Every winter, many Quebecers ask themselves the same question: «Am I deficient in vitamin D?» This is no coincidence. The Vitamin D in Quebec holds a special place, where the northern latitude and limited sunlight from October through March restrict the main natural way to produce it: through sun exposure of the skin. This vitamin supports bone health and contributes to the functioning of the immune system. Understanding its role, the possible signs of a deficiency, its sources, and the value of a blood test helps you make informed choices—in consultation with a healthcare professional.
On this page
- The Role of Vitamin D in the Body
- Why Deficiency Is Common in Quebec
- Possible signs of a deficiency
- Sources: sunlight, diet, supplements
- Table of Food Sources
- Blood Test (25-OH-D): Who Should Get It?
- The Safety of Supplements
- Myths and Misconceptions
- Frequently asked questions
The Role of Vitamin D in the Body
Vitamin D is a fat-soluble vitamin which acts in the body much like a hormone. Its best-established role involves the bones: it helps the body absorb calcium and phosphorus from food, two minerals that are essential for a strong skeletal system.
Bone and Muscle Health
Without an adequate intake of vitamin D, calcium absorption decreases, which can eventually weaken the bones. Here are its main recognized benefits:
- Promote the intestinal absorption of calcium and phosphorus
- Help maintain normal bone health throughout life
- Helps maintain normal muscle function
- Supporting tooth mineralization
Immune System
Vitamin D also contributes to the normal functioning of the immune system. Research continues to explore its various roles, but caution is advised: supporting normal function is not the same as preventing or curing a disease. No supplement can replace established preventive measures, and any questions about your health should be discussed with a healthcare professional.
Why Deficiency Is Common in Quebec
The main factor explaining the prevalence of vitamin D deficiency in Quebec is related to the geography. The skin produces vitamin D when exposed to the sun’s ultraviolet B (UVB) rays. However, at our northern latitude, these rays are too weak for much of the year to allow for this synthesis.
It's all because of winter and the latitude
- Low levels of sunlight in winter : During the cold season, the sun's angle is too low for UVB rays to trigger effective production in the skin.
- Short Days : Fewer hours of daylight mean fewer opportunities for exposure.
- Modest clothing : In cold weather, exposed skin is kept to a minimum.
- Life Inside : We spend most of our time at work, at school, or at home.
Who Is at Greater Risk?
Certain people are more likely to have lower vitamin D levels: older adults, whose skin is less efficient at synthesizing the vitamin; people with darker skin; those who spend little time outdoors or cover up a lot; people living in care facilities; and those with certain conditions that affect fat absorption. These are merely risk factors: only a healthcare professional can assess your individual situation.
Key Takeaways
- Vitamin D primarily helps the body absorb calcium and maintain strong bones.
- It also plays a role in the normal functioning of the immune system.
- The skin produces it in response to the sun's UVB rays.
- In Quebec, the sun's rays are too weak in the winter because of the high latitude.
- Older adults, dark skin, and limited sun exposure are risk factors.
- If you have any concerns about your health status, please discuss them with a healthcare professional.
Wondering if a health screening is right for you? Our service locations in Quebec offer blood draws, and you can set up a meeting online or choose a online consultation to discuss it with a professional.
Possible signs of a deficiency
Vitamin D deficiency often progresses without obvious symptoms, which makes it difficult to detect without analysis. When present, the signs are nonspecific: they can have many other explanations. Therefore, they alone are never sufficient to conclude that there is a deficiency.
Symptoms Sometimes Reported
- General fatigue or lack of energy
- Diffuse bone or muscle pain
- Muscle weakness
- Joint discomfort
Because these symptoms are common to many conditions, you should not self-diagnose. If you experience these symptoms on a persistent basis, the best course of action is to speak with a healthcare professional, who will determine what needs to be investigated and whether testing is warranted in your case.
Sources: sunlight, diet, supplements
There are three complementary ways to meet one’s vitamin D needs: sun exposure, diet, and, if necessary, supplements. In Quebec, none of these sources alone is sufficient for everyone, which is why it is important to understand their limitations.
The Sun
Exposure of the skin to UVB rays enables the synthesis of vitamin D. However, this process is limited in winter at our latitude, and prolonged sun exposure poses risks to the skin. Therefore, this is not a strategy that should be adopted without qualification, especially during hours when UV rays are intense.
Food
Few foods are naturally high in vitamin D. Fatty fish are the best sources, and many products are fortified with it. In Canada, cow’s milk and fortified soy beverages must contain added vitamin D. Here are some common sources:
- Fatty fish: salmon, trout, herring, sardines, mackerel
- Cow's milk and fortified plant-based beverages
- Certain fortified yogurts and margarines
- Egg yolk
- Certain mushrooms exposed to UV light
Supplements
For many people in Quebec, supplements are a reliable way to ensure adequate intake, especially in the winter. Health Canada and Osteoporosis Canada recognize the importance of supplementation for certain groups. However, the appropriate amount depends on age, health status, and other factors: this is a decision to be made with a healthcare professional—never a dose to adjust on your own.
