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Experts urge smokers to quit cigarettes entirely. They say one of the best tactics is to understand why you smoke. Getty Images
  • Researchers say that people who smoke five cigarettes a day are doing almost as much damage to their lungs as people who smoke 30 cigarettes a day.
  • They say it takes “light” smokers about 1 year to develop as much lung damage as “heavy” smoking does in 9 months.
  • They note that a lighted cigarette releases 7,000 chemicals, 69 of which are considered to be cancer-causing substances.

Smoking five or fewer cigarettes a day can cause almost as much damage to your lungs as smoking two packs a day.

That’s according to a recent study from Columbia University that examined the lung function of 25,000 people, including smokers, ex-smokers, and those who have never smoked.

The researchers reported that “light” smokers who smoke five or fewer cigarettes a day had a decline in lung function that was similar to people who smoke more than 30 cigarettes a day.

They concluded it would take a light smoker 1 year to lose the same amount of lung function a heavy smoker would lose in 9 months.

“Light smokers should be informed that any level of cigarette smoking is bad for health, and they should be strongly encouraged and strongly supported in their efforts to quit smoking,” Elizabeth Oelsner, MD, MPH, lead author of the study and a professor of medicine at Columbia University Vagelos College of Physicians and Surgeons in New York, told Healthline.

“There have been marked declines in rates of current smoking, and current smokers are smoking fewer cigarettes per day on average,” Oelsner said. “Nonetheless, the number of deaths from chronic obstructive pulmonary disease (COPD) has increased, and COPD is now the third-leading cause of death worldwide. I think the risks of ‘light’ or ‘social’ smoking are very much underestimated by most people.”

In the United States, cigarette smoking is the leading cause of preventable disease and death. About 480,000 people die every year due to smoking.

Experts estimate 34 million adults smoke, and more than 16 million live with a smoking-related disease.

Regardless of whether a person smokes five cigarettes a day or two packs a day, the negative impact on the body is significant.

When cigarettes burn, more than 7,000 chemicals are released. At least 69 of those chemicals are known to cause cancer.

These chemicals cause injury to the cells inside the lungs. When the injured cells become inflamed and swollen, the body attempts to repair the damage. During that process, normal, healthy lung tissue can be broken down as the body attempts to fix the damage caused by smoking.

The average smoker takes 10 puffs of a cigarette over a period of 5 minutes. A person who smokes 25 cigarettes every day will receive a hit of nicotine 250 times. Nicotine is just one of the toxic chemicals found in cigarettes.

“There’s a reason why nicotine is used in insecticides. It’s a poison,” Russell Buhr, MD, PhD, a pulmonary and critical care physician at the Ronald Reagan UCLA Medical Center in Los Angeles, told Healthline.

“It can cause damage to the cells inside the lungs, in particular the ones that help clear out mucus from the linings. That mucus not being cleared out properly can cause damage to the air tubes inside the lungs just from direct contact, and it also provides a nice home for bacteria and infections to move in,” he said.

“Those frequent infections can accelerate lung function decline in addition to the direct damage from the nicotine and the tobacco smoke exposure themselves,” Buhr added. “There’s multiple ways in which smoking causes damage to the lungs.”

Lung function — the amount of air a person can breathe in and out — naturally declines with age. But smoking accelerates this process.

“Your airway walls become weaker and collapse when you exhale, trapping air inside the lungs. When you take your next breath, you stack the new air on top of the trapped air. The simple act of breathing thus becomes difficult and uncomfortable,” Husham Sharifi, MD, a pulmonologist at Stanford Health Care in California, told Healthline.

“Losing lung function means you will have a tougher time getting oxygen to critical organs, like your heart and your brain,” Sharifi said. “This can affect your cognition and your heart health, even before you account for the damage that smoking does to the blood vessels of the brain and heart. You may eventually need supplemental oxygen from a tank to maintain an adequate amount of oxygen delivery to your body.”

Since 2002, there are more former smokers than current smokers in the United States. In 2015, 68 percent of smokers in the United States said they wanted to quit completely.

Brooks Kuhn, MD, MAS, a pulmonology and critical care specialist at University of California Davis Health, says individuals need to be motivated to successfully quit smoking.

“The best way for an individual to quit smoking is to start with a thoughtful reflection of why they smoke,” Kuhn told Healthline. “Without identifying the driving reason for continued tobacco — whether it be anxiety, habit, pleasure, for the social interaction — it is incredibly difficult to quit. Triggers for these drivers are inevitable, and a cessation plan without acknowledgment of what benefit the patient perceives from tobacco will be challenging.”

Experts emphasize that people who seek help from a medical professional are much more likely to be successful at quitting smoking. Options to help people quit include counseling, nicotine replacement, and behavioral therapy.

“Smoking is an addiction. Just like many addictions, it is hard to stop unless you get clinical help,” Osita Onugha, MD, MBA, director of the Thoracic Surgery Research and Surgical Innovation Lab at the John Wayne Cancer Institute in California, told Healthline.

“The more support and resources we can provide people who are smoking, the greater chance we can get them to quit smoking,” he said.

Buhr says that getting people to quit is complicated by significant lobbying by the tobacco industry.

“There’s a lot of public health policy that could potentially be very good being stymied by tobacco industry lobbying. This is a multibillion dollar industry, and it’s not going to go quietly,” Onugha said.

Although quitting can be difficult, he says any reduction in the amount someone smokes is better than no reduction at all.

“We can’t let perfect be the enemy of better,” Onugha said. “Smoking less when I’m trying to get patients to quit is always better than smoking more. But the only safe amount of smoking is zero. I think that’s pretty clear. We have 70 years of data on that at this point. There is no ambiguity there when you ask lung or heart doctors about this. The only safe amount of smoking is zero.”