If you have pre-existing health or cardiac conditions you may want to limit or avoid ephedrine. Here's one study:
Researchers at Harvard and Columbia Find Ephedra Safe and Effective in Combating Excess Weight
Study Published in The International Journal of Obesity Also Reveals Significant Weight Loss in Subjects
A study conducted by researchers at Harvard and Columbia Universities and published in two respected medical journals has concluded that Ephedra dietary supplements are safe and effective for the use of losing weight and promoting increased health. This is another victory for the effective yet sometimes controversial herb, which is a prime component of WIN's popular BIOLEAN® dietary supplement.
The study was published in abstract form in the Federation of American Societies for Experimental Biology's FASEB Journal and as a full study in The International Journal of Obesity.
In this study, the Harvard/Columbia researchers found that herbal Ephedra, when combined with caffeine, lowered body weight, fat and body mass index. This news comes on the heels of a comprehensive science-based risk analysis performed by Cantox Health Sciences International, in which researchers found that Ephedra was both safe and beneficial for weight loss at the 90 mg per day dosage.
In August 2000, a seven-member panel of experts completed a multi-disciplinary review of Ephedra, also known as Ma Huang, and concluded that there is no association between serious adverse events and Ephedra when consumed as directed. Conservative estimates indicate that over three billion servings of Ephedra products are consumed each year.