When the majority of people hear the term Vitamin D, they will immediately associate it with images of sunshine, warm climates, and the summer season. That is to say, many people are aware of the essential vitamin and our primary source of obtaining it, but: what exactly is Vitamin D, how important is it, and how much is actually enough?

First and foremost, Vitamin D is a prohormone, in other words, “it is converted into a hormone by our body” (Fookes, 2018). It is deemed a fat soluble vitamin, as it can be readily absorbed with fat and is often stored in the liver and fatty tissues, and can take on several different forms. The primary two forms of Vitamin D are Vitamin D2, otherwise known as ergocalciferol, and Vitamin D3, or cholecalciferol (Raman, 2017). The vitamin has, for the most part, been universally accepted as being absolutely essential to human health, playing a fundamental role in several of our bodies key functions, including but not limited to: calcium absorption, modulating cell growth, and our immune system function (Fookes, 2018). 

As mentioned, the primary source of Vitamin D is the sun. Our bodies, specifically our skin, make Vitamin D when exposed to UV by converting the cholesterol in our skin to Vitamin D3 (Raman, 2017). However, obtaining the nutrient from a natural source such as the sun means that there are numerous factors that can disrupt or reduce the amount of Vitamin D our bodies are getting. For example, where you live, the season, the weather, and even the time of day can all substantially alter the amount of Vitamin D our body creates (Vitamin D). As a result of these factors, people that live further away from the equator, are elderly in age, or suffer from an illness or disability that prevents regular sun exposure, are all more likely to be at risk of a Vitamin D deficiency (Fookes, 2018). For this reason, it is especially important to note that there are two other sources from which Vitamin D can be obtained: food and supplements. Vitamin D can also be obtained through a small variety of foods, including mushrooms, butter, cheese, egg yolk, and fatty fishes such as salmon, as well as from various forms of natural supplements (Fookes, 2018).

While the current Health Canada recommendation stands at 400 IU (10 µg) per day of Vitamin D, the scientific community has largely agreed that this is often insufficient (Raman, 2017). In fact, it was reported that approximately 42% of people in the United States are currently suffering from low Vitamin D levels (Bjarnadottir, 2017). That being said, there is no definitive cut-off point for deficiency, which has led to some controversy surrounding what exactly is considered a sufficient verses an insufficient level of Vitamin D within the scientific and medical communities. The Institute of Medicine (IOM) declares any Vitamin D level above 20 ng/ml sufficient, while the Endocrine Society states that the threshold to be considered sufficient in Vitamin D is slightly higher, at 30 ng/ml (Fookes, 2018). It is also important to note that the exact level of Vitamin D needed for each individual may vary depending on a multitude of factors including: their age, race, geographic location, time of year, sun exposure, and typical clothing attire. Against this background, research has shown that a “daily vitamin D intake of 1000–4000 IU, or 25–100 micrograms, should be enough to ensure optimal blood levels in most people” (Bjarnadottir, 2017). A 2009 study published in Osteoporosis International  found that Vitamin D levels of approximately “75 to 110 nmol/l provide optimal benefits for all investigated endpoints without increasing health risks”, which is a level approximately 9 out of 10 people do not achieve. These levels can be best obtained with oral doses of Vitamin D in the range of 1,800 to 4,000 IU per day (Bischoff-Ferrari, 2009). Bearing this in mind, an upper or maximum limit of 4000 IU (100 µg) per day of Vitamin D is commonly agreed upon, meaning individuals should not exceed this limit without first discussing it with a healthcare practitioner (Fookes, 2018).

