Updated in October 2026 according to the latest recommendations from Health Canada, Osteoporosis Canada, and the Endocrine Society.
Quebec's fall and winter are well known for their short days and lack of sunlight. From October to March, the sun is too low in Quebec for our skin to produce sufficient amounts of vitamin D. That is why we ask ourselves the same question every year: should we take a vitamin D supplement, and how much? Recommendations have evolved in recent years. Here is what you need to know.
In brief
- Adults' daily requirement: 600 IU per day up to age 70, 800 IU after age 70.
- Health Canada recommends a 400 IU supplement daily for all adults over 50.
- Do not exceed 4000 IU per day without medical advice (tolerable upper intake level).
- Recent large studies do not show that vitamin D prevents cancer, heart disease, or fractures in healthy adults.
- In Quebec, it is difficult to meet your needs through diet alone in winter: a low-dose supplement is a simple option.
What is vitamin D and what does it do?
Vitamin D is a fat-soluble vitamin that our skin produces when exposed to the sun's UVB rays. It is also found in some foods and supplements. Its best-established role is bone health: it helps the intestines absorb calcium and phosphorus, two essential minerals for strong bones and teeth. A prolonged deficiency can cause rickets in children and osteomalacia in adults, and contribute to osteoporosis.
Vitamin D also contributes to muscle and immune system function. However, as you will see below, the benefits of supplementation for other diseases are much more modest than was thought a few years ago.
The new vitamin D recommendations
Daily requirements (Health Canada)
The recommended dietary allowances (RDAs) used by Health Canada are as follows:
| Age group | Recommended intake per day | Tolerable upper intake level per day |
|---|---|---|
| Children aged 1 to 18 | 600 IU | 2500 to 4000 IU depending on age |
| Adults aged 19 to 70 | 600 IU | 4000 IU |
| Adults over 70 | 800 IU | 4000 IU |
| Pregnancy and breastfeeding | 600 IU | 4000 IU |
These amounts include vitamin D from food and supplements. In addition, Health Canada recommends that everyone over 50 take a 400 IU supplement daily, in addition to eating foods that contain it. Osteoporosis Canada reiterates these same guidelines in its position statement updated in 2026 and notes that some people at risk may need more, as recommended by a health professional.
What has changed: the Endocrine Society guideline (2024)
In 2024, the Endocrine Society published a new guideline based on the strongest clinical trials. Its main conclusions:
- Healthy adults aged 19 to 74: there is no demonstrated benefit to taking more than the recommended intake (600 to 800 IU) to prevent disease.
- People who might benefit from a supplement: children and adolescents, adults aged 75 and older, pregnant women, and people with prediabetes who are at high risk.
- A small daily dose is preferable to a large dose taken at spaced intervals (weekly or monthly), especially for people aged 75 and older.
- No routine blood testing: for a healthy person, measuring vitamin D in the blood is not recommended, and there is no validated “target level” for preventing disease.
In other words, the old popular advice of “1000 to 2000 IU for everyone” is no longer supported by the evidence for most healthy adults. The right dose depends on your age, diet, and situation.
What does the science say about the other benefits?
For a long time, people believed that vitamin D could protect against several diseases. Large clinical trials have since tempered these expectations:
- Cancer and cardiovascular disease: the VITAL study, involving nearly 26,000 adults who took 2000 IU per day for about 5 years, showed no reduction in cancer or cardiovascular events.
- Fractures: in the same study, 2000 IU per day did not reduce fractures in healthy adults who were not deficient.
- Colds and respiratory infections: a meta-analysis published in the BMJ shows a modest protective effect, especially with daily intake and among people who had low vitamin D levels to begin with.
- Mood and depression: the evidence remains mixed. Vitamin D does not replace mental health care or light therapy for seasonal depression.
The key message: vitamin D is essential, and a deficiency should be avoided. But taking more when you already have enough provides no demonstrated additional benefit.
Why are Quebecers at risk in winter?
In summer, brief exposure to sunlight allows our bodies to produce vitamin D. In Quebec, from about October to March, UVB rays are too weak for this. In addition, the cold leads us to cover nearly all of our skin. People at greater risk of vitamin D deficiency include:
- people aged 50 and over, and especially those aged 70 and over;
- people who spend little time outdoors or cover their skin for cultural or religious reasons;
- people with dark skin, who produce less vitamin D from sunlight;
- people with obesity or a condition that affects fat absorption (celiac disease, Crohn's disease, bariatric surgery);
- people who consume neither fish nor fortified products (for example, a vegan diet without fortified plant-based beverages).
What about athletes?
Athletes who train mostly indoors, or outdoors in winter while well covered, may also have lower vitamin D levels. A deficiency can harm bone health and increase the risk of stress fractures. However, in an athlete who is not deficient, studies do not show a clear performance improvement with a supplement. If you have had stress fractures or repeated injuries, talk to your doctor or dietitian.
What foods provide vitamin D?
