WASHINGTON (Latimes.com) -- The Food and Drug Administration has sent a letter to the nation's dietary supplements industry warning them against spiking their products with steroids, prescription drugs and other prohibited substances.

Since 2007, the FDA said, it has found nearly 300 products marketed as supplements that contain potentially dangerous or illegal ingredients, most of them sold as diet, or weightlifting.
“These tainted products can cause serious adverse effects, including strokes, organ failure and death,” FDA Commissioner Margaret A. Hamburg said in a statement. The “manufacturers selling these tainted products are operating outside the law.”
FDA officials did not immediately offer specifics on the number of people thought to have been harmed by tainted supplements.
Unlike drugs, dietary supplements don't have to be proven safe before being sold, and manufacturers have wide latitude to make health claims.
The FDA's letter notes that manufacturers and distributors are responsible for ensuring that their products comply with the law and provided an e-mail address.
Five major trade associations – the Council for Responsible Nutrition, Natural Products Assn., United Natural Products Alliance, Consumer Healthcare Products Assn. and American Herbal Products Assn. – joined the FDA on a press call to publicize the crackdown.
The FDA letter described a laundry list of prohibited ingredients:
“FDA laboratory tests have revealed an alarming variety of undeclared active ingredients in products marketed as dietary supplements, including anticoagulants (e.g., warfarin), anticonvulsants (e.g., phenytoin), HMG-CoA reductase inhibitors (e.g., lovastatin), phosphodiesterase type 5 inhibitors (e.g., sildenafil), non-steroidal anti-inflammatory drugs (NSAIDs) (e.g., indomethacin), and beta blockers (e.g., propranolol).”
The letter also noted that products marketed as dietary supplements have been found to contain fenfluramine, a pharmaceutical ingredient removed from the market for safety reasons, while others contained chemicals of unknown safety as well as controlled substances including benzodiazepines and anabolic steroids.