Reviewed: Ozgoli G, Goli M, Simbar M. Effects of ginger capsules on pregnancy, nausea, and vomiting. J Altern Complement Med. 2009:15(3):243-246.
Researchers from Iran recently conducted 2 trials to evaluate the safety and effectiveness of ginger (Zingiber officinale, Zingiberaceae) for treating female reproductive complaints. The first study compared ginger preparations to non-steroidal anti-inflammatory drugs (NSAIDs) for relieving dysmenorrhea (painful or difficult menstruation). The second study evaluated ginger as a treatment for nausea and vomiting during pregnancy.
Dysmenorrhea is experienced by more than half of menstruating women. NSAIDs can be effective in relieving dysmenorrhea, but NSAIDs and other pain relievers commonly cause adverse side effects and are contraindicated in some people. Ancient medical texts refer to the use of ginger for relief of dysmenorrhea, but there are no published clinical trials to support its effectiveness. The researchers therefore conducted a study to compare the effects of ginger, mefenamic acid (a mild analgesic and fever-reducing NSAID used in some types of arthritis and for the relief of moderate short-term menstrual pain), and the NSAID ibuprofen on dysmenorrhea.
For the non-randomized, double-blind trial, the researchers recruited 150 female college students who were 18 years or older and had primary dysmenorrhea. The women completed a questionnaire that assessed menstrual characteristics and severity of pain. Those with moderate to severe dysmenorrhea were enrolled in the study and alternately allocated to 1 of 3 groups: the ginger group, the mefenamic acid group, or the ibuprofen group. Depending on their assigned group, the women were instructed to take either four 250-mg capsules of ginger rhizome powder (Zintoma; Goldaroo Company; Tehran, Iran), four 250-mg capsules of mefenamic acid (Ponstan; Razak Co.; Iran), or four 400-mg capsules of ibuprofen (Brufen; Roozdaru Co.; Iran) each day, beginning on the first day of their menstrual period and continuing for 3 days. After the 3 days, the women rated the severity of their dysmenorrhea, the degree of pain relief, and their satisfaction with the treatment. Only one menstrual cycle was studied.
All 150 women completed the study. There were no significant differences in baseline characteristics among the 3 groups. Dysmenorrhea severity decreased in all 3 groups (P values not reported) after 3 days. Severity of symptoms, improvement in pain relief, satisfaction with the treatment, and compliance with the capsules were not significantly different among the groups. None of the women reported any serious adverse side effects during the study.
The authors conclude that ginger is as effective as mefenamic acid and ibuprofen in decreasing menstrual pain. They also point out certain limitations of this study. The study subjects were alternately assigned to an experimental group rather than randomly assigned; however, baseline characteristics were similar among subjects in all 3 groups, and there is no indication of bias in group assignments. The study did not compare the effect of ginger on other menstrual symptoms, such as nausea, headaches, and fatigue. The scale used to rate dysmenorrhea severity was a verbal, 4-point scale, and the authors suggest that use of a 10-point visual analog scale or other standardized scale may detect more subtle differences in response among the experimental groups.
One issue the authors do not address is the dosage of comparator drugs used in this study. It is not clear if the doses selected for this study (1,600 mg ibuprofen and 1,000 mg mefenamic acid) are typical doses used for treatment of primary dysmenorrhea in the local population. In the United States, daily doses of 2,400-3,200 mg ibuprofen are commonly recommended for treatment of moderate or severe dysmenorrhea and may be more effective than the 1,600 mg dose of ibuprofen used in this study. The recommended dose for mefenamic acid is 1,500 mg per day. It is therefore unclear as to how much of a placebo-effect occurred in this study. It would have been better if a placebo group had been included for comparison. Another limitation is that the study was very brief; typically, dysmenorrhea studies are conducted over a 3 month period. In addition to correcting the limitations discussed by the authors, future trials should assess the safety and efficacy of ginger during several menstrual cycles, investigate a range of ginger doses, and include populations of women other than young college students.
The second study assessed the effects of 1,000 mg of ginger administered in capsule form on the severity of nausea and vomiting in pregnant women. Up to 90% of women experience nausea and vomiting during pregnancy. Little is known about the safety of antinausea drugs during pregnancy, so some pregnant women turn to herbs or other complementary therapies for relief. Ginger has long been used to relieve stomach upset in the traditional medicines of many cultures.
This single-blind, randomized, placebo-controlled trial was conducted at prenatal clinics and Isfahan Shahid Beheshti Hospital in Isfahan, Iran. Seventy healthy, pregnant women who were less than 20 weeks gestational age and who reported mild to moderate nausea with or without vomiting were enrolled in the trial. The women were randomly allocated to an experimental group or a matched control group. Women in the experimental group took four 250-mg capsules containing ginger root powder (Zintoma; Goldaroo Company; Tehran, Iran) daily for 4 days. Women in the control group took 4 placebo capsules containing lactose daily for 4 days. The women were instructed to take a capsule in the morning, at noon, in the afternoon, and at night.
Before starting the study, women rated the severity of their nausea and vomiting using a 10-point visual analog scale (VAS). The women were instructed to avoid fatty foods and to eat smaller, more frequent meals during the study. The women completed a questionnaire each day and recorded the severity of their nausea on the VAS twice a day (at noon and at bedtime). On the fifth day, the women were interviewed by a researcher to assess compliance with the dietary instructions and capsule use.
Of the 70 women who started the study, 67 completed the study (32 in the ginger group and 35 in the placebo group). There were no significant differences in nausea intensity between the 2 groups at baseline. Women in the ginger group reported significantly greater improvement in nausea than women in the placebo group (P < 0.05) during the 4-day trial. Nausea intensity declined in 84% of women in the ginger group and 56% of women in the placebo group (P < 0.05). The incidence of vomiting did not decrease significantly in the placebo group but decreased a significant 50% in the ginger group after 4 days (P < 0.05). None of the women reported any adverse side effects from the capsules. While compliance with the capsules was excellent in both groups, only about half of the women in each group reported complying with the dietary advice.
The authors conclude that daily treatment with 1,000 mg of ginger is a safe and effective way to decrease the intensity of nausea as well as the incidence of vomiting during pregnancy. However, the authors’ conclusions that 1,000 mg is the appropriate dose cannot be asserted given that this study was not a dose-ranging study. Also, the authors’ conclusion that this dose is safe cannot be asserted since there has been no long-term, follow-up studies of the infants, and, given the small sample size, only very large changes in pregnancy outcomes would have been seen.
The results of this study are consistent with 9 published randomized controlled trials, which have also evaluated the effectiveness of ginger for nausea and vomiting during pregnancy. In these trials, daily doses ranged from 1,000 mg to 1,500 mg and the ginger products included capsules containing ginger powder or ginger syrup, which is mixed with a beverage.
The authors point out that the short duration of this trial is a limitation. Another limitation that the authors did not discuss is whether the study was adequately blinded. Ginger capsules have a distinctive odor and flavor and it is possible that the people taking the placebo were aware that they had the placebo treatment. This could have contributed to the study outcome. Future trials should assess the safety and effectiveness of ginger over a longer period of time, should improve study blinding, and enroll pregnant women with severe nausea and vomiting to expand the understanding of this herb’s effectiveness during pregnancy.
—Heather S. Oliff, PhD