Few foods naturally contain it. Fatty fish are the best sources. In Canada, cow's milk and margarine must be fortified with vitamin D, and many plant-based beverages and yogurts are also fortified.
| Food | Serving | Vitamin D (approximately) |
|---|---|---|
| Cod liver oil | 1 tbsp (15 ml) | 1360 IU |
| Cooked farmed rainbow trout | 75 g | 570 IU |
| Cooked sockeye salmon | 75 g | 500 IU |
| Mushrooms exposed to UV rays | 125 ml (½ cup) | 350 IU |
| Cow's milk or fortified plant-based beverage | 250 ml (1 cup) | 100 to 200 IU depending on the product |
| Canned sardines | 2 sardines | 45 IU |
| Whole egg | 1 large | 45 IU |
| Canned light tuna | 75 g | 35 IU |
Amounts vary depending on the species, farming method and brand. For fortified products, check the Nutrition Facts table.
Example: to get 600 IU in one day from food, you would need, for example, a serving of salmon or trout and 1 to 2 cups of fortified milk. This is doable on some days, but difficult to maintain every day. That is why a low-dose supplement is often practical in winter.
How to choose and take your supplement properly
- Choose vitamin D3 (cholecalciferol), the most common form. Vegan versions made from lichen are also available.
- Aim for a small daily dose, for example 400 to 1000 IU depending on your age and diet, rather than a large weekly or monthly dose.
- Take it with a meal that contains a little fat for better absorption.
- Add up all your sources: multivitamins, calcium supplements and fortified foods often contain vitamin D. Do not exceed 4000 IU per day without medical advice.
- Ask for advice from your doctor, pharmacist or dietitian if you are pregnant, have a chronic illness, take medication or belong to a high-risk group.
Frequently asked questions
How much vitamin D should you take per day in Quebec?
Adults need 600 IU per day up to age 70 and 800 IU per day after age 70, from all sources combined. Health Canada also recommends a 400 IU daily supplement starting at age 50. Do not exceed 4000 IU per day without medical advice.
Should I take vitamin D in winter if I am under 50?
It is not necessary if your diet contains enough of it (fatty fish, milk or fortified plant-based beverages). If you eat little of these foods, a supplement of 400 to 1000 IU per day from October to March is a simple and safe option.
Should I have a vitamin D blood test?
For a healthy person, routine testing is no longer recommended. Your doctor may order it if you have a bone disease, an absorption problem or another risk factor.
Does vitamin D prevent colds and flu?
The effect is modest. Taking it daily seems to slightly reduce the risk of respiratory infections, especially in people who were deficient in vitamin D. It is not a shield against viruses.
Can you take too much vitamin D?
Yes. At very high doses and over a long period, vitamin D can raise calcium levels in the blood and cause kidney problems. That is why the tolerable upper intake level is set at 4000 IU per day for adults.
Conclusion
Vitamin D remains essential, especially for bone health, and Quebec winters make it difficult to get enough. But the new recommendations encourage moderation: a small daily dose appropriate for your age is enough for most people, and very high doses have not been shown to provide any additional benefit. Start with foods that contain it, add a supplement if needed, and ask a healthcare professional for advice if you have questions about your situation.
Danielle Dubois, nutritionist
Founder of Zenit Nutrition
This article is provided for informational purposes and does not replace the advice of your doctor, pharmacist, or nutritionist.
References
- Demay MB, Pittas AG, Bikle DD, et al. Vitamin D for the Prevention of Disease: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2024;109(8):1907-1947. doi:10.1210/clinem/dgae290. PMID: 38828931
- Ross AC, Manson JE, Abrams SA, et al. The 2011 report on dietary reference intakes for calcium and vitamin D from the Institute of Medicine: what clinicians need to know. J Clin Endocrinol Metab. 2011;96(1):53-58. PMID: 21118827
- Morin SN, Feldman S, Funnell L, et al. Clinical practice guideline for management of osteoporosis and fracture prevention in Canada: 2023 update. CMAJ. 2023;195(39):E1333-E1348. PMID: 37816527
- Manson JE, Cook NR, Lee IM, et al. Vitamin D Supplements and Prevention of Cancer and Cardiovascular Disease. N Engl J Med. 2019;380(1):33-44. PMID: 30415629
- LeBoff MS, Chou SH, Ratliff KA, et al. Supplemental Vitamin D and Incident Fractures in Midlife and Older Adults. N Engl J Med. 2022;387(4):299-309. PMID: 35939577
- Martineau AR, Jolliffe DA, Hooper RL, et al. Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ. 2017;356:i6583. PMID: 28202713
- Ogan D, Pritchett K. Vitamin D and the Athlete: Risks, Recommendations, and Benefits. Nutrients. 2013;5(6):1856-1868. PMID: 23760056
- Health Canada. Vitamin D and calcium: Revision of the dietary reference intakes. canada.ca
- Osteoporosis Canada. Position statement on vitamin D, 2026. osteoporosis.ca
- National Institutes of Health, Office of Dietary Supplements. Vitamin D – Fact Sheet for Health Professionals (food content). ods.od.nih.gov