Thousands of consumer complaints made about the ephedra-containing dietary supplement Metabolife do not contain enough information to prove the stimulant causes heart attacks and strokes, health officials revealed Wednesday. The General Accounting Office, a special investigative branch of Congress, studied the 16,000 records of phone calls turned over by Metabolife International last year, determining that because the reports were made by patients, not doctors, a definite association between ephedra and dangerous side effects could not be made. Rand Corporation, a nonprofit, independent research and analysis institution, conducted a similar investigation into the complaints, determining that further investigation is needed before a positive link can be made.

The U.S. Food and Drug Administration, however, continues to emphasize the existence of other evidence linking dietary supplements containing ephedra to serious health problems. In February, the FDA announced that supplements containing ephedra will soon be required to carry warning labels alerting consumers to the stimulant's dangerous side effects.