January 17, 2012
Two new studies on vitamin D supplementation suggest slight benefits in bone health for people living with HIV. However, neither provided enough evidence to recommend widespread vitamin D supplementation.
Before we get into the studies, let's have a quick Biology 101 refresher. Vitamin D helps our bodies absorb calcium, the key mineral in bones. When our levels of vitamin D decrease, levels of a parathyroid hormone increase. This hormone draws calcium out from the bones, leading to higher chances of osteoporosis and fracture.
The first study, from the National Institutes of Health (NIH), tested whether or not vitamin D supplementation helped prevent bone loss among young HIV-positive individuals on Viread (tenofovir).
Because parathyroid hormone levels are elevated in people taking tenofovir in much the same way as they are in people with vitamin D deficiency, the researchers theorized that vitamin D might counteract the bone-depleting effects of tenofovir. ...
[...] About 200 18- to 25-year-olds on antiretroviral therapy took part in the study. Study participants included young adults taking tenofovir and those receiving other forms of anti-HIV treatment. Each month, the adolescents and young adults in the study took a 50,000-unit dose of vitamin D or placebo.
At the end of the three months, parathyroid hormone levels had fallen about 14 percent among participants taking tenofovir and vitamin D but remained unchanged in participants taking other kinds of anti-HIV medication. However, youth taking tenofovir still had higher parathyroid hormone levels than those on other anti-HIV drugs. The researchers don't know if longer treatment with vitamin D would further reduce parathyroid hormone levels.
The second study, authored by U.K. researcher Kathryn Childs (whom we interviewed at CROI 2009) and colleagues, analyzed findings from previous studies on vitamin D deficiency and bone health in people living with HIV. Like the NIH study, the researchers ended up finding some benefits of vitamin D supplementation, but not enough evidence to advise it for every HIV-positive person.
Both cross-sectional and longitudinal studies showed that vitamin D deficiency was widespread in HIV-positive patients. Moreover, there was evidence that starting HIV therapy, especially regimens containing efavirenz (Sustiva, also in the combination pill Atripla), was accompanied by a drop in concentrations of vitamin D. Studies also showed that bone turnover increased in the early years of antiretroviral therapy.
However, the clinical consequences of vitamin D deficiency and reduced bone turnover were unclear. Nor was there sufficient evidence to advocate widespread use of vitamin D supplements by HIV-positive patients.
It is now well established that low bone mineral density and vitamin D deficiency are both common in patients with HIV. Because of this, measuring vitamin D levels is becoming a standard component of HIV care and vitamin D supplements are being widely used.
Despite this, evidence for clinical benefit and cost effectiveness of this approach to patient management is currently lacking.
This analysis reaffirms the results of six vitamin D studies we highlighted back in 2010. Many of the conclusions we saw then are still the same: Vitamin D deficiency is common among the general population, and risk factors include being Latino or African American, having low exposure to sunlight, having high blood pressure, and being overweight.
In addition, some HIV-related factors linked to vitamin D deficiency include duration of infection, CD4 count below 200, current HIV meds, and viral load. However, we're still not sure if having HIV is itself a cause of vitamin D deficiency.
As for HIV medications, according to the Aidsmap article, "[S]tudies consistently showed that treatment with efavirenz [Sustiva, also in the combination pill Atripla] resulted in reductions in vitamin D levels. There was little or no evidence that protease inhibitors, NRTIs or tenofovir (Viread, also in the combination pills Truvada and Atripla) reduced vitamin D concentrations." (Despite tenofovir's tendency to increase parathyroid hormone levels, as the NIH study found, it does not on its own appear to decrease vitamin D levels).
Clearly, both studies call for more research, including an examination of how vitamin D deficiency is related to antiretroviral-related bone loss, and whether or not calcium supplementation will help. And with more people starting treatment at a young age, we're sure to see more long-term questions. For now, monitoring of vitamin D levels is still recommended, with doctor-advised supplementation when needed.
The NIH researchers will conduct a follow-up study to find out if lower parathyroid hormone levels lead to improvements in bone health.
Warren Tong is the research editor for TheBody.com and TheBodyPRO.com.
Follow Warren on Twitter: @WarrenAtTheBody.
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