High kava use increases gamma-glutamyl transpeptidase (GGT) levels in the blood. Research is clear that “while elevated GGT and white blood cells [lymphocytes] were abnormal [to those unfamiliar with kava’s effects on the liver], this does not mean that this abnormality is of concern”. Additionally, high kava use over a prolonged period can cause kava dermopathy, or a drying and flaking of the skin. However, this subsides a week or so after use is slowed or ceased, without residual effects.

Kava’s level of safety is recognised in 2000+ years of traditional knowledge and use, and a 2016 World Health Organisation’s (WHO) kava risk assessment report: "On balance, the weight-of-evidence from both a long history of use of kava beverage and from the more recent research findings indicates that it is possible for kava beverage [made with noble cultivars] to be consumed with an acceptably low level of health risk." That same report also cited research showing kava as statistically safer than Paracetamol. Additionally, the 2019 Drug Harms Ranking Study assessed kava as the least-most harmful drug of the 22 assessed substances, with the harm to the user scored at 2, and harm to others 1 (total 3 harm-points). The harm to user score includes the GGT level rise and kava dermopathy (as discussed above) which are reversable. Kava’s safety is reflected in its regulation as a ‘food’ in some countries. However, the WHO (including the UN/WHO Kava CODEX Alimentarius) ‘food’ classification and harm ranking is caveated on kava beverage made only from noble drinking cultivars of Piper methysticum and prepared using a traditionally influenced water-based method. This ‘food’ safety recognition does not extend to contemporary products, extracts and pop-culture products made from, and including, Piper methysticum.

Kava wash-down

Coinciding with kava’s move away from its traditional use environment is the growing practice of washdown in which alcohol is consumed together with, or following, kava consumption. Alcohol, even at very small quantities following, or with, kava use, is known to potentiate the effects of kava. There is concern that the use of ethanol by the pharmaceutical/nutraceutical industry to extract kavalactones potentially caused a chemotype disruption and was a contributing factor in European Kava Ban hepatoxicity cases. It is suspected that kava wash-down increases the likelihood of in-vivo chemotype disruption and liver complication. Kava wash-down is potentially dangerous, as are Piper methysticum products that contain alcohol or used it in processing.

Kava, Piper methysticum preparations and Kratom

Research shows that over 60% of ‘kava bars’ in the USA either mix kratom (Mitragyna speciosa), or have it available to mix, with their kava or pop-culture Piper methysticum drinks. Kratom is a Southeast Asian leaf with addictive, opioid-like effects, and is said to give kava a ‘euphoric hit’. Although the practice of mixing addictive kratom with safe kava is frequently denied, a large collection of kava bar ‘menus’ and social media posts provide a plethora of evidence of this practice. More concerning are reports in online addiction support groups from kava bar patrons who believed they had been drinking kava, only later to learn this had been adulterated with kratom and had led to dependency. The FDA advises that “kratom is not lawfully marketed in the U.S. as a drug product, a dietary supplement, or a food additive.” Kava bar attendees are advised to seek clarification on kava / Piper methysticum preparation ingredients. Customers are strongly advised not to consume ‘kava shots’ or kratom Piper methysticum drinks. These are marketed under names including Phlex, Feel Free, Flayvorz, etc. and are potentially dangerous.

General kava safety comments

Research warns, "[i]t is important to keep in mind that not all … [Piper methysticum preparations are] equal in efficacy and safety and therefore it is critical to characterize a … [Piper methysticum] product with detailed knowledge of its preparation method and chemical composition. Many factors, ranging from cultivars, parts of the plant used, preparation methods, and solvents employed for extraction, affect the composition of the final kava products." Additionally, kava misinformation (see section under), practices such as Kava wash-down, kava drug interactions and unethical behaviour including adulterating Piper methysticum with kratom has led to regulatory confusion.