windowsill for a couple of hours before cooking. The guide on that tour actually talked about this, and I've been doing it ever since. It won't replace a supplement, but it's a genuinely functional (and kind of delightful) food trick.



Food Sources of Vitamin D (and How to Actually Eat Them More Often)


Vitamin D is a bit different from most nutrients—it’s naturally found in very few foods. That means getting enough comes down to being intentional with a few key choices, especially in Canada. Starting from large to small impact, here's some tips & a few recipes to get your D from the sea(food) and beyond.



Fatty Fish (your highest-impact option)

Examples: salmon, sardines, trout, tuna

Easy ways to include:

Why it matters: Just 1–2 servings per week can significantly boost your intake.


Fortified Dairy & Plant-Based Alternatives

Examples: milk, fortified soy/almond beverages, yogurt

Easy ways to include:

  • Use milk or fortified plant-based beverages in coffee, tea, or smoothies

  • Make a yogurt parfait with fruit and nuts

  • Add milk instead of water to oatmeal, soups, pancakes, or sauces

  • Swap your regular coffee for a latte or chai latte

Why it matters: In Canada, milk is fortified by default—making it one of the most reliable daily sources.


Fortified Foods (easy add-ons)

Examples: orange juice, margarine, cereals (ex: multigrain cheerios), plant-based beverages

Easy ways to include:

  • Have a small glass of fortified orange juice with breakfast

  • Choose fortified cereal with milk

  • Use soft margarine instead of butter on toast

Tip: Check labels—vitamin D levels can vary between brands.


Eggs (small but consistent source)

Where it’s found: egg yolk

Easy ways to include:

Why it matters: Not a huge source, but easy to include regularly.


UV-Exposed Mushrooms (plant-based option)

Why they’re unique: One of the only plant sources of vitamin D

Easy ways to include:


Putting It All Together (Real-Life Combos)

Think simple, not perfect:

  • Breakfast: yogurt parfait + fortified cereal + milk

  • Lunch: tuna sandwich + latte

  • Dinner: salmon + roasted vegetables + margarine on potatoes

  • Snack: smoothie made with fortified milk


Vitamin D is hard to get from food alone—especially in Canada. The goal isn’t perfection, it’s consistency:

  • Include fortified foods daily

  • Aim for fatty fish a couple times per week

  • Layer in small sources like eggs and mushrooms where you can


If this still feels like a stretch, that’s where a personalized plan (and sometimes supplements) can help fill the gap.



So What Did I Do?


I talked to my healthcare provider. I got tested. I have started taking a vitamin D3 supplement at an appropriate dose for my level (D3 is generally preferred over D2, as it's more effective at raising blood levels). And I will schedule my retest to confirm my levels have normalized in 3-6 months.


Supplement Tip: Both vitamin D2 and D3 can meet your needs, though D3 is generally more easily absorbed. It's available in liquid, chewable, or pill form, and you should always choose a supplement with a Natural Product Number (NPN) to confirm it meets Health Canada's safety standards.


I also became more intentional about the things I could control — getting outside even briefly in these dreary months, eating fatty fish more regularly (hello another reason to eat anchovies!), and actually checking the vitamin D content on my multivitamin label (spoiler: it was 800 IU, which in context wasn't doing the job on its own).

"The thing about vitamin D is that it's one of the most common deficiencies, it's easy to test for, and it's correctable. There's no reason to be running low if you have access to a simple blood test."

Who Should Especially Pay Attention


While anyone can become deficient, vitamin D deficiency may be more common in older adults, people with darker skin, those who are homebound or rarely go outside, and people with certain medical conditions that affect absorption. In Canada, given our geography and climate, I'd argue nearly all of us deserve a baseline test.



A few groups worth flagging specifically: anyone under significant prolonged stress (which can deplete reserves and affect immune function), those who work primarily indoors, people who cover most of their skin, and anyone who has gone a full winter or more without sunlight exposure or supplementation.


Quick Reference of Daily Vitamin D Recommendations (Canada)

  • Ages 1–70: 600 IU (15 μg) per day

  • Over 70: 800 IU (20 μg) per day

  • Upper limit (all adults): 4,000 IU (100 μg) per day without medical supervision

  • Health Canada also recommends 400 IU supplementation for adults over 50


Testing costs in Ontario: ~$54 with HCP requisition; $79–$89 self-ordered; Free through a Healthcare Practitioner requisition for certain people who qualify based on their health conditions and risk factors.


Always work with your healthcare provider before starting high-dose supplementation — because fat-soluble vitamins build up, toxicity is possible with unsupervised mega-dosing.


I share this not to be alarmist, but because I think there's something useful in the admission. Knowing the information isn't the same as applying it to yourself. I had all the knowledge — and still a stressful, sunless year quietly depleted something important to me.


The good news is that vitamin D deficiency is among the most correctable nutritional issues there is. A blood test, a conversation with your provider, and a consistent supplement protocol can genuinely shift how you feel. That's worth something.


If any of this sounds familiar — the fatigue, the aches, the year without sun — I'd encourage you to start the conversation. And if you're a current client, bring it up at our next session. It may be one of the simpler pieces of the puzzle.




Disclaimer: This post reflects my personal experience and is intended for general educational purposes only. It is not a substitute for individualized medical or nutrition advice. Always speak with your healthcare provider before making changes to your supplement regimen, especially if you have underlying health conditions or take medications that may interact with vitamin D metabolism.


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