Ask an Expert: Cancer prevention for the ex-smoker

Q: "I quit smoking 15 years ago after smoking a pack or two a day for 28 years. Now I want to do all I can to lessen the effects of my earlier bad habits. Are there any dietary measures, supplements or other strategies you know of that may help prevent cancer?"

Answer from John R. Handy, Jr. , M.D., co-director of Providence Thoracic Oncology Program and director of Providence Thoracic Surgery Program

Congratulations on quitting. As a past smoker, yes, you are at higher risk of developing lung cancer than someone who never smoked. However, in the absence of cigarette smoke, your lungs have been steadily repairing themselves. After 10 years without tobacco, your risk of lung cancer dropped to one-third of what it would have been if you had kept smoking. Now your risk is even lower, and the longer you continue to abstain from cigarettes, the more your risk of lung cancer will fall. Unfortunately, your risk will never be as low as that of a lifelong non-smoker. But you have already taken the most important step to reduce your chance of lung cancer.

The second-most-important step is to avoid smoky places and people who are smoking. About 90 percent of lung cancers are caused either by smoking personally or by exposure to secondhand smoke. The American Cancer Society says that a nonsmoker who is married to a smoker has a 30 percent greater risk of developing lung cancer than the spouse of a nonsmoker does. “Smokers” include anyone who uses regular or low-tar cigarettes, cigars or pipes. Cigars and pipes are only slightly less likely to cause lung cancer than regular or low-tar cigarettes.

As for supplements and dietary measures: Finding substances that protect people who are at higher risk of cancer is an area of great research interest. Researchers have studied vitamin supplements (including C, E, and retinoids such as vitamin A and beta carotene), but none has panned out. In some studies, the mineral selenium, an antioxidant (a nutrient that blocks the actions of free radicals, which damage cells), appeared promising in reducing the rate of lung cancer in current and former smokers. But in other studies, it did not. Researchers continue to explore this mineral.

While the value of supplements in cancer prevention remains unclear, the benefits of vitamins and antioxidants found naturally in food are a different matter. Eating a proper diet is the third important step you can take to reduce cancer risk.

Some studies indicate that a diet that is low in fruits and vegetables may make a person more vulnerable to the cancer-causing agents in tobacco smoke. Conversely, growing evidence is suggesting that a diet rich in fruits and vegetables lowers cancer risk.

You've heard this before, from many directions (mom, for example): Eat a variety of fruits and vegetables — five or more servings daily. Researchers are still learning about the various micronutrients and interactions involved in fruits, vegetables and whole grains. But lycopene-rich foods look particularly helpful.

Lycopene is an antioxidant that some researchers believe helps prevent or slow the growth of lung, prostate and stomach cancers. Extra-good sources of lycopene are tomatoes (tomatoes that are cooked with a little olive oil, as in tomato sauce, are a better source than raw tomatoes or juice), apricots, guava, watermelon, papaya and pink grapefruit.

The lycopene may be working in consort with other antioxidants and compounds in these fruits, so you can't take a shortcut with lycopene supplements. Get it in foods.

As a bonus, this diet — along with continuing to abstain from smoking — will improve your general health and help you avoid other diseases, such as heart disease and stroke. I also encourage you to exercise and to pay attention to your emotional health and your social network.

The final step may be more difficult to achieve, depending on your situation: Live and work in an environment that is free of the chemicals that are known to cause cancer. Workplace or environmental carcinogens include the following:
  • Airborne asbestos fibers
  • Radon (a radioactive gas produced naturally when uranium breaks down)
  • Other radioactive ores in addition to uranium
  • Inhaled chemicals or minerals such as arsenic, beryllium, vinyl chloride, nickel chromates, coal products, mustard gas, and chloromethyl ethers
  • Fuels such as gasoline
  • Diesel exhaust
Typical city air pollution has not been linked to higher rates of lung cancer.

You can see the value of research studies in helping ex-smokers and others avoid lung cancer. You might enjoy the chance to participate in a clinical trial looking at these or other questions. The Providence web site has an updated list of clinical trials that are currently available through the Robert W. Franz Cancer Research Center, which is part of the Earle A. Chiles Research Institute at Providence Cancer Center.

November 2005

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