Life Extension Magazine®

Man coughing after smoking a cigarette putting himself at risk

Smoking: The Leading Cause of Avoidable Death

Recently, The New England Journal of Medicine reported that smoking raises the risk of nearly every known disease, from kidney and liver disease to diabetes and Crohn’s disease. For those who do not smoke, avoiding second- and thirdhand smoke is imperative.

Scientifically reviewed by: Dr. Vanessa Pavey, ND, in August 2023. Written by: Susan Cartwright.


In a recent study published in The New England Journal of Medicine, researchers found that smoking was responsible for diseases beyond those traditionally linked to smoking such as lung cancer and heart disease.1

Tobacco smoke contains more than 7,000 chemicals, including cancer-causing chemicals, toxic metals, and poisonous gases.2

New studies show that smoking increases risks of infection, intestinal ischemia, and kidney and liver disease.1 These disorders were not previously connected with tobacco use.

With more than 42 million Americans smoking, causing approximately half a million deaths a year, smokers will clog our medical system and drain it of resources as they face a spectrum of diseases.3

It is important that you take steps to avoid inhaling secondhand smoke and to clean up lingering toxins that are referred to as thirdhand smoke. Thirdhand smoke is defined as “residual tobacco smoke contamination that remains after the cigarette is extinguished.”

Chemicals in Tobacco Smoke 2

Tobacco smoke contains a deadly mix of more than 7,000 chemicals. Hundreds are toxic. About 70 can cause cancer. Here are some of the chemicals.

Cancer-causing chemicals:

  • Formaldehyde. Used to embalm dead bodies.
  • Benzene. Found in gasoline.
  • Polonium-210. Radioactive and very toxic.
  • Vinyl chloride. Used to make pipes.

Toxic metals:

  • Chromium. Used to make steel.
  • Arsenic. Used in pesticides.
  • Lead. Once used in paint.
  • Cadmium. Used in making batteries.

Poisonous gases:

  • Carbon monoxide. Found in car exhaust.
  • Hydrogen cyanide. Used in chemical weapons.
  • Ammonia. Used in household cleaners.
  • Butane. Used in lighter fluid.
  • Toluene. Found in paint thinners.

Leading Cause of Death

Cigarette smoking is the leading avoidable cause of death worldwide. All forms of tobacco use raise a person’s risk of virtually every chronic disease that plagues humanity. For example…

  • Smokers are 5 times more likely to die from pneumonia.6
  • Smokers have a 48% increased colon cancer risk.7
  • Smokers have a 1.7-fold increased risk of Crohn’s disease.8
  • Smokers have a 129% increased risk in developing nonalcoholic fatty liver disease.9
  • Smokers have a 2-fold increase in the risk of dying from amyotrophic lateral sclerosis, or Lou Gehrig’s disease.10

The worst part is that these dangers exist even if you don’t smoke. Secondhand smoke, also known as passive smoking, is surprisingly destructive.9,11-27 Researchers are even discussing thirdhand smoke as an emerging and important concept in both the environmental and public health fields.28-30 Thirdhand smoke is defined by experts as “ residual tobacco smoke contamination that remains after the cigarette is extinguished.”31

Tobacco smoke contains more than 7,000 chemicals, including cancer-causing chemicals, toxic metals, and poisonous gases (see sidebar).2 With so many deadly molecules in just one puff, it is no wonder that tobacco use raises levels of the two major sources of aging in the body: oxidant stress and inflammation.12,32-44

To make matters worse, researchers have studied the epigenetic influence of inhaled toxins from tobacco smoke. Epigenetics is the field that studies the biological mechanisms that turn genes on and off. It is believed that lung cancer, chronic obstructive pulmonary disease (COPD), asthma, and cardiovascular disease are linked with epigenetic changes due to tobacco smoke.45-49 It is believed that one DNA mutation is introduced into the genome for every 15 cigarettes smoked.50

The good news is that stopping smoking benefits all smokers, regardless of their age or how long they have smoked.34,51-57 It also benefits those around them who are exposed to the secondhand smoke and thirdhand residual tobacco toxins that remain after the cigarette is extinguished.

