Why is Vitamin D so important?

Posted by Jaime Camirand, RHN

You’ve probably heard that you need more vitamin D, but this might raise some questions: What does vitamin D actually do? Why is such an important vitamin so hard to get enough of? And does it really live up to its reputation?

Vitamin D is a fat-soluble vitamin with some unique qualities. Unlike most other nutrients, humans are able to synthesize it under the right conditions, and yet many people are lacking it. It also has several complex roles, and has been touted as more of a “hormone” due to the way it behaves in the body. Studies have explored links to many different aspects of health, as well as high rates of deficiency, putting vitamin D on everyone’s radar as a must-have nutrient.


One of the best known functions of vitamin D is helping to build and maintain strong bones and teeth. Calcium intake is often top of mind when it comes to bone health, but it can’t do its job without the help of vitamin D. While calcium is an important part of the structure, vitamin D is needed to properly absorb calcium and allow it to get to the right places.1 It’s also required for proper muscle development and strength, supporting the skeletal system both directly and indirectly.5 For these reasons, vitamin D is closely tied to bone density and oral health, but research has also uncovered several other functions that relate to broader well-being and prevention of illness.

Immunity is another area where vitamin D shines. It has been identified as a critical nutrient for a healthy immune system, helping to modulate various immune responses and playing a major role in protective immunity. Studies have shown that vitamin D can help to lower our susceptibility to illnesses, reducing incidence, duration and severity. Unfortunately, this means that low levels of vitamin D have been associated with higher rates of autoimmune diseases, colds, flus and other infections.3

Vitamin D is known to have many modulating effects within the body, including the nervous system, cardiovascular system and endocrine system. This means adequate amounts are needed for all of these systems to run smoothly and work at their best. For example, vitamin D plays an important role in brain health, and research has linked low levels of vitamin D to higher rates of depression.6 Other studies have shown associations between vitamin D deficiency and risk of cardiovascular disease, diabetes, cancer and overall mortality.5  While there’s more to be learned about the exact mechanisms of vitamin D, it’s clear that it has many protective effects and is essential for optimal health.


Sometimes referred to as the “sunshine vitamin”, vitamin D can be created naturally by the body in response to sunlight. With adequate exposure, human skin will convert the sun’s rays into an active form of vitamin D that is then transported through the bloodstream for various uses and stored for later.1 This is one of the main sources, although it can be obtained from certain foods as well, including sardines, salmon, cod liver oil and egg yolk. Mushrooms are another source of vitamin D that also relies on the sun. Much like humans, they convert sunlight to an absorbable form that we can then consume as an excellent dietary source of vegan vitamin D.4 


Not only is vitamin D one of the most important nutrients for human health, but unfortunately, it also happens to be one of the most common deficiencies. It’s estimated that around 40% of North Americans and two thirds of the rest of the world could be low in vitamin D.2,7,8

Sunlight is a major source, although exposure alone doesn’t guarantee sufficient levels. There are many factors that affect our ability to create vitamin D, including angle of the sun, skin pigmentation, sunscreen use, amount of skin exposed and time spent in the sun.1 For example, living in locations with less direct sunlight could mean a higher risk of deficiency, especially during winter months. Vitamin D synthesis also declines with increasing age, as well as darker skin tones.1

Modern lifestyles have resulted in more people living and working indoors and away from direct sunlight. There’s also much more awareness of sun damage, and many people take measures such as sunscreen or extra layers of clothing to protect their skin from harm. This means that dietary sources of vitamin D and supplementation are more important than ever and could be essential for immunity, bones and overall health.




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