Recently the USA’s Institute of Medicine made a public statement in which the dose of Vitamin D to meet bone health requirements was applied to the entire VitD scientific debate as the determining dose.[1]
“Despite the many claims of benefit surrounding vitamin D in particular, the evidence did not support a basis for a causal relationship between vitamin D and many of the numerous health outcomes purported to be affected by vitamin D intake,” the report stated.
So is the IOM off the mark
The extensive number of papers published on Vit D and its effects over the last few years. Vitamin D is unique among the vitamins in that man can synthesise it via the action of UV radiation upon the skin. This combined with its ability to act on specific target tissues via vitamin D receptors (VDR) make its classification as a steroid hormone more appropriate.
Multiple lines of evidence suggest that there is a plausible biological basis for vitamin D’s effects on cancer, inflammatory responses, bone health, and metabolic responses including insulin responsiveness and blood glucose. However, the full extent and magnitude of these responses, and relevance to supplementation has not yet been fully characterised.
But – there is considerable and substantial observations reported in several large epidemiologic studies that show an inverse correlation between 25-hydroxy vitamin D levels and mortality, there is without question an association between vitamin D and mortality from cancer, cardiovascular disease, and all cause mortality. However, it has not been established that there are cause-effect relationships, as this cannot be established by epidemiologic study. The type of studies required for this will take a long time – do we want to wait?
An example of the type of epidemiological studies that support oral supplementation where skin exposure is compromised came out in the International Archives of Medicine on the 11th Nov 2010.[2]
Here the authors state: Vitamin D receptors have been mapped throughout the brain suggesting a role for vitamin D in psychosomatic disorders. Results from previous epidemiological studies on relation between vitamin D status and depression are equivocal. Also, limited information is available relating vitamin D status with depression in young adult US population.
After studying almost 8,000 individuals they state:
In this large population based study, likelihood of having depression in persons with vitamin D deficiency is significantly higher compared to those with vitamin D sufficiency. Early diagnosis and intervention are paramount because coexistence of vitamin D deficiency and depression has serious negative consequences on health.
They looked at blood levels of (≤75 nmol/L) a range considerably above the minimum required for bone health.
While the adverse health effects of 25-hydroxy vitamin D levels of less than 30 ng/ml have been established, the evidence supporting achieving higher 25-hydroxy vitamin D levels remains insufficient, limited to epidemiologic observations on cancer incidence and other medical conditions. However, should 25-hydroxy vitamin D levels of greater than 30 ng/ml be shown to be desirable for ideal health, then vitamin D deficiency has potential to be the most widespread deficiency of the modern age. There are a number of questions that can be extrapolated from this so state the IOM:
1. What is the ideal level of 25-hydroxy vitamin D levels to achieve cancer-preventing, bone health-preserving or reversing, and cardiovascular health preventive benefits,
2. the racial and genetic (vitamin D receptor, VDR) variants that may account for varying effects in different populations,
3. whether vitamin D restoration has potential to exert not just health- preserving effects, but also treatment effects, specifically as adjunct to conventional cancer and osteoporosis therapies, and
4. How such vitamin D restoration is best achieved.
5. Until the above crucial issues are clarified, we advise Americans that vitamin D is a necessary and important nutrient for multiple facets of health but, given current evidence, are unable to specify a level of vitamin D intake that is likely to be safe, effective, and fully beneficial for all Americans.”
Comment
Personally I find this highly conservative approach relevant where people may be considering long term high dose therapy >10,000iu per day for months, but very depressing when looking at the risk to reward benefits of oral supplementation. In turn I feel that the other fat soluble vitamins can be taken in conjunction with vitamin D and that a balanced ratio will confer a safe long term supplementation strategy.
But to avoid any problems with my mood after reading the IOM report I have topped up my oral intake of Vitamin D!
References
[1] Dietary Reference Intakes for Calcium and Vitamin D View Web Page
[2] Ganji V, Milone C, Cody MM, McCarty F, Wang YT.Serum vitamin D concentrations are related to depression in young adult US population: the Third National Health and Nutrition Examination Survey. Int Arch Med. 2010 Nov 11;3:29. View Full Paper
