Dear readers, this week’s question comes from Midhun, who asked about vitamin D and how much he should be taking. He looked up the government of Canada’s recommended dietary allowance (RDA) and didn’t understand the dichotomy.
While I’ve written about vitamin D in the past and it’s a nutrient that has received a lot of attention in recent years, it’s really important, especially at this time of year in Canada, to understand what is optimal. In fact, health policy makers and researchers in Canada have been sounding the alarm about inadequate vitamin D levels for years.
In her April 2015 research paper titled D-fence against the Canadian Winter: Making Insufficient Vitamin D Levels a Higher Priority for Public Health, published in the University of Calgary’s The School of Public Policy Journal, Jennifer D. Zwicker writes: “Increasing vitamin D intake should be considered a public health priority. Vitamin D deficiency is known to be linked to rickets in children and osteomalacia in adults (bone softening and malformation) as well as osteoporosis (loss of bone density, increasing susceptibility to fractures). However, a growing body of evidence also suggests that vitamin D may have a role in the prevention of chronic diseases such as heart disease, high blood pressure, diabetes, cancer, cognitive decline, Parkinson’s disease, multiple sclerosis and arthritis.”
Find the complete PDF here.
The reason she and others are concerned and why we’re so low in vitamin D is our latitude. Canada simply does not get enough sun in the winter months to provide sufficient vitamin D levels, even if the weather were such that we could suntan. We are too far from the equator. This is exacerbated in those with darker skin tones, because they need more UV rays to synthesize the same amount of vitamin D. This is because the melanin in the skin (what creates skin colour) literally acts as a barrier to too much vitamin D synthesis. It is unknown to what degree that contributes to the epidemics of health issues in these populations, but many nutritionists suspect it is related.
Zwicker recommends greater fortification of foods and public health strategies to promote supplements. The discussion of fortifying junk foods has come up in the past, but critics worry that allowing any foods to be fortified will allow companies to market junk food as health food.
In October 1999, Health Canada published a document titled Proposed Policy Recommendations: Addition of Vitamins and Minerals to Foods, which laid out the intentions to review nutrient recommendations in collaboration with researchers from the United States and to create united dietary recommendations going forward, as well as how to determine the guidelines for adding vitamins and minerals to foods. You can read the document here. The complete updated dietary reference intakes can be found here.
The revised recommendation for vitamin D for adults under the age of 70 is 15ug, which translates to 600IU. If you’ve read anything about vitamin D for the last oh, say 15 years, you are probably scratching your head right now and looking for your bottle of vitamin D.
It’s not your memory. The recommendations are woefully inadequate according to independent researchers. We’ll review some of that shortly. The official justifications for this can be read here, but I suspect it may have something to do with conflicts of interest related to funding from lobby groups. To increase the dietary RDI for vitamin D would be to endorse more fatty fish, organ meat, and eggs (yolk specifically), as pointed out in this article by Harvard Health.
You can see why that is problematic for policy makers in today’s political climate around meat. For more on this issue, you can follow the work of science journalist Nina Teicholz. She addresses the issue head on in her article “The scientific report guiding the US dietary guidelines: is it scientific?” The article was featured in the British Medical Journal and can be found here. Teicholz has subsequently created a non-partisan, non-profit organization called The Nutrition Coalition to lobby the government to consider research when revising their dietary guidelines.
What is vitamin D and how do we get it?
Well, for starters, it’s technically not even a vitamin. And it’s not singular. It’s a group of hormone precursors, very similar in structure to steroid molecules. As many readers may already know, the most important players in this group (as we currently understand it) are vitamins D2 (ergocalciferol) and D3 (cholecalciferol).
Vitamin D3 is so essential for our health that we have a built-in mechanism to ensure we get enough, irrespective of dietary intake. It’s actually manufactured by our bodies when our skin is exposed to UV rays (specifically the UVB rays) from the sun. This synthesis requires our own cholesterol and activation by our liver and kidneys. It’s unique among vitamins, not only because we generate it from the sun, but also because almost every cell in our bodies has a vitamin D receptor, which has the ability to impact the expression of our genes. This is science we are just starting to understand, but it indicates this little secosteroid is essential in a way no other nutrient is.
Animal foods are the best source of vitamin D3, but dietary consumption alone is not enough to reach optimal levels. It’s present in certain fish, fish oils, liver, and quality egg yolks, quality butter.
