A new study backs up case reports tying the weight-loss herb ephedra to the risk of stroke but the risk appears confined to higher doses, according to researchers.
Overall, the investigators found, ephedra-containing products were not associated with a higher risk of hemorrhagic stroke --strokes caused by a bleeding in the brain.
However, daily doses of more than 32 milligrams (mg) were linked to a three-fold increase in hemorrhagic stroke risk,.
Ephedra, also known as Ma huang, is used in some dietary supplements marketed as weight-loss aids or energy-boosters. The herb has similar chemical properties to amphetamines and has been linked to side effects such as heart arrhythmia, psychotic reactions and seizures.
There have also been reports of heart attack and stroke. Ephedra affects the vascular and nervous systems, and one theory is that blood pressure spikes are one way the herb could promote hemorrhagic stroke--particularly when combined with caffeine, as is often the case in supplements.
32 mg per day is the maximum allowed dose under Canadian law.
Last year, Canadian health officials requested a voluntary recall of certain ephedra-containing products that exceeded that dosage mark. That came after authorities reported 60 cases of adverse cardiovascular or nervous-system effects tied to ephedra.
In the current study, researchers from the University of Michigan in Ann Arbor looked at data on more than 700 young to middle-aged hemorrhagic stroke patients. Patients were compared with nearly 1,400 "controls" who hadn't suffered a stroke.
The researchers found that the odds of hemorrhagic stroke more than tripled for people who reported taking ephedra doses above the 32-mg mark within three days of their stroke.They point out, however, that their results are based on only a small number of people reporting ephedra use.
In the US, where the supplement industry is not tightly regulated and there is no maximum allowed ephedra dose, some medical and consumer groups have called for a ban on the herb. he industry maintains that ephedra is safe when used as directed.
In 1997, the US Food and Drug Administration proposed limiting the allowable doses of ephedra and taking other steps to restrict its use. It withdrew the proposals in 2000 after industry groups and a congressional audit said they were not supported by scientific evidence. Last year, the government again said it would delay limiting the use of ephedra until results from ongoing studies of its safety were in.
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