What is Vitamin D?
Vitamin D, also known as calciferol, is an essential vitamin that has many functions. It plays a role in absorbing calcium, helps in building and maintaining strong bones, supports the immune system, and improves muscle functions like balancing and reducing the risk of falls and injuries (Mavar et al., 2024).
There are two types of vitamin D; vitamin D3 (cholecalciferol) and vitamin D2 (ergocalciferol). Vitamin D3 comes from animals and is also synthesized in humans when our skin epidermal cells come in contact with sun rays (Chang & Lee, 2024). Whereas vitamin D2 comes from plants and fungi containing the precursors for vitamin D2 (Mavar et al., 2024). Vitamin D is also a fat-soluble vitamin, meaning that it is stored in the body’s fat cells. Fat in the small intestine also enhances vitamin D absorption (Mavar et al., 2024). This makes sense as most of the naturally occurring vitamin D-rich foods are high in dietary fat.
Furthermore, sunlight exposure remains the most common intake of vitamin D for humans as there are very few foods that contain vitamin D naturally. Certain food products on the shelves are fortified with vitamin D in regulation with Health Canada to maintain sufficient levels of vitamin D in our diets. Without sufficient levels of vitamin D in our bodies, we may suffer from vitamin D deficiency.
Vitamin D Deficiency
Vitamin D deficiency is classified by insufficient serum vitamin D levels and is a rising global public health concern. Vitamin D deficiency can increase the risk of many health conditions. Some of these include our bones becoming brittle and thin due to lack of vitamin D, causing osteoporosis and rickets in children (Chang & Lee, 2024). The global increase in vitamin D deficiency could be due to lifestyle changes, as more people are spending time indoors, limiting sun exposure according to Mavar et al. Aging populations are also more susceptible to vitamin D deficiency as their ability to synthesize vitamin D from sun exposure weakens and becomes less effective (Mavar et al., 2024).
Furthermore, people residing in the Northern hemisphere of the world are more at risk of vitamin D deficiency, due to a lack of sun exposure (Mavar et al., 2024). There are other risks to our health due to vitamin D deficiency, such as respiratory infections and autoimmune diseases (Mavar et al., 2024). Which is why we need to maintain sufficient levels of vitamin D in our bodies. To do so, we can incorporate more vitamin D into our daily lives. The main sources of vitamin D include: supplements, food, and sunlight exposure.
Supplements
Health Link BC recommends that we choose supplements that have a Natural Product Number (NPN) because they meet Health Canada’s safety measures. There are three main kinds of supplements: liquid, chewable, and pill form.
- Liquid form is recommended for children 4 and under
- Chewable form is for anyone who can chew and swallow safely
- Pill form is for anyone who can swallow a pill safely
Please follow the labels for dosage and instructions on the intake of the supplement. Take caution and speak to your health care provider when incorporating vitamin D into your diet as taking excessive amounts can lead to vitamin D toxicity and detrimental health outcomes (Mavar et al., 2024).
Health Canada recommends taking daily supplements of vitamin D and incorporating vitamin D rich foods into your daily diet.
Dosage recommendation:
| Age range | Recommended dosage | Upper intake level |
| 0-12 months | 400 IU (10 µg) | 1000 IU (25 µg) |
| 1-3 years | 600 IU (15 µg) | 2500 IU (63 µg) |
| 4-8 years | 600 IU (15 µg) | 3000 IU (75 µg) |
| 9-70 years (including pregnant and breastfeeding individuals) | 600 IU (15 µg) | 4000 IU (100 µg) |
| 70 and over | 800 IU (15 µg) | 4000 IU (100 µg) |
Foods Rich in Vitamin D
There are very few foods that contain vitamin D naturally. Most of the vitamin D we consume in Canada is from fortified foods – where vitamin D is added. It is recommended by Health Link BC to check the nutrition facts table to see if vitamin D has been added.
Here are some vitamin D-rich foods to incorporate into your diet:
- Egg yolks
- Soft Margarine
- Fatty fish such as – salmon, artic char, rainbow trout
- Unsweetened low-fat milk
- Unsweetened fortified plant-based beverages
- Mushrooms
Vitamin D Metabolism
As vitamin D enters the bloodstream via food or dietary supplements, it is in an inactive state, meaning it is not contributing to the many functions in the body. It is essential for vitamin D to convert to its active form in order to have many functions and carry out positive effects. The vitamin D precursor binds to vitamin D receptors and is transported to the liver to be converted to calcidiol – the main form of vitamin D circulating in the bloodstream. Calcidiol is then transported to the kidneys to be converted to its most active form, calcitriol. From there, vitamin D3 becomes functional throughout the body in places like the immune system, small intestine, pancreas, cell functions, and bones (Mavar et al., 2024).
Refer to the figure for a detailed visual representation of the vitamin D metabolism and pathway.
Sunlight
Our bodies can make vitamin D when our skin is exposed to UV rays from sunlight. This ultraviolet radiation skin exposure is the major source of vitamin D most people get (Chang & Lee, 2024). However, many factors can influence vitamin D synthesis in the skin such as season, time of day, cloud cover, skin pigmentation, smog, and sunscreen use (Health Canada, 2022). Our skin produces vitamin D through a thermal reaction that occurs after UV radiation from the sun enters the skin (Mavar et al., 2024). The vitamin D precursor in our skin epidermal cells converts into pre-vitamin D3. It is then converted to calcidiol in the liver, which converts to its active form (calcitriol) in the kidney (Chang & Lee, 2024). After vitamin D3 is synthesized/activated, it then moves through our bodies to provide various functions as mentioned above.
However, sun exposure is classified as a Group 1 carcinogen which is known to cause cancer in humans. So, Health Canada recommends incorporating vitamins from foods or supplements as a safer measure of daily vitamin D intake.
Key Takeaways:
- Vitamin D is important for our bodies as it provides numerous functions that are both fundamental and beneficial for maintaining our overall health.
- The main sources of vitamin D include: supplements, food, and sunlight exposure.
- Our bodies activate vitamin D from its inactive state to perform the many functions it has across our bodies.
- Health Canada recommends incorporating vitamin D from foods or supplements on a daily basis as sun exposure may be an inconsistent source or may increase the risk of skin cancer.
- Everyone is different! – Please consult with your health care provider before incorporating vitamin D into your diet or sunbathing
Visit Health Link BC for more information and resources regarding Vitamin D.
References
Chang, S., & Lee, H. (2019). Vitamin D and health – The missing vitamin in humans. Pediatrics & Neonatology, 60(3), 237 – 244. https://doi.org/10.1016/j.pedneo.2019.04.007
Government of Canada. (2022, May 2). Vitamin D. Canada.Ca, www.canada.ca/en/health-canada/services/nutrients/vitamin-d.html.
Mavar, M., Sorić, T., Bagarić, E., Sarić, A., & Matek Sarić, M. (2024). The Power of Vitamin D: Is the Future in Precision Nutrition through Personalized Supplementation Plans? Nutrients, 16(8), 1176. https://doi.org/10.3390/nu16081176
Province of British Columbia. (2021, September 1). Vitamin D and your health. British Columbia | HealthLink BC. https://www.healthlinkbc.ca/healthlinkbc-files/vitamin-d-and-your-health
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