Dong quai is an herb present in at least one popular health remedy. This herb has been used in traditional Chinese medicine for over 2,000 years, but its efficacy has not been evaluated. Hirata and colleagues assessed the estrogenic effects of dong quai and its effect on menopausal symptoms. They also measured dong quai's effect on estradiol and estrone levels.

The double-blind, placebo-controlled study included 71 women who were postmenopausal for at least six months and had a significant problem with hot flushes or night sweats. The initial assessment included a Papanicolaou smear to determine the maturation values of vaginal cells, ultrasonography to measure the thickness of the endometrial lining, and measurement of serum estradiol, estrone and sex hormone–binding globulin (SHBG) levels.

Serum estrogen levels and vaginal cell maturation were checked again after 12 weeks, and endometrial ultrasonography was performed in the sixth, 12th and 24th weeks of the study. Women who were found to have an endometrial thickness of more than 5 mm at the final visit underwent endometrial biopsy to exclude endometrial abnormalities. Patients also kept a diary of the number of vasomotor episodes they experienced each day. At each visit, the Kupperman index was used to assess each patient's degree of symptoms. Patients were randomized to receive placebo or dong quai, in a dosage of three capsules three times daily, which is equivalent to 4.5 g of dong quai root daily. At the end of the study, no statistically significant difference in endometrial thickness was found between the dong quai group and the placebo group. The average maturation value of vaginal cells in both groups was less than 40 at 12 weeks, which is consistent with a menopausal, nonestrogenic pattern. No statistically significant changes occurred in the serum estradiol, estrone and SHBG levels. While the Kupperman index and the number of vasomotor episodes in both groups were reduced by 25 to 30 percent from initial values, no statistically significant differences were noted between the two groups.

The authors conclude that dong quai alone is no more useful than placebo in the treatment of menopausal symptoms, and they state that women should be discouraged from using this herb as a remedy for these symptoms.