What You Need to Know
The Age-Accelerating Dangers of Smoking

The Age-Accelerating Dangers of Smoking

  • More than 50 years after the Surgeon General’s first report found smoking harmful for health, researchers are still discovering numerous ways in which tobacco harms the human body.
  • All forms of tobacco, smoked or otherwise, raise the risk of almost every disease or chronic condition known.
  • Hypertensives that smoke have an increased risk (19% to 33% depending on pack-years) of dying from cardiovascular disease.66
  • Smoking raises the risk of serious stomach conditions by 132% over that of nonsmokers.88
  • Diabetes and obesity are exacerbated and potentially even caused by smoking.
  • It’s never too late. Quitting now benefits all smokers and those exposed to them.51,57

Lung Conditions Caused by Smoking

While smoking clearly raises the risk of lung cancer, both active and passive smoking also produce numerous other lung disorders that can shorten life span.

Smoking radically raises the risk of developing pneumonia, a condition that remains a leading killer of older adults.58,59 In one study, smokers were 5 times more likely to die from pneumonia than nonsmokers, and at a substantially younger age.6

Smoking’s powerful pro-inflammatory effects can be seen in a study of patients with chronic obstructive pulmonary disease who continued to smoke.60 Two measures of inflammation, high-sensitivity C-reactive protein (hs-CRP) and fibrinogen, rose sharply after a single cigarette, with the effects lasting up to 35 minutes. Such constant exposure to an acute inflammatory stimulus wreaks havoc on delicate lung tissue.60

Unfortunately, many smokers who develop chronic obstructive pulmonary disease believe that the damage is done, and that there is little point in trying to quit. However, this is not the case. According to a study published in 2014, nonsmokers with the disease had vastly better lung function than did current smokers.61 The authors concluded that “tobacco cessation is warranted in smokers with chronic obstructive pulmonary disease.”61

Smoking Damages Endothelial Cells

The impact of smoking on cardiovascular disease remained controversial until the early 1960s, when the giant Framingham heart disease study showed smoking’s heart-related dangers.62 By 1964, the results of that study were so alarming that the Surgeon General issued the first of the now-familiar warnings about smoking.4,5 Today smoking is known as an independent and entirely preventable risk factor for atherosclerosis and cardiovascular disease.63

No doubt these cardiovascular impacts are due to a number of harmful toxins found in cigarette smoke. In addition to nicotine and carbon monoxide, cigarette smoke contains countless cardiac toxins, including the toxic metal cadmium, which some researchers believe contributes directly to the increased cardiovascular risk experienced by smokers.64

Smoking is especially damaging to the delicate endothelial cells lining arterial walls.65 These cells are critical in maintaining the health of blood vessels and controlling blood flow and pressure. They are also extremely sensitive to oxidant stress. Multiple components of cigarette smoke conspire to harm endothelial cells, and damaged endothelial cells lay the groundwork for formation of cholesterol-laden, inflammatory plaque.65

Smoke-induced inflammation in and around plaque triggers swelling that can block arteries and increase the stickiness of platelets. This leads to clot formation that can abruptly stop blood flow, producing a heart attack or stroke.65

Smoking also induces “tissue remodeling,” a process that encourages overgrowth of smooth-muscle cells that form artery walls, resulting in thickening and stiffening of the arteries.65

Smoking has even greater negative effects on the heart and blood vessels of people with high blood pressure.66 One recent study showed that hypertensive people who smoked less than 20 pack-years (one pack-year is defined as 20 cigarettes smoked every day for one year) had a 19% increase in cardiovascular death compared with those who never smoked, and those who smoked more than 20 pack-years had a 33% increase in death risk from cardiovascular disease.66

Cigarette smoking has a profoundly harmful effect on blood cholesterol levels as well, causing a reduction in beneficial HDL (“good”) cholesterol levels. It does this by damaging enzymes that normally assure proper fat loading into the HDL cholesterol complex.63

Unfortunately, smokers using conventional cholesterol-lowering treatments such as a statin remain at a high cardiovascular risk. In fact, one study showed that smokers taking statin drugs had an 86% increase in the risk of having a “major cardiovascular event” such as a heart attack, stroke, or death compared with nonsmokers on statins.67

The good news is, it’s never too late to receive the benefits of quitting smoking, especially when it comes to cardiovascular disease. According to a study published in the European Heart Journal, those who stopped smoking after having a heart attack reduced their risk of dying by 36% over just two years.57

What You Need to Know
What Is a Pack-Year?

