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How Much Vitamin D Should I be Taking?
It seems like an easy answer, right? You pull up the Health Canada website, look up “vitamin D” and wham. The number is right there. For children and adults 9 – 70 years of age, Health Canada recommends 600 IU or 15mcg of vitamin D per day. But, as with most things in life, it isn’t always so clear cut. Let’s take a look.
How does the body make vitamin D?
Our body actually produces vitamin D naturally. When ultraviolet radiation from the sun hits our skin, it converts a kind of cholesterol called 7-Dehydrocholesterol found in the epidermis into vitamin D3.
This vitamin D3 then undergoes several conversions in the liver and kidney to become 25-hydroxyvitamin D (which is what we measure in blood tests) and 1,25-dihydroxyvitamin D (which is what our body mainly uses).
This is what the process looks like.
Factors that affect your vitamin D production
A lot can affect how much vitamin D is produced in the body. The most common one is how much UV we actually receive. Canadians receive less overall because of the latitudes in which we live. A lot of us spend more time indoors (And with our winters, who can blame us?). Sunscreen and skin with more melanin further cut the amount of UVB available.
Body fat affects things too. Because vitamin D is a fat-soluble vitamin, researchers think that too much body fat can act like a sink, trapping 25(OH)D in fat cells and lowering levels in the blood stream.
Age can affect how well we convert vitamin D in the kidneys. Seniors and those over the age of 50 are more at risk of a deficiency.
Finally, individuals may have genetic polymorphisms, or gene mutations, that can make conversion difficult at various stages. For instance, vitamin D 25-hydroxylase, or cytochrome P450 2R1, is responsible for converting vitamin D3 into 25(OH)D in the liver. Someone with a mutation in the CYP2R1 gene, responsible for encoding the enzyme, may need a dietary supplement of 4000 IU of vitamin D3 versus someone without the mutation who may get by with 1000 IU.
By looking at all these factors, you can get a sense of how much vitamin D3 you should supplement with daily, bearing in mind that dietary vitamin D3 intake also needs to be converted into usable forms.
The surest way to figure this out is to do a blood test. A blood panel looks at how much converted 25(OH)D is available in blood, and a good target range is between 40 and 60 nanograms per millilitre. A daily supplementation of 1000 IU of vitamin D3 will roughly raise blood availability of 25(OH)D 5 nanograms per millilitre.
Many physicians shy away from vitamin D tests. They assume that most Canadians are deficient, and will simply recommend the Dietary Recommended Intake dose. However, people with issues transporting or converting vitamin D may not supplement enough under this regimen.
My recommendation is for Canadians to test vitamin D levels before supplementation, and again after a month, to make sure that supplementation is enough and to make sure conversion is functioning.
Always keep your own copies of blood tests – it’s useful for developing an understanding of your own health history.
Can you take too much vitamin D?
It’s important to find the right level of vitamin D to take. As with most things, taking too much vitamin D has its hazards. Vitamin D improves the absorption of dietary calcium, and too much vitamin D can lead to hypercalcaemia, or excessive calcium in the blood. There, calcium can form calcium phosphate crystals that become blood plaques. Taking vitamin K2, which affects calcium transport, with vitamin D3 can help mitigate the risks of hypercalcaemia.
Jonothon Mainland is a licensed Naturopathic Doctor, VP Medical Director at CanPrev & Orange Naturals, and has been involved with natural health product formulation & education for over a decade.
ND Notes is a health and wellness resource developed by the naturopathic doctors and healthcare practitioners at CanPrev and Orange Naturals. We design and develop natural health products that are safe, effective, and easy to use.