Kava Root: Why Only One Part of the Plant Ends Up in Your Cup

A kava plant is a fairly unremarkable shrub. Heart-shaped leaves, woody stems, a couple of meters tall. Nothing about the part you can see is worth harvesting.

Everything people have wanted from this plant for the last few thousand years is underground, and even down there, not all of it counts.

Kava root is the underground portion of the Piper methysticum plant, and it's the only part used to make kava.

It holds the kavalactones, the compounds responsible for kava's calming effects, at concentrations ranging from roughly 3% to 20% of dry weight.

The leaves and upper stems are excluded, both by tradition and by international food standards, because they contain almost no kavalactones and do contain compounds nobody wants to drink.

Which underground part you get changes the strength of your kava considerably, and the packet rarely tells you. Here's what's actually in the bag.

What Is Kava Root?

Kava root is the underground part of Piper methysticum, harvested, dried and ground into the powder used to make kava drinks.

The plant is a slow-growing perennial from the pepper family, cultivated across Vanuatu, Fiji, Tonga, Samoa and Hawaii. It's sterile and reproduces only from cuttings, so every kava plant alive is a clone of one a farmer planted deliberately.

Growers leave it in the ground for years before harvest, because kavalactones accumulate with age.

What comes out of the soil is a knotty central stump with a fringe of thin roots trailing off it.

According to the IARC monograph on kava, those lateral roots can extend two to three meters. Everything above ground is left in the field, minus the cuttings kept for replanting.

For the plant itself, the cultivation history and the chemotype system, we've written a separate guide to Piper methysticum.

Is Kava Root Actually a Root?

Partly. A good deal of what's sold as kava root is rhizome, which is an underground stem rather than a root.

The distinction sounds like botanical hair-splitting, and for most purposes it is. But it matters here because the two parts don't have the same potency, and the words get used loosely on packaging.

In Fiji, these are named and sold separately. Lateral roots are waka, the rhizome is lawena, and the woody chips left over are makas.

Most other producing countries mix the two underground parts together and sell the result as kava root, which is why the same weight of powder from two suppliers can behave very differently.

Which Part of the Kava Plant Has the Most Kavalactones?

Lateral roots come out on top, followed by the rhizome, with stems trailing far behind.

This was mapped in detail by a 2020 study in GigaScience, which separated a noble Fijian kava plant into individual tissues and measured them.

Kavain, dihydromethysticin and desmethoxyyangonin all followed the same pattern: lateral roots highest, crown roots next, stems lowest by a wide margin.

One caveat: the vendors selling premium waka tend to skip.

The same study noted that while lateral roots measured higher than crown roots on all three compounds, the difference between the two root types wasn't large enough to reach statistical significance in their analysis.

The gap that was unambiguous, across every method they used, was roots versus stems.

So treat waka as the likely stronger option rather than a guaranteed one, and treat any stem content as a genuine problem.

Why Is Only the Root of the Kava Plant Used?

Because the aerial parts carry almost no kavalactones and do carry an alkaloid that isn't found in meaningful amounts underground.

That alkaloid is pipermethystine. It concentrates in the leaves and stem peelings, and the GigaScience tissue analysis found it in whole stem samples but not in the root tissues.

In cell studies published in Toxicological Sciences, pipermethystine damaged human liver cells at concentrations where kavalactones did not, with 100 micromolar exposure causing around 90% loss of cell viability in 24 hours.

What Does the Codex Standard Say About Kava Root?

It permits roots, peeled rhizomes and basal stems up to the first node, and explicitly excludes upper stems, leaves, peelings and extraction residues.

The Regional Standard for Kava Products, adopted by the Codex Alimentarius Commission in 2020, is the closest thing kava has to an international rulebook.

It's short, and worth knowing because it turns folk practice into something checkable.

Alongside the plant parts, it requires that kava products come from a Noble cultivar, that wild Piper wichmannii and two-day varieties are excluded, and that the product is free of leaves, bark and stems, free of visible mould, and dried to a moisture content no higher than 12%.

That last pair matters more than it sounds. Kava is dried in humid tropical conditions and then shipped, and damp root is exactly where mould gets a foothold.

Why Is Kava Root Peeled?

The outer bark is removed from the rhizome and stump before processing, and the peelings themselves are treated as waste rather than product.

The Codex standard says the underground parts should be washed and peeled where tissues have been exposed to sunlight, and lists peelings among the excluded materials. Commercial kava biomass is normally traded as peeled rhizome for the same reason.

