Studies Reveal Which Supplements May Cause Cancer


Updated | 2020-07-12


cancer word under magnifier

The role of the U.S. Department of Health and Human Services' National Toxicology Program (NTP) is to generate, interpret, and share toxicological information about potentially hazardous substances in the environment. According to NTP, the long-term (2 year) use of some botanicals or herbal supplements have been shown to cause cancer. Albeit these studies were performed in rats and mice, this information is concerning, and it is crucial that the public is aware of these findings. The only herbs with no evidence for long-term carcinogenicity were ginseng, green tea, and milk thistle. Ongoing toxicology studies at NTP include: black cohosh, dong quai, Echinacea, Garcinia Cambogia, Usnea lichen, and valerian.


Long-term (2 year) use of herbal medicines studied at NTP and their potential to cause cancer in rats and mice.

Herbs Male Rats Female Rats Male Mice Female Mice
Aloe Clear Clear No No
Ginkgo Some Some Clear Clear
Ginseng No No No No
Goldenseal Clear Clear Some No
Green Tea No No No No
Kava Kava Equivocal No Clear Clear
Milk Thistle No No No No

National Toxicology Program's Cancer Evaluation Criteria:

Clear Evidence of Carcinogenic Activity is demonstrated by studies that are interpreted as showing a dose-related (i) increase of malignant neoplasms, (ii) increase of a combination of malignant and benign neoplasms, or (iii) marked increase of benign neoplasms if there is an indication from this or other studies of the ability of such tumors to progress to malignancy.


Some Evidence of Carcinogenic Activity is demonstrated by studies that are interpreted as showing a chemical-related increased incidence of neoplasms (malignant, benign, or combined) in which the strength of the response is less than that required for clear evidence.


Equivocal Evidence of Carcinogenic Activity is demonstrated by studies that are interpreted as showing a marginal increase of neoplasms that may be chemically related.


No Evidence of Carcinogenic Activity is demonstrated by studies that are interpreted as showing no chemical-related increases in malignant or benign neoplasms.



Written by Korey Brownstein, Ph.D.

Korey Brownstein