One cigarette a day. Sometimes only at the end of a meal, sometimes at a social event, sometimes “only when it feels right.” Many people are convinced this does not really count as smoking, certainly not the kind that should raise concern. After all, there is no cough, no shortness of breath, no sense that something is wrong. But medicine, it turns out, does not measure smoking by how it feels, but by what happens inside the body, often from the very first inhalation.
Is there truly a “tolerable” number of cigarettes, or is this one of the most widespread health illusions of the modern era? We turned to experts to dismantle the myth of “light smoking”: what actually happens in the body even when smoking very little, which damages accumulate below the radar, and whether there is a real difference between heavy smoking and a single cigarette that seems insignificant but repeats itself over years.
To understand whether this is a negligible habit or a genuine medical risk, it is necessary to return to the basics: what smoking actually does to the body. That broader picture is outlined by Dr. Lior Seluk, a pulmonary specialist and head of the Airway Diseases Center at Sheba Medical Center, one of Israel’s largest hospitals.
“During smoking, the smoke settles in the lungs, irritates them and creates inflammation that later leads to more and more diseases, beyond the cough or phlegm that some people experience immediately,” he says. “The smoke contains components that are highly toxic. They are absorbed into the body and can cause various diseases, including lung cancer, COPD (chronic obstructive pulmonary disease) and pulmonary fibrosis.”
Smoking also worsens other lung conditions. “Even asthma, a very common disease, can become more severe and trigger attacks,” Dr. Seluk says. “The tar in cigarettes that we inhale also settles in the lungs and interferes with the mechanisms that clear bacteria and infections. Beyond that, nicotine itself is addictive and causes people to become dependent and spend money on cigarettes throughout their lives.”
For many people, however, the discussion about the harms of smoking remains abstract as long as it is associated mainly with heavy smokers. The real question, the one that comes up in almost every conversation about smoking, concerns small doses: Does even one cigarette a day count as a problem, and what about those who define themselves as “social smokers” only? Here, Sluk says, science paints a far less reassuring picture than many would like to believe.
“Smoking one or two cigarettes a day is clearly harmful,” he stresses. “There have been fairly large studies in recent years that examined exactly this issue. The more you smoke, the more cumulative damage there is, but even smoking a few cigarettes a month, for someone who calls themselves a social smoker, causes harm.”
He adds that studies found something surprising: “Even smoking five or six cigarettes a month significantly increases the risk of developing diseases linked to cigarette damage. And as smoking increases, the damage becomes much more substantial, with a much higher risk of developing smoking-related illnesses.”
Beyond the lungs, smoking harms the cardiovascular system from the earliest stages, damage that begins at the level of the blood vessels themselves and can end in life-threatening events.
“Smoking increases the risk of stroke and heart attacks,” says Dr. Iren Kruchin, a senior cardiologist with Clalit Health Services in the Dan–Petach Tikva district, a large central region of Israel. “It causes dysfunction of the endothelium, the inner lining of blood vessels, leads to artery constriction and accelerates the development of atherosclerosis.”
She explains that atherosclerosis is caused by the buildup of fatty plaques that adhere to the artery wall and can block it, either gradually or suddenly. “Smoking worsens this process by damaging the endothelium. When nicotine is inhaled, the artery constricts and its ability to relax is impaired. Over time, it becomes narrower.”
In addition, Dr. Kruchin says, “Smoking also causes platelet aggregation and the formation of blood clots. A clot can completely block an artery, especially if there is already an atherosclerotic plaque inside it. In such a situation, a heart attack or stroke can occur.”
What about the common claim that one or two cigarettes a day are not really harmful? Dr. Kruchin rejects it outright. “One or two cigarettes a day, which everyone thinks is nothing, can cause damage,” she says. “According to new studies, light smoking can lead to harm. Some processes happen immediately, even without prolonged exposure, such as blood vessel constriction and increased clotting and platelet adhesion. This happens at the moment of inhalation. You do not need to smoke many cigarettes for this to occur. One inhalation is enough.”
Social smoking, once in a while, is not exempt from effects either. “Of course, the cumulative effect is lower when someone smokes once a week instead of 10 to 20 cigarettes every day,” she says. “The cumulative effect rises especially after smoking five or more cigarettes a day and also depends on the number of years a person has smoked. Not everything happens from a single cigarette, but even one cigarette causes damage.”
In the end, the question of whether it is one cigarette a day, two a week or “only at events” turns out to be less relevant than many would like to think. From a medical perspective, the exposure itself, even when it seems marginal, activates biological mechanisms that do not distinguish between light and heavy smoking.
“The conclusion is not to smoke at all,” Seluk says. “Some people, instead of quitting, go from a pack a day, 20 cigarettes, to just a few cigarettes a day. But that also causes harm. It is better to stop smoking completely, and better yet, not to start at all. That is my message to young people who start smoking because it looks cool and their friends smoke. Later they become addicted, and there is real damage.”
Dr. Kruchin echoes that message. “It is better not to smoke at all, not one cigarette and not two,” she says. “Smoking causes not only lung and airway damage and skin problems, but also heart attacks, strokes and very severe damage to the blood vessels in the legs, which can lead to serious disability.”