What Is a Pack-Year?

A pack-year is how scientists measure how much a person has smoked over a long period of time. Pack-years are calculated by multiplying the number of packs of cigarettes smoked per day by the total number of years the person has smoked. For amounts less than a whole pack, that number is first divided by 20 (the number of cigarettes in a pack) and then multiplied by the number of years smoked.114 For example, 10 pack-years means a person has smoked a pack of cigarettes every day for 10 years, two packs of cigarettes per day for five years, or 10 cigarettes a day for 20 years.

Smoking Doubles Diabetes Risk

Smoking creates a double risk when it comes to diabetes. Not only does it increase a person’s risk of developing diabetes, it dramatically exacerbates the age-accelerating effects of having diabetes.19,68-73 There’s a good reason for this. High blood sugar damages blood vessels and components of tobacco smoke further aggravate that damage, raising the risk of diabetic complications such as kidney and eye disease.68 In addition, smoking is known to be associated with insulin resistance, inflammation, and disturbances of blood lipids, all of which are already increased by having diabetes.68

Smoking has a negative effect on blood sugar control and insulin requirements.69 Studies show that a marker of long-term glucose level (hemoglobin A1c) was significantly higher in type I diabetics that smoked than in nonsmokers, and smokers required higher insulin doses to control their blood sugar.69 The study also showed that diabetics who smoked had lower levels of protective HDL cholesterol (which further confirms the cholesterol effect discussed earlier), and they also had a significantly increased amount of protein in their urine, a marker of early kidney damage.69

The grave cardiovascular effects of smoking in diabetics are highlighted by a 2015 study showing that smoking sharply raises the risk of having dangerously thickened carotid arteries.19 Importantly, these risks occurred in both active and passive smokers. Having thickened carotid arteries is a serious risk because the carotids are the brain’s main source of blood. If they become blocked, the result is a catastrophic and often fatal stroke.

Unfortunately, secondhand (passive) smoke can be just as dangerous as smoking itself for diabetics. Compared to diabetics with no exposure to secondhand smoke, women diabetics exposed to secondhand smoke experienced a 3.5-fold increased risk of cardiovascular disease and a 2.2-fold increased risk of having plaque in their carotid arteries.19

Male active and passive smokers had thicker carotid arteries as well, and male active smokers had a 2.9-fold increase in the risk of having carotid plaque.19

Smoking also complicates other diabetes-related health risks. For example, type II diabetics who are heavy smokers (but who don’t drink) are at a 64% increased risk of having a large waist circumference, a 78% increased risk for having elevated blood triglycerides, and a more than 200% increased risk for having low protective HDL-cholesterol levels.73

Tobacco Use and Body Weight
Mitochondria and Aging

Many smokers, especially younger ones, feel that smoking helps them either lose weight or keep from gaining it. A recent study proved that notion completely wrong, and in fact demonstrated that people who have smoked for more than 20 years were 54% more likely to be overweight than nonsmokers.115 Use of oral tobacco (like snuff or chewing tobacco) also increases the risk of obesity.116


Smoking and Obesity

Smokers already have an elevated risk of developing type II diabetes, but that risk is even greater in smokers who are overweight or obese.71 In one study, men of normal weight who smoked had a nearly 3.5-fold increase in the risk of developing diabetes compared to normal-weight nonsmokers, while obese smokers had a nearly 4-fold increased risk of developing diabetes compared with obese nonsmokers. While a 4-fold increase is bad enough, remember that this increased risk is in addition to the increased risks of diabetes presented by obesity itself. Increasing that risk by a factor of four therefore has an outsized impact on diabetes risk.71

Worldwide, the combination of smoking and obesity produces excess death and disability.74 Smoking has been associated with the presence of abdominal obesity in patients with type II diabetes. Thus, smoking exacerbates the already high health risks posed by obesity and diabetes (often called “diabesity”).75 This directly contradicts the myth that smoking contributes to weight loss.

