Vitamin D
Prepared for CHFA by Blair Cameron, MSc.
Short bio: Blair Cameron holds a Master of Science in Human Health and Nutritional Sciences from the University of
Guelph where he specialized in micronutrient nutrition and science communication.
What it is and what it does
Vitamin D is a steroid hormone essential for many of our body’s vital functions. The first
documented and most well known purpose of vitamin D is its role in maintaining bone
health. It enables the absorption of calcium from the digestive tract to ensure the body
has adequate reserves to build bone tissue.
While vitamin D appears in a number of forms, the one that seems to be of most benefit
is D3 (cholecalciferol).
Deficiency in vitamin D causes rickets in children, a condition that leads to bent bones
due to inadequate bone mineralization. Many older Canadians are also at risk of bonemineralization problems including osteomalacia and osteoporosis, both of which are
associated with inadequate vitamin D.
Health Canada recommends that most Canadians require at least 600 IU per day of
vitamin D to maintain bone health, while those over 70 years require a minimum of 800
IU/day.
“Did You Know?”
Did you know that one of the
only natural, food-based
sources of vitamin D is
mushrooms? Just a few
minutes of exposure to UV
light can maximize their
vitamin D production, just like
in our skin. Leave your
mushrooms gill-side up on
your windowsill for an extra
vitamin D boost. Portobello,
oyster and shitake
mushrooms tend to have the
highest levels.
Over the past couple of decades, research has shown vitamin D to have an essential role in many aspects of our
health. Most prominently, elevated vitamin D levels have been linked to decreased risk of breast canceri and colon
cancerii. In addition, supplemental vitamin D has been linked to decreased risk of auto-immune conditions such as
rheumatoid arthritisiii, protection from mood disorders such as depressioniv as well as increasing muscle strengthv.
An important and underappreciated role of vitamin D, especially in the winter months, is its function in the immune
system. A growing body of research shows that having enough vitamin D increases the germ-fighting action of some
immune cell types, while increasing the immune cell population, which prepares the body for future infections.
Researchers in Japan found that when school children were supplemented with 1200 IU/day, they were two-times
less likely to get the flu than un-supplemented kidsvi. Another study found that intake of 2000 IU/day prevented and
reduced the severity of upper respiratory tract infectionsvii.
This established, yet growing, body of research highlights the need for Canadians to ensure they obtain enough
vitamin D to optimize their body’s functioning.
Where we get it from
Vitamin D is often called the “sunshine” vitamin due to its production in the skin when exposed to sunlight. A
precursor molecule is “initiated” by UV-B rays to “pre-vitamin D,” which then moves into the blood where it is further
“activated” in the liver and kidney.
In the summer months, vitamin D production is maximized after about 10 minutes of mid-day sun exposure.
However, between late October and March, the tilt of the Earth’s axis scatters UV-B rays through the atmosphere,
meaning that there is no vitamin D produced in the skin of those of us living in the Northern Hemisphere. This,
coupled with an indoor lifestyle, has resulted in Canadians having chronically low levels of vitamin D with some
estimates suggesting that 70-97% of Canadians have insufficient levelsviii.
Because of its proven benefits in bone-health, the government has mandated fortification with vitamin D of some
foods such as milk and milk alternatives. Natural, unfortified foods are rare and low in vitamin D, with the exception of
certain mushroom species (see sidebar).
An excellent, safe and cost-effective way to ensure you have optimal vitamin D levels is to consume a vitamin D
supplement daily, particularly during the winter months. There are many products available at different dosages and
different forms including tablets, capsules, or liquid drops.
Tips for Shopping
Here are some quick tips to keep in mind when shopping for a vitamin D supplement:
1) When selecting a vitamin D supplement, make sure it comes in the “vitamin D3” form. This form, called
“cholecalciferol” is the active form in the body. Some products are sold in the plant-based “vitamin D2” form,
which has been shown to be much less active in the body.
2) Research shows that health benefits are more pronounced when daily doses are taken rather than
infrequent “bolus” doses. Consider taking a supplement that provides a single lower-dose every day rather
than once a week.
Frequently Asked Questions
1) How do I know if I need more vitamin D? Is there a test?
Your health care practitioner can do blood test to assess your circulating vitamin D levels and
provide guidance on what dose might be right for you. There may be an added cost to have this
analysis done due to the growing popularity of vitamin D blood tests. As mentioned above, it is
estimated that most Canadians have insufficient levels of vitamin D, and may benefit from a
supplement at Health Canada’s recommended intake level.
2) Should I take a vitamin D supplement with food?
Vitamin D is a fat-soluble vitamin. This means that it should be taken with some form of fat or oil to
be best absorbed in the digestive tract. Taking it with food or at the same time as an Omega-3
supplement (see our info page here) can help to optimize absorption.
3) How much is too much vitamin D?
Health Canada has recently changed the upper limit of safe vitamin D intake from 2000 IU/day to
4000 IU/day. Because vitamin D is a “fat-soluble” vitamin, there is the risk that it can build up in
tissues if very high doses are taken for a long period of time. Research is still exploring what the
optimal levels of intake should be.
4) Is supplemental vitamin D safe for me and my family?
Consuming supplemental vitamin D is safe for all ages, when taken at the recommended dosage.
In fact, even newborns should have a vitamin D supplement of 400 IU/d.
Health Canada recommends the following levels for adequate vitamin D status:
Babies/infants 0-12m: 400 IU/d
Males/females 1y-70y: 600 IU/d
Males/females 70y +: 800 IU/d
A final note
Consult with your health care practitioner regarding questions about any supplements you are taking. This document
should not take the place of medical advice.
Anderson LN, Cotterchia M, Vieth R, Knight JA. Vitamin D and calcium intakes and breast cancer risk in pre- and
postmenopausal women. Am J Clin Nutr. 2010; 91(6):1699-707.
ii Ma Y, Zhang P, Wang F, Yang J, Liu Z, Qin H. Association between vitamin D and risk of colorectal cancer: a systematic review
of prospective studies. J Clin Oncol. 2011; 29(28):3775-82.
iii Song GG, Bae SC, Lee YH. Association between vitamin D intake and the risk of rheumatoid arthritis: a meta-analysis. Clin
Rheumatol. 2012; 31(12):1733-9.
iv Anglin RE, Samaan Z, Walter SD, McDonald SD. Vitamin D deficiency and depression in adults: systematic review and metaanalysis. Br J Psychiatry. 2013; 202:100-7.
v Muir SW, Montero-Odasso M. Effect of vitamin D supplementation on muscle strength, gait and balance in older adults: a
systematic review and meta-analysis. J Am Geriatr Soc. 2011; 59(12):2291-300.
vi Urashima M, Segawa K, Okazaki M, Kurihara M, Wada Y, Ida H. Randomized trial of vitamin D supplementation to prevent
seasonal influenza A in schoolchildren. Am J Clin Nutr. 2010; 91:1255-60.
vii Bergman P, Lindh AU, Björkhem-Bergman L, Lindh JD. Vitamin D and Respiratory Tract Infections: A Systematic Review and
Meta-Analysis of Randomized Controlled Trials. PLoS One. 2013; 8(6):e65835.
viii Schwalfenberg GK, Genuis SJ, Hiltz MN. Addressing vitamin D deficiency in Canada: a public health innovation whose time
has come. Public Health. 2010; 124(6):350-9.
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