Piper methysticum, better known as kava, is an herb with sedative properties. It has been used for centuries in the Pacific Islands as an alcohol-like beverage and is valued today for its relaxing effects. Caffeine—a common stimulant found in coffee, tea and chocolate—may be combined with kava for its energy-boosting effects. Understanding the individual and combined effects of kava and caffeine allows you to get the most benefit from each supplement.
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Both kava and caffeine are available in many different forms. In the Pacific Islands, kava is brewed into a tea and consumed traditionally as an alcohol-like beverage. Today, it is sold in the form of pills, powders and tinctures and is often used as a supplement for conditions like anxiety and insomnia.
Caffeine occurs naturally in tea, coffee beans, cacao beans and herbs like yerba mate and guarana. It is also added to many energy drinks, sodas and a variety of drugs like antihistamines and headache medications.
While kava’s exact mechanism of action is not known, it is thought to work by stimulating the release of GABA—a neurotransmitter associated with muscle tone and relaxation. For this reason, kava is sometimes used to relieve anxiety. According to the National Institutes of Health, kava extract is superior to placebo for treating anxiety symptoms.
As a mild stimulant, caffeine has essentially the opposite effect. It speeds heart rate and breathing while increasing alertness and energy. Combined with kava, caffeine may offset the drowsiness that can sometimes occur as a side effect of the herb.
The most serious side effect of kava is liver damage. Science Daily states that kavain—a major component of kava—triggers liver damage by narrowing blood vessels and causing the lining of liver cells to retract. While this side effect is rare, people should be informed of the possibility for liver damage when taking kava.
Side effects of caffeine include nervousness, insomnia, headache and irritability. In excess, caffeine may lead to overdose that can sometimes be fatal. More common side effects include shakiness, frequent urination and nausea.
The only way to completely avoid side effects like liver damage is to abstain from using kava. People with a history of liver or kidney damage should avoid taking the herb altogether. Don't drive until you know how kava affects you, and start with the lowest effective dose to gauge its effects.
To prevent overdose, monitor your daily intake of caffeine from all sources. If insomnia occurs, stop consuming caffeine six hours before bedtime.
Combining caffeine with kava may increase the risk for side effects. If you experience signs of liver damage such as yellowing of the eyes or skin, abdominal pain or pale stool, stop using kava and seek immediate medical attention.