Tobacco Causes Intestinal Problems

Smoking is a major risk factor for a host of gastrointestinal disorders, including peptic ulcers, inflammatory bowel diseases such as Crohn’s disease and ulcerative colitis, and cancers of the gastrointestinal tract.7,8,76-88

A study published in International Journal of Molecular Medicine showed that there are numerous factors involved in the connection between smoking and gastrointestinal disorders. First, cigarette smoke wreaks havoc on the vital mucosal cells that line the entire gastrointestinal tract. In a healthy body, these cells normally replace themselves every few days. Not only does smoking inhibit this critical cell renewal, it can outright kill them.83

In addition, this study found that smoking reduces blood flow to the intestine, potentially impairing nutrient uptake and waste disposal, and also damages the intestinal immune system, which is a vital factor in preventing both infections and cancers. But by far, the most fundamental cancer-inducing and cancer-promoting impacts of smoking seem to be damage to DNA, stimulation of new blood vessel growth to tumors, and loss of normal immune surveillance for malignant cells.83

These effects can be seen in the clear link between smoking and cancer risk. The longer a person has smoked, and the more that person smoked, the higher the risk. For instance:

  • People who have smoked at any point in their lives have a 19% increased risk of colorectal cancer, especially rectal cancer.7
  • Those who have smoked for more than 20 years have a 26% increased risk of these cancers.7
  • People who smoke about a pack a day have a 30% increased risk.7
  • And those who have smoked more than a pack daily or smoked for more than 30 years have a 48% increased rectal cancer risk.7

In addition to their increased cancer risk, current cigarette smokers have a 132% increased risk of developing a painful and potentially serious stomach condition called peptic ulcer disease.88

Nicotine itself increases the likelihood of another painful condition, gastrointestinal reflux disease (GERD), because it relaxes the sphincter muscle at the lower end of the esophagus. This allows damaging stomach contents to wash into the esophagus where they cause pain and increase cancer risk.78 Even infants exposed to secondhand smoke are significantly more likely to develop gastrointestinal reflux disease.79

In addition to increasing the risk of developing gastrointestinal reflux disease, animal studies show that cigarette smoke can accelerate the damage done by gastrointestinal reflux disease, which is especially concerning since it increases the risk of a precancerous condition called Barrett’s esophagus.77 In fact, human studies reveal that smokers with gastrointestinal reflux disease have a 44% increased risk of Barrett’s esophagus compared with nonsmokers with gastrointestinal reflux disease.80,82

With its powerful pro-inflammatory effects, it is hardly surprising that smoking increases the risk of inflammatory bowel disease.8 Specifically, studies show that current smokers have a 1.7-fold increased risk of Crohn’s disease, while former smokers have a 3-fold elevated risk of ulcerative colitis.8

Smoking increases the likelihood of complications from diverticulitis, including intestinal perforations and recurrent episodes of diverticulitis even after surgical treatment.86

It also increases the risk of developing colonic polyps, which are small growths in the lining of the colon that are often an early stage in the development of colorectal cancers. Current smokers have a 70% elevated risk of developing polyps, while former smokers have a 31% greater risk than that of people who have never smoked.85

Smoking’s Impact on the Kidneys

Smoking’s Impact on the Kidneys


The kidney is not an organ most people think about as a target of smoking-induced damage, but both active and passive smoking can cause substantial damage to kidney function.13-15,89-95

Smoke induces powerful oxidant stresses on kidney cells.14 Two specific elements of cigarette smoke, cadmium and lead, are directly toxic to the structures that clear the kidney of metabolic waste.14 These microscopic filters are called glomeruli, and each kidney has about a million of them.96

The impact of smoking on the kidney is known to be greater in men than in women,90 with one study showing a 29% increase in the risk of kidney failure in male smokers compared to people who never smoked.92

But perhaps the most alarming part about smoking’s dangerous impact on the kidneys is that you don’t have to be a smoker to experience serious smoke-induced kidney damage.

