September 27, 2010
At the XVIII International AIDS Conference (AIDS 2010), a noteworthy oral poster discussion entitled "Shining Light on Vitamin D Deficiency" showcased six studies that tried to identify risk factors that made HIV-positive people more susceptible to vitamin D deficiency.
Vitamin D deficiency has been a hot-button issue within the HIV community recently. The main value of vitamin D in our bodies is to allow for enough calcium and phosphate absorption from food. Without enough vitamin D, those nutrients are instead drawn from our bones, which leads to lower bone density. Low vitamin D levels have also been linked to a higher risk of cardiovascular disease, diabetes and other complications.
The first of the six AIDS 2010 vitamin D studies was an analysis of 1,760 participants (1,254 of whom were HIV positive) from WIHS (Women's Interagency HIV Study) in the United States.1 Vitamin D deficiency was found in 88 percent of the women, but was not associated with HIV status. Women who were African American had higher rates of vitamin D deficiency overall. And among HIV-positive women, the use of Sustiva (efavirenz, Stocrin) was associated with vitamin D deficiency.
The second study, looking at 465 HIV-positive people at Los Angeles clinics, found low vitamin D levels in two thirds of the group.2 Though the researchers suggested that people with HIV should receive vitamin D measurements and take supplements, they didn't identify any particular risk factors for vitamin D deficiency and noted that more research needs to be done.
The third study looked into risk factors for vitamin D deficiency in a diverse group of 200 HIV-positive individuals at a private practice in Houston, Texas.3 The researchers found deficiency in 64 percent of these individuals, with risk factors being African-American race, higher body mass index, smoking cigarettes and low daily vitamin D intake.
The fourth study was a review of the medical records of 342 HIV-positive people at St. Luke's-Roosevelt Hospital Center in New York.4 Vitamin D deficiency was found in 59.9 percent of the group and was associated with being African American and having decreased sun exposure during winter months.
The fifth study was an analysis of data collected from 312 HIV-positive individuals at Chelsea and Westminster Hospital in the United Kingdom.5 Given the high prevalence of vitamin D deficiency in people with HIV, the researchers set out to see if antiretroviral therapy played a role. However, they found no significant association between low vitamin D levels and any antiretroviral class or specific agent. They did, however, find that low vitamin D levels were correlated with non-Caucasian ethnicity and female sex.
The last study looked at 281 people on HAART (highly active antiretroviral therapy) in Milan, Italy.6 Again, vitamin D deficiency was extremely common, showing up in 80.1 percent of the group. Risk factors associated with vitamin D deficiency were being overweight and being in a season with less sun exposure. Because Viread (tenofovir) has been associated with a greater risk for bone problems in people with HIV, the researchers attempted to determine whether Viread could be at all tied to low vitamin D levels. However, this study found no sign of such a relationship: Among the 164 individuals taking Viread, 77.4 percent had low vitamin D levels, about the same rate as the study group on the whole.
We know that vitamin D deficiency is highly prevalent among the general population. What we're less sure of is what role HIV or HIV medications play in increasing that risk among people with HIV -- and whether an HIV-positive person with low vitamin D levels is actually more likely to break a bone as a result.
The six studies presented at AIDS 2010 tended to agree on some general risk factors: Being overweight, female and African American were all associated with vitamin D deficiency. And since our bodies absorb sunlight and convert it into vitamin D, it makes sense that less sun exposure during colder months (or months in which the sun is out less) would lead to lower vitamin D levels.
But is having HIV itself also a risk factor? We simply aren't sure yet. In each of these studies, there were low vitamin D levels in the majority of HIV-positive people, but two of the studies suggested that having HIV was not a risk factor. Complicating efforts to pin down whether HIV is a factor is the fact that vitamin D deficiency is so common in the entire population. It may take a much larger study than any of the six highlighted above to specifically answer the question of whether HIV status itself causes vitamin D levels to drop.
Is taking HIV medication a risk factor? Again, we don't know yet. WIHS appeared to find an association between vitamin D deficiency and Sustiva (a conclusion that was also reached by the SUN study presented at CROI earlier this year7), while the Chelsea and Westminster Hospital study found no association with any particular HIV drug or drug class. (It also didn't find a link between low vitamin D levels and low bone mineral density, which conflicts with some previous study results -- and suggests that while vitamin D may be an important nutrient, vitamin D deficiency could have less to do with bone problems than some may think.)
The obvious conclusion we can draw from all this is that we need more research on vitamin D deficiency among people with HIV. We don't know the reasons why yet, but no matter what the risk factors are, it seems clear that vitamin D levels are low across the board. Therefore, it's something that people living with HIV should be concerned about and should discuss with their doctors.
Warren Tong is the research editor for TheBody.com and TheBodyPRO.com.
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