Understanding Vitamin D and Preventing Deficiency


With the shortened fall days and long winter months ahead, it’s time we all consider our Vitamin D levels and how best to supplement with the “sunshine vitamin.”

During the summer as Canadians, our major production of vitamin D starts inside our skin when it is exposed to ultraviolet B radiation from sun. Because of our northern latitudes, during the winter months we produce virtually zero vitamin D through our skin.  Instead in the winter, our bodies rely on the vitamin D made and stored throughout the summer or that we consume through diet and supplements.

Natural food sources of Vitamin D include fatty fish, egg yolk, cheese and beef liver. Over the counter vitamin D supplements, and even cod liver oil are suitable ways to supplement with extra vitamin D.   There are foods that have been fortified with vitamin D such as orange juice and cereals which is added during processing, however, the bioavailability of these fortified foods has come into question in recent years.

The fact is, that by the end of winter, many of us Canadians are deficient in vitamin D because we did not make and store enough from the sun during our short summer months and we do not supplement enough or not at all.  According to Statistics Canada, approximately 40% of all Canadians test below the recommended Vitamin D levels during the winter and during the summer, 25% of the Canadian population still does not meet the recommended cut-off.

Factors such as higher northern latitudes, darker skin pigmentation, sunscreen use, minimal outdoor summertime sun exposure, excess cloud and smog cover and excess body weight can all decrease our body’s level of vitamin D. Medications including anticonvulsants, steroids and statins can have a negative impact on vitamin D status.

Health effects of Vitamin D

Vitamin D has long been recognized as an essential component of healthy bones and teeth and for maintaining our levels of calcium and phosphorous. Severe Vitamin D deficiency in infants and children causes the condition called rickets, characterized by soft and misshaped bones and teeth and muscle weakness.

Emerging research is beginning to uncover more connections between vitamin D and human health. Vitamin D plays a key role in balancing the body’s immune system and may play a role in preventing infections and autoimmune disease such as multiple sclerosis.

Other avenues of research have shown the link between treating vitamin D deficiency and treating mental disorders such as seasonal affective disorder and depression.  Vitamin D has also been used to improve muscle strength and balance and to prevent falls and fractures in the elderly.

It also shows promise in the treatment of certain pain conditions including fibromyalgia, chronic fatigue and restless leg syndrome.  Finally, there are population studies that have shown an association between higher levels of vitamin D and a decreased incidence of heart disease and cancers of the breast, prostate and colon.

Testing and Supplementing with Vitamin D:

While there remains much to be discovered when it comes to the health effects of vitamin D, there is just as much to research when it comes to the right blood levels of vitamin D we need to maintain long term health.

Traditionally, a patient needed to be in severe vitamin D deficiency to be diagnosed by a blood test.   But over the years doctors and researchers have re-evaluated the 25-hydroxy vitamin D blood level to catch more people that are vitamin D deficient.

The same changes have occurred in the supplementing of vitamin D.  Historically, doctors would only prescribe very small amounts of vitamin D and only to the most deficient of patients.  We have begun to prescribe larger doses in recognition that people need more vitamin D than previously believed.

And there are still many researchers and physicians who believe we haven’t gone far enough and our current standards of vitamin D deficiency diagnosis and treatment are too conservative and that many patients are still not being treated with enough vitamin D to achieve optimal health.

For adult patients within my own practice, I often will recommend a vitamin D supplement during the winter at dosages between 1000-4000 IU (international units) per day.  This may depend on numerous factors including their age, body size, skin colour, level of sun exposure, diet and specific health issues and medications.

In terms of targeting the right level of vitamin D in the blood, again depending on the health needs and goals of my patient, I will often attempt to achieve a level somewhere between 60-100 nmol/L of 25-hydroxy vitamin D.

Another important point I like to make with patients is that vitamin D is a fat-soluble vitamin, which means it is best absorbed when taken with a meal, especially one that contains fats. I also tell them to look for a supplement in the form of vitamin D3 (cholecalciferol) and not D2 (ergocalciferol) for increased bioavailability.

At the end of the day, there are numerous factors that will influence your vitamin D needs and having an informed discussion with your health care practitioner is the best way to find out how much vitamin D supplementation is right for you and what blood level of 25-hydroxy vitamin D to target.


Any of our doctors at the Advanced Naturopathic Medical Clinic would be happy to help you in determining your vitamin D needs through testing, analysis and supplementation.