Peeling has a second effect that only turned up recently.

When the GigaScience team measured separated tissues, the crown root peel held the highest concentrations of kavain and desmethoxyyangonin, two kavalactones that are absorbed quickly. 

They suggested that removing the peel may smooth out the experience by taking out the fastest-hitting fraction, making the traditional practice a deliberate choice rather than an accident of tidiness.

Peelings have still shown up in commerce as a cheap filler. That's the practice most often blamed for the European liver injury cases in the early 2000s, which we cover in our guide to what kava is.

What Is Kava Root Made Of?

Mostly starch and fiber, with kavalactones making up between roughly 3% and 20% of dry weight.

Fresh kava rhizome is about 80% water.

Once dried, the IARC monograph puts a typical composition at around 43% starch, 20% fiber, 12% residual water, and roughly 15% kavalactones, with that last figure varying widely by cultivar and by how long the plant grew.

Six kavalactones account for roughly 96% of the active resin: kavain, dihydrokavain, yangonin, desmethoxyyangonin, methysticin and dihydromethysticin. Their ratios differ between cultivars, which is what the chemotype system tracks.

The practical consequence of that 3% to 20% spread is that grams of root tell you almost nothing about dose.

Ten grams of one root can carry several times the kavalactones of ten grams of another, which is why we cover this properly in our guide to kava dosage.

How Is Kava Root Processed Into Powder?

Harvest, wash, separate, peel, chop, dry, grind. The steps are simple, and the failure points are all about moisture.

1. Harvest after several years. Kavalactones build up over time, so plants are typically left in the ground for years rather than seasons before being dug up whole.
2. Wash and separate. Soil is washed off, and the underground parts are divided. In Fiji, this is where waka, lawena and makas are sorted into separate grades.
3. Peel the rhizome. The outer bark comes off the stump and basal stem. Peelings are set aside as waste under the Codex standard.
4. Chop into chips. The material is sliced so it dries evenly rather than rotting from the inside.
5. Dry thoroughly. The moisture target is under 12%. Rushed or humid drying is where mould contamination enters the supply chain.
6. Grind to powder. Dried chips are milled. Medium grinds suit strainer-bag preparation, while micronized kava is milled fine enough to drink without straining.

Once it's powder, none of this is visible. That's the whole problem with the category.

How Can You Tell if Kava Root Has Been Adulterated?

Ground root hides its origins well, which is why the documented adulteration problems are worth knowing about.

The IARC monograph collects several. Powdered kava sold in Fijian markets has been measured to contain only 71% to 78% of the expected active constituents. Adulteration with sawdust, flour and soil has been reported.

Other Piper species that resemble kava but lack kavalactones entirely, mainly Piper auritum and Piper aduncum, have been sold as the real thing.

Small amounts of the mould toxins ochratoxin A and aflatoxin B1 have been detected in kava root samples.

None of this requires expertise. It mostly requires a supplier willing to say what's in the bag, and the ones that won't are telling you something.

Is Kava Root Safe?

Traditional water-prepared noble root has a long record of use, but kava has been linked to rare cases of serious liver injury, and that risk hasn't been fully explained.

The National Center for Complementary and Integrative Health notes that kava products have been linked to rare instances of liver damage, some of them severe. Several countries suspended sales in the early 2000s as a result.

Much of the discussion since has focused on what those products were made from. Many involved solvent extracts rather than water preparations, and stem peelings and non-noble cultivars have both been raised as contributing factors.

That points towards well-sourced noble root prepared with water being the lower-risk end of the spectrum. It doesn't make it a clean bill of health, and cases involving water-prepared kava have also been reported.

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Kava Root: The Bottom Line

Kava root is the only part of the plant worth using, and which underground part you get changes what you experience.

Lateral roots carry the most kavalactones, the rhizome carries fewer, and stems and leaves carry almost none while adding compounds with no history of safe use.

Kavalactone content swings between roughly 3% and 20% of dry weight, so weighing your powder is not the same as knowing your dose.

Buy noble root with a stated origin and plant part, prepare it with water, and treat any product that won't tell you what's in it as a product that has a reason.

Frequently Asked Questions

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. This article is general information, not medical advice. Kava has been linked to rare cases of liver injury. Talk to a healthcare professional before using kava, particularly if you have a liver condition, drink alcohol, are pregnant or breastfeeding, or take any medication.