Clinical Briefs: Ginseng and Hypertension
Source: Stavro PM, et al. Long-term intake of North American ginseng has no effect on 24-hour blood pressure and renal function. Hypertension 2006;47:791-796. Epub 2006 Mar 6.
Goal: To evaluate the effect of North American ginseng (NAG) on mean 24-hour ambulatory blood pressure (ABP) and renal function after 12 weeks use in hypertensive subjects.
Design: Randomized, controlled, double-blind crossover trial.
Subjects: Fifty-two people from Toronto with hypertension (data from 37 subjects, 30 men, were included in the main analysis).
Methods: Subjects recruited through newspaper advertisements were randomized to receive, following a four-week open label placebo run-in, 3 g NAG followed by cornstarch placebo, or cornstarch placebo followed by 3 g NAG (identical capsules). Participants ingested the capsules orally in divided doses (bid) during the first 12 weeks (between 7-9 am and again between 7-9 pm). Following an eight-week washout period subjects took the crossover treatment for 12 weeks in the same manner. ABP monitors were fitted, weight was recorded, and blood samples were drawn at the beginning of the run-in and at study's end after a 10-12 hour fast overnight and discontinuation of blood pressure medications (8 hours). During the two days that the ABP monitor was worn (activated between 9-10 am) no NAG or placebo was ingested. Participants also filled out a 24-hour diary of activity, sleep, and drug schedules. Primary outcome measure was mean 24-hour ambulatory systolic blood pressure at 12 weeks. Additional blood pressure measures, body weight, and serum cystatin C levels were secondary outcome measures.
Results: No significant treatment effect was found for mean 24-hour systolic blood pressure or most other blood pressure parameters (including day and nighttime readings). At week 12, diastolic blood pressure readings for the NAG group were higher at 1 pm than in the placebo group, but this was considered insignificant since mean daytime and 24-hour diastolic blood pressure readings did not differ between the groups. No significant change was noted in body weight or serum cystatin C between the two groups at the end of the study.
Conclusion: In hypertensive individuals, 12 weeks of NAG has no effect on ambulatory blood pressure or renal function.
Study strengths: Use of 24-hour ambulatory blood pressure monitoring rather than office blood pressure; intention-to-treat analysis included.
Study weaknesses: Significant dropout rate with small sample (15/52, or 29%); compliance estimated by pill count; the authors state that ginsenosides remain in human plasma for approximately 12 hours, while 12-week ABP monitor readings were initiated at least 12 hours after the last ingestion of NAG.
Of note: While there are many species of ginseng, Panax quinquefolius (NAG) and Panax ginseng (Asian or Korean ginseng) comprise the majority of ginseng consumed worldwide; ginseng is used by 10-20% of adult Asians and by up to 5% of adults in Western countries, while estimates are that 20-40% of people in these same regions have hypertension; concerns about ginseng causing elevated blood pressure come primarily from a 1979 observational study noting development of hypertension in 14 subjects after three months of use; a single batch of NAG, reportedly representative of NAG on the world market, was used in the current trial; subjects were permitted to take their antihypertensive agents during the study; a previous trial by the same study group showed that even NAG batches differing in quality and ginsenoside content had no acute effect on blood pressure.
We knew that: Though data are conflicting, ginseng has been reported to improve cognitive function, immune system activity, and glycemic control, and is widely perceived to be a tonic that enhances overall vitality; serum cystatin C is a marker of glomerular filtration rate and cardiovascular mortality; the 3 g dosage employed in this study is the same dosage typically used in traditional Chinese medicine and matches the average intake reported to cause hypertension in the 1979 study that gave rise to cautions; NAG contains a three- to five-fold higher ginsenoside content than do both forms of Panax ginseng; early data on Panax ginseng suggest that it might actually lower blood pressure.
Clinical import: Concern about using ginseng in people with hypertension was raised more than two decades ago and has made its way into the general mindset of practitioners under the heading "contraindication." The current study suggests that long-term ingestion of NAG does not have a lasting effect on blood pressure in hypertensive patients, but the trial is flawed. Aside from the significant dropout rate, the 12-hour lag time between measurement of 24-hour ABP and last ingestion of NAG is at least puzzling, making firm conclusions elusive. As the authors point out, it would be interesting to determine the effect of NAG on blood pressure in people with untreated mild hypertension or pre-hypertension. Likewise, a larger trial involving hypertensive patients with fewer dropouts and improved methodology would be welcome. Practitioners should keep in mind that this trial only addressed North American ginseng, so results do not apply to all forms of ginseng in therapeutic use. It is possible that NAG may be safely employed in hypertensive patients where indicated, but the current study does not prove this true. Monitoring of blood pressure in this setting remains the prudent course until more definitive data become available.
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