We can get vitamin D2 from mushrooms that have been exposed to UV rays, fortified foods, and lower quality supplements. But it’s not the desired form of this hormone group for therapeutic value. You can check the label of your dairy and baby formula products to see which form of vitamin D they contain, and then take that with a grain of salt.
According to this study published in the New England Journal of Medicine, we don’t really know how much vitamin D - or which form - is being added to our fortified products. Note that most of the infant formula tested contained 200x or more vitamin D than was on the label. With fortified foods it’s hard to know what exactly you’re getting.
What does vitamin D do?
Vitamin D is best known for its role in bone and dental health. Without adequate vitamin D children can develop rickets, and adults are at risk of premature bone aging and resulting fractures, as adequate vitamin D is needed for calcium, phosphate, and magnesium absorption and regulation. These play a direct role in bone growth and density, as well as neuromuscular function, immunity, and inflammation. Additionally, vitamin D helps regulate hormones and has a positive impact on mood, concentration, learning, and memory.
Vitamin D also helps keep abnormal cells from multiplying in breast and colon tissues. Isn’t it interesting how these cancers have proliferated since the campaign to push sunscreen? Vitamin D synthesis can’t happen in the presence of sunscreens with SPF 15 or higher. There is additional data to support that vitamin D deficiency increases our overall risk of cancer and our risk of melanoma, the deadliest type of skin cancer. Low vitamin D levels are associated with a number of serious diseases.
“A growing number of studies point to vitamin D deficiency as a risk factor for heart attacks, congestive heart failure, peripheral arterial disease (PAD), strokes, and the conditions associated with cardiovascular disease, such as high blood pressure and diabetes,” according to John Hopkins Heart and Vascular Institute.
How do you know you need it?
If you live in Canada in the winter it’s safe to say you’re not getting enough from the sun. And if you have brown skin or are vegetarian, you very likely need to supplement with more. Serum 25-hydroxy-vitamin-D testing is the best way to know your vitamin D status. The upper end of the optimal range is 50nmol/L. <30nmol/L means you’re suboptimal and between those two you may need to supplement accordingly. To give you an idea of safety, levels >125nmol/L are considered a possible reason for concern. So the levels I’m recommending are very safe.
Certain populations are known to be more likely to be deficient in vitamin D and should be supplementing with the guidance of a professional and annual testing to determine blood levels. At risk populations include:
- those over 65 - older skin often doesn’t produce as much vitamin D as it used to
- those with darker skin tones - it takes more sun to synthesize the same amount of vitamin D in darker skin
- those who work indoors, wear sunscreen all the time, or cover much of their skin when outside
- those who live in places where the sun’s rays are weaker and/or they don’t get as much exposure to the sun for good parts of the year
- those who have a gastrointestinal condition like Crohn’s disease or celiac disease or who have bile issues (both important for vitamin D synthesis and uptake)
- those who are vegetarian or vegan (animal products are the best sources of the active form of vitamin D if they don’t get enough sun exposure or supplement)
- those who have severe kidney disease (the kidneys have to convert it to the active form)
- those who have to avoid the sunlight for other medical reasons
- those who do shift work
It’s estimated that in the U.S. up to 90 per cent of those with darker skin tones and 75 per cent of those with lighter skin are deficient in this key hormone, so in Canada you can amplify this.
Are there any safety concerns?
Fat soluble supplements are stored in the tissues, so they build up over time. As such, toxicity can develop if you are continually taking too much. It’s best to have your physician test your levels annually as part of your checkup.
How do I best get it?
When possible, it’s always best to get vitamin D from sunlight - but supplementing is a safe way to get additional vitamin D.
My preference when I do advise clients to supplement is to use quality, sustainable cod liver oil (CLO) as this is a whole food supplement with vitamins A and D in the proper ratios (4-8x the A to D), as well as EPA and DHA omega 3s for maximal benefit. It’s theorized that this A:D ratio helps protect against vitamin D toxicity. Add a daily dose of vitamin K2 in the form of Emu oil or natto and you have done more to protect your bones and hormones than anything else you can do.
For detailed information on dosing, please see Brittany’s cheat sheet. It’s easy to download as a reference and I can’t do a better job of it!
Thank you, Midhun, for the great question. As always, if readers have a health or nutrition related question, I welcome you to write to me by email. And if you’re looking for more specific health information check out my website, where you can contact me directly. I provide 1:1 health coaching and a variety of webinars online to help people better manage their health holistically. Stay safe and enjoy this wonderful snow!
Namaste!
Nonie Nutritionista
CNP, ROHP