Pau d’arco is a bark tea from South American trees with a long history of traditional use against infections, inflammation, and pain. Lab studies support some of these uses, particularly its antifungal and anti-inflammatory properties, but human clinical trials remain scarce. Most of what we know comes from cell and animal research on its two key active compounds: lapachol and beta-lapachone.
Where Pau D’Arco Comes From
Pau d’arco (also called taheebo or lapacho) comes from the inner bark of several Tabebuia tree species native to tropical regions of South and Central America. Indigenous groups have used it as a tea for centuries, applying it broadly to bacterial infections, fungal infections, and inflammatory conditions. Today it’s sold as a dietary supplement in capsule form (typically 500 mg of bark per capsule, taken once or twice daily) and as loose bark for brewing tea.
It is not FDA-approved for treating any disease. The FDA has issued warning letters to companies marketing pau d’arco products with medical claims, classifying those products as unapproved drugs. What you’ll find on shelves is regulated only as a dietary supplement, meaning potency and purity can vary between brands.
The Active Compounds and What They Do
The bark contains dozens of plant chemicals, but two naphthoquinones get the most scientific attention: lapachol and beta-lapachone. These are the compounds behind most of pau d’arco’s studied effects. Lapachol has shown the ability to slow the growth and spread of tumor cells in lab settings. Beta-lapachone has demonstrated strong toxicity against both mouse and human cancer cell lines, triggering a process called apoptosis, where damaged cells essentially self-destruct. The bark also contains flavonoids, coumarins, and other compounds that may contribute to its overall effects, though they’re less studied individually.
Antifungal Activity
One of the most consistent findings in lab research is pau d’arco’s ability to inhibit Candida, the yeast responsible for thrush, vaginal yeast infections, and gut overgrowth. Both lapachol and beta-lapachone have demonstrated antifungal effects against multiple Candida species, including C. albicans (the most common), C. parapsilosis, and C. tropicalis. This aligns with the bark’s traditional use against fungal infections across South America.
The catch: these results come from test tubes, not human trials. Effective concentrations in a petri dish don’t always translate to effective concentrations inside a living body, especially given the absorption challenges described below.
Anti-Inflammatory Effects
Pau d’arco extracts have shown a notable ability to dial down inflammatory signaling. Research published in Scientific Reports found that bark extracts potently reduced the production of several key inflammatory molecules in human immune cells, including TNF-alpha, interleukin-6, and interleukin-1 beta. Some extracts outperformed a clinical-grade positive control in suppressing these signals.
Animal research adds another layer. One study found that dissolving pau d’arco bark powder in water helped prevent chemically induced colitis in mice, suggesting potential relevance for inflammatory bowel conditions. For people drawn to pau d’arco for joint pain, gut inflammation, or general inflammatory issues, this line of evidence is the most promising. But again, controlled human studies confirming these effects at typical supplement doses don’t yet exist.
Cancer Research: Early Stages
Pau d’arco’s connection to cancer is real but preliminary. In the lab, lapachol reduced tumor formation in fruit fly models and decreased the ability of cervical cancer cells to invade surrounding tissue. Beta-lapachone triggered cancer cell death in human liver cancer cell lines by activating the cell’s built-in self-destruction pathway. Bark compounds also blocked a signaling route called STAT3 that many cancers rely on to keep growing.
A phase I clinical trial at the National Cancer Institute tested a beta-lapachone-based drug (ARQ 761) alongside standard chemotherapy in patients with advanced pancreatic cancer. That trial focused on finding a safe dose rather than proving effectiveness, and it has since been completed. No pau d’arco product or derivative is approved for cancer treatment. The gap between killing cancer cells in a dish and shrinking tumors in a person is enormous, and pau d’arco hasn’t crossed it yet.
The Bioavailability Problem
One of the biggest challenges with pau d’arco is getting its active compounds into your bloodstream in meaningful amounts. Beta-lapachone dissolves poorly in biological fluids, which severely limits how much your body absorbs after drinking the tea or swallowing a capsule. Researchers have experimented with advanced delivery systems like polymeric micelles to improve absorption, but these aren’t available in consumer supplements. This means the concentrations that produce dramatic effects in lab studies may be difficult or impossible to achieve by drinking bark tea.
This doesn’t mean the tea has zero effect. Traditional users have reported benefits for generations, and the bark contains many compounds beyond just lapachol and beta-lapachone. But it does mean you should temper expectations set by headlines about cancer-killing or infection-fighting properties observed in isolated cell experiments.
Safety Concerns and Drug Interactions
At typical supplement doses, pau d’arco is generally tolerated. Higher doses are a different story. Animal toxicology studies on lapachol found serious side effects at elevated doses, including moderate to severe anemia, abnormal blood clotting times, and signs of kidney stress. In primates, high repeated doses proved fatal.
The blood-clotting issue deserves special attention. Pau d’arco increases anticoagulation, meaning it makes your blood slower to clot. This creates a meaningful interaction risk if you take blood thinners, anti-inflammatory painkillers like meloxicam or nabumetone, or other herbs that affect clotting such as American ginseng or alfalfa. If you’re on any medication that thins blood or affects clotting, combining it with pau d’arco could amplify that effect unpredictably.
Other practical cautions: pregnant and breastfeeding women are typically advised to avoid it due to insufficient safety data. Nausea and digestive upset are the most commonly reported side effects at standard doses. Because supplement quality isn’t standardized, the actual lapachol content in products can vary widely, making it harder to predict your exposure to active compounds.