Vitamin D is known as ’the sunshine vitamin’ for good reason – we need the ultraviolet rays of the sun to trigger production of vitamin D3 within our skin. So it’s no wonder why vitamin D levels are a concern for Canadians; many days of the year, there is no sunlight to be seen, and during the short days of winter, we may leave the house in the dark, and come home from work in the dark. When we are outside, we’re covered up due to the cold. The result of all of this is less vitamin D and, potentially, adverse effects on our health. Should we panic? Megadose vitamin D? Move to the tropics? (No, maybe, and might be a good idea)
Let’s separate fact from fiction, and hopefully, begin to understand why Canadians need to consider their vitamin D status.
It is actually a hormone
‘Vitamin’ is actually a misnomer when it comes to vitamin D. Vitamin D behaves more like a hormone than a vitamin, triggering complex cascades of activity across various areas of the body, such as within the skeletal system and immune system. Unlike most vitamins, vitamin D has to be activated in order to exert its effects.
Firstly, we need sunshine to trigger vitamin D3, or cholecalciferol, synthesis within the skin; D3 is then metabolized into 25-hydroxyvitamin D by the liver, before heading to the kidneys where it will be converted into the active form – 1,25-dihydroxyvitamin D. It is this activated form that plays a role in calcium homeostasis and immune function. Since we can theoretically synthesize vitamin D3 as long as we have adequate sunlight, independent of our diet, it is not technically a vitamin.
We’re not getting enough of it
The main source of vitamin D3 is exposure to sunlight. Not surprisingly, inadequate sunlight is the main contributor to vitamin D deficiency.(1) The short days and weak sunlight that we experience in Canada is inadequate for sufficient vitamin D3 synthesis due to the relationship between solar UV rays and the atmosphere of the earth. (2) The half-life of 25-hydroxyvitamin D is only a few weeks meaning that we cannot ’stock up’ on vitamin D via a single trip to the tropics during the winter.
Additionally, air pollution absorbs UVB radiation, reducing the effectiveness of sunlight triggering vitamin D3 synthesis.(3) Residents of Canadian cities experience the effect of a Northern latitude, compounded with air pollution.
There are many factors that affect our levels
It’s not just where we live that plays a role in our vitamin D levels – the color of our skin, our age, and what we put on our skin also plays a large role. Melanin pigment protects the skin from UV radiation, decreasing the damage caused by UV rays while also reducing the UV radiation available for vitamin D3 synthesis; as a result, those with darker skin need a lengthier time in the sunlight to produce sufficient vitamin D3.(4) People over the age of 70 will produce 30% of the vitamin D a younger person will produce in the same amount of sunlight.(5) Sunscreens were created to absorb UVB radiation; by design, the application of sunscreen decreases the effect of UV radiation on the skin, thereby decreasing vitamin D3 synthesis. Wearing a sunscreen with an SPF of 30 was shown to reduce vitamin D3 synthesis by 95%.(6)
Additionally, vitamin D is considered a fat-soluble vitamin, meaning it requires some dietary fat in the gut for absorption to occur (when we eat food or supplements that contain D3). An inability to digest or absorb fat adequately can interfere with vitamin D absorption. And since the conversion of D3 requires the liver and kidneys, alterations in the functioning of either organ can affect vitamin D levels.
All of these factors, in addition to where we live and how much time we spend outside, can play a role in our vitamin D levels.
Inadequate vitamin D levels cause more than rickets
Vitamin D receptors (VDRs) have been found outside the skeletal system, on immune cells, endothelium cells, neurons, myocytes, and cardiomyocytes, indicating widespread actions of vitamin D, beyond calcium homeostasis.(7) Many of us have heard of rickets – the debilitating consequence of vitamin D deficiency that leaves children with skeletal deformities and muscle weakness. But there are many other consequences of vitamin D deficiency, likely due to the various locations of VDRs.
Vitamin D deficiency has been linked to a wide variety of significant health complications including hypertension, insulin resistance, obesity, and all-cause mortality.(8) In a study of pregnant women, vitamin D deficiency was associated with higher risks of gestational diabetes, preeclampsia, and anemia.(9)
The discovery of VDRs on various immune cells, such as monocytes, dendritic cells, and activated T cells, has deepened our understanding of how vitamin D plays a significant role in immune signaling. As a result, vitamin D deficiency can be detrimental to immune system, leading to increased likelihood of cancer and autoimmune conditions. Patients with multiple sclerosis (MS) typically have lower serum levels of vitamin D (10); rates of MS decrease in areas closer to the equator.(11) Researchers have suggested a link between vitamin D deficiency and higher risk of cancer.(12) 1,25-dihydroxyvitamin D has been shown to inhibit cancer cell proliferation.(13,14)
The effects of vitamin D deficiency can also be felt psychologically. Seasonal affective disorder (SAD), a mood disorder characterized by depressive symptoms, occurs during darker times of the year, coinciding with less sunlight and a lesser ability to synthesize vitamin D3. Symptoms of depression significantly improved in a study of vitamin D supplementation in comparison to placebo.(15) This improvement makes sense when we consider that there are VDRs located on our brain tissue.
