One of my projects for 2009 has been to optimise my vitamin D levels. My first ever check was in April, which revealed a frankly low vitamin D level of 15 ng/ml (37 mmol/l). I subsequently set about correcting this by taking 3000 IU of vitamin D (in gel caps) a day. In July my level had risen to 31 ng/ml (better, but not ideal). Since then, I have been taking 5000 IU of vitamin D a day. A recent test reveals that my vitamin D level as 44 ng/ml. This is three times as much as I had back in April, and now puts me in what some would regard as the ideal range (40-60 ng/ml). My plan is to stay on my current dose and re-check levels in a few months time.
I was reminded of the importance of optimising vitamin D levels in a piece published this week in the Journal of the American Medical Association [1]. The piece highlights a voluminous and growing body of evidence linking vitamin D deficiency or insufficiency with an increased risk of a wide range of conditions including osteoporosis and bone fracture, muscle weakness, cancer, autoimmune disease, diabetes, schizophrenia, depression, lung dysfunction, kidney disease, and cardiovascular disease.
The piece also highlights the fact that low levels of vitamin D can be common. For example, in one study of Americans aged 1-21, the prevalence of vitamin D deficiency or insufficiency (vitamin D < 15 ng/ml and 15-29 ng/ml respectively) was found to be 70 per cent. Moreover, the point is made that recommend intake levels are due for revision ” in an upward direction.
Such recommended amounts need to embrace two fundamental things: what dosages are likely to keep the majority of people out of deficiency/insufficiency, and what levels are safe. What seems clear is that while optimal dosages vary between people, many individuals (such as I) require several thousand IUs each day to maintain good levels of vitamin D in their bodies. You can read more about this here.
And what of safety? The current upper limits quoted in the article are 1000 IU for infants (children aged up to one year) and then 2000 IU thereafter. The article quotes Professor Michael Holick, professor of medicine, physiology and biophysics at Boston University School of Medicine in the US, and a long-time advocate of vitamin D. Holick thinks the risks of reaching toxic levels of consumption are overstated. According to the JAMA piece He [Holick] would raise the upper limit to 5000 IU per day for children and suggested that an adult could receive up to 10 000 IU of vitamin D per day without any adverse effects.
The article ends with Holick’s response to the question of whether doctors are getting the message regarding the potential importance of vitamin D. Holick claims “What happens is the patient hears about this in the news and brings it to her physician’s attention. The physician is then reluctant to do the test, but when he does, he finds the patient is vitamin D deficient”and then he gets religion.”
This strikes me as an important example of how individuals can contribute to the education of their doctors. I was only telling a journalist yesterday how important it is, I think, for doctors to be prepared to be taught a thing or two by their patients.
References:
1. Mitka M. More evidence on low vitamin D levels fuels push t revise recommended intake. JAMA 2009;302(23):2527-2528
