New and updated guidelines on recommended vitamin D intake have been published this week in the online issue of the Canadian Medical Association Journal (CMAJ).
Dr. David Hanley, professor at the University of Calgary Faculty of Medicine, and member of Osteoporosis Canada’s (OC) Scientific Advisory Council, is the lead author of the paper on behalf of Osteoporosis Canada.
“OC’s current recommendations on vitamin D intake for Canadians are more than 10 years old, and since then, there has been a lot of new and exciting research in this area,” says Hanley, who is also a member of the McCaig Institute for Bone and Joint Health and the Calgary Institute for Population and Public Health (CIPPH) at the U of C. “Because of these research advances, we felt it was time to update OC’s 2002 Clinical Practice Guidelines for the treatment and management of osteoporosis.”
Vitamin D, often called the sunshine vitamin, is mainly obtained from sun exposure of our skin. However, Canadians are not getting enough. Supplements are necessary to obtain adequate levels because a person’s diet has minimal impact. “Canadians are at risk of vitamin D deficiency from October to April because winter sunlight in northern latitudes does not allow for adequate vitamin D production,” says Julie Foley, president & CEO of Osteoporosis Canada. “Also, because vitamin D requirements for an individual may vary considerably depending on many factors, it’s very important to check with your physician about how much vitamin D you should be taking.”
Vitamin D is essential to the treatment of osteoporosis because it promotes calcium absorption from the diet and is necessary for normal bone growth. Some research suggests it may also ward off immune diseases, infection and cancer.
The new guidelines recommend daily supplements of 400 to 1000 IU for adults under age 50 without osteoporosis or conditions affecting vitamin D absorption. For adults over 50, supplements of between 800 and 2000 IU are recommended.
“A daily supplement of 25 mcg (800 IU) should now be regarded as a minimum dose for adults with osteoporosis,” writes Hanley with co-authors. “Canadians can safely take daily vitamin D supplements up to the current definition of tolerable upper intake level (50 mcg [2000 IU]), but doses above that require medical supervision.”
The authors conclude with a call for research into optimal doses and safe upper limits for vitamin D intake. Despite a great deal of new research in the past decade, these major clinical questions still have not been addressed.
Yes it sounds plausible that vitamin d deficiency would be a problem in Northern countries – but it’s wrong. The huge state of the art July 2010 study Common genetic determinants of vitamin D insufficiency: a genome-wide association study found that none of the genes they identified are linked with skin pigmentation.
Confirmation of that interpretation in an article Here :- ” the accompanying (Lancet) editorial points out, it is somewhat surprising that none of the genes identified are linked with skin pigmentation”
.
A systematic review of the association between common single nucleotide polymorphisms and 25-hydroxyvitamin D concentrations
“We speculate that recently identified U-shaped relationships between 25OHD concentrations and disease outcomes (i.e. increased risk at both high and low concentrations) may reflect a mixture of genotype-defined subgroups.”
‘Genetics to Blame for Vitamin D Deficiency?’
“Researchers conducted a genome-wide association study (Common genetic determinants of vitamin D insufficiency: a genome-wide association study) that involved almost 34,000 people of European descent from 15 different studies. They used radioimmunoassay and mass spectrometry to determine vitamin D concentrations and found that variants at three genetic sites, or “loci,” were significantly associated with vitamin D concentrations. The presence of harmful alleles at three “loci” more than doubled the risk of Vitamin D insufficiency.”
Maybe non-whites are the ones who benefit from doubling their vitamin D levels ? Nope – Vitamin D, Adiposity, and Calcified Atherosclerotic Plaque in African-Americans “positive associations exist between 25-hydroxyvitamin D and aorta and carotid artery CP in African-Americans”
Many people are naturally low in vitamin D, forcing vitamin D levels up by taking supplements can only do harm. If you think you can improve yor health by conforming to the advice of Holick or – God forbid – that of Hollis, Cannel & Co at the vitamin D ‘Council’ who recommend (>50ng/ml) then you are in for an unpleasant surprise.
Vitamin D and homeostasis
Mad dogs and ….