We may need a lot more than Health Canada currently recommends
In 2015, Statistics Canada reported that 68% of Canadians tested had sufficient levels of serum vitamin D.(16) However, they deemed ‘sufficient’ as blood concentrations of 50nmol/L and above, a number significantly lower than the level the Vitamin D Council deems sufficient.(17) The Vitamin D Council recommends maintaining a level of 125nmol/L (50ng/ml); they make this recommendation based on genomic research, equatorial data, healthy breast milk levels of vitamin D, parathyroid activity, and toxicity research. Osteoporosis Canada recommends levels >75nmol/L.(18) Many renowned autoimmune researchers, including Dr Terry Wahls, MD, recommend optimizing vitamin D to between 125-250nmol/L (50-100ng/ml).(19)
The recommended dietary allowance (RDA) of vitamin D is currently 600IUs/day, according to the latest recommendations by Health Canada.(20) The upper tolerable limit is set at 4000IUs/day – this is quite a range! And with 50nmol/L deemed a sufficient serum level, many Canadians are told they have sufficient levels without consideration of what their optimal levels may be. That is, if you can manage to have your vitamin D levels tested. Currently, MSP only covers the cost of vitamin D testing if you are under 19 years of age; the test is ordered by a specialist; or you are experiencing: malabsorption syndromes, renal failure, unexplained bone pain, unusual fractures, or other evidence of metabolic bone disorders.(21)
“The BC population is at risk of low vitamin D levels from autumn to spring. There is no clinical utility in performing vitamin D tests on patients who are thought to be at risk for sub-optimal vitamin D levels and who would benefit from vitamin D supplementation.”(21)Ministry of Health of BC
No wonder there is so much confusion as to how much vitamin D to take – or get. Without a serum vitamin D test, it is impossible to know how low your levels go during the winter, and how much they increase during lighter months. It becomes a challenge to determine how much vitamin D3 to take, and how to alter that dosage throughout the year. This is particularly worrisome for anyone living exclusively in Canada, or who has a family history of autoimmune conditions, has already been diagnosed with an autoimmune condition, has a family history of colorectal cancer, experiences depression, has gastrointestinal issues, is pregnant, is concerned about bone density …. Okay, you get the idea. Vitamin D is a concern for all of us here in the Great White North.
What’s a Canuck to do?
Firstly, talk to you family doctor. See if you fall within the exemption to have MSP cover the cost of a serum vitamin D test. If not, and you are seeing a specialist (such as an endocrinologist, rheumatologist, or oncologist), see if they are open to ordering the test. If you have been diagnosed with an autoimmune condition, cancer, cardiovascular disease, or depression, your specialist may be curious as to whether vitamin D is playing a role in your condition. Get them on board!
If these avenues do not work out for you, chat with your ND; many have access to private labs that can run a simple blood test to see what your vitamin D level is. It will be measured as 25-hydroxy-vitamin-D and is reflective of how much vitamin D you get from the sun, food, and supplementation. Once you know where you’re at, you and your doctor can make an informed decision about how to get your levels within optimal range – and keep them there – even as the seasons change.
Currently, we can’t seem to agree on how much time to spend in the sun.(22) But the leading consensus is that we begin to emphasize non-burning sun exposure in an effort to achieve adequate vitamin D levels.(23,24) To put it in perspective – in Calgary, it takes about 2 hours and 42 minutes to make 600 IUs of vitamin D in November; in July, it takes 1 minute.(25)
Ideally, we are able to make optimal levels of vitamin D in the lighter months from the sunlight we experience. In the darker months, we measure our levels and make up the difference with a high-quality vitamin D3 supplement that includes a small amount of vitamin K2, as well as foods that include vitamin D, such as wild salmon, sardines, mackerel, grass-fed beef liver, eggs, shiitake mushrooms.
Even without testing, Canadian adults should, at the very least, aim to get 600IUs vitamin D per day. But remember, this RDA is far lower than necessary to raise most of our levels of vitamin D to the therapeutic range.
About the Author:
- Holick MF, “Vitamin D: Photobiology, Metabolism, Mechanism of Action, and Clinical Applications” in Primer on the Metabolic Bone Diseases and Disorders of Mineral Metabolism ed. Murray Favus. 4th edition 1999. Lippincott Williams & Wilkens.. Philadelphia, PA. p. 92-98
- Wahls, T. The Wahls Protocol. (2014). New York, NY: Penguin Group; p.272.