I see this stated in many places on the internet, but seldom referenced. The original claim was made in the book: 

Lebot, Vincent. & Merlin, Mark David. & Lindstrom, Lamont Carl.  1992,  Kava : the Pacific drug / Vincent Lebot, Mark Merlin, and Lamont Lindstrom  Yale University Press New Haven

Kava beverages are becoming more popular these days. Out of curiosity, I looked into the shelf life of premixed kava. It turns out there was a research article already published on this topic. Conclusion? 2 days. When you mix kava, 2 days is about the maximum time you want it to sit around.

Moral of the story? Don’t let your grog sit around; drink it down!

Cannibalism: Fiji's unique and disturbing version of the keto diet. ​

Pacific Horticultural and Agricultural Market Access (PHAMA) has been working to establish the National Fijian Quality Standard for kava. This quality standard has been described in the Fijian Kava Quality Manual, released in 2017. The manual touches on all aspects of kava including: transplanting seedlings, soil, fertilizers, pests, harvest, post harvest, storage, and transport. It also emphasizes testing and best practices throughout. It's a great document. 
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Makas are the fibrous plant matter leftover in your strainer bag when you make a kava beverage in the traditional way. In Fiji, makas are called cosas, which is synonymous with 'fiber' or 'trash'. There are many reasons why it's important to filter makas from your beverage. First, many think that makas cause nausea and that they can accelerate the onset of dermopathy. Also, makas are lower in kavalactones, so including them in powder will dilute the potency. Manufacturers of instant kava are able to charge a premium because they take special, proprietary steps to remove makas. It's preferable to remove makas from undried roots, but I wondered if I could find an effective way using whole, dried roots. 
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