New research undermines the view that chewing tobacco is not as hazardous as smoking. Smokeless tobacco actually exposes users to more of a dangerous carcinogen and and more nicotine than cigarettes do.

In the study, the median level of a biomarker for a compound known as “nicotine-derived nitrosamine ketone” (NNK) was as much as 73% higher among smokeless-tobacco users compared with smokers (3.76 vs. 2.18 pmol/mL urine). Similarly, the median level of cotinine, a biomarker for nicotine exposure, was 32% higher among smokeless tobacco users (2.83 vs. 2.15 pmol/mg creatinine).

Stephen D. Hecht, PhD, and his colleagues at the University of Minnesota in Minneapolis pooled baseline data from six previous intervention studies about tobacco dependence. Three studies involved 420 smokers and three involved 182 smokeless-tobacco users.

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In each instance, NNK-biomarker levels were higher among smokeless-tobacco users than smokers. “Our results raise serious questions about the strategy of using smokeless tobacco as a substitute for cigarette smoking,” the study concludes.

Smokers in the study consumed a mean of 25.8 cigarettes/day. Most (69%) smoked either light (6.5-14.5 mg tar), or (30%) ultralight (≤6.5 mg tar) cigarettes. The smokeless-tobacco users consumed a mean of 4.2 tins/week of Copenhagen, Kodiak, Skoal, or unspecified brands (each tin contains approximately 1 oz of tobacco).

The study describes NNK as “the most carcinogenic” substance in tobacco for laboratory animals. It has been primarily linked to lung tumors, as well as to tumors in the pancreas, nasal mucosa, and liver.

In their introduction, the researchers note that some clinicians encourage smokers to make the switch to chewing tobacco or snuff because they believe these products are less harmful than cigarettes. The investigators designed their study to explore that notion.

“NNK exposure in smokeless-tobacco users presents an unacceptable risk and should not be encouraged,” the study concludes. “Long-term use of nicotine-replacement therapy (NRT) may be a better option” (Cancer Epidemiol Biomarkers Prev. 2007;16:1567-1562).

An expert at the CDC agrees that chewing tobacco and snuff “are not safe products.” “The toxins and carcinogens in cigarettes and smokeless tobacco are absorbed in different ways, so the spectrum of diseases is different,” says Corinne Husten, MD, chief of the epidemiology branch of the CDC’s Office on Smoking and Health.

In addition to NNK, smokeless tobacco contains 27 other carcinogens, according to the CDC. It causes oral and pancreatic cancers, Dr. Husten says, and is strongly associated with leukoplakia and receding gums. It may harbor other dangers as well (Table 1).

“Cigarette smoking has been around for 100 years, and we’re still finding new associations between smoking and different diseases. I expect the same will prove true with smokeless tobacco products in the future,” she says. Dr. Husten concedes that NRTs have a success rate of only 20%-30%. But people who want to quit smoking have “more options than ever before,” she says, without resorting to chewing tobacco or snuff.

The FDA has approved seven medications to encourage smokers to quit their habit: nicotine in a patch, gum, lozenges, nasal spray, or inhaler; bupropion (Zyban); and varenicline tartrate (Chantix). Coaching, counseling and support groups are also available and effective, especially when combined with medication. “One of the best things clinicians can do is encourage their patients to call 800.QUITNOW,” Dr. Husten advises. “They will get coaching from a health-care professional and practical strategies for what to do in situations that trigger a craving.”

Many smokers fail to quit because they don’t take their medication properly, she adds. “They try to get by with the least amount possible instead of following the prescription. These medications are really analogous to antibiotics in that you have to take all of the doses prescribed even after you start to feel better. If the patient says NRT did not work, ask if he followed the instructions exactly.”

Clinicians should also try different forms of NRT, combinations of medications, or longer duration of therapy, Dr. Husten counsels. “Smoking should be treated as you would any chronic disease. Like diabetes, you may have to try different medications and strategies to get it under control.”

Urge patients to not get discouraged. “People learn with each attempt to quit,” Dr. Husten observes. “They use what they learn the next time they try, and that improves the chances they will be successful.” Not everyone who uses smokeless tobacco is avoiding cigarettes. Many users simply prefer chewing or sniffing tobacco to smoking it.

The CDC currently estimates 3% of American adults use smokeless tobacco. Almost all of them are men. Usage is higher among young white men and boys; in the South and Midwest, and among those employed in blue-collar, service, or laborer jobs or those who are unemployed. In addition, a significant number of preteens and adolescents chew tobacco (about 8% of high school students and 3% of middle-schoolers).

Tobacco companies are promoting these products aggressively. The five largest companies spent $251 million on advertising campaigns during 2005, according to the CDC.

Ms. Dembrow is a senior editor with The Clinical Advisor.