Vitamin D has just taken a bit of a tumble, according to a new article in JAMA published last week. Sanders et al. found that giving elderly patients (over 70 years old) an oral mega-dose of 500,000 IUs of Vitamin D actually increased the risk of falls and fractures by 15 and 26 percent, respectively, compared to placebo.
I was really surprised by these findings, and I’m going to try to put them into context and explain why these results should be treated with caution.
I’m a big fan of Vitamin D, and there is a huge amount of research currently being done on this nutrient and its role in numerous conditions including bone health, cancer (breast, colorectal and others) and multiple sclerosis.
As far as bone goes, you need Vitamin D in order to absorb calcium and phosphate (key chemicals for bone structure) from your diet. Rickets, or softening and bending of the long bones of the body, is a result of Vitamin D deficiency.
So you can see why Vitamin D might be a critical supplement for elderly people to consider taking. Osteoporosis and osteomalacia run rampant, significantly increasing the risk of falls and fractures. You’d think that by supplementing Vitamin D, it would preserve bone structure and reduce falls and fractures.
Well… in contrast to what Sanders et al. just observed, there is a strong case for Vitamin D being beneficial:
“The association between low–vitamin D concentrations and falls has been shown in epidemiologic studies and randomized clinical trials and is supported by meta-analyses.”
A number of systematic reviews of the scientific literature are unanimous in their support of Vitamin D supplementation as a protective factor in falls and fractures. Bischoff-Ferrari et al. recently reported in a meta-analysis published in the British Medical Journal:
“Supplemental vitamin D in a dose of 700-1000 IU a day reduced the risk of falling among older individuals by 19%.”
So how did Sanders et al. end up with these contradicting results?
Well, there are a few things to consider. Primarily, the dosage regimen may not have been appropriate. 500,000 IU is a huge dose to receive orally. It averages out to about 1,350 IU per day. But that’s not how your body works. You will absorb a large amount of Vitamin D, which then signals to your body to start to degrade it.
One thought about what might have led to these intriguing results is that the body, in response to this huge spike in Vitamin D, works to degrade it quickly through tissue enzymes (one of which is CYP24). This could possibly lead to a local (tissue level) low Vitamin D status, and could thus lead to falls and fractures. It’s complex pharmacokinetics.
Another thought, as noted by Dawson-Hughes and Harris in an accompanying Comment, is that the beneficial effects of good Vitamin D status led these elderly folks to be up and about, and therefore have more opportunities for falls and fractures:
“[S]ome evidence suggests that vitamin D may improve physical performance, reduce chronic pain, and improve mood in older adults. Such benefits may have led to increased mobility and opportunity for falls among the women who received the [Vitamin D3] supplement.”
I don’t think there’s much weight to this argument though, because there was not a significant difference in active behaviour between the two treatment groups.
What is the take home message about these findings?
Well, it points to the fact that annual mega-dosing of Vitamin D may not be beneficial, and may in fact be harmful. (No kidding! – exasperated sigh – Paracelsus, one of the fathers of modern day toxicology is widely quoted as saying “the dose makes the poison.”)
One thing is clear from epidemiological studies, animal studies, clinical trials and meta-analyses: regular intake of moderate amounts of Vitamin D (700-1000 IU/day), whether daily or weekly, does have beneficial effects on fall and fracture rates in the elderly. Dawson-Hughes and Harris again:
“The findings raise the possibility that infrequent high doses of vitamin D are counterproductive. They also raise some question about the ultimate value of the common clinical practice of treating vitamin D–deficient patients with loading doses of vitamin D.”
These are challenges clinicians are facing. Adherence to daily doses of any supplement or medication in the elderly is low. But we need to carefully consider the very real adverse effects that come along with mega-dosing of anything.
References after the jump.
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High-fructose corn syrup, a disaccharide (sugar) derivative from the mountains of corn produced in the mid-west has been used extensively in thousands of food products as a cheap and effective sweetener.
