A recently published research article shows that garlic supplementation reduces the plasma level of saquinavir, a protease inhibitor. This is important research as it sheds more light on the interaction between pharmaceuticals and natural supplements. However, it is equally important to put this research into context and consider its limitations.
Let's begin with the findings of this garlic/saquinavir study. This study found that the blood levels of saquinavir were reduced by 51% with garlic supplementation (equivalent to two raw 4-gram cloves a day) in nine healthy, HIV-negative participants. The researchers believe that allicin, a compound released by garlic, may be responsible for the interaction.
Next, saquinavir is an antiretroviral that has poor bioavailability and is not likely to be used clinically as a sole protease inhibitor. It is necessary to combine it with another protease inhibitor (ritonavir) to boost saquinavir to therapeutic levels. Therefore, the methods used in this study are not representative of what happens clinically. In other words it's not clear how garlic would affect saquinavir levels in a highly active antiretroviral therapy (HAART) regimen when combined with ritonavir.
Since saquinavir is metabolized in a similar fashion as other protease inhibitors and some non-nucleoside reverse transcriptase inhibitors, there is concern that garlic may affect the levels of these HAART medications as well. It is not clear whether the effect of garlic on saquinavir is due to changes of the bioavailability (absorption of saquinavir in the stomach), or metabolism (removal of saquinavir from the blood by the liver). Therefore, more research is needed to determine if the other protease inhibitors and non-nucleoside drugs would be similarly affected by garlic.
Another issue to consider with garlic is that it is a foodstuff. Some people eat large doses of garlic on a regular basis. Most people use it as a seasoning and consume it at levels well below those that may interact with saquinavir. However, caution should be taken to avoid large amounts of fresh, raw garlic, especially as whole cloves, since they may release high levels of allicin. Allicin is the compound believed to interact with saquinavir and other protease inhibitors. Cooked garlic should be considered safer, since it does not release allicin.
Finally, let us consider how the general media has displayed this research. Headlines have read, "Garlic pills may block AIDS drugs." The media can distort what research findings are. It is important to consider all the information offered as well as the context. It is helpful to ask questions to clarify what the findings are and to determine the limitations of any research.
The discussions regarding this research come to the same conclusion: More research is needed to understand the interaction between garlic and HIV medications. It is also agreed that caution should be used when taking supplemental garlic with HIV antiretrovirals. The Bastyr Research Institute is currently conducting an NIH-funded study in close collaboration with the University of Washington to measure the effects of garlic on the cholesterol levels of people on antiretrovirals. To address the concerns that the garlic/saquinavir study raises, the Bastyr study will closely monitor viral loads of the participants. In addition, anyone on saquinavir as a sole protease inhibitor is not eligible for participation in the study. If you have questions regarding this clinical study, call 425/602-3171 or www.bastyr.edu/research/recruit/.