Winter is coming and soon many of us will be spending most of our non-working hours in the dark.
For those who do not go South for the winter, getting adequate vitamin D can be a challenge.
Vitamin D is most well known for its role in maintaining bone health, along with calcium and phosphorus. However, there is also a growing body of research suggesting its role in preventing certain cancers, chronic diseases and boosting our immune system.
While it is estimated that 10-15 minutes of sunshine is adequate to produce enough vitamin D from the body, sunscreen, time of day, cloud cover, smog, skin pigmentation, age and latitude can all affect this process.
So how much Vitamin D do I need?
The current RDA (recommended daily allowance) is 600 IU for 1-70 year olds. This includes all food and supplements and assumes zero sun exposure.
Can I get this from food?
Yes, but it is not easy. In Canada, milk (and milk substitutes), infant formulas, margarine and some orange juices are fortified with vitamin D. It is also naturally occurring in egg yolks, beef liver and fatty fish.
A cup of milk has about 100 IU, whereas fish ranges from 150-700 IU for a 75g serving.
What about a supplement?
Health Canada currently recommends supplements of 400 IU for all adults over the age of 50. Osteoporosis Canada is more aggressive, recommending 400-1,000 IU for those under 50 who do not have osteoporosis, and 800-2,000 for those over fifty or who currently have osteoporosis.
I would not exceed this dose without medical supervision.
Can I take too much?
Yes! Too much vitamin D can cause calcium to deposit in soft tissues, damage kidneys and cause kidney stones.
The safe upper limit for adults is 4000IU, but is much lower for children.
Vitamin toxicity almost exclusively happens when taken in supplement form.
If you are obstinate about taking supplements, I would recommend starting a habit of drinking at least two cups milk or fortified beverage daily, and eating fish and eggs a couple of times a week, at least during the winter.
-Serena Caner is a registered dietician who works at Shuswap Lake General Hospital.