Men who chew tobacco may be doing harm to their reproductive health, says a group of doctors in a new, international study.1
"The main drive of our study was to direct the public attention towards an important side effect of tobacco chewing," explained study leader Ashok Agarwal, PhD, at the Cleveland Clinic's Glickman Urological Institute, in an interview with Priority Healthcare. "For the first time, we describe the negative effects of tobacco chewing on male fertility. This correlation is of considerable importance, as tobacco chewing is very common among young males who are in the reproductive age group."
An Increasing Trend
Citing government statistics, Agawal and his colleagues wrote that smokeless tobacco consumption has tripled in the United States in recent years.
"A national survey conducted on 5,894 college and university students from different regions of the United States revealed that 8 percent to 15 percent of the students used smokeless tobacco," Agarwal and his colleagues wrote. "Moreover, a recent study has identified that 14.8 percent of male high school students in the United States were current users in 2001."
The habit is more common in lower-income men, among amateur and professional baseball players, and in parts of the world such as India, China and Southeast Asia, the researchers stated.
A 'Very Dangerous' Habit
"Smoking is not the only adverse effect of tobacco products," Agarwal warned. "Smokeless tobacco can also be very dangerous. Its impact extends beyond local effects to include manifestations in different systems of the human body as a result of infiltration by components in the product."
Yet while it's known that smokeless tobacco contains several cancer-causing substances, the association between chewing tobacco and male infertility has remained "controversial", Agarwal's group wrote. While some previous studies had suggested that chewing tobacco negatively impacts sperm concentration, movement and appearance,2,3 other studies had found no link.4,5
Comparing Tobacco Chewing with Sperm Health
In hopes of clearing up the confusion, Agarwal, a professor of Surgery and director of the Center for Advanced Research in Human Reproduction, Infertility, and Sexual Function, at the Glickman Urological Institute, and his team analyzed the medical records of a group of patients treated at an overseas infertility clinic. In all, information on nearly 640 men who had undergone infertility evaluations over a 5-year period was reviewed. Each patient chewed tobacco regularly, and the researchers grouped them according to the frequency of the habit. Semen analyses had been performed on all the patients, as well, during the study period. Thus, the researchers compared the frequency of tobacco chewing with each patient's semen analysis result to determine if there was any possible association.
A Correlation Found
The sperm in the samples taken from men who chewed tobacco less often were healthier compared to those who chewed more often, Agarwal's team found. "Semen samples from men with a mild tobacco chewing habit had normal sperm count, motility [movement], morphology [appearance], and viability according to the [World Health Organization] standards," the investigators wrote. "On the other hand, samples from men in the moderate and severe groups were characterized by teratozoospermia [abnormally shaped sperm]."
Men who chewed tobacco more often also tended to have less sperm in their semen sample, according to the study. The differences were striking; in men with a mild habit, only about 1% of the semen samples had no sperm. In those with a moderate tobacco-chewing habit, about 3% of the samples were without sperm. However, in those who chewed tobacco frequently, approximately 14% of the semen samples were absent sperm. Collectively, sperm concentration, motility, and morphology were all affected in men who chewed tobacco more often compared to those who used the habit more infrequently.
Even in men who had normal sperm count, motility and viability, those who chewed more often had samples with abnormally appearing sperm, Agarwal and his co-researchers wrote.
"Our study reports for the first time a significant decrease in semen quality (sperm count, motility, morphology, and viability) associated with a chewing tobacco habit in men undergoing infertility evaluation," wrote the study team. While the study's findings contradict other studies, the number of patients evaluated in this research was much larger, which may be the reason why differences were noted, Agarwal and his colleagues stated.
Even Mild Tobacco Chewing May be Harmful
Despite the fact that infrequent tobacco chewing was less detrimental to sperm in this study, Agarwal stressed that this doesn't necessarily mean that taking up the habit less often isn't harmful. "In our study, we evaluated the sperm integrity and function using classical criteria for evaluation, which only tell us of any gross anomalies," he told Priority Healthcare. "Other hidden problems might be occurring in the sperm as a result of mild tobacco chewing, leading eventually to infertility."
Additionally, this study did not ascertain whether chewing tobacco directly affects healthy sperm, just that an association between the two exist. Despite that, the researchers have several possible theories behind why tobacco-chewing may be harmful to sperm. Since the body absorbs nicotine during chewing, this substance could negatively affect sperm, they speculated, pointing to previous animals studies that found exposure to nicotine caused significant changes in testes.
"Men addicted to tobacco chewing also have the least access to infertility medical services," wrote the study team. "Therefore, prevention and cessation programs should be directed towards specific high-risk groups."
1. Said TM, Ranga G, Agarwal A. Relationship between semen quality and tobacco chewing in men undergoing infertility evaluation. Fertil Steril 2005 Sep;84(3):649-53.
2. Kunzle R, Mueller MD, Hanggi W, Birkhauser MH, Drescher H, Bersinger NA. Semen quality of male smokers and nonsmokers in infertile couples. Fertil Steril 2003 Feb;79(2):287-91.
3. Saleh RA, Agarwal A, Sharma RK, Nelson DR, Thomas AJ Jr. Effect of cigarette smoking on levels of seminal oxidative stress in infertile men: a prospective study. Fertil Steril 2002 Sep;78(3):491-9.
4. Lewin A, Gonen O, Orvieto R, Schenker JG. Effect of smoking on concentration, motility, and zona-free hamster test on human sperm. Arch Androl 1991 Jul-Aug;27(1):51-4.
5. Dikshit RK, Buch JG, Mansuri SM. Effect of tobacco consumption on semen quality of a population of hypofertile males. Fertil Steril 1987 Aug;48(2):334-6.
John Martin is a long-time health journalist and an editor for Priority Healthcare. His credits include overseeing health news coverage for the website of Fox Television's The Health Network, and articles for the New York Post and other consumer and trade publications.