Products such as teas, tonics, tablets and creams have been discovered on the internet marketed with claims such as "Treats all forms of cancer", "Shrinks malignant tumors", and "Causes cancer cells to commit suicide".
These claims are unsubstantiated and in violation of the Federal Food, Drug, and Cosmetic Act, according to the FDA.
It has sent out warning letters demanding the violations be rectified.
This is the latest in a long line of efforts to crack down on false health claims that can discredit the dietary supplements industry as a whole - and indeed the industry's credible majority has invested significantly in efforts to retain its reputation in the face of the few companies who are not playing by the rules.
"Although promotions of bogus cancer 'cures' have always been a problem, the internet has provided a mechanism for them to flourish," said Margaret Glavin, the FDA's commissioner for regulatory affairs.
"These warning letters are an important step to ensure that consumers do not become the victim of false 'cures' that may cause greater harm to their health."
Offending companies Companies alleged to be making false claims includ Vitasalus, Vitapurity, Nutrition 2000, JHS Naturals, H&L Worldwide, and Herbs for Cancer.
The products claimed to help fight cancer contain ingredients such as blood root, shark cartilage, Cat's Claw, a herbal tea called Essiac, and mushroom varieties including Agaricus, Shitake and Reishi.
The letters warned: "You should take prompt action to correct the violations described above and prevent their future recurrence.
Failure to do so may result in enforcement action without further notice.
"The Act authorizes the seizure of illegal products and injunctions against manufacturers and distributors of those products."
The FDA is also advising consumers to consult their health care provider about ending their use of the products and to seek medical attention if they have experienced any adverse side effects.
Monitoring claims
The FDA regulates the use of health claims on product labels.
The key principles it adheres to are that claims must be truthful, not misleading and appropriate to the product they are used on.
Crucially, any product that treats or cures a disease is regulated as a drug, and not under the Dietary Supplement Health & Education Act (DSHEA), which regulates supplements.
The warning letters are part of an ongoing campaign by FDA, in partnership with the law enforcement agency Federal Trade Commission (FTC) and Canadian government agencies, to prevent deceptively-marketed products from reaching consumers.
Parties that fail to resolve the violations are subject to enforcement action up to and including seizure of illegal products, injunction, and possible criminal prosecution.
Previous examples of FDA's enforcement actions include last year's seizure of seven supplements and pamphlets valued at $41,000 from Charron Nutrition.
The stock, which was seized by US marshals in Florida at FDA's request, included Glucobetic, Neuro-betic, Ocu-comp, Atri-oxi, Super-flex, MSM-1000, and Atri-E-400 capsules.
These were being distributed and promoted by Tallahassee-based Charron Nutrition for use in treating diabetes, arthritis and other serious health conditions.