The mint flavouring in menthol cigarettes makes it easier for young people to start smoking and harder for smokers to quit, US health officials said on Tuesday.
In a review of existing research, the US Food and Drug Administration said that, although there's little evidence that menthol cigarettes are more or less dangerous than non-menthol cigarettes, findings suggest that "menthol use is likely associated with increased smoking initiation by youth and young adults".
Studies also indicate that "menthol in cigarettes is likely associated with greater addiction [because] menthol smokers show greater signs of nicotine dependence and are less likely to successfully quit smoking", the review said.
Evidence suggests that "menthol's cooling and anaesthetic properties" can make cigarette smoke taste less harsh, so it's "likely that menthol cigarettes pose a public health risk above that seen with non-menthol cigarettes", the agency said.
The FDA said it was posting the review to gather "all comments, data, research and other information" in the next 60 days "to determine what, if any, regulatory action with respect to menthol in cigarettes is appropriate".
In 2009, Congress passed the Family Smoking Prevention and Tobacco Control Act, giving the FDA regulatory authority over the tobacco industry.
"Menthol cigarettes raise critical public health questions," FDA Commissioner Dr Margaret Hamburg said in an agency news release. "The FDA is committed to a science-based approach that addresses the public health issues raised by menthol cigarettes, and public input will help us make more informed decisions about how best to tackle this important issue moving forward."
The menthol in cigarettes has been a controversial ingredient for years.
Also on Tuesday, a just-published study suggested that menthol's interactions in the brain may play a role in its appeal to smokers.
If that's true, menthol could contribute to nicotine addiction, said review author Nadine Kabbani, a neuroscientist and assistant professor at George Mason University in Falls Church, Virginia. "If that's the case," she said, "then it's important for regulatory bodies to consider the implications of menthol on public health."
Earlier this month, Joseph Califano Jr, a former health, education and welfare secretary in the Jimmy Carter administration, and Louis Sullivan, a health and human services secretary in the George H.W. Bush administration, called in The New York Times for menthol to be banned as a cigarette flavouring. "Menthol flavourings not only lure children to start smoking, but they also make it harder for menthol smokers to quit," they wrote.
Menthol, a derivative from the peppermint plant, may be best known as an ingredient in medicines such as cough drops. But many smokers are familiar with its use in cigarettes. According to the American Legacy Foundation, which advocates against tobacco use and wants a ban on menthol cigarettes, its effects include "covering up the tobacco taste and reducing the throat irritation associated with smoking, particularly among first-time users".
The foundation said young and black smokers are especially drawn to menthol cigarettes.
"Studies have failed to provide unequivocal evidence that menthol plays a significant role in smoking initiation, addiction to nicotine or cessation," said Dr Brad Rodu, a professor of medicine and the endowed chairman of tobacco harm reduction research at the University of Louisville.
Still, it's clear that menthol cigarettes are popular. Is it just a matter of personal preference? Kabbani, who has studied menthol cigarettes herself, examined the potential role of another factor – menthol's impact in the brain – in her new review.
She wrote that new research suggests that menthol affects how cells in the brain go about the business of processing nicotine, an addictive ingredient in tobacco. Specifically, she said, the presence of menthol appears to affect the ability of nicotine to bind with "receptors" in cells.
"This is a very important scientific discovery because if menthol does alter the actions of nicotine on its target receptor in the brain, then it is very likely to contribute to nicotine addiction," she said. "Additional studies are now necessary to test this."
What's next? Future research in mice can offer insight into the effects of menthol in cigarettes on pleasure in the brain, Kabbani wrote in her review. And, she wrote, research into genetic variations could offer insight into why some people are more prone to addiction to menthol cigarettes.
Rodu, the University of Louisville tobacco researcher, said the evidence doesn't support banning menthol, especially in light of two recent studies that found that the risk of lung cancer is actually lower among those who smoke menthol cigarettes compared to smokers of other cigarettes.
The review appeared online on July 23 in the journal Frontiers in Pharmacology.
For more about smoking, try the US National Library of Medicine.