Living in Canada, one may muse over (and maybe even complain about) the lack of sunlight, especially in winter. In Vancouver, where I live, the average number of daylight hours on December 22 is one half of what we get on June 21: 8.04 hours compared to 16.23. But who's counting?
Besides making it harder to get out and get active, that lack of sunlight during winter can have health impacts, including lower levels of vitamin D -- which the body produces in response to sunlight. You've likely heard news stories in the past few years about research into the sunshine vitamin's role in health. Low levels of vitamin D have been linked to many medical conditions, but what does all this research mean for people with HIV living in Canada? While there is much left to learn, researchers are finding that people with HIV need to make sure they are getting enough vitamin D.
Classified as a vitamin through the happenstance of history, vitamin D is actually a hormone, meaning that it acts as a chemical messenger in the body and is important for regulating many chemical activities in cells. We know for sure that it is involved in bone health. It also helps with the absorption of the bone-building minerals calcium and phosphorus from the intestines.
Clues for where else vitamin D may act in the body come from where receptors for the vitamin are located. Based on the location of those receptors, vitamin D may be involved in muscle, brain and liver function. Those receptors are also found on immune cells, such as CD4 cells and macrophages, leading researchers to speculate that vitamin D may play a role in immunity.
The body can produce vitamin D in a multi-step pathway that starts in the skin, where heat from sunrays kicks off the process. The liver and the kidneys work next, transforming intermediate forms, called vitamin D2 and vitamin D3, into the active form of the vitamin, calcitriol. Blood tests vary in what form of vitamin D they measure. The most common test measures total vitamin D2 and D3.
There is debate over ideal blood levels of vitamin D. Based on studies of bone health and blood levels of calcium and parathyroid hormone, the American Endocrine Society suggests that the results of vitamin D blood tests be interpreted in this way:
- 75 nmol/l or higher is sufficient
- between 50 and 74 nmol/l is insufficient
- 49 nmol/l or less is deficient
According to a 2009 Statistics Canada study, about one-third of Canadians had sufficient levels of vitamin D. The same study indicated that one in 10 people were deficient. (Note that the study used an older, lower cut-off of less than 37.5 nmol/l to define deficiency.)
Not being exposed to enough sun or wearing sunscreen (which blocks the formation of vitamin D in the skin) can lead to inadequate levels of vitamin D. Other factors that can put people at risk for deficiency include obesity (having a BMI higher than 30), older age and health conditions such as liver and kidney damage or inflammation of the intestines (Crohn's disease, for example).
Less D With HIV?
Scientists are beginning to think that HIV, perhaps through its associated ongoing inflammation, might also change how well the body can produce vitamin D. There is no clear evidence that vitamin D deficiency is more common in people living with HIV than in HIV-negative people. However, in a recent large cohort study of people with HIV in Europe, Argentina and Israel, only one in 10 (11 percent) had vitamin D levels above 75 nmol/l.
In the trial, most (82 percent) of the people were taking antiretroviral therapy (ART). This is of note because some anti-HIV drugs may affect vitamin D levels. Efavirenz (Sustiva and in Atripla) and AZT (Retrovir/zidovudine, also in Combivir and Trizivir) have been linked to vitamin D deficiency.
Protease inhibitors (PIs), on the other hand, particularly darunavir (Prezista), have been associated with higher levels of vitamin D. Hal Huff, ND, head supervisor of the Naturopathic HIV/AIDS Clinic at the Sherbourne Health Centre in Toronto, is involved in the Canadian HIV Vascular Study, which is looking at the relationships between anti-HIV drugs, cardiovascular disease and metabolic problems. In the study, he says, "participants with the highest vitamin D status were more likely to be on PI-based ART rather than on a non-nuke such as efavirenz."
The study did not find a connection between efavirenz and low vitamin D levels; in fact, Dr. Huff says that vitamin D levels in the efavirenz group were relatively high, even in comparison with the general Canadian population. This would make it difficult to see a link between choice of anti-HIV drug and vitamin D levels.
Certain other medications that people with HIV commonly take may also affect vitamin D levels, including:
- the antibiotic rifampin (used to treat tuberculosis)
- the antifungal drugs clotrimazole and ketoconazole
- anti-inflammatory drugs such as corticosteroids
- the anti-seizure drugs phenobarbital, carbamazepine and phenytoin
- the anti-cancer drug Taxol and related compounds
- the herb St. John's wort and its extracts, hypericin and hyperforin
If you are taking any of these drugs or herbs, talk to your doctor about vitamin D.
Over the past few years, there have been reports linking vitamin D deficiency to various health conditions. In HIV-negative people, low levels of vitamin D have been linked to some types of cancer -- most notably colon cancer, but possibly also prostate and breast cancers. In HIV-positive people, type 2 diabetes and cardiovascular diseases, including heart attack and stroke, have been linked to low levels of the vitamin.
Dr. Huff and the other researchers with the Canadian HIV Vascular Study did not find a link between low vitamin D status and thickness of the carotid artery in the neck -- a sign of cardiovascular disease -- though this might have been because the group had relatively high levels of the vitamin.
They did note a possible link with high blood pressure; however, this does not mean that low vitamin D levels cause high blood pressure. "In our study, as in others, individuals with higher vitamin D status are less likely to be overweight," says Dr. Huff. "And, of course, being overweight increases the risk of elevated blood pressure."
