Last November, Dr. Reinhold Vieth, a professor in U of T’s departments of nutritional sciences, and laboratory medicine and pathobiology, was one of several medical professionals who participated in a conference on the “vitamin D deficiency crisis” in North America. Dr. Vieth has been studying the health effects of vitamin D for more than 30 years. He spoke recently with U of T Magazine editor Scott Anderson.
What do we know about the health benefits of vitamin D?
In the 1990s, clinical trials indicated that calcium and vitamin D reduce bone fracture rates. Higher vitamin D levels are also associated with a lower risk for multiple sclerosis, breast and colon cancers, and juvenile and adult-onset diabetes, as well as lower rates of cardiovascular disease.
How much vitamin D needs to be present in the body for positive health effects to occur?
More than 75 nanomoles per litre (nmol/L). The average Canadian has about 65, although it varies by season. It also varies by skin type. People with darker skin tend to have less.
One of the main sources of vitamin D is sunlight. Yet we’ve been warned that spending too much time in the sun causes skin cancer. What is the best course of action?
In summer, sunbathing for 10 minutes on your front and 10 minutes on your back makes about 10,000 units of vitamin D. This is the equivalent of 100 glasses of milk or 25 vitamin pills – and enough for most people to produce the desired 75 nmol/L of vitamin D in their blood. We require – and are designed to survive – a certain amount of sunshine. People just need to remember to cover up before they burn.
“Crisis” is a strong word. Why do you think there is a vitamin D deficiency crisis in Canada?
I fear we will see a sharp rise in disease due to vitamin D deficiency, particularly among new Canadians. People native to northern latitudes have lighter skin so they can absorb more vitamin D from sunlight. Many new immigrants have moved from a southern environment, for which their skin colour is optimized, to Canada, for which their skin colour is not optimized.
Young people of non-European ancestry living in Canada have low vitamin D levels, predisposing them to a long-term risk for some diseases. People from India or equatorial Africa require six times the sun exposure to make the same amount of vitamin D as a white person. At Canadian levels of exposure, they don’t have to worry about skin cancer. Unfortunately public health messages try to “keep it simple.” So we end up telling the black African person to keep out of the sun just as much as the pale Scottish person.
What’s the solution?
I think everybody would benefit from taking vitamin D supplements in the winter. There’s no harm in taking 2,000 units. For a dark-skinned person it’s appropriate to take more than that, but no one’s telling them to.
Health Canada’s recommended levels are much lower, are they not?
Health Canada recommends 200 units a day for people under 50. But the food and nutrition board in the U.S. is reviewing dietary guidelines for vitamin D and by late May is expected to announce a new recommended daily allowance. This board is jointly sponsored by Health Canada, so any changes announced there will also be made here.
Should we have our vitamin D level measured each time we go to the doctor?
I believe we should pay as much attention to vitamin D as we do to cholesterol.
Recent Posts
U of T’s Feminist Sports Club Is Here to Bend the Rules
The group invites non-athletes to try their hand at games like dodgeball and basketball in a fun – and distinctly supportive – atmosphere
From Mental Health Studies to Michelin Guide
U of T Scarborough alum Ambica Jain’s unexpected path to restaurant success
A Blueprint for Global Prosperity
Researchers across U of T are banding together to help the United Nations meet its 17 sustainable development goals
5 Responses to “ The Vitamin D Crisis ”
I was pleased to read the Q/A with Dr. Vieth on the Vitamin D crisis. My interest in vitamin D goes back many years, and from my collection of scientific papers and newspaper articles I have learned that Dr. Vieth is a world-renowned authority on the subject.
His closing statement that we should pay as much attention to vitamin D as we do to cholesterol caught my eye. I discovered in 1983 that the French do exactly that. We moved to St.Germain-en-lai when our youngest child was 18 months old. The pediatrician gave her the most thorough medical I had ever seen, which included, in addition to weight and height, a great deal of "measuring" with a tape. After making some calculations he prescribed for her FOUR times as much vitamin D as she'd been given here. He was absolutely shocked by the small amount that she had been given in Canada and proceeded to explain the importance of vitamin D for general health as outlined by Dr.Vieth.
I was very impressed with the French health care system's Vitamin D protocol and I was able to discuss it with German, Swedish and Dutch parents whom I met at the Lycee International where our older children were enrolled. According to them it was standard practice in western continental Europe for the pediatricians to determine by measurement the exact vitamin D needs of each child. This is a far more sensible approach than to give each child an average amount, as the Canadian government recommends.
I'm wondering if vitamin D policy is connected with the recent Olympic results. Norway, a country of merely 4 million people earned almost as many medals as Canada. Furthermore, the Norwegian athletes, who have been getting all the vitamind D they need since infancy, shone in the physically demanding sports of cross country skiing and biathlon. Amongst the successful Canadian athletes, there were very few men - could this be the result of giving each Canadian child the same amount of vitamin D? Such a protocol is bound to discriminate against boys who tend to be bigger than girls.
In addition to reading his scientific papers, I have heard Dr.Vieth on CBC recommending more vitamin D. I am completely baffled that the Federal Government has not acted on his recommendations. With Dr.Vieth's research and the experience of the Europeans, there is absolutely no need for Health Canada to do more research with the U.S. It looks like a stalling tactic to me.
I wish the Ontario Ministry of Health would set up workshops under the supervision of Dr.Vieth. Medical doctors from France could be invited to them to train Ontario doctors in the correct way to measure the bone structure of each child in order to prescribe the exact amount of vitamin D. The payoff would be fewer serious diseases, savings in medicare costs and perhaps some great athletes.
Margaret Tyson
BA 1960
Ottawa
[...] I think everybody would benefit from taking vitamin D supplements in the winter. There’s no harm in taking 2,000 units. For a dark-skinned person it’s appropriate to take more than that, but no one’s telling them to…I believe we should pay as much attention to vitamin D as we do to cholesterol.’ Dr. Reinhold Vieth, University of Toronto [...]
Thank you Dr. Vieth for highlighting this important topic. The bitter truth that we all are undermining the effects of vitamin D is shocking indeed.
I am a 70-year-old man with darker skin. How many unit of vitamin D should I take? I've also read that it is better to take Vitamin D in oil form. Can you offer any suggestions?
@Jean-Louis: Dr. Vieth recommends taking at least 2,000 units of vitamin D a day. But it's best to discuss this with your own doctor.