Why "Natural" Does Not Mean Safe: Real Examples From Regulators
Five documented cases where plant-based products drew warnings or bans: ephedra, aristolochic acid, comfrey, kava and he shou wu, with what each source says and what it does not.
Content last updated . This page has not been medically reviewed.
"Natural" describes where something comes from, not whether it is safe. FDA says natural does not always mean safe. [1] The cases below are plant products that drew a warning or restriction from a regulator or health agency. Each entry says who said what and when, and what is not known. This page is not a list of products to avoid or buy, and it gives no preparation or use instructions.
The cases at a glance
| Plant or ingredient | What the source says | Body and year | Strength of the record |
|---|---|---|---|
| Ephedra (Ephedra sinica Stapf); ephedrine alkaloids | Supplements containing ephedrine alkaloids were banned from sale in the US | FDA, 2004; described by NIH [2] | Regulatory action based on safety risks |
| Aristolochic acid (plants of the family Aristolochiaceae, for example Aristolochia species) | Described as a potent carcinogen and nephrotoxin; import alert for products labeled as containing Aristolochia | FDA [3]; advisories April 2001 [4] | Documented human harm to kidneys |
| Comfrey (Symphytum officinale L.) | Pyrrolizidine alkaloids: liver toxicity when taken by mouth | FDA, July 2001 [5]; EMA, 2015 [6] | Firm in animals; human evidence described as limited by FDA in 2001 |
| Kava (Piper methysticum G.Forst.) | Rare cases of liver injury, some serious or fatal | FDA consumer advisory, March 2002 [7]; NIH [8] | Case reports; causes not settled |
| He shou wu (Reynoutria multiflora (Thunb.) Moldenke, formerly Polygonum multiflorum) | Liver injury reports; regulator notices | Described in a 2019 review [9] | Case reports; compounds responsible not identified |
Plant names were checked against GBIF this session. [10]
Ephedra (ma huang)
Traditional use. NIH says ephedra has a long history of medicinal use in China and India for colds, fever, headaches, congestion, coughing and wheezing. [2]What regulators found. FDA banned the sale of dietary supplements containing ephedrine alkaloids in the United States in 2004. [2] NIH says the ban was because of serious safety risks. [2] NIH reports that, even in relatively low doses and short-term use, ephedra has been linked to harmful effects such as high blood pressure, heart attack, seizure, stroke and psychosis. [2] Before the ban, research showed a modest short-term weight-loss effect, which NIH describes as insufficient to outweigh the serious risks. [2]
What this does not show. NIH's page concerns dietary supplements containing ephedrine alkaloids; it does not say that every use of every ephedra preparation was studied. For the traditional-medicine view, see Ma huang tang and ephedra safety.
Aristolochic acid
Plants in the Aristolochiaceae family contain aristolochic acid. [3] FDA's import alert calls aristolochic acid a potent carcinogen and nephrotoxin (a substance toxic to the kidneys). [3] It states that products containing it cause renal damage and can cause or contribute to renal failure. [3] FDA's alerts page lists a consumer advisory and a letter to health professionals on botanical products containing aristolochic acid from April 2001. [4] Read more at Aristolochic acid and kidney injury.Not shown here: we did not read figures on how many people were harmed, so we give none.
Comfrey
FDA's July 2001 letter to industry groups described the pyrrolizidine alkaloids in comfrey as "firmly established to be hepatotoxins in animals" (substances toxic to the liver). [5] The same letter acknowledges that information is generally lacking to establish a cause-and-effect relationship in humans. [5] The European Medicines Agency (EMA) summary says comfrey root contains pyrrolizidine alkaloids, which have toxic effects on the liver when taken by mouth, and that no significant risk is expected for short periods of skin use of comfrey root medicines. [6] That EMA page (published 2015) also lists a 2024 addendum and a later consultation on a revised monograph, which we did not read, so details may have changed. [6] See Comfrey. This page gives no preparation instructions for comfrey.Kava
Traditional use. NIH says Pacific Islanders have used kava beverages for thousands of years for ceremonial and medicinal purposes. [8]What regulators and NIH report. FDA's March 2002 consumer advisory said kava-containing products have been associated with liver-related injuries, and that people with liver disease, liver problems, or who take drugs that can affect the liver should consult a physician before using kava supplements. [7] NIH says various kava products have been linked to rare cases of liver injury, some serious or fatal. [8]
What is not settled. NIH says it has been suggested that undesirable varieties or inappropriate plant parts may be responsible for liver toxicity, and lists other possibilities. [8] More in Kava.
