Recently, we have seen claims in advertising and on the internet in support of taking massive amounts of vitamin D. These outrageous claims suggest the vitamin offers miracle cures and prevention of chronic diseases like diabetes, MS, asthma, kidney disease, arthritis and many more. Unfortunately, as we all know, if it sounds too good to be true, it probably is.
The claims of those flogging high-dose vitamin D are typically based on observational research. That is, the claims are saying that people with adequate vitamin D levels have lower rates of many chronic illnesses. Or to put another way: “healthy people tend to be healthy.”
Vitamin D helps your body grow and repair bones and teeth, improve muscle strength and reduce inflammation. A deficiency of the vitamin can lead to rickets (a disorder in which bones soften and become prone to fractures and deformity, usually in children) and other health problems. Vitamin D along with calcium can improve bone health and reduce fractures. It may also protect against osteoporosis, high blood pressure, cancer and other diseases. However, too much vitamin D can also be harmful.
In general, the recommended level of daily vitamin D is 600 to 800 International Units (IU) for people up to 70 years of age. Our principal source of vitamin D is from the sun: about 10 minutes per day produces as much as you need; over the winter months in northern regions like Canada, this is not likely enough. What you eat can also contribute. In Canada, milk is fortified with vitamin D as are some juices. Supplements can round out recommended daily intake.
How much vitamin D do we need? The Canadian Cancer Society recommends 1000 IU daily. Most informed sources consider the upper limit to be 2000 IU per day, though others consider 4000 IU as the maximum. Research from John Hopkins Medical has shown that levels higher than the top of the recommended range confer no additional benefit. In fact, there is a suggestion of potential harm from higher vitamin D levels in healthy people.
Taking too much vitamin D can lead to side effects. These may include being very thirsty, reduced appetite, bone pain, sore eyes, diarrhea, a frequent need to urinate among others. Because vitamin D is fat-soluble your body has a hard time getting rid of it if you take too much. Large amounts of vitamin D can lead to too much calcium in your blood and kidney stones. Taking too much, even if it does no harm, is at best a waste of money.
Faced with marvellous claims such as those advocating high-dose vitamin D should make us ask questions. However convincing and whatever the so-called evidence, we must ask whether there is genuine science supporting the claims, or is there another agenda at play? True, scientists do not all agree on how much is too much, but there is consistency in the science. Most sources consider that we should get no more than 4000 IU daily. Whatever your perspective, before moving to high levels of vitamin D, talk to you family doctor or pharmacist.
Dr. Paul Martiquet is the Medical Health Officer for Rural Vancouver Coastal Health including Powell River, the Sunshine Coast, Sea-to-Sky, Bella Bella and Bella Coola.