Vitamin D in a Canadian winter

By the · Updated · No ads or affiliate links
Bottom line

Canadian winters are a weak source of vitamin D from skin. The dietary allowance used in Canada and the United States is 600 IU a day from ages 1 to 70 and 800 IU a day from age 71, with an adult upper limit of 4,000 IU. A children's 400 IU chewable is not an adult winter dose. Products at 5,000 IU sit above that upper limit unless a clinician is treating a measured deficiency. Certification tells you the bottle matched a public list. It does not pick the dose for you.

From roughly October through March, a walk at Canadian latitudes is a poor way to make vitamin D. Reviews of sun exposure and vitamin D status describe how little useful ultraviolet reaches the skin in the cold months (PMID 37691266, PMID 32918230). Northern populations also show high rates of low vitamin D in winter in the European surveys that mapped the same problem (Cashman and colleagues, PMID 26864360).

The dose on the public reference sheets

The National Academies figures, republished by the NIH Office of Dietary Supplements, set the recommended dietary allowance at 15 micrograms (600 IU) a day for ages 1 to 70 and 20 micrograms (800 IU) a day for ages 71 and older. The adult tolerable upper intake level is 100 micrograms (4,000 IU) a day. Health Canada directs readers to those same reference intakes on its vitamin D page. Food plus a supplement is how many adults get there when the sun is not contributing.

A blood test is the way to find a deficiency. This page is not a target for a 25-hydroxyvitamin D number, and it is not a prescription.

What "best" cannot mean here

We do not name a best brand. We can say which doses match the allowance, and which named products were on a public list on 15 October 2026. Vitamin D3 is the form used in most of those products and in most trials. D2 exists and is a different card.

Jamieson Kids Chewable Vitamin D3 400 IU holds a Health Canada licence, NPN 80015933: 10 micrograms (400 IU), ages 3 and older. A licence means it may be sold in Canada. It is not a purity seal, and it is a children's product. It is the wrong bottle to treat as an adult winter supplement.

USP Verified vitamin D3 products on the public directory included Nature Made at 1,000 IU and 2,000 IU and Member's Mark at 2,000 IU. Several brands also list 5,000 IU softgels. That dose is above the 4,000 IU adult upper limit. It belongs with a clinician who has seen a low blood result, not in a default winter routine.

The product-by-product list is certified vitamin D products compared. How the allowance, the survey numbers, and the upper limit fit together is in how much vitamin D adults need.

Sources

  1. NIH Office of Dietary Supplements. Vitamin D fact sheet for health professionals. NIH ODS.
  2. Health Canada. Vitamin D. Health Canada.
  3. Cashman KD, et al. Vitamin D deficiency in Europe: pandemic? Am J Clin Nutr. 2016. PMID: 26864360.
  4. Webb AR, et al. Making the sunshine vitamin — how much sun exposure is needed to maintain 25-hydroxy vitamin D concentration? Photochem Photobiol. 2024. PMID: 37691266.
  5. Webb AR, Engelsen O. Ultraviolet exposure scenarios: risks of erythema and benefits of cutaneous vitamin D synthesis. Adv Exp Med Biol. 2020. PMID: 32918230.