Nonetheless, regardless of these debates the scientific community is united in their awareness that Vitamin D has a multitude of health benefits, many of which are still being discovered. One study in particular used randomized control trials to prove that “Vitamin D supplementation was related to a statistically significant 12% reduction in mortality” (Keum & Giovannucci, 2014). While another study published in the Cochrane Central Register of Controlled Trials found that their evidence suggested Vitamin D supplements at “moderate to high doses” may reduce the risk of Cardiovascular Disease (Wang, 2010). Additionally, and perhaps most intriguing of all, was a study published in the Cochrane Database Systemic Reviews, which consisted of 56 randomised trials with 95,286 participants providing “usable data on mortality”. After administering Vitamin D to the group of participants, ranging from 18 to 107 years of age, for 4.4 years, the researchers concluded that “Vitamin D decreased mortality in all 56 trials analysed together” (Bjelakovic et al., 2014).  Lastly, Vitamin D has more recently been speculated to reduce the health impacts of COVID-19 (Lovnicki, 2020). While it is important to note that in the case of many of these studies, isolating out a specific root cause for the specific biological effect or change in human health from the various other uncontrollable factors of daily life is rather difficult, as is differentiating between correlation and causation, and therefore, many of the researchers of these studies agree that more extensive research is needed to further validate these results and understand the full capabilities of Vitamin D.

In summary, ensuring sufficient quantities of Vitamin D on a daily basis is unequivocally essential to good health. While the scientific community may be still experimenting and deliberating new and abstract health benefits of the vitamin, it is indisputably vital to good bone healthy, our calcium and phosphorus levels, our immune system, and protecting our bodies against various cardiovascular and respiratory diseases. Undoubtedly, one of the most significant steps anyone can take is to have their vitamin D level determined by a simple blood test. From there, they can assess if any further action, such as Vitamin D supplementation is needed, and if so, by how much. This simple step may be one of the largest and most important public health strategies available to us.  Any questions or concerns regarding your personal Vitamin D levels or the best way to increase your intake of Vitamin D should be directed to a healthcare professional.

For more information, please contact Focal Point Research Inc.  We are leading North American Regulatory and New Product Consultants for Medical DevicesNatural Health ProductsOTC DrugsCosmetics, and other consumer products regulated by Health Canada and the U.S. FDA.


Bischoff-Ferrari, H.A., Shao, A., Dawson-Hughes, B. et al. Benefit–risk assessment of vitamin D supplementation. Osteoporos Int 21, 1121–1132 (2010). https://doi.org/10.1007/s00198-009-1119-3

Bjarnadottir, A. (2017). How Much Vitamin D Should You Take For Optimal Health? Retrieved from: https://www.healthline.com/nutrition/how-much-vitamin-d-to-take

Bjelakovic, G., Gluud, L. L., Nikolova, D., Whitfield, K., Wetterslev, J., Simonetti, R. G., Bjelakovic, M., & Gluud, C. (2014). Vitamin D supplementation for prevention of mortality in adults. The Cochrane database of systematic reviews, (1), CD007470. https://doi.org/10.1002/14651858.CD007470.pub3

Fookes, C. (2018, October 23).  Vitamin D. Retrieved from: https://www.drugs.com/vitamin-d.html

Keum, N., & Giovannucci, E. (2014). Vitamin D supplements and cancer incidence and mortality: a meta-analysis. British journal of cancer, 111(5), 976–980. https://doi.org/10.1038/bjc.2014.294

Lovnicki, C. (2020, November 3). COVID-19 and Vitamin D: Correlation or Coincidence? Retrieved from: https://focalpointresearch.net/canadian-regulatory/covid-19-and-vitamin-d-correlation-or-coincidence/

O’Connor, A. (2020, June 10). Exploring the Links Between Coronavirus and Vitamin D. Retrieved from https://www.nytimes.com/2020/06/10/well/live/coronavirus-vitamin-d-immunity.html

Raman, R. (2017, October 8). What Vitamin D Dosage Is Best? Retrieved from: https://www.healthline.com/nutrition/vitamin-d-dosage

Vitamin D. Government of Canada. Retrieved from: https://www.canada.ca/en/health-canada/services/nutrients/vitamin-d.html

Wang, L., Manson, J. E., Song, Y., & Sesso, H. D. (2010). Systematic review: Vitamin D and calcium supplementation in prevention of cardiovascular events. Annals of internal medicine, 152(5), 315–323. https://doi.org/10.7326/0003-4819-152-5-201003020-00010