To the extent that the major external risk factors for cancer are diminished, cancer will occur at a later age, and the proportion of cancer caused by normal metabolic processes will increase. Aging and its degenerative diseases appear to be due in good part to oxidative damage to DNA and other macromolecules. 12 DNA is oxidized in normal metabolism because antioxidant defenses, though numerous, are not perfect. Smoking contributes to about 35 percent of U.S. cancer, about one-quarter of heart disease and about 400,000 premature deaths per year in the United States. 14 Tobacco is a known cause of cancer of the lung, bladder, mouth, pharynx, pancreas, stomach, larynx, esophagus and possibly colon.
Tobacco causes even more deaths by diseases other than cancer.
Smoke contains a wide variety of mutagens and rodent carcinogens. Smoking is also a severe oxidative stress and causes inflammation in the lung. Thus, smokers must ingest two to three times more Vitamin C than non-smokers to achieve the same level in blood, but they rarely do. Inadequate concentration of Vitamin C in plasma is more common among the poor and smokers. Men with inadequate diets or who smoke may damage the DNA of their sperm as well as the DNA in the rest of their cells.