Key Takeaways
- The RDA is 600 IU a day for ages 1–70 and 800 IU over 70; the safe upper limit for adults is 4,000 IU a day from all sources.
- Health Canada advises everyone aged 51+ to take a daily 400 IU vitamin D supplement, and says about 1 in 5 Canadians don't get enough.
- On blood tests, below 30 nmol/L is deficient and 50 nmol/L or above is adequate for most people; overdoses come from supplements, never from sunshine.
Canada's Sunshine Problem Comes With a Daily Vitamin Recommendation
Vitamin D is the nutrient Canadians are worst positioned to make for themselves. Your skin produces it from sunlight, but Health Canada lists the obstacles plainly — season, cloud cover, smog, sunscreen, limited time outdoors, age and skin melanin all cut production — and concludes: "These factors can apply to many people living in Canada. This is why we recommend vitamin D from foods or a supplement every day." By Health Canada's estimate, about 1 in 5 people living in Canada are not getting enough.
The targets
- Ages 1–70: 600 IU (15 µg) per day
- Over 70: 800 IU (20 µg) per day
- Infants: 400 IU (10 µg) per day
- Upper limit, adults: 4,000 IU (100 µg) per day from food, drinks and supplements combined
Health Canada's most specific advice: if you are 51 or older, take a daily supplement containing 400 IU — and keep eating vitamin D foods on top of it.
Food helps, but the list is short
Vitamin D occurs naturally in very few foods, and in Canada most dietary vitamin D comes from fortified products. Per the NIH's tables: a cup of fortified milk has roughly 120 IU (Canada roughly doubled the required fortification of milk and margarine under 2022 rules, with industry compliance due by the end of 2025), 3 oz of sockeye salmon about 570 IU, rainbow trout 645 IU, an egg yolk about 44 IU. Fatty fish is the one food that moves the needle on its own.
D2 or D3?
Two forms exist: D2 (ergocalciferol) and D3 (cholecalciferol). Both are absorbed well, but the NIH notes most evidence shows D3 raises blood levels more, and keeps them higher for longer. Either form absorbs best taken with a meal that contains some fat.
Testing, and the overdose myth
Status is measured with a blood test for 25-hydroxyvitamin D. On the scale used by the NIH and the Food and Nutrition Board: below 30 nmol/L is deficient, 30 to under 50 is inadequate for bone health, and 50 nmol/L or above is adequate for most people. Push far the other way — above 125 nmol/L — and adverse effects appear.
And the overdose route matters: you cannot get too much vitamin D from sunshine — the skin limits its own production. Toxicity, which drives blood calcium dangerously high (nausea, confusion, kidney stones, in extreme cases kidney failure), comes almost always from excessive supplements. More is not better; the 4,000 IU ceiling is real.
The Twikup Take
Canada fortifies milk, mandates margarine fortification, and still tells everyone over 51 to just take the 400 IU pill — that's the country quietly admitting geography wins. Hit the 600–800 IU target, respect the 4,000 IU ceiling, and let fatty fish do the heavy lifting when it's on the plate. And if you want more, just ask your doctor first.
This article is general information, not medical advice. If you suspect a deficiency or take medications that affect vitamin D, ask your doctor about testing before supplementing.
Image: AI-generated illustration.