Table of Food Sources
Here is a comparative overview of dietary sources of vitamin D. Actual vitamin D content varies by product and fortification; refer to the nutrition facts labels on the packaging.
| Source | Type | Note |
|---|---|---|
| Salmon, trout, herring | Natural | Among the best dietary sources |
| Sardines, mackerel | Natural | Fatty fish rich in vitamin D |
| Cow's milk | Enriched | Mandatory Enrichment in Canada |
| Soy beverage | Enriched | Mandatory Enrichment in Canada |
| Egg yolk | Natural | Modest contribution |
| Mushrooms Exposed to UV Light | Natural | Content varies by product |
| Supplement | Supplement | Useful in winter for certain groups, according to expert opinion |
Blood Test (25-OH-D): Who Should Get It?
Vitamin D levels are measured through a blood test that determines the 25-hydroxyvitamin D, often abbreviated as 25-OH-D. It is the most commonly used marker for assessing a person’s vitamin D status. However, this test is not routinely recommended for everyone.
Why it isn't done systematically
Health organizations, including INESSS and INSPQ, note that routine testing in healthy individuals with no risk factors generally offers no proven benefit. For many people, judicious supplementation during the winter can be considered without first measuring vitamin D levels. Testing is particularly useful in specific clinical situations.
Who could benefit from this?
A healthcare professional may find it useful to measure 25-OH-D levels in certain situations, such as:
- Certain conditions that affect absorption or metabolism (digestive, kidney, or bone diseases)
- Monitoring of bone conditions such as osteoporosis
- Taking certain medications that affect vitamin D
- Persistent, unexplained symptoms that require investigation
It is the healthcare professional who determines whether a test is appropriate in your case and how to interpret the results. A single number does not stand on its own; it makes sense only in the context of your overall health.
The Safety of Supplements
Vitamin D supplementation is generally well tolerated when taken within recognized guidelines. Since it is a fat-soluble vitamin, it accumulates in the body: taking excessive amounts over a long period of time is not without risk.
Why «More» Doesn’t Mean «Better»
Prolonged excessive intake can lead to high blood calcium levels, which can cause adverse effects. Health Canada publishes maximum tolerable intakes that should not be exceeded without medical supervision. The tendency to double doses «just to be sure» is not a good idea; the goal is an adequate intake, not a maximum one.
Best Practices
- Discuss your actual needs with a healthcare professional or a pharmacist
- Follow Health Canada's dietary reference values and upper limits
- Take into account any other supplements and medications you are taking
- Do not exceed the specified amounts without consulting a healthcare professional
This article does not recommend any specific dosage. The appropriate amount for you depends on your individual circumstances and should be decided in consultation with a healthcare professional.
Myths and Misconceptions
«Summer in Quebec is enough to build up reserves for the winter.»
Nuanced. The skin does produce vitamin D in the summer, but those stores aren't guaranteed to last through the entire cold season, especially for people at risk. That's why the question of winter supplementation comes up for many people.
«Everyone should get their vitamin D levels checked.»
False. For healthy individuals with no risk factors, routine testing is generally not recommended. It is reserved for specific clinical situations, as assessed by a healthcare professional.
«The more vitamin D I take, the better.»
False. It is a fat-soluble vitamin that accumulates in the body. Prolonged excessive intake can be harmful. The goal is to ensure an adequate intake, within the limits set by Health Canada.
«Using a tanning bed is a good way to get your fill.»
False. Tanning beds pose recognized risks to the skin and are not a recommended source of vitamin D. Diet and, if necessary, supplements are safer options.
«Vitamin D prevents colds and the flu.»
Nuanced. Vitamin D supports the normal functioning of the immune system, but it is not a cure for infections. No supplement can replace established preventive measures.
Frequently asked questions
Do you need to be on an empty stomach for a vitamin D test?
A 25-OH-D test does not usually require fasting. However, be sure to follow the instructions on your prescription, especially if other tests are ordered at the same time.
What is the best source of vitamin D in Quebec during the winter?
In the winter, the body produces little vitamin D. Diet (fatty fish, fortified foods) and, for many people, supplements become the main sources. Talk to a healthcare professional about your situation.
Is a vitamin D test covered by RAMQ?
Coverage depends on the clinical context and the applicable criteria. The healthcare professional who orders the test will inform you of the procedure to follow and the conditions that apply to your situation.
Do children need vitamin D?
The needs of children, particularly infants, are important topics governed by specific guidelines. These issues should be discussed with a healthcare professional, who will tailor their advice to the child’s age and situation.
Is it possible to have too much vitamin D?
Yes. Since it accumulates in the body, prolonged excessive intake can cause adverse effects. Following Health Canada’s guidelines and seeking professional advice can help avoid this risk.
How can I tell if I'm deficient in vitamin D?
The signs of a deficiency are nonspecific, and a blood test is not always necessary. The best approach is to talk to a healthcare professional, who will assess your risk factors and determine whether a test is warranted.
Sources
- Osteoporosis Canada
- Health Canada
- Quebec National Institute of Public Health (INSPQ)
- Quebec Professional Order of Dietitians (OPDQ)
- National Institute for Excellence in Health and Social Services (INESSS)
- Government of Quebec — Health
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