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Vitamin D… What’s the Big Deal?

Vitamin D… What’s the Big Deal?

Author: Elora Rider
Dietetics Student &
Research assistant in the Faculty of Medicine and Dentistry
at the University of Alberta 

Vitamin D is one of the most interesting nutrients! It plays so many roles in our body, from bone health and cell growth to immune function. Vitamin D is one of those nutrients that is still being researched heavily and there are so many things about it that we do not know, but if you ask me that is what makes it all the more exciting.

I’m sure a lot of you have heard about vitamin D. In fact a lot of people know that they probably are not getting enough, but they do not entirely understand why. So first I want to give you all a quick crash course in how our bodies get this nutrient.

How do we get Vitamin D? 

The body’s main source of vitamin D actually has nothing to do with the food we eat. Our body gets almost all of its vitamin D from when our skin is exposed to sunlight, creating a reaction that produces vitamin D. During the summer if we spend some time in the sun our body can actually make enough vitamin D to meet our needs. However, our Canadian winters don’t allow the right sun exposure to create the vitamin D we need, especially as most of our skin is covered up in sweaters or jackets. This is when we have to rely on other sources for vitamin D.

Vitamin D can come from our diet, but there is something very important to know when consuming vitamin D. Vitamin D is fat soluble! What this means is it needs to be dissolved in some type of fat in our gut in order to be absorbed. This is actually a pretty significant thing to know and we can explore it more when we discuss how to supplement!

Why Do We Need Adequate Vitamin D? 

Cognition- Low levels of vitamin D are associated with increased risk of depression. Depression is a complex disease with many contributing factors and vitamin D levels alone are not the sole contributor and they may not be causal. There is some evidence that vitamin D supplementation may better mood in some individuals with low levels, who have seasonal affective disorder.

Immunity- Many different immune cells in our body have vitamin D receptors on them. Vitamin D likely impacts our immune function and ability to fight off disease. Vitamin D can influence how our immune cells move around and enhance their function. Vitamin D may also play a role in these cells dividing and finding their identity.

Bone health- Vitamin D is essential in the proper absorption and utilization of calcium. It assists the gut in absorbing dietary calcium. All calcium comes solely from the things we eat or supplement with, so having help with absorption is a big deal! Calcium is used not only to lay down bone, but it is also an essential electrolyte that plays a major role in cellular signalling.

Muscle Health- There is some evidence that maintaining adequate vitamin D levels may be protective against muscle loss and muscle strength loss as we age.

Hormone health- Vitamin D not only acts like a hormone itself, but it plays a role the regulation of other hormones. One example is testosterone, where deficiency of vitamin D is associated with lower levels of testosterone. Vitamin D is not the only thing that impacts this hormone’s level in our body, but it does influence it along with many other factors.

Heart Health- Vitamin D may play a role in blood pressure regulation, however this is still an active area of research. Deficiency may be associated with increased risk for a number of cardiovascular diseases.

Cell Growth- Vitamin D helps regulate when cells divide. This is important as we want cells to be dividing only when appropriate. Cell division is extremely complex, but happens in our bodies constantly. This nutrient likely also plays a role in helping new cells find their identity and assisting old cells when it is their time to die.

Vitamin D Deficiency: MedlinePlus

Food Sources of Vitamin D

We should all focus on trying to get our vitamins and minerals from our diet. A healthy diet is so important and, in my opinion, eating good food is way more fun than taking supplements. However, there are times when it is not possible to get enough of the nutrients we need through diet alone. Vitamin D in particular is quite difficult to obtain only through the foods we eat, and this is why many people in nutrition recommend everyone in Canada supplement with vitamin D, especially in the colder months.

Food sources with naturally occurring vitamin D include eggs and fatty fish. There are also many different foods that are fortified with vitamin D. In Canada, by law all fluid cow’s milk must be fortified with vitamin D. Other milk products may be fortified but it is not legally required. Some foods such as orange juice and margarine may also be fortified with vitamin D.

How Can I Supplement?

We talked about the importance of vitamin D being fat soluble and I promised to explain why it is important to understand that, so let me paint a picture for you. Most people who supplement with vitamin D take a hard-pressed pill. They usually take it before bed or early in the morning, with a glass of water but without eating. If we understand how vitamin D is absorbed, we can see how this might be a problem. The little pressed pill has no fat to be dissolved in and therefore we can not really absorb the nutrient we are trying to get!


So here are my tips on getting the most out of your Vitamin D supplement. 

  • Take your supplement with some fat! This could be with any of your meals as long as they have fat in them. Or you could eat a little fat on its own and take your supplement with that. This could be something like nuts, peanut butter, or cheese!
  • Buy a vitamin D that is dissolved in oil already. This is easier for most people in my opinion as you don’t have to plan out when you are going to take your vitamin D supplement. It is already dissolved in a very small amount of fat and so you can take it at any time.

Lastly try to choose a D3 supplement when looking for vitamin D, because D3 is the form that is more readily absorbed.

Who is at Higher Risk for Having Low Vitamin D?

People at northern or southern latitudes who have limited seasonal sun exposure, such as us Canadians. 

The elderly are at an increased risk of having a low vitamin D status, because as we age our skin starts becoming less efficient at using the sunlight to produce vitamin D.

Individuals who have darker skin need more sun exposure to make vitamin D. This is because the melanin which causes the darker skin tone acts to protect the skin from UV light.

People who wear long clothing year-round or individuals who work night shifts are at an increased risk for having a low vitamin D status, because they have limited exposure to sunlight.

Those who have obesity may be at higher risk of having lower levels of circulating vitamin D. This is because vitamin D is fat soluble and can be stored in the fat of our bodies. When it is stored in this tissue it may become less accessible to our body when we need it.

Individuals who experience malabsorption may be at higher risk of vitamin D deficiency. This could occur with diseases such as crohn’s, cystic fibrosis, liver disease, celiac, and pancreatic diseases that alter enzyme function or production. This is because vitamin D may have a harder time being absorbed in the intestines of these individuals.

How Much Vitamin D Should I Be Taking?

Current recommendations from Health Canada comes mainly from research that looked at the link between how much vitamin D is needed to maintain good bone health.

There could possibly be changes in the future as we continue to learn more about the roles of vitamin D in our body and what levels may be needed. 

Recommendations differ between age groups and needs may differ if someone is experiencing abnormal vitamin D levels in the blood or if they are experiencing particular disease states. It is recommended that you ask your doctor to test your vitamin D levels if you are concerned about deficiency.


Daily Recommended Intake:


1- 18 years old: 600 IU per day


19 to 50 years old (including pregnant and lactating women): 600 IU per day

70 years old and up: 800 IU per day

Of note, Health Canada Recommends that everyone over the age of 50 should supplement with 400 IU of vitamin D per day.

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