vitamin D. The potential benefits of supplementation include:
- fewer falls and fractures
- increased bone density
- prevention of influenza virus
- prevention or reduction in asthma attacks
- increased insulin sensitivity
- decreased blood pressure
- and the prevention of some cancers and autoimmune disease
- Serum 25 hydroxyvitamin D (the standard blood test for vitamin D status) may not be a reliable indicator as it's half-life is 3 weeks. Also, 25 hydroxyvitamin D is only one of more than 50 vitamin D metabolites in blood and it is questionable as to the validity of using it as the primary indicator.
- The safety and efficacy of vitamin D supplementation cannot be inferred from data regarding the safety and efficacy of sunlight exposure. Many of the promoted benefits of vitamin D supplementation are actually from studies looking at sunlight exposure itself.
- Vitamin D is a fat-soluble nutrient and hence it can accumulate within the body and cause other concerns. For more information: http://www.ndhealthfacts.org/wiki/Vitamin_D
- Most of the studies on vitamin D supplementation are less than 20 weeks long hence the long-term safety of dosages greater than 2,000 IU/day is questionable.
- Vitamin D levels decline in response to inflammation. Therefore blood work that indicates low levels of vitamin D may be more indicative of inflammation level versus vitamin D status.
- There are some studies that indicate that vitamin D supplementation may exacerbate atherosclerosis.
- Studies suggest that moderate dosages of vitamin D may be protective against cancer; whereas high doses were not and may actually increase the risk.
- Bone density measurements were better with low-to-moderate dosages of vitamin D.
If you have any questions about the optimal amount of vitamin D supplementation for yourself, talk to your naturopathic doctor.
Gaby, Alan 2011 Controveries in Nutrition. Presented at the Ontario Association of Naturopathic Doctors annual Conference.