Dr. Huff's comments highlight a weakness with much of the current research into vitamin D. The studies so far have shown a link between two factors, such as low vitamin D levels and cancer, but they cannot prove that low levels cause cancer. More rigorous studies are needed to prove a cause-and-effect relationship, and researchers are undertaking such studies to provide firm evidence.
Finally, Dr. Huff adds that the results of the study may not apply to everyone: "It is important to keep in mind that our study population was composed predominantly of white middle-aged HIV-positive men. For instance, they do not speak to the potential problem of vitamin D deficiency in HIV infection among women, Aboriginal [people], persons with dark skin or the elderly."
There is one area where experts are confident that vitamin D plays a role: bone health. A lack of the vitamin can result in soft bones (osteomalacia) and brittle bones (osteoporosis). Also, several studies have shown that elderly people who take vitamin D plus calcium have stronger bones and fewer broken bones. Vitamin D is needed by the body to properly use calcium, so the two micronutrients should be taken together (they are often sold in a combined pill).
Enough of the Good Stuff
For people with HIV, who often have bone problems, the role of vitamin D in bone health is reason enough to be aware of their vitamin D status. The anti-HIV drug tenofovir (Truvada, also in Atripla and Complera) has been linked to thinner bones, so people taking that drug have an additional reason to pay attention to vitamin D. All people with HIV should consider talking with their doctors about vitamin D and the possibility of having their blood levels checked. People with certain other health conditions, including osteopenia or osteoporosis, can often have the cost of a vitamin D blood test covered by provincial and territorial healthcare programs.
If vitamin D is important, and it seems that many people don't get enough, where can they get more? There are three sources of vitamin D: sunlight, food and supplements.
Sunlight: Many factors affect skin production of vitamin D, making it difficult to provide general guidelines. For example, skin colour affects the time needed to make adequate quantities of the vitamin. (Dark-skinned people require between three and five times as much sun exposure to make the same amount of vitamin D as light-skinned people.) Also, many people wear sunscreen to help lower the risk of skin cancer. Moreover, exposure to enough sun is unlikely for much of the Canadian winter. HIV and HIV treatment can also slow or reverse vitamin D production. For all of these reasons, people should look to other sources.
Food: Natural food sources of this vitamin are few: dairy foods (especially certain cheeses, and milk, which by law is fortified with vitamin D), fortified soy and rice milks, orange juice, margarine and certain fatty fish, including salmon, tuna and mackerel. A number of other foods, including cereals, are also fortified with vitamin D.
The recommended daily intake for HIV-negative people between the ages of 9 and 70 is 600 IU. To achieve these amounts naturally, Eating Well with Canada's Food Guide recommends that all Canadians over the age of two consume 500 mL (two cups) of fortified milk or soy beverages every day. The American Endocrine Society suggests that people with certain medical conditions, including HIV, should have two to three times that amount (see How much D for people with HIV?). That would mean four to six cups of fortified beverage a day!
Supplements: The most reliable way to get your vitamin D is through a supplement, and vitamin D3 is the form of vitamin to look for on supplement labels. Vitamin D3 is available as a pill and also in a liquid formulation. At the Sherbourne Health Centre's HIV clinic, the usual recommended intake is 2,000 IU per day. "We err on the side of providing more than what might be necessary," Dr. Huff says. "Certainly, supplementation is most important October through April, particularly among persons with dark skin, a higher BMI, and in those who avoid summer sun exposure."
Even with supplements, it might not be easy to get vitamin D blood levels as high as they need to be. It may require high doses, such as 4,000 IU per day, taken for months to raise levels. Researchers are studying the effect of very high doses, such as 50,000 IU twice a week, over short periods. Early results are promising, with blood levels of the vitamin rising in the majority of people in some studies. More importantly, the doses seem safe and do not affect viral load or CD4 counts. Other trials are planned or underway with the goal of finding a safe and effective dose for HIV-positive people.
While taking a vitamin D supplement should be safe for most people, individuals with certain conditions that cause the immune system to become overly active and produce excess active vitamin D should only supplement under a doctor's supervision. These conditions include tuberculosis, chronic fungal infections and lymphoma.
It remains to be seen whether vitamin D will live up to all the hype, but its role in bone health is reason enough for us all to pay attention to our intake. Evidence suggests that taking a daily multivitamin and mineral supplement is probably not enough to ensure that people with HIV are getting enough vitamin D. A specific supplement of vitamin D3 is likely a good thing, and it comes with the added bonus of providing an excuse for not heading out into the cold Canadian winter.
|How Much D for People With HIV?|
- HIV-positive adults (19 to 70 years): at least 1,200 to 1,800 IU/day for healthy bones, maybe more to achieve other possible health benefits
- HIV-positive older adults: (70+ years): at least 1,600 to 2,400 IU/day
- Adults should not take more than 4,000 IU/day without letting their doctor know
Source: The American Endocrine Society, 2011.
For more information about vitamin D, check out TreatmentUpdate 185 and A Practical Guide to Nutrition, both available online at www.catie.ca or by calling 1.800.263.1638.
R. Paul Kerston's work at the Positive Living Society of BC includes treatment outreach. When he's not spreading the word on treatment, he can be found trotting the globe (40 countries and counting) and indulging in his longtime passion for theatre performance.