A new study from the University of Missouri in partnership with scientists in Africa has uncovered evidence that botanical supplements and their antioxidants may reduce the effectiveness of prescription medications.1 The researchers examined the effects of a widely used African botanical supplement, Sutherlandia, and found that it may disrupt the effectiveness of a common anti-tuberculosis (TB) drug, possibly leading to the development of active TB and drug-resistant forms of the pathogen in some patients.

William R. Folk, PhD, University of Missouri School of Medicine.

William R. Folk, PhD, University of Missouri School of Medicine.

For the study, William R. Folk, PhD, professor of biochemistry at the University of Missouri School of Medicine, joined with colleagues to monitor South African patients who were taking either Sutherlandia or a placebo, along with the world-standard anti-TB drug, isoniazid. Sutherlandia is a supplement commonly taken in Africa to fight symptoms of infection and some chronic diseases, such as diabetes. The researchers observed that several patients taking the Sutherlandia supplement developed active TB despite taking isoniazid.

“We believe that the antioxidants in Sutherlandia can directly disrupt how isoniazid functions within the body to prevent tuberculosis,” Folk says. “Isoniazid is very reliable in preventing the active form of this potentially deadly microbe, which is present in nearly one-third of all humans. But if individuals concurrently take a botanical supplement, they could undo the good that the scientifically proven drug is accomplishing.

“More than one-third of the world’s population is susceptible to active TB,” Folk adds, “so it is unfortunate that Sutherlandia, which traditionally is taken to prevent or treat infections, can actually cause them to develop the disease, and perhaps also cause the microbe to become a drug-resistant ‘superbug.’”

Folk says the finding could apply to many different botanical supplements and medications, including cancer-fighting drugs. He says it is important for future research to examine potential interactions between drugs and antioxidant-laden supplements.

“With so many people around the world turning to botanical supplements to help with a wide range of health issues, it is vital that we explore how these supplements interact with established medical drugs,” Folk says. “Many drugs use pathways that could be disrupted by antioxidants, so we need for physicians to better advise their patients. Many physicians do not know everything that their patients take, so it is important for people to inform their physicians, and for physicians to ask, so they can better advise their patients what is best for their health.”

According to Folk, other botanicals and dietary supplements can certainly affect diagnosis and treatment. “What is important is good communication between patient and physician, and each should know of interactions that are established, such as grapefruit, or St. John’s wort, and many drugs and medicines,” he continues. “Also, some antioxidant vitamins occasionally taken in high amount, like vitamin C, vitamin E, or related compounds, may be harmful.”

Folk adds that he and his team are seeking funds from the National Institutes of Health to study the interactions between botanicals and TB in experimental animals.


  1. Folk WR, Smith A, Song H, et al. Does concurrent use of some botanicals interfere with treatment of tuberculosis? Neuromol med. 2016;18(3):483–486; doi: 10.1007/s12017-016-8402-1.