Kava kava (Piper methysticum) is possibly the most well-researched herbal supplement in the world. Numerous studies have been published in the last 30 years demonstrating everything from kava's efficacy in reducing anxiety and sleeping difficulties to its positive effects on reaction time [3, 4, 5, 6, 7, 8]. There are even emerging studies that suggest some compounds in kava root may have a preventative effect on the development of certain types of cancer cells [7, 8]. Best of all, there is ample research indicating that kavalactones are well-tolerated by the body when prepared and used appropriately [1, 2, 8].

Safety Studies: In response to concerns about the possible effects of kava supplements on the liver, the British Herbal Medicines Association (BHMA) and the World Health Organization (WHO) commissioned studies to determine kava's safety and develop purity standards for kava root extracts. The detailed report from the BHMA, which you can also read on this site, found that the few side effects of kava were transient and mild, and mostly occurred at higher doses of kava [1]. The side effects observed at these higher doses were a reversible skin condition known as kava dermopathy, shortness of breath, changes in blood platelet count, and slight elevation of the liver enzyme gamma glutamyl transferase (GGT). However, even though this enzyme was elevated, the researchers did not observe any signs of liver toxicity [1].

The board determined that the cases of liver toxicity at lower therapeutic doses of kava recorded in Germany and Switzerland were likely caused by substandard raw kava material that contained admixtures of stems and leaves (which are never used in traditional South Pacific kava preparations)[1, 2]. Combination with alcohol, benzodiazepines and related prescription anti-anxiety medications was another possible risk factor for hepatotoxicity with kava supplements in the cases examined [2].

Anxiety: The most recent study to emerge on kava kava's effect on anxiety is also one of the best. A team from the University of Melbourne, led by Jerome Sarris, conducted an 8-week placebo-controlled study of kava extract versus placebo in treating 75 volunteer subjects diagnosed with generalized anxiety disorder (GAD)[3]. Subjects were split into a control and an experimental group, with the controls receiving dummy pills while the experimental group received 120mg of kava root extract. As the study progressed, both groups regularly self-reported their anxiety levels using the Hamilton Scale, a standard test used to measure anxiety. After 8 weeks, all the subjects in the kava group showed a reduction in anxiety that was statistically significant compared to the control group. Furthermore, of the experimental group, 26% of people diagnosed with severe GAD experienced remission of their anxiety symptoms (compared to a 6% remission rate in the control group not taking kava)[3]. Sarris and his team noted that the experimental group tolerated the kavalactones very well: they observed no abnormalities in liver function or habituation to kavalactones in the group for the duration of the study [3].

Reaction Time: Scientific studies dating back as early as 1987 have been published demonstrating that even higher than usual doses of kava do not have a detrimental effect on reaction time or intellectual performance in memory-related tasks [4]. A 1989 study [5] compared an extract of kavain at doses of 200mg, 400mg, and 600mg with the conventional benzodiazepine drug clobazapam at a dose of 30mg. A control group given a placebo was also included in the study. The results demonstrated that the subjects given the kavain actually showed an improvement in attention, reaction time, motor reflex, and intellectual performance (measured by the Pauli test)[5]. Subjects given the 200mg dose of kavain also reported improvements in wakefulness, mood, and general well-being, while those given the 600mg dose experienced more sedation (but still less than that produced by clobazapam)[5].

A more recent placebo-controlled randomized double-blind trial--the gold standard in clinical research--involved 12 healthy volunteers in a word-recognition memory task. The subjects were goven either an inert placebo, the standard anti-anxiety drug oxazepam, or a kava extract. The oxazepam group exhibited a pronounced slowing in reaction time and a reduction in the number of correct responses to the memory task [6]. In contrast, the researchers observed an enhancement of memory performance following kava [6]. In other words, the kava increased rather than decreased the subjects' reaction time and accuracy in memory-related tasks. The evidence in favor of kava in this area is encouraging, as a slowing of reaction time and mental fogginess are two common undesirable effects from conventional anti-anxiety drugs.

Insomnia: Though the use of kava to treat insomnia doesn't have quite the bevy of research behind it as its benefits for anxiety, studies have been done suggesting kava may have benefits for those with insomnia--especially when that insomnia is a result of anxiety or stress. Insomnia encompasses a range of symptoms, including difficulty falling asleep, reduced hours spent asleep, and corresponding detrimental effects on daytime mood, alertness, and energy levels [7]. A study by Wheatley (2001) examined the effects of extracts of kava and valerian (in different study periods), and found that both herbs showed significant reductions in stress, leading to better sleeping outcomes [7]. 58% of the study subjects did not experience any side effects from either kava or valerian; of those that did, 16% of subjects reported vivid dreams with valerian, and 12% experienced some mild dizziness with kava [7].

Cancer: Yes, you read that right--some of the most cutting-edge research on kava is looking into the potential of certain compounds in the root for preventing different cancers; specifically bladder cancers, and lung cancers that result from smoking tobacco. The first study comes from Dr. Xiaolin Zhi of the University of California Irvine: his team tested a preparation of flavokawain A, a compound found in kava root, on precancerous bladder cells in mice and found that the compound encouraged the cells to undergo apoptosis (cell death) [8]. The preliminary paper also stated that there was no observed toxicity in the mice given flavokawain A, an important metric to establish for any potential therapy [8].

A second recent study by the University of Minnesota College of Pharmacy and Texas Tech examined special preparations of kava compounds and their role in preventing lung cancers in mouse models that are used to predict lung cancers in humans [9]. The kava compounds used in the study prevented 99% of cancers predicted to develop, a prevention rate that the authors of the study associated with a sigificant reduction in the rates of DNA damage caused by the compounds in tobacco. The researchers speculated that some kava compounds may have a protective effect on DNA [9].

We hope the above review has been a helpful guide to the current clinical research on the health benefits of kava kava. We believe in providing our readers with the best information available on kava, including the many studies that have published in recent years attesting to its benefits for stress relief, anxiety, insomnia, and long-term health. Aloha!

REFERENCES

1. "Safety and Benefits of Kava Kava." March 12th, 2002. Submission to Committee for the Safety of Medicines, British Herbal Medicines Association.

2. "Assessment of the Risk of Hepatotoxicity with Kava Products." 2007. World Health Organization Press.

3. Sarris, Jerome, Con Stough, Chad A. Bousman, Zahra T. Wahid, Greg Murray, Rolf Teschke, Karen M Savage, Ashley Dowell, Chee Ng, and Isaac Schweitzer. 2013. "Kava in the treatment of generalized anxiety disorder." Journal of Clinical Psychopharmacology

4. Russell, PN, D Bakker, and NN Singh. 1987. "The effects of kava on alerting and speed of access from long-term memory." Bulletin of the Psychonomic Society 25: 236-237.

5. Saletu, B, J Grunberger, and L Linzmayer. 1989. "EEG brain-mapping, psychometric and psychophysiological effects of kavain--a kava plant derivative." Human Psychopharmacology 4: 169-190.

6. Munte, TF, HJ Heinz, M Matzke, and J Steintz. 1993. "Effects of oxazepam and an extract of kava roots (Piper methysticum) on event-related potentials in a word-recognition test." Neuropsychobiology 27: 46-53.

7. Wheatley, D. 2001. "Kava and Valerian in the treatment of stress-induced insomnia." Phytotherapy Research 15 (6): 549-51.

8. Vasich, Tom. February 25th, 2014. "Can Kava Cure Cancer?" UC Irvine News.

9."Preliminary Study in Mice Suggests Possible Cancer-Protective Effect of South Pacific Herb." January 8th, 2014. American Botanical Council.