HIV patients taking antiretrovirals should avoid garlic, St. John’s wort

Other health products were fine

Many people infected with HIV look to natural health products to supplement their conventional medical care, and clinicians, understandably, are concerned about drug interactions.

Most of the time, there’s little risk of problems, but patients and clinicians should be aware of potential risk when HIV patients ingest St. John’s wort and supplemental garlic, a researcher says.

"We looked at all natural health products, and the important interactions we found may exist with St. John’s wort, garlic, and possibly vitamin C," says Ed Mills, DPH, MSc, a fellow at McMaster University in Hamilton, Ontario, Canada, and a lecturer at Oxford University in Oxford, United Kingdom. Mills also is the director of the division of clinical epidemiology at the Canadian College of Naturopathic Medicine in Toronto, Canada.

Since conducting the first study, investigators have ruled out vitamin C, Mills adds.

"Since that time we have redone the vitamin C [part of study], and we found it did not have the potential to interact in our clinical study," Mills says. "Garlic and St. John’s wort are a valid concern."

Mills and co-investigators looked at clinical studies that examined drug interactions and assessed their methodological quality, he says.

Investigators found there was an important interaction between garlic and protease inhibitors and an important interaction between St. John’s wort and indinavir.1

"The use of natural health products is in line with the belief system of many people living with HIV, and they use the products to improve their quality of life," Mills notes.

So when the clinical community reacts by suggesting HIV patients should not take any natural health products because of the potential for interactions, the patients’ response is that they are being forced into increased medicalization, he says.

The research is limited in addressing this issue, he says.

"A lot of studies on the topic have inferences drawn from it that are weak," Mills says.

"There have been studies like that in the past about St. John’s wort, but the concern is there are side effects of St. John’s wort in the long term," Mills says. "It uses enzyme systems that metabolize antiretroviral drugs, so it can reduce the level of antiretroviral drugs in the body."

Mills says the research suggests HIV patients should avoid St. John’s wort, although it’s an important herb because many people with HIV do have depression, which is what it is used to treat by some people.

The studies involving garlic used large doses of garlic, and these also competed for the same pathway as antiretroviral drugs, Mills says.

"We don’t think people should be concerned about the amount of garlic in their food," Mills says. "Garlic has some evidence of a [positive] effect on heart conditions, so it’s disappointing that it would compete for the same pathway, but we don’t recommend people take garlic supplements."

Vitamin C and milk thistle, which is used for liver conditions, were found to have no interactions with antiretroviral drugs, so they likely are safe to take, Mills says.

"It’s not easy for the HIV population to make decisions, and further research is needed on this issue," Mills says. "But this information has to be balanced, and I don’t think people should be overly concerned about drug interactions with natural health products—even the studies on St. John’s wort were inconsistent."

Clinicians should discuss natural health use in an open and nonjudgmental manner, realizing that use of complementary medicine is in line with many of their patients’ beliefs, Mills suggests.

"The problem is that data are so limited at the moment that it’s difficult to say with certainty that anything is safe," Mills says. "But clinicians should provide a balanced view, saying researchers have looked at all drug interaction trials and at the moment the only thing patients should be concerned about are St. John’s wort and garlic."

As antiretroviral drug use spreads to sub-Saharan Africa and other parts of the world, more research on interactions of antiretrovirals and natural health products should be a research priority, Mills says.

"Further research is required to look at the safety of traditional medicines for use in that population," Mills says. "The current minister of health in South Africa is recommending the use of traditional plants in South Africa, and there is in vitro evidence that this traditional plant, an African potato, does interact with antiretroviral drugs so research is needed quite quickly."


  1. Mills E, et al. Natural Health Product—HIV Drug Interactions: A Systematic Review. Int J of STD AIDS. 2005;16:181-186.