Smokeless tobacco products are not necessarily a safe alternative to smoking

Nov 3 2005

According to the U.S. Centers for Disease Control and Prevention, nearly one-fourth of Americans are smokers. That's more than 60 million people who are at increased for lung cancer, the leading cause of cancer-related deaths nationwide.

Despite the risks, many people have trouble kicking this addictive habit. As a result, health officials and doctors are trying to find less harmful alternatives to cigarette smoking. But some products, like smokeless tobacco, may not be effective replacements, according to research presented today during the American Association for Cancer Research's 4th annual Frontiers in Cancer Prevention Research meeting in Baltimore.

"While new products are being developed and marketed as less harmful alternatives to cigarettes, they should be evaluated for efficacy in reducing smoking use, as well as actual reduced incidence of related diseases," said William G. Nelson, V, M.D., Ph.D., of Johns Hopkins University and Program Chair of the meeting. "With such a large population at risk for serious health consequences, we need to move quickly on strategies to thwart this dangerous habit."

Smokeless oral tobacco products including lozenges and moist snuff may be safer than cigarette smoking, but neither represents a good alternative for those wishing to quit smoking, according to studies conducted by scientists at the University of Minnesota.

Instead, the best aid appears to be medicinal nicotine products such as the patch.

"Collectively, these results indicate that most smokeless tobacco products are not necessarily a safe alternative to smoking and are inferior to medicinal nicotine products with respect to carcinogen exposure," said Stephen Hecht, Ph.D., of the University of Minnesota Cancer Center and lead author of the study. "Smokeless tobacco products should not be considered an acceptable substitute for cigarette smoking, especially when relatively harmless medicinal nicotine products are available."

In their study, the Minnesota researchers evaluated carcinogen levels in smokeless tobacco and medicinal nicotine products as well as carcinogen biomarker levels present in the users. The study compared the carcinogen levels of several types of oral tobacco products made in the U.S, which have carcinogen levels at least 100 times that of other consumer products designed for oral use. The lowest levels were found in hard snuff lozenges and only trace amounts were found in medicinal nicotine products. The most prevalent strong carcinogens in smokeless tobacco products are the tobacco-specific nitrosamines (cancer causing chemical agents), of which the strongest carcinogens are in N'-nitrosonornicotine (NNN) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK).

In a separate study, 54 users of popular U.S. smokeless tobacco brands used their usual brand for two weeks and were then randomized to use either Swedish snus (a type of snuff) or a nicotine patch for four weeks. Levels of the strongest carcinogens were measured in the urine at baseline, then two weeks and four weeks after switching to snus or patch. Carcinogen levels were significantly lower in those who previously used smokeless tobacco after the switch to snus or patch. Importantly, among subjects who used the nicotine patch, carcinogen levels were significantly lower than in those who used snus, suggesting that medicinal nicotine is a safer alternative than snus.

The new results conflict with some prior research that suggested that smokeless tobacco, including moist snuff, may be a less harmful alternative to cigarette smoking because many of the carcinogens in cigarette smoke are either reduced or not present in smokeless tobacco.

One of the most popular forms of smokeless tobacco (ST) in the U.S. and parts of Europe is moist snuff, which is used by placing the product in the mouth. Because there are fewer side effects and risks associated with its use than with standard cigarette smoking, use of snuff has been proposed as a safer alternative for smokers unable or unwilling to quit using tobacco.

The "Swedish experience" is used as evidence that ST is effective in smoking cessation and harm reduction because there is a reduced use of cigarettes and increased consumption of moist snuff, while the incidence of tobacco-related cancers has decreased. But the correlation appears to be largely related to other factors.

In a study from the University of Florida, researchers conclude that use of smokeless tobacco in Sweden was not associated with smoking cessation. In fact, it's possible that smokeless tobacco may actually encourage some teens to take up smoking.

What's more, recent cohort studies suggest that U.S. males are more likely to switch from smokeless tobacco to cigarettes than the reverse. Use of both smokeless tobacco and cigarettes is a more common pattern in the U.S. than switching from cigarettes to smokeless tobacco.

"Based on this evidence, we feel that the use of smokeless tobacco is rarely a successful strategy for smoking cessation in the U.S., and may actually be a risk factor for starting to smoke," said Scott Tomar, of the University of Florida, and lead author of the study.

"There is insufficient evidence that using smokeless tobacco is effective, feasible or acceptable as a smoking cessation strategy in most populations," he added.

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