He shou wu
A 2019 review in Frontiers in Pharmacology reports that clinical adverse reactions to raw and processed Polygonum multiflorum root have been increasing, especially liver injury. [9] The review also says the components responsible for the liver effects have not yet been identified. [9] It describes a UK regulator notifying the public of a case of liver damage from a preparation, and a 2005 China Food and Drug Administration bulletin on liver damage from a preparation. [9] Our traditional-medicine page is He shou wu. This is a secondary source: we did not read the regulators' original notices.What these cases have in common
- A plant origin did not prevent serious harm in the cases above.
- Harm may be rare, delayed or hard to link to one product, which is why case reports and regulator notices matter. See documented, reported and theoretical risks.
- Traditional use and a modern product can differ in form, amount and quality. See Banned and restricted ingredients.
If you have used any of these and feel unwell, contact a clinician. For a medical emergency call 911; for poisoning, Poison Help is 1-800-222-1222.
Frequently asked questions
Was ephedra banned in the United States?
FDA banned dietary supplements containing ephedrine alkaloids in 2004, according to NIH. [2]
What does aristolochic acid do?
FDA's import alert says products containing it cause renal damage and can cause or contribute to renal failure. [3]
Is comfrey proven to harm the liver in people?
FDA called its pyrrolizidine alkaloids firmly established liver toxins in animals, and said information was lacking to establish cause and effect in humans. [5] EMA says they have toxic effects on the liver when taken by mouth. [6]
Is kava safe?
NIH links various kava products to rare cases of serious or fatal liver injury. [8] People with liver disease or who take liver-affecting drugs were advised by FDA in 2002 to consult a physician first. [7]
Why do cases like these matter if the plants are traditional?
Traditional use is a history of use, not a safety test. Research findings and traditional use are kept separate here, and neither replaces the other. A pharmacist or clinician can help with a specific product.
References
- U.S. Food and Drug Administration. Mixing Medications and Dietary Supplements Can Endanger Your Health. Read 2026-10-22.
- National Center for Complementary and Integrative Health (NIH). Ephedra: Usefulness and Safety. Read 2026-10-22.
- U.S. Food and Drug Administration. Import Alert 54-10: aristolochic acid. Read 2026-10-22; the page's date was not shown in what we read.
- U.S. Food and Drug Administration. Alerts, Advisories & Safety Information (archived entries for aristolochic acid, April 2001). Read 2026-10-22.
- U.S. Food and Drug Administration. FDA Advises Dietary Supplement Manufacturers to Remove Comfrey Products from the Market, letter dated July 6, 2001 (archived copy). Read 2026-10-22.
- European Medicines Agency. Symphyti radix (comfrey root): herbal medicinal product, public summary first published 2015. Read 2026-10-22.
- U.S. Food and Drug Administration. Consumer Advisory: Kava-Containing Dietary Supplements May be Associated with Severe Liver Injury, March 25, 2002 (archived copy). Read 2026-10-22.
- National Center for Complementary and Integrative Health (NIH). Kava: Usefulness and Safety. Read 2026-10-22.
- Liu Y, et al. Polygonum multiflorum-induced liver injury: clinical characteristics, risk factors, material basis, action mechanism and current challenges. Frontiers in Pharmacology. 2019. Read 2026-10-22.
- GBIF Secretariat. GBIF Backbone Taxonomy (Reynoutria multiflora, Piper methysticum, Ephedra sinica, Symphytum officinale, Hypericum perforatum checked through the GBIF species API). Read 2026-10-22.