'The use of smokeless tobacco is rarely a successful strategy for smoking cessation in the US, and may actually be a risk factor for starting to smoke.'

Nicotine products, such as the patch, seem to work better, the research suggests.

"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," reports Stephen Hecht, PhD, 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," he adds.

Strong Carcinogens in Smokeless Tobacco

Researchers at the University of Minnesota evaluated carcinogen levels in smokeless tobacco and medicinal nicotine products, as well as carcinogen biomarker levels present in users.

They compared several types of oral tobacco products that have carcinogen levels at least 100 times higher than other consumer products designed for oral use.

The most prevalent strong carcinogens in smokeless tobacco products are the tobacco-specific nitrosamines (cancer causing chemical agents). The strongest carcinogens are found in N'-nitrosonornicotine (NNN) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK).

The lowest levels were found in hard snuff lozenges, while only trace amounts were found in medicinal nicotine products.

Medicinal Nicotine Is Safer

In a separate study, 54 users of popular US 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 a patch.

Carcinogen levels were significantly lower after the switch from smokeless tobacco products 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.

ST May Be Smoking Risk Factor

One of the most popular forms of smokeless tobacco in the US 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, 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 US 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 US 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 US, and may actually be a risk factor for starting to smoke," says lead author Scott Tomar of the University of Florida.

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

Almost 25% of Americans Smoke

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

Many people have trouble kicking this addictive habit, despite the known risks. As a result, health officials and doctors are trying to find less harmful alternatives to cigarette smoking. But smokeless tobacco may not be an effective replacement.

"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," says William G. Nelson, V, MD, PhD, of Johns Hopkins University.

"With such a large population at risk for serious health consequences, we need to move quickly on strategies to thwart this dangerous habit," he urges.