Multiple studies have shown that nonsmokers exposed to secondhand tobacco smoke have a substantially elevated risk for malignancies in the kidney.91,95 One possible reason for this is that exposure to smoke produces potentially cancer-inducing DNA damage in kidney cells.25

In addition, an animal study found that passive cigarette smoke leads to significant fibrosis (thickening) of the glomeruli (the kidney’s filters), which causes the kidneys to be less functional.13 A human study verified the dangers, showing that both active and passive smoke exposure produces kidney damage. This was demonstrated when urinalyses from both groups showed early loss of protein in the urine, a powerful sign of impending kidney disease.15

Unfortunately, adults aren’t the only ones impacted. A large national study demonstrated increasingly poor function of the kidney’s filtration system in teens exposed to smoke, clearly showing that the dangerous effects of secondhand smoke begin as early as adolescence.89 Even school-aged children show alarming signs of kidney problems if they are exposed to secondhand smoke. One study found that children exposed to secondhand smoke have a 164% higher risk of having protein in the urine, compared to those not exposed.93

Fortunately, it’s never too late to reduce the risks associated with smoking. Researchers found a protective effect on the kidneys in people who had stopped smoking for more than 10 years.95

Tobacco Damages the Liver

The liver is the body’s primary detoxification organ. It performs thousands of chemical reactions daily to neutralize toxins from the environment. Smoking-induced DNA damage has been linked to abnormal expression of toxin-metabolizing enzymes in the liver.97

The metabolic detoxification that occurs in the liver starts with phase I enzymes that convert a toxic chemical into a less harmful chemical that can be metabolized by phase II enzymes. Unfortunately, if the toxic load is too heavy, it can induce or cause over-activity of phase I enzymes, resulting in high levels of free radicals.

Smoking increases the expression of phase I enzymes, which results in an increased risk of cancer in other parts of the body, such as the lungs. Here we see the impact of the close interrelationships between organs and systems: Smoking induces liver damage that can raise the risk for lung cancer.97

Another dangerous liver disease that’s on the rise is nonalcoholic fatty liver disease (NAFLD), a condition in which fat accumulates in the liver. This silent disease produces no symptoms, but can continue to grow until it progresses into a potentially deadly disorder known as nonalcoholic steatohepatitis. Nonalcoholic steatohepatitis can progress to liver fibrosis, a state in which most liver tissue is replaced by the equivalent of scar tissue, and in which liver failure becomes imminent.

Recent studies show that cigarette smoking is associated with an acceleration of nonalcoholic fatty liver disease progression, putting smokers at a massively elevated risk for catastrophic liver failure.98 Compared to people who have never smoked, former smokers had a 45% increase, heavy smokers had a 129% increase, and obese smokers had a shocking 800% increase in their risk of developing this liver disorder.9

With the growing number of obese children, the risk of pediatric nonalcoholic fatty liver disease is also rising. If these children are exposed to secondhand smoke, they are 4 times as likely to develop nonalcoholic fatty liver disease compared to kids in nonsmoking households. As always, the more smoke exposure, the higher the risk: For every additional pack per day smoked in the home, the risk of nonalcoholic fatty liver disease rises an additional 80%.99

Although most people tend to think of liver cirrhosis as a disease related to alcohol consumption, recent studies show that smoking has a surprisingly strong impact as well.100 Compared with people who never smoked, women smokers are more than twice as likely, and men are 40% more likely, to develop liver cirrhosis.100 And the combination of tobacco and alcohol use is even more damaging, with laboratory studies showing that the two together substantially increase the risk of both liver and pancreatic damage.101

Smoking also nearly doubles the risk of developing hepatocellular carcinoma, the most common liver cancer among men. And for male smokers who are also infected with hepatitis C, the risk of developing this cancer increases by nearly 140-fold.102

Wild Green Oat Extract for Smoking Cessation
Wild Green Oat Extract for Smoking Cessation

When a tobacco user ingests or smokes nicotine, a chain of events that results in the release of dopamine produces a satisfying, even euphoric, initial sensation.117

