The study was the scientific equivalent of a cold shower for anise-fond Romeos. But American researchers now say they've tried to repeat the work and can't come up with good & plenty evidence that licorice suppresses testosterone, the sex hormone.
The notion that eating licorice might muzzle testosterone isn't absurd. Its active ingredient is glycyrrhizic acid, a compound that interrupts the conversion of a testosterone precursor into the male hormone. So when Italian endocrinologists showed that seven men who ate licorice for four days saw the testosterone in their blood plunge 35 percent, it made some sense.That finding prompted a wave of interest into the power of licorice over sex hormones, and fruitful keywords for Internet searches.
Now, the lead author of the new study, Robert Josephs, a psychologist at the University of Texas in Austin, says the black licorice effect is a red herring. The finding will appear in the Nov. 10 issue of The Lancet.
"It's safe to go back in the water," he says.
Josephs and his colleagues at Texas and the University of Michigan tried to replicate the Italian work by feeding 20 college men 5.6 grams (less than a quarter ounce) of licorice daily for four days. They then measured testosterone levels in the men's saliva, but found less than a 10 percent drop from baseline, not enough to wilt their sex drive.
Josephs' group repeated their experiment, this time giving 11 men and 10 women a different brand of licorice. But again, the drop in testosterone was marginal for both sexes. Although the Italian group measured blood testosterone, the American researchers say saliva is an equally sensitive indicator of the hormone's presence.
Taken together, they say the two runs produced effects on testosterone roughly 10 times weaker than that generated by the Italian researchers. "What's amazing is that no matter what we manipulated, we got the same very, very modest effect," Josephs says.
Joseph's group attributes the difference two factors: the Europeans goofed in their statistical analysis, and they appear to have included in their study someone with abnormally high testosterone, skewing the average for the rest of the men. "If you had one guy who just had a freakishly high starting testosterone level, that would comfortably explain their result," he says.
The researchers did see a marked increase in the men's saliva levels of cortisol, an important stress hormone, suggesting that people with high blood pressure might want to avoid eating the candy.
Dr. Mario Palermo, one of the researchers on the Italian study, defends his findings. "I don't think it's a mistake. The data are real," says Palermo, an endocrinologist at the University of Sassini. Palermo says he and his colleagues performed their study "at least two times," and have unpublished evidence showing "absolutely the same result."
In this debate, however, Josephs says size is crucial. "We're not questioning the mechanism. The mechanism is sound. The point of contention here is effect size. In medicine, effect size is literally the difference between life and death." Or, in this case, love and, well, not.
The trade publication Professional Candy Buyer reports that between 1995 and 1998, total annual licorice sales in the United States grew from $153 million to $175 million.
What To Do
Licorice has been used for millennia to treat everything from coughs to ulcers. Ancient Greeks used it to treat asthma and cancer sores, while Roman warriors apparently drank it like gladiatorial Gatorade. A supply of licorice was even discovered in King Tut's tomb.
The black form of the candy is made from the liquid used to boil roots from the licorice plant grown in Turkey, Russia and China. The red version is faux licorice.
You can get more information about the health effects of licorice (but beware of exaggerated claims) on this Magic of Licorice site.
Botanical.Com also has information about the candy.