The anti-cancer activity of xanthohumol was first discovered around 10 years ago by a team at Oregon State University in the US.
But although some brewers are now marketing products enriched in the compound, such as Germany's Xan, the US researchers say beer is unlikely to offer any anti-cancer benefits.
“Beer is the major dietary source of xanthohumol, but the average content of xanthohumol in beer may not be high enough to produce a significant inhibitory effect on benign prostate hyperplasia (BPH) in humans,” wrote lead author Emily Colgate.
Indeed, lead researcher Emily Ho said that a person would have to drink more than 17 beers to consume the same amount found effective in the study.
“Nevertheless, xanthohumol can be isolated from hops in large quantities and be examined further for its use as a dietary supplement for the prevention of BPH or prostate cancer in humans,” said Colgate.
The new research, published on-line ahead of print in the journal Cancer Letters (doi: 10.1016/j.canlet.2006.02. 015), investigated the effects of xanthohumol extracted from hops (2.5 to 20 micromole doses) on the BPH-1 and PC3 cell lines as models for BPH and prostate cancer.
The Oregon State researchers found that both xanthohumol and its oxidation product, xanthoaurenol, decreased the number of cancer cells in a dose dependent manner. The hop extracts also promoted apoptosis (programmed cell death).
They also investigated the effect of xanthohumol and xanthoaurenol on the signaling of nuclear factor-kappa B(NF-kB), a protein that is said to activate a variety of human malignancies, including prostate cancer.
In BPH-1 cells, the 20 micromolar dose of xanthohumol or xanthoaurenol resulted in a 42 per cent decrease in NF-kB activity.
“These studies suggest that inhibition of NF-kB and induction of apoptosis may be a critical mechanism by which xanthohumol acts as anti-proliferative agent in prostate hyperplasia,” said the researchers.
While the results to date are highly promising, the researchers caution that more research is needed before it is known if the highly controlled and pure laboratory conditions can be applied to humans.
Josephine Querido, science information officer at Cancer Research UK, echoed the notes of caution from the researchers, but said the results were interesting.
Querido told NutraIngredients.com:
"The results of this study are interesting, but they should not encourage people to drink more beer.
So far, the effects of xanthohumol have only been investigated in laboratory cells, so further studies are needed to see whether the chemical shows the same anti-cancer properties in humans," she said.
“Animal toxicity studies provide evidence that xanthohumol may not be harmful to humans but further safety and efficacy studies in vivo are needed before xanthohumol can be recommended as a human dietary supplement for BPH or prostate cancer,” concluded the Oregon State researchers.
A number of food supplements containing hops are already on the market, and scientists in Germany have developed a beer that contains 10 times the amount of xanthohumol as traditional brews. The drink, called ‘Xan', is being marketed as a healthy beer, but research is ongoing to determine if the liquid is effective against cancer.
The beer is only available in Germany, is said to be 80 per cent more expensive than the competition, and is being microbrewed in a collaboration between the Weihenstephan brewery, said to be the oldest brewery in the world, and the Technical University of Munich.
Oregon researcher Jan Stevens said he managed to taste a sample. “It tastes good. It has a bit of a fresh taste,” he said.
