Vitamin D is Important Throughout the Year

Vitamin D is a lipid-soluble steroid hormone with numerous cellular and molecular functions. The body makes vitamin D in a chemical reaction that occurs when sunlight hits the skin; it is also found in some foods such as fatty fish and in supplemental form.

Vitamin D deficiency is a disturbing public health problem worldwide in all age groups. This is the case even countries with low latitude, where it was previously assumed that UV radiation was adequate enough to prevent this deficiency, and in countries where vitamin D fortification is implemented. Between 70% and 97% of Canadians demonstrate vitamin D insufficiency and many Canadians have profoundly deficient levels. More than 50% of Canadian children, have vitamin D levels below the Canadian Pediatric Society (CPS) recommendation 20–39-year-olds have the lowest (59%) level of vitamin D.

Vitamin D aids in the function of brain cells. Vitamin D receptors are widespread in brain tissue, and vitamin D’s biologically active form 1,25-dihydroxy-vitamin D3, has shown neuroprotective effects, Vitamin D deficiency has several consequences when it comes to brain health, including increased risk for cognitive impairment, and depression. In addition, pregnant mothers who are vitamin D deficient have children with an increased risk for autism and schizophrenic disorders. Vitamin D deficiency also causes widespread neurotransmitter that can lead to several brain and mental health disorders.

People over 50 have an increased risk of vitamin D deficiency, which increases with age. As we age, we lose some of our ability to synthesize vitamin D from sunlight. Vitamin D needs to be activated in the kidney before the body can use it, and this function also decreases with age. In addition, older people who are homebound are less likely to get outdoor exercise and activity.

Vitamin D can modulate the innate and adaptive immune responses, and deficiency is associated with increased susceptibility to infection. In a meta-analysis, vitamin D supplementation has been shown as safe and effective against acute respiratory tract infections.

In Canada, health care insurance no longer covers vitamin D testing.

As a result, medical practitioners in Canada are no longer routinely screening for vitamin D status, it is still a good idea to have levels checked to help determine how much vitamin D is adequate for each individual. 

Vitamin D & Magnesium Connection

According to more recent evidence, an adequate balance of magnesium and vitamin D is essential for maintaining the physiologic functions of various organs and adequate magnesium intake is needed to activate vitamin D. Those with optimum magnesium levels require less Vitamin D supplementation to achieve sufficient Vitamin D levels. The potential associations of low vitamin D with increased mortality, particularly due to cardiovascular diseases and colorectal cancer, were found to be modified by magnesium ingestion.

It is common to have conflicting evidence: there are some observational studies that suggest that vitamin D3 deficiency can result in obesity, diabetes, cardiovascular disease, depression, osteoporosis different kinds of cancer especially breast, prostate and colon cancers. The U.S. Preventive Services Task Force found that subsequent randomized controlled trials don’t provide sufficient evidence that vitamin D supplementation prevents cardiovascular disease, cancer, or fractures and only a handful of “probable” relationships between serum vitamin D concentrations and these clinical outcomes.

Perhaps one of the reasons not all studies show benefits is that most people have insufficient levels of magnesium?

Note: Vitamin D is a fat-soluble vitamin and requires fat to be absorbed efficiently.

The table below outlines Health Canada’s dietary intake guide for vitamin D, assuming minimal exposure to sunshine. The US Office of Dietary Supplements/National Health Institute provide the same recommendations.


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