Vitamin D for Kids — Why Most Canadian Children Are Deficient and What to Do About It

Canada is one of the most vitamin D deficient countries in the world. The geography makes it almost inevitable — for roughly six months of the year, the sun sits too low in the sky for Canadians to synthesise vitamin D through skin exposure, even on clear days. In cities like Toronto, Montreal, and Vancouver, the vitamin D synthesis window runs from approximately May to October. The rest of the year, no amount of time outdoors produces meaningful vitamin D.

For adults, this is a significant concern. For children — whose bones are growing, whose immune systems are developing, and whose brains are in a critical phase of maturation — it is a more urgent one.

Most Canadian children are not getting enough vitamin D. Here is why it matters, where to get it from food, and what Health Canada actually recommends.

Vitamin D is not a single nutrient with a single function. It is a hormone precursor that influences dozens of biological processes — many of which are especially critical during childhood.

Vitamin D is not a single nutrient with a single function. It is a hormone precursor that influences dozens of biological processes — many of which are especially critical during childhood.

Bone development — Vitamin D regulates the absorption of calcium and phosphorus, the two minerals most essential for bone formation. Without adequate vitamin D, calcium cannot be absorbed effectively regardless of how much dairy or calcium-rich food a child consumes. Severe deficiency produces rickets — a condition causing soft, weak bones — but even mild deficiency impairs bone density and development in ways that may not be visible until adulthood.

Immune function — Vitamin D receptors are present on virtually every immune cell in the body. Vitamin D regulates the immune response, reduces the risk of respiratory infections, and modulates the inflammatory processes that underlie many chronic conditions. Children with adequate vitamin D levels get sick less often and recover faster than those who are deficient.

Mood and mental health — Vitamin D receptors are found throughout the brain, and deficiency is consistently associated with increased rates of depression, anxiety, and mood instability. The connection between low vitamin D and low mood is well established in adults — and increasingly recognised in children, particularly during the winter months when deficiency is most acute.

Muscle function — Vitamin D supports muscle strength and coordination. Children who are significantly deficient may experience muscle weakness, fatigue, and generalised aches that are easy to misattribute to other causes.

Cognitive function — Vitamin D plays a role in brain development and neurotransmitter production. Adequate levels during childhood are associated with better cognitive performance, attention, and academic outcomes.

Limited sun exposure for most of the year — In Canada, the UVB radiation needed to synthesise vitamin D through skin exposure is only available from approximately May to October at most latitudes. From November through April, no amount of outdoor time produces meaningful vitamin D — the sun angle is simply too low.

Indoor lifestyles — Even during the summer months, children spending most of their time indoors — at school, in after-school activities, on screens — have limited sun exposure. Sunscreen, while essential for skin cancer prevention, also reduces vitamin D synthesis significantly.

Dark skin tones — Melanin in darker skin reduces the skin's ability to synthesise vitamin D from sunlight. Children with darker skin tones require significantly more sun exposure to produce the same amount of vitamin D as children with lighter skin — making dietary and supplemental sources even more important.

Dairy-free and low-fat diets — Vitamin D is fat-soluble and found primarily in fatty foods. Children avoiding dairy or eating low-fat diets have fewer dietary sources of vitamin D. Low-fat milk contains less vitamin D than whole milk; dairy-free alternatives vary significantly in their vitamin D fortification.

Limited dietary sources — Very few foods contain meaningful amounts of vitamin D naturally. The list is short: oily fish, egg yolks, and liver. Most of the vitamin D in the Canadian food supply comes from fortified foods — milk, some orange juices, some cereals — rather than naturally occurring sources.

Health Canada recommends the following daily vitamin D intake for children:

• Infants 0-12 months: 400 IU per day
• Children 1-18 years: 600 IU per day
• Upper tolerable limit for children: 2,500-4,000 IU per day depending on age

The Canadian Paediatric Society recommends that all Canadian children receive vitamin D supplementation, particularly during the fall and winter months — and year-round for children at higher risk of deficiency including those with darker skin tones, limited sun exposure, or dietary restrictions.

600 IU per day is the minimum recommended intake. Many paediatricians and nutrition researchers argue the optimal intake for Canadian children — particularly during winter — is higher, in the range of 1,000-2,000 IU per day. Discuss with your child's paediatrician for personalised guidance.