Once the stimulus goes away, users are then left with a relative dopamine deficiency that causes cravings and the subsequent dependence on yet another dose of nicotine.118

This cycle caught the attention of Japanese scientists who decided to test an extract that worked on dopamine pathways. A group of male smokers took 300 mg wild green oat extract after each meal (900 mg per day) for 28 days. Average cigarette consumption before supplementation was close to one pack per day (20 cigarettes). At the end of the study, the average consumption fell to 8.9 cigarettes per day. This was an impressive 54% decrease in tobacco use from baseline.119

Tobacco Smoke Damages Bones

Osteoporosis, a condition in which the bones become weak and brittle, is on the rise in all societies as people are living longer. While age is one of the contributing factors, smoking is also a known risk for osteoporosis.103,104 It interferes with sex hormone production, intestinal calcium absorption, adrenal hormone metabolism, and the normal bone remodeling process.105

Osteoporosis affects men as well as women and studies show that the longer a man has smoked, the greater his risk of developing osteoporosis.106 A study of otherwise healthy young male military recruits demonstrated that relatively short durations of smoking produce significant loss of bone mineral density, highlighting the fact that a person doesn’t have to be a lifetime smoker to have bone loss.107

In animal studies, even secondhand smoke exposure had numerous negative effects on bones, including decreasing bone mineral content and density, inhibiting new bone formation while increasing bone resorption, decreasing the thickness of the hard outer layer (cortex) of the bone, and producing weaker, more easily fractured bones.16

Researchers studied secondhand smoke exposure in a group of postmenopausal women who had never smoked.108 Among those women who had lived with family members who actively smoked, the risk of developing hip osteoporosis was increased more than 3.5-fold, while those who lived with smokers who consumed more than 20 cigarettes per day had a more than 5-fold increased risk of low back osteoporosis, and a more than 4-fold risk of osteoporosis of the hip.108

Smoking Damages Brain Cells

Smoking has been found to have a negative impact on brain cells, increasing the risk of devastating diseases such as amyotrophic lateral sclerosis (Lou Gehrig’s disease) and Alzheimer’s.

The many toxins in cigarette smoke, particularly the production of formaldehyde in smoke, is thought to damage the delicate lipid (fat) membranes of brain cells, which results in the loss of brain cells and function. In one study, the risk of dying from amyotrophic lateral sclerosis, a neurodegenerative disease that can strike even in early middle age, was increased by nearly 2-fold in smokers compared with people who had never smoked.10

Active or former smokers are also at an increased risk for Alzheimer’s disease. And even if a person doesn’t develop Alzheimer’s outright, laboratory studies reveal that smoking can induce pathological brain changes similar to the disease. Studies suggest that oxidative stress is one of the primary mechanisms behind damage to brain cells in smokers.109

While epidemiological studies point clearly to an increased risk for Alzheimer’s disease in smokers, the data are less clear in Parkinson’s disease. In fact, studies have indicated that smoking could have a small protective effect against Parkinson’s, possibly due to drug-like effects of nicotine.110-112 Nevertheless, the many other toxic compounds in cigarettes make smoking a poor preventive strategy for these neurodegenerative diseases.113

Health Consequences Causally Linked to Smoking



Cigarette smoking is the leading avoidable cause of death worldwide. Even after 50 years of public service announcements, tobacco companies still rake in billions of dollars in profits. While it is common knowledge that smoking causes lung cancer, most people are still unaware of the fact that smoking—indeed, any tobacco use—dramatically accelerates aging in all body systems.

Tobacco smoke contains thousands of chemical compounds that can do substantial damage to almost every organ and system in the body. Tobacco use sharply raises levels of oxidant stress and inflammation, increasing the risk for a plethora of diseases and serious conditions.

You should avoid contact with secondhand smoke and thoroughly clean walls, ceilings, and other places where smokers have left their toxic waste behind. This “thirdhand” smoke is emerging as an important concept in environmental and public health fields,28-30 and is defined as “residual tobacco smoke contamination that remains after the cigarette is extinguished.”31

If you have any questions on the scientific content of this article, please call a Life Extension® Health Advisor at 1-866-864-3027.


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