Herbs and Cancer Treatment: Interactions and Cautions
What cancer centers and NIH say about herbs and antioxidant supplements during chemotherapy and other cancer treatment, which interactions are documented, and why the oncology team must know.
Content last updated . This page has not been medically reviewed.
Safety first. Supplements can cause side effects and interact with medicines. Read mushroom safety and interactions before you use any mushroom product.
If you are being treated for cancer, tell your oncology team and pharmacist about every herb, tea, extract and supplement before you start it, and do not start new ones on your own. Memorial Sloan Kettering Cancer Center states that people undergoing treatment for cancer should not receive any dietary supplements unless they are prescribed by a doctor or given as part of an approved clinical trial. [1] The National Cancer Institute adds: tell your doctor about any dietary supplements, even vitamins. [2] This page is information only. It does not say any herb treats cancer, and nothing here replaces the oncology team's advice. Do not stop a prescribed medicine on your own.
What the evidence says about herbs and cancer itself
The National Cancer Institute states that there are no studies that prove that any special diet, food, vitamin, mineral, dietary supplement, herb, or combination of these can slow cancer, cure it, or keep it from coming back. [2] Laboratory or animal findings about a plant compound are preclinical and should not be read as treatment evidence.Why interactions matter during treatment
Memorial Sloan Kettering frames the question as whether a supplement is likely to interact with your cancer medicines. [1] NCCIH says St. John's wort, for example, can weaken the effects of many medicines. [3] The sources below give specific named examples.| Herb or supplement | What the source says | Label |
|---|---|---|
| St. John's wort, Hypericum perforatum | NCCIH says it can weaken the effects of many medicines, and lists some cancer medications including irinotecan, imatinib and docetaxel. [3] See St. John's wort interactions. | Documented interaction (NCCIH) |
| Echinacea, Echinacea purpurea | Memorial Sloan Kettering says patients undergoing chemotherapy should use caution with echinacea, as it may reduce the efficacy of some anticancer medications or cause adverse effects. [4] See echinacea. | Cautionary statement (hospital database) |
| Turmeric, Curcuma longa | Memorial Sloan Kettering says to talk with your healthcare providers about turmeric, including foods containing it, if you are getting chemotherapy, and notes that in lab experiments turmeric stopped some chemotherapy medications from working against breast cancer cells. [5] | Preclinical finding plus caution |
| Noni, Morinda citrifolia | Memorial Sloan Kettering says the antioxidant effects of noni products may decrease the activity of some chemotherapeutic agents. [6] See noni. | Theoretical caution (hospital database) |
A herb missing from this table is not cleared. "Proper evidence not found" for a complete list: the National Cancer Institute and Memorial Sloan Kettering pages read for this page do not provide one.
Antioxidant supplements and cancer treatment
The National Cancer Institute describes several randomized trials of antioxidant supplements during cancer treatment. The trials had mixed results, and some found that people who took antioxidant supplements during cancer therapy had worse outcomes, especially smokers. [7] In some preclinical studies, antioxidants promoted tumor growth and spread in mice. [7] NCI says that until more is known these supplements should be used with caution and that people with cancer should inform their doctors about any dietary supplement. [7] These findings concern antioxidant supplements generally, not a particular herb, and do not transfer automatically to tea or food.Liver and other organ effects
Some herbs have liver or kidney concerns. See Herbs and liver injury and Herbs and kidney disease. Cancer Research UK states that herbal medicines might have side effects and interact with other medicines. [8]Before surgery and during radiation or recovery
See Herbs before and after surgery. For other specific situations, no source read here gives herb-by-herb guidance, so ask the oncology pharmacist.What a reader can do
- Bring a complete list (product name, plant name and part, form) to every appointment.
- Ask the oncology pharmacist to check each item; see supplements and cancer treatment and how to check an interaction.
- Be cautious with claims that a herb "cures" cancer or "detoxes" the body. See Natural cure claims online.
Frequently asked questions
Can I take herbal supplements during chemotherapy?
Memorial Sloan Kettering says people undergoing cancer treatment should not receive dietary supplements unless prescribed by a doctor or given in an approved clinical trial. [1] Ask your oncology team about your specific situation.
Do antioxidants protect me during cancer treatment?
Not established. The National Cancer Institute describes mixed trial results, with some finding worse outcomes for people taking antioxidant supplements during therapy. [7]
Which herbs interact with cancer medicines?
Named examples include St. John's wort, echinacea, turmeric and noni, each with different strength of evidence. [3][4][5][6] The list is not complete.
Is there a herb that treats cancer?
The National Cancer Institute says there are no studies proving that any herb can slow cancer, cure it or keep it from coming back. [2]
Who should I tell?
Tell your doctor and pharmacist about any dietary supplement, even vitamins. [2]
References
- Memorial Sloan Kettering Cancer Center, About Herbs, Botanicals and Other Products. Read 2026-10-23.
- National Cancer Institute (US), Complementary and Alternative Medicine. Read 2026-10-23.
- NCCIH (US), St. John's Wort. Read 2026-10-23.
- Memorial Sloan Kettering Cancer Center, Echinacea (About Herbs). Read 2026-10-23.
- Memorial Sloan Kettering Cancer Center, Turmeric (About Herbs). Read 2026-10-23.
- Memorial Sloan Kettering Cancer Center, Noni (About Herbs). Read 2026-10-23.
- National Cancer Institute (US), Antioxidants and Cancer Prevention. Read 2026-10-23.
- Cancer Research UK, Herbal medicine. Read 2026-10-23.