The honest reality is that food alone is unlikely to meet a Canadian child's vitamin D needs during winter. The dietary sources are limited, and the amounts they provide fall short of the recommended daily intake without supplementation. That said, maximising dietary vitamin D is worthwhile and every source counts.

Salmon and oily fish are the richest natural dietary sources of vitamin D available. A 75g serving of cooked salmon provides approximately 400-600 IU of vitamin D — close to the full daily recommended intake in a single serving. Sardines and mackerel provide similar amounts. Two servings of oily fish per week contributes meaningfully to vitamin D intake and also provides omega-3 fatty acids essential for brain development.

Eggs — specifically the yolk — contain approximately 40 IU of vitamin D per egg. This is a modest amount, but eggs are eaten daily by many children and contribute consistently to overall intake. Eggs from hens raised outdoors or fed vitamin D-enriched feed contain higher amounts.

Fortified cow's milk is one of the most significant dietary sources of vitamin D in the Canadian diet. Canadian regulations require that cow's milk be fortified with vitamin D — a 250ml glass provides approximately 100 IU. Three glasses of milk per day covers roughly half the daily recommended intake.

Fortified plant-based milk alternatives — soy milk, oat milk, almond milk — are required to be fortified with vitamin D in Canada when sold as a beverage, providing approximately the same amount per serving as cow's milk. Check the label to confirm fortification levels, as they vary between brands.

Fortified orange juice — some brands of orange juice are fortified with vitamin D, providing approximately 100 IU per 250ml serving. Check the label.

Mushrooms — particularly mushrooms exposed to UV light — can contain meaningful amounts of vitamin D2. Some commercially available mushrooms are specifically UV-treated and labelled accordingly. While vitamin D2 from mushrooms is less bioavailable than the vitamin D3 from animal sources, it is a meaningful plant-based contribution.

Liver and cod liver oil — both are exceptionally rich in vitamin D but are rarely eaten by children. Cod liver oil in small amounts — a teaspoon provides approximately 400 IU — is worth considering for children with significant dietary restrictions, though it should not be used in high doses due to the risk of vitamin A toxicity.

The Canadian Paediatric Society and Health Canada both recommend vitamin D supplementation for Canadian children, particularly during fall and winter. Given the near-impossibility of meeting vitamin D needs through diet alone during the months when sun exposure is absent, supplementation is the most practical and reliable solution for most Canadian families.

A daily supplement of 400-1,000 IU of vitamin D3 is the most commonly recommended range for children aged 1 and over. Vitamin D3 (cholecalciferol) is the preferred form — it is more bioavailable and more effective at raising blood vitamin D levels than vitamin D2.

Vitamin D supplements for children are available as drops, gummies, and chewable tablets. Drops are the most practical for younger children and can be added to food or drink invisibly.

before starting supplementation, particularly at higher doses. While vitamin D toxicity from supplementation is rare, it is possible at very high doses. A paediatrician can recommend an appropriate dose based on your child's age, diet, skin tone, and sun exposure.

Serve salmon or oily fish twice a week. Baked salmon with rice and vegetables, canned salmon in a pasta or sandwich, sardines on whole grain toast — two servings per week makes a measurable difference to vitamin D intake.

Use whole milk rather than low-fat. Vitamin D is fat-soluble — it is better absorbed alongside dietary fat. Whole milk provides both the vitamin D and the fat needed for its absorption.

Include eggs regularly. A hard-boiled egg in the lunchbox every day or scrambled eggs at breakfast several times a week contributes consistent small amounts of vitamin D alongside choline, protein, and healthy fat.

Choose fortified plant-based alternatives carefully. If your child drinks plant-based milk, check the label for vitamin D fortification and choose brands with the highest levels.

Use vitamin D-fortified foods as a baseline. Fortified milk, fortified juice, and fortified cereals are not sufficient on their own — but as a consistent baseline alongside dietary sources and supplementation, they contribute meaningfully to overall intake.

Vitamin D deficiency is not a niche concern for Canadian children — it is a near-universal reality for much of the year. The geography of Canada makes adequate vitamin D through sun exposure alone impossible during fall and winter, and the dietary sources are limited enough that food alone rarely bridges the gap.

The practical response is straightforward: maximise vitamin D through food — salmon twice a week, eggs daily, fortified milk — and discuss supplementation with your child's paediatrician. A daily vitamin D3 supplement during the fall and winter months is one of the simplest, most evidence-supported things a Canadian parent can do for their child's bone health, immunity, mood, and cognitive development.