Chewing tobacco may be smokeless, but it could be far from harmless to the heart and blood vessels, a small study suggests.

Chewing tobacco is a known risk factor for oral cancers, but in contrast to the case with Smoking, the cardiovascular effects of the habit have been unclear. The new study, of 16 healthy, young tobacco users, suggests that smokeless tobacco has immediate effects on blood pressure, heart rate and adrenaline release that, over time, could spell trouble for the cardiovascular system.

Researchers found that a round of tobacco dipping not only bumped up the young men’s blood pressure, but also dampened the body’s normal stabilizing response to blood pressure spikes.

“We don’t know yet if it will have long-term consequences,” said lead researcher Dr. Robert Wolk of the Mayo Clinic in Rochester, Minnesota.

However, he told Reuters Health, it’s possible that over time, chewing tobacco could lead to chronic high blood pressure or other ill effects on the heart and blood vessels.

Finding out whether this is the case will be important, Wolk said, as the dipping habit is on the rise among young males, particularly athletes.

For their study, Wolk and his colleagues looked at various measures of cardiovascular and nervous system activity among 16 young men before and after the volunteers used chewing tobacco.

Normally, when a healthy person’s blood pressure shoots up, nervous system activity shifts in order to bring the pressure back down - slowing the heart rate and decreasing resistance in blood vessels throughout the body.

“The body wants to decrease your blood pressure,” Wolk said.

However, he and his colleagues noticed that after the study participants used chewing tobacco, their heart rates increased “strikingly,” despite an increase in their blood pressure, and their levels of the hormone adrenaline shot up roughly 50 percent. Resistance in the body’s peripheral blood vessels, which should have decreased in response the blood pressure elevation, held steady instead.

The findings are published in the Journal of the American College of Cardiology.

Taken together, Wolk said, the results suggest that chewing tobacco triggers a “marked increase” in activity of the sympathetic nervous system - the part of the nervous system that, among other things, constricts blood vessels and boosts blood pressure and heart rate in response to stress, danger or other stimuli.

Nicotine is the likely culprit, according to Wolk, since the researchers did not see the same effects when they had study participants use a nicotine- and tobacco-free “placebo” chew.

Besides the potential for long-term damage to the cardiovascular system, chewing tobacco may pose a more-immediate risk to people who already have Heart disease, Wolk noted.

Adrenaline, he explained, can promote blood clotting, so the surge in the hormone caused by smokeless tobacco could potentially contribute to a Heart attack in susceptible people - though, Wolk said, that’s speculation for now.

SOURCE: Journal of the American College of Cardiology, March 15, 2005.