Kava and lung cancer: what preclinical research shows

2024-01-25 · 5 min read

By the kava.fyi editorial team · Last updated: 25 January 2024

Lung cancer remains one of oncology's toughest challenges. According to data cited in a review article published in 2023 in the International Journal of Molecular Sciences, around 2.2 million new cases of lung cancer and 1.8 million deaths from it were recorded worldwide in 2020, accounting for about 11.4 percent of all diagnosed cancers and as much as 18.0 percent of all cancer deaths. Late detection and still unsatisfactory treatment outcomes mean researchers are intensively looking for ways to prevent the disease before it develops, not only to treat it.

Where the idea that kava might matter here came from

The lead that started this whole line of research is epidemiological. In 2000, a researcher named Steiner was the first to propose the hypothesis that kava, a drink made from the root of Piper methysticum traditionally consumed on the islands of the South Pacific, might reduce the risk of cancer in humans. He observed an inverse relationship between the level of kava consumption and cancer incidence in several countries in the region. Particularly intriguing was the fact that in countries with high kava consumption, cancer rates were lower in men than in women, the opposite of the global pattern, even though it is men who traditionally drink kava most often. This is still only an epidemiological observation, not proof of cause and effect, but it was enough to set off decades of laboratory research.

What animal studies show

Over the past two decades, research teams, mainly affiliated with the University of Florida, have tested the potential of kava and individual kavalactones in various animal models of carcinogenesis, including cancers of the lung, bladder, prostate and colon. One of the best-documented results is the effect of dihydromethysticin, one of the kavalactones: this compound effectively inhibited the formation of lung tumours in A/J strain mice exposed to NNK, a potent tobacco-derived carcinogen, leading in some studies to an almost complete blocking of tumour development, even though protection against DNA damage in these experiments ranged from 75 to 88 percent. Another kavalactone, kavain, proved effective at preventing bladder cancer induced by a different carcinogen in mice. This is an important distinction: different kava constituents may act on different types of cancer and through different mechanisms, which makes simple generalisations difficult.

The review's authors stress something that matters for understanding the whole phenomenon: no single chemical compound isolated from kava has fully reproduced the effectiveness of the whole, natural mixture of kavalactones observed in the epidemiological data. This is called a polypharmacological effect: the various kavalactones, despite their close structural similarity, have different pharmacokinetic properties and evidently act in a complementary rather than interchangeable way. For this reason, the authors suggest that it is the traditional, complex kava mixture, prepared for generations in a culturally standardised way, rather than a single isolated substance, that may be a better candidate for further translational research, provided the product is subject to rigorous quality control.

It is worth stressing: these are animal models in which the cancer is deliberately induced by administering a potent carcinogen, not models reflecting the natural development of lung cancer in humans. Applying such results directly to people calls for great caution.

A possible mechanism: lung inflammation

Preliminary mechanistic studies suggest that kava inhibits activation of the nuclear factor NF-kB, a protein that plays a key role in inflammatory responses. Because chronic lung inflammation is a well-documented risk factor for lung cancer, the review's authors propose that kava may reduce carcinogenesis risk at least partly by suppressing the inflammation caused by tobacco smoke. This, however, as the authors themselves stress, is a hypothesis that needs further study in more advanced animal models that better reflect the chronic, inflammatory nature of lung cancer risk in humans.

One small study in smokers

The only piece of this puzzle that concerns humans directly is a small pilot study in which kava showed potential for reducing tobacco use and dependence among smokers, accompanied by a drop in participants' blood cortisol levels. The review's authors suggest that this effect may stem from kava's relaxing properties, and that reducing stress could in theory itself lower lung cancer risk if chronic psychological stress really is a significant risk factor for it. This, however, is a single, small pilot study, not proof that kava is effective for quitting smoking or for cancer prevention.

What these studies do not say

This is the most important caveat in the whole subject: the data described above come almost exclusively from preclinical research, meaning studies carried out on cells and animals, not from clinical trials in people who have lung cancer or are at risk of it. There is currently no evidence that drinking kava prevents lung cancer in humans, or that it can be used to treat it. The review's own authors state plainly that further research involving people is needed before any practical application of these findings can be discussed. Kava is neither a medicine nor a preventive agent in oncology, and treating it as such would be an overinterpretation of the scientific data.

It is also worth remembering that kava is metabolised in the liver, so it should not be combined with alcohol or with medications processed by that organ. People with cancer or undergoing oncological treatment should discuss any decision to take plant supplements with their treating doctor, because interactions with medications used in oncology are not well studied. It is also worth adding that in Poland kava is classified as a designer substance banned for sale as a food, which in itself rules out buying it legally on the domestic market, regardless of whatever scientific potential is attributed to it.

If you are interested in exactly how the individual kavalactones work at a biochemical level, read our article kavalactones: how kava works, and on the classification of kava cultivars by the content of individual compounds, see kava cultivars. We write more about kava's safety for the liver in the article kava and the liver.