Does ashwagandha help with cancer? What the research does and doesn't show

The evidence doesn't support ashwagandha, in any form or dose, as a treatment or a way to prevent cancer. What gets cited for this claim is almost entirely test-tube and animal research on withanolide compounds — real findings, but a long way from a human trial. The handful of actual human studies that exist are small, early, and mostly conducted in people already undergoing cancer treatment.

What the evidence doesn't support

It doesn't support ashwagandha as a cancer treatment, a replacement for chemotherapy or radiation, or a way to lower a healthy person's cancer risk. It also doesn't support using it, on its own judgment, alongside cancer treatment without medical supervision. The laboratory finding that withanolides are toxic to cancer cells in a dish, or shrink tumors in mice, is a starting point for research — it is not evidence that a capsule of root powder does the same thing in a person.

What the trials found

The most direct human data comes from a 2026 phase 1 trial of RH324, an investigational leaf-extract drug developed from Withania somnifera and granted FDA allowance for study as a botanical drug. Nine people with advanced non-small cell lung cancer took it for 28 days; five completed the full course including follow-up imaging. The trial's purpose was to check safety and tolerability, and it met those goals — no serious safety problems were reported. Imaging comparisons before and after treatment were exploratory, and no new metastatic lesions appeared over the study period. This is a safety study of a different, investigational pharmaceutical extract, not a test of whether ashwagandha treats lung cancer, and a trial this small and this short cannot answer that question either way.

A second study, from 2013, is the one usually cited for breast cancer specifically. It compared 100 breast cancer patients on standard chemotherapy against a matched group taking the same chemotherapy plus 6 grams a day of Withania somnifera root extract — a concentrated extract, not the plain root powder most capsule products contain, and several times the amount typically printed on a root-powder label. The group taking the extract scored better on two fatigue scales and several quality-of-life measures than the chemotherapy-only group. Two-year survival was numerically higher in the extract group (72% versus 56%), but that difference wasn't statistically significant, and the study wasn't randomized — patients weren't assigned to groups by chance, which makes it easier for other differences between the groups to explain the result. The authors said as much themselves, calling for a larger, randomized trial before drawing conclusions.

No trial has tested whole ashwagandha root powder, at any dose, in people with or without a cancer diagnosis, for cancer prevention or treatment. Both studies above used a concentrated extract at several times our daily amount, in people already receiving standard medical cancer treatment.

Questions people ask

Is ashwagandha safe for breast cancer survivors?

No trial has specifically studied ashwagandha's safety in breast cancer survivors after their treatment has ended. The one breast cancer trial above enrolled patients during active chemotherapy, not survivors afterward, and it didn't look at interactions with hormone therapies like tamoxifen or aromatase inhibitors that many survivors take for years. Given that, this is a question for an oncologist familiar with a person's specific diagnosis and medications, not something a general article can answer.

Does ashwagandha cause cancer?

No human study has reported ashwagandha causing cancer. That said, the case reports of liver injury linked to ashwagandha — including at a daily amount close to what a typical two-capsule root-powder serving provides — mean it isn't risk-free, and anyone with an existing liver condition should talk to a doctor before using it.

What about ashwagandha and prostate cancer?

The interest here also traces back to laboratory research on withanolides and prostate cancer cell lines, not a human trial. No study has tested ashwagandha, in any form, as a treatment or preventive measure for prostate cancer in people.

Can I take ashwagandha during chemotherapy?

The one trial that tested this combined a much higher extract dose with specific chemotherapy regimens under close medical supervision and monitoring. Ashwagandha has documented liver-injury case reports and measurable effects on thyroid hormone levels — both relevant during cancer treatment, when the liver is often already under strain and some regimens include thyroid-affecting drugs. This is a decision to make with an oncology team, not on a supplement label's say-so.

When to talk to a doctor

Anyone with a current or past cancer diagnosis, or currently in chemotherapy, radiation, or hormone therapy, should talk to their oncologist before adding ashwagandha or any supplement. It is not a substitute for cancer screening, diagnosis, or treatment, and nothing above supports using it as one. If jaundice, dark urine, unusual itching, or pain under the right ribs develop while taking it, stop and see a doctor — these can be signs of the liver injury documented in case reports at daily amounts close to a typical root-powder serving.

Related reading: ashwagandha and stress: what the research does and doesn't show, ashwagandha and your thyroid, and ashwagandha and cortisol.