Should We All Be Taking A Vitamin D Supplement?

Today is World Vitamin D Day and I’m thrilled you’ve decided to join me in celebration.

Once thought of simply in terms of enhancing calcium absorption, today vitamin D is held in high regard as a potentially pivotal nutrient in the prevention and management of a variety of conditions.

I’m sure many of you have seen the headlines in the news which state that nearly 80% of COVID-19 patients were found to be vitamin D deficient.

You might also recall my article on men’s sexual health, and how inadequate vitamin D status has been linked with sexual dysfunction.

With these salient points in mind, the goal of this article is actually quite simple – to help you better understand why Vitamin D3 is the top selling vitamin supplement on

Let’s get right to it then.

Vitamin D In The Canadian Context

Vitamin D is unique among essential nutrients in that our bodies can synthesize it upon exposure to the sun.

Well, kinda.

We can’t really make vitamin D from the sun in Canada between the months of October and March because the sun’s rays are essentially too weak during those times.

That’s more than half the year, for those who are counting.

On top of that, our ability to synthesize vitamin D also declines with age – which is why Health Canada formally recommends all Canadians > 50 years old take 400 IU daily.

Quite a conundrum, isn’t it?

It gets better.

Based on national data looking at circulating blood levels deemed to be acceptable for optimal bone health, up to 40% of the Canadian population may not have enough vitamin D in their system during the winter months.

The proportion of those below the cut off is obviously lower in the summer, and it appears that women and those who use a vitamin D supplement tend to have higher levels.

Fair enough, but surely food has a role to play here?

The Vitamin D  – Food Sources

Vitamin D is elusive in more ways than one.

Fish is, by a significant margin, the richest source of vitamin D in our food system.

Fatty fish, such as salmon and trout, are particularly high in vitamin D.

Perhaps unsurprisingly,  a 2015 study out of the American Journal Of Clinical Nutrition demonstrated that the consumption of fatty fish significantly influences an individual’s circulating vitamin D levels especially over a 6 month period.

But there are a few problems here.

Number one –  Health Canada’s current recommended fish intake levels ( 2 servings or 150 grams per week) is quite modest relative to fish’s uniquely relevant vitamin D and omega-3 levels.

For reference, two servings of salmon (~150 grams) contains about one day’s worth of vitamin D intake (~600 IU).

In the American Journal Of Clinical Nutrition paper cited above, the author’s concluded that even though it significantly increased vitamin D levels, fatty fish consumption around recommended levels was unlikely to be sufficient for most people to achieve optimal D status.

Number two – Even in the context of these modest recommendations, surveys show that only a small number of Canadians consume fish at the suggested levels.

Given the amount of people I’ve worked with, point number two doesn’t surprise me all that much because it is pretty common to encounter clients who either don’t like fish or live with someone ( ie: family, partner) whose disdain for fish means it cannot be prepared in the household at all.

Other people perhaps are less familiar with fish and how to cook it, or are restrained by economical considerations ( which can be at least partially maneuvered around by being  more open to using canned or at the very least frozen varieties – I might even have a book to help with that).

Finally, I do also appreciate that concerns over mercury intake also weigh on people’s minds.

But how much mind should you pay to mercury?

This is what Health Canada has to say:

Most Canadians don’t need to be concerned about mercury exposure as a result of fish consumption. In general, the types of fish that are most popular in Canada are also relatively low in mercury.”

According to FDA data out of the US, salmon in the American food system is among the fish with the lowest mercury content.

Certainly something to think about, yet the problem remains unresolved.

What next?

The Vitamin D-lemma – Are Supplements The Solution?

The last time Health Canada looked very closely at our vitamin D intake from food they found the following:

1) Up to 90% of Canadians do not consume enough vitamin D from food – which should now be unsurprising to you

2) This number dropped to ~>50% when both food and supplemental sources were considered  – okay, we are onto something here

These data appear to paint a relatively clear picture about the potential role of vitamin D supplementation in Canada and offer some insight into why vitamin D3 is the top selling supplement on

Over the ten year period since the data above were collected, supplemental vitamin D use in Canada has increased and led to a reduced rate of inadequate vitamin D intake among supplement users.

With that in mind, a 2010 paper published by the Canadian Medical Association Journal admitted that, for many Canadians, supplementation is the only means to achieve an optimal circulating vitamin D status.

The journal article recommends vitamin D intakes varying between 400-2,000 IU per day depending on age and various osteoporosis risk factors.

Official Health Canada recommendations on vitamin D requirements can be found here.

Vitamin D – More Than Just Osteoporosis Prevention

You probably don’t need me to tell you that both public and scientific interest around vitamin D has soared over the last decade plus.

And for good reason.

Although it is commonly looked at through the lens of osteoporosis prevention,  the emerging science tells us that there is probably more to Vitamin D than just enhanced calcium absorption.

Not that bone health isn’t a relevant consideration across broad swaths of the population though, with observational studies showing adequate vitamin D status reduces the risk of injury ( ie; stress fracture – 4- 6 weeks out) of college athletes.

As someone who plays soccer and has suffered stress fractures in his younger years, the salience of such findings aren’t lost on me.

Beyond my own injury woes, vitamin D has generated great interest for potentially meaningful roles in immune health, mental health, cardiovascular health and more.

Vitamin D3 status & supplementation, for example, is being increasingly linked to risk reduction in certain populations across a variety of conditions including diabetes and cancer.

And while I promised myself to keep this article to under 1,250 words, if this manner of discussion interests you I’d suggest carrying on with a look at a pretty neat article by Harvard University and see where your curiosity takes you from there.

Final Thoughts And A Friendly Book Suggestion

I sincerely hope you’ve enjoyed today’s article and depart today’s post with a much better appreciation for the reasons behind the mass popularity of vitamin D supplementation, while also leaving with a better understanding of why you might be a candidate for it yourself.

You may also be reconsidering the frequency of your fish intake.

With that in mind, there is simply no more appropriate manner to end today’s article then with a plug for my Easy 5 Ingredient Pescatarian Cookbook.

It will certainly help anyone looking to up their fish intake ( and thus Vitamin D status).

I hope you will consider picking it up, as it is quite well reviewed!

Until next time,

Andy “D” Santis  RD MPH


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