Challenges in herbal research: a randomized clinical trial to assess blinding with ginger.

OBJECTIVE: To assess methods to blind study participants to encapsulated ginger (Zingiber officinale). DESIGN: A randomized double-blind placebo controlled trial. SUBJECTS: Eighty healthy male and female volunteers. OUTCOME MEASURES: Whether participants can accurately determine if they receive a ginger or placebo capsule and a bottle filled with ginger or placebo capsules. RESULTS: Forty-two subjects correctly identified the capsule they received. Of those who received placebo, over 82% correctly identified their capsule. Only 22.5% of those who received ginger correctly identified their capsule. The likelihood of guessing ginger between the groups was statistically similar (p<0.01). 65% correctly guessed which bottle they had received (p=0.0073). Participants receiving the bottle filled with ginger capsules successfully identified their bottle 75% of the time (p=0.0016) compared to the 55% of the placebo group (p=0.5). CONCLUSIONS: Volunteers cannot determine which type of individual capsule they receive but can distinguish a bottle filled with ginger capsules.