Supplementation with Vitamin D - How Much is Enough?

4 Minutes

Vitamin D, also known as the sunshine vitamin, is necessary for human survival. While it is one of the more ‘popular’ vitamins in terms of supplementation, it is common to feel uncertain about how much vitamin D to take and if it is even required to supplement at all! Today we will be diving into what exactly vitamin D is, the causes of low vitamin D levels, and existing evidence behind vitamin D supplementation.

Vitamin D food sources

What is Vitamin D?

Vitamin D is a fat-soluble vitamin that is found naturally in a variety of foods including fatty fish, eggs, and cheese. Milk, cereals, and orange juice are examples of foods that are consistently fortified with Vitamin D in Canada. Aside from ingestion, vitamin D is also produced in the body when sunlight (in particular, UV rays) hits exposed skin.

One of the main purposes of vitamin D is to increase the absorption of calcium in the gut. This way, increased amounts of calcium allow your bones to grow properly and stay strong over time. There is also evidence that vitamin D helps reduce inflammation in the body, as well as supports the function of different types of cells.

A lack of vitamin D can result in rickets in children, a condition where the bones soften and become weaker, as well as osteomalacia, which is a similar condition that primarily affects adults. Both of these conditions can be prevented by adequate vitamin D supplementation.

What Causes Low Vitamin D?

As previously discussed, vitamin D is found in certain foods and synthesized in the body following exposure to sunlight. There are many causes of low vitamin D, with the main reasons being dietary patterns, poor absorption of vitamin D, and low sunlight exposure.

Those who limit or completely restrict milk and dairy products in their diet are likely to be vitamin D deficient. This is simply because dairy products often contain and are sometimes fortified with vitamin D. In addition, individuals who follow a vegetarian or vegan diet are likely unable to take in an adequate amount of vitamin D. Although fruits and vegetables contain vitamin D, foods high in vitamin D are skewed towards fatty fish, organ meats and dairy products.

It is important to note that even if vitamin D intake is adequate, those affected by conditions that limit fat absorption will likely experience vitamin D deficiency. Vitamin D is fat soluble - what this means is that the absorption of fat in the gut also facilitates the transit of vitamin D. Fat malabsorption conditions include liver disease and gut conditions such as inflammatory bowel disease.

Finally, the lack of exposure to sunlight is determined by a variety of different factors. Those who are homebound, live at northern latitudes where the hours of sunlight are reduced, and wear clothing that covers exposed skin fall under this category. Without skin exposure to sunlight, the body cannot produce vitamin D at sufficient levels.

Treatment for Vitamin D Deficiency

It is recommended that adults and children treat vitamin D deficiency by increasing vitamin D intake via dietary changes and supplements. There is conflicting evidence regarding dosing for the purposes of supplementation, and Health Canada has published guidelines on dietary reference intakes for vitamin D (shown below).

Treatment for Vitamin D Deficiency

Research suggests that a daily dose for vitamin D of 800 IU or less is more beneficial than 800 IU or more to reduce death from all causes. Even though supplementation may be required, using high doses of vitamin D to correct deficiencies may result in adverse effects such as over-calcification of the bones. It is extremely important to seek advice from a healthcare provider prior to supplementation with vitamin D, to ensure doses of vitamin D are both safe and effective.

Vitamin D

Canadians live at more northern latitudes in colder temperatures. While vitamin D deficiency is not uncommon, it is key to maintain a sense of balance during supplementation. EasyDrugs pharmacists are available to answer your questions about vitamin D supplementation, and you can even order vitamin D supplements online for quick delivery!


  1. Office of Dietary Supplements - Vitamin D [Internet]. [cited 2021 Dec 17]. Available from:
  2. Canada H. Vitamin D and Calcium: Updated Dietary Reference Intakes [Internet]. 2008 [cited 2021 Dec 17]. Available from:
  3. Zheng Y, Zhu J, Zhou M, Cui L, Yao W, Liu Y. Meta-Analysis of Long-Term Vitamin D Supplementation on Overall Mortality. PLOS ONE. 2013 Dec 3;8(12):e82109.