Vitamin D

Most people know of Vitamin D and probably take it for its role in bone health and supporting strong bones and/or to reduce the risk of developing osteoporosis.  Vitamin D has important roles in the body beyond helping to maintain bone mineral density.  It also plays a major role in immune health as well.

The Benefits of Vitamin D

Bone Health: Vitamin D is just one of many factors along with physical activity, other nutritional habits, genetics and lifestyle to help maintain bone mass. It helps with calcium absorption in the intestines which helps to maintain blood calcium levels and thus, keeps calcium in the bones helping to maintain bone mineral density (1)

Muscle strength: There is some research that shows Vitamin D is able to increase muscle synthesis and growth via increasing type 2 muscle fibres in the muscle which can also help to reduce falls (1)

A positive for Mood: A case report demonstrated that correcting vitamin D deficiency reduced depression scores in women (2).  This can be related to reducing the inflammation that is associated with depression.  Less inflammation enables the brain to produce more serotonin.  Vitamin D is just one of many treatments for depression and reducing inflammation - addressing food sensitivities, gut health and figuring out the root cause of the inflammation is key.  This may be a vitamin to consider if you experience seasonal depression or seasonal affective disorder.

Immune Health: It helps to regulate the immune system and reduces the amount of pro-inflammatory cytokines while increasing anti-inflammatory cytokines.  This helps to reduce inflammation and can be a good option for autoimmune conditions (3).

Skin Health: It can be beneficial in many skin conditions like eczema, psoriasis, and acne through regulating keratinocyte differentiation and/or its role in supporting the immune system (4).

How Do You Obtain Vitamin D?


Unfortunately, the availability of the vitamin through food sources is limited with salmon and other fatty fish, eggs, and milk being the main sources.  This means vegetarians and vegans and whoever avoids fish, dairy, and/or eggs have to rely on a vitamin D supplement.



Vitamin D can be made through skin exposure to UVB radiation (sun’s rays).  UVB radiation reacts with cholesterol on the skin surface to begin the vitamin D formation cascade (1).  If we live near the equator where the UVB rays are strongest, there is a better chance of having adequate vitamin D levels, especially for fair-skinned individuals.  Living in the northern hemisphere, our UVB rays are weaker, especially in the winter months which means our skin cannot make as much vitamin D.

It’s important to mention those individuals who are darker skinned and have more melanin will have reduced Vitamin D formation in the skin as the melanin soaks up the UVB rays rendering less UVB available for converting the cholesterol to initiate the formation of vitamin D.


The lack of dietary and UVB exposure make supplements a good choice for obtaining therapeutic levels.  Doses can range from 1000IU or more for adults based on your health status and therapeutic need, which is why it is best to consult a healthcare professional to determine how much you should be taking.


The Science on Vitamin D...

Calcitriol (1,25-hydroxyvitaminD3) is the active form of Vitamin D.  Calcitriol is responsible for increasing intestinal calcium absorption, binding to vitamin D receptors in the body and performing vitamin D functions.  In order to obtain calcitriol, one must have a well-functioning liver and kidneys.  This is why many individuals with kidney disease will often be given prescription calcitriol since their kidneys unable to make sufficient vitamin D.

vitamin D synthesis

Test Your Levels!

Ideally, it is good to test your vitamin D prior to supplementing to obtain a baseline value and to know if the supplement is working and your levels are increasing upon re-testing.

If you already have been taking Vitamin D for years, it is always a good idea to test to make sure your levels are going up and within optimal range.  If your levels are not increasing, there could be an absorption issue in the gut (especially if you have digestive symptoms or find you don’t absorb fat as well as vitamin D is best absorbed with fat) that needs to be fixed.

Further, vitamin D is a fat-soluble vitamin which means that it gets stored in fat tissue.  Increased Vitamin D levels can lead to increased calcium absorption and high blood calcium levels.  High calcium, in severe cases, can cause nausea, vomiting, frequent urination, weakness, bone pain, and calcium-based kidney stones.  While Vitamin D toxicity is rare, it is something to be aware about, especially if you have been taking vitamin D for a long period of time. (5)

MDs are reluctant to test Vitamin D and are actually unable to order it unless they have a very good medically documented reason for doing so.  Fortunately, naturopathic doctors can fill this gap by ordering Vitamin D testing – yes there will be a small fee, but it is better to know and make sure supplementation is working for you!

Vitamin D testing


  1. Laird E, Ward M, McSorley E, Strain JJ, Wallace J. Vitamin D and bone health; potential mechanisms.  2010 Jul;2(7):693-724.
  2. Endocrine Society. (2012, June 25). Treating vitamin D deficiency may improve depression. ScienceDaily. Retrieved November 23, 2019 from
  3. Aranow C, MD. Vitamin D and the immune system. J Investig Med. 2011 Aug;59(6):881-886.
  4. Mostafa WZ, Hegazy RA. Vitamin D and the skin: focus on a complex relationship: a review.  J Adv Res.  2015 Nov;6(6):793-804.
  5. Marcinowska-Suchowierska E, Kupisz-Urbanska M, Lukaszkiewicz J, Pludowski P, Jones G. Vitamin D toxicity – a clinical perspective. Front Endocrinol (Lausanne).  2018;9:550.

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