• Dr. Juliet Ghodsian

The Long Dark: Vitamin D deficiency in the Winter Months

As we head into the back-stretch of the long dark, winter months, it is important to discuss the true health impacts of our limited sun exposure here in British Columbia. Between the months of September and March, the angle of the sun to the Earth’s atmosphere is such that almost no UV light rays will penetrate down to the surface. The lack of UV light equals no ability to activate vitamin D inside our own bodies. For this reason, we are all at risk of developing vitamin D deficiency at some point over the course of the winter, despite a healthy intake in the diet.

The role of Vitamin D in our health is becoming increasingly more important as our understanding of the immune system grows. Although we call it a vitamin, Vitamin D actually functions more like a hormone in your body. Different forms of vitamin D play important roles in the health of your bones and muscles, with the production of energy and to decrease risk of depression and maintain mood balance.

The role of vitamin D in relationship to your immune function, however, is very complex. Newer research is demonstrating that Vitamin D travels via the blood stream to interact with the cells in your bones, intestines, colon, brain, and individual immune cells ( ex. Dendritic cells). These vitamin D molecules essentially function as messenger who can turn on and off different genes and processes in these parts of your body. It is through this messenger process that Vitamin D strengthens your Innate Immune response, activates immune cells (dendritic cells, monocytes, macrophages, B cells and Tcells) to fight infection and modulates the production of immunoregulatory chemicals called cytokines. It is safe to say that adequate levels of vitamin D are required for your body to mount an active immune response to an infectious disease of any kind. It helps maintain the health of the gut mucosal barrier, and also the levels of secretory IgA, an antibody that functions as a first line of defense against infections in the gastrointestinal and respiratory tracts. Therefore, one affect of Vitamin D deficiency is an increased risk of infection and illness as well as prolonged recovery time.

Not only does Vitamin D help to activate and turn on your immune system to help you fight off infection, it also plays a role in stimulating production of immune cells that play a role in calming and regulating your immune function. Vitamin D helps to stimulate the production of T regulatory cells whose main function is to differentiate between self and non-self. Having an immune system that knows which cells are invading pathogenic bacterias and which are normal liver cells is a very important piece of the puzzle! If your immune system cannot tell the difference between your own cells and infectious organisms, the end result is what we call autoimmunity. Self attacking self. Similarly, low vitamin D status in the mother during pregnancy results in a greater risk of allergic or atopic conditions like eczema or asthma in childhood. Developing a deficiency of vitamin D will increase your likelihood of an overactive ( allergy, autoimmunity) or an underactive immune response depending on your constitution and genetics.

What can we do to optimize our vitamin D status?

Increase dietary intake of the following food Sources of Vitamin D:

Fatty fish, like tuna, mackerel, and salmonFoods fortified with vitamin D, like some dairy products, orange juice, soy milk, and cerealsBeef liverCheesEgg yolks

Know the following top causes of Vitamin D Deficiency:

· Minimal sun exposure

· Deficient intake in the diet

· Fat Malabsorption

Underlying digestive insufficiency or inflammatory conditions of the gut can put you at risk of malabsorption of fat soluble vitamins like vitamin D. This means that even adequate intake in the diet or supplementation with low levels of vitamin D ( 1000 IU) per day could be insufficient to keep your blood levels in range.

Book an appointment today to evaluate your vitamin D status this winter! Rule out any limiting factors in optimal absorption and intake and find the right level of supplementation for you.


-Association between vitamin D status in early pregnancy and atopy in offspring in a vitamin D deplete cohort.


-Vitamin D/Vitamin D Receptor Signaling Is Required for Normal Development and Function of Group 3 Innate Lymphoid Cells in the Gut.


-The Role of the Status of Selected Micronutrients in Shaping the Immune Function