The Cancer Chronicles Read Online Free PDF Page B

cancer. Conversely there is evidence thatcaloric restriction reduces the likelihood of cancer. You lower your metabolism. Like a lizard.
    Nancy included a variety of vegetables and fruits in our diet mostly because she liked them. But she had reason to worry more than some others about cancer. Her mother had suffered through a mastectomy and chemotherapy shortly before we married. After sixteen years of slumber, the cancer returned. We didn’t know if her breast cancer was among those linked to a familialgenetic defect. If so Nancy might have inherited a susceptibility, though not a fate.
    She had other risk factors. She was forty-three and we had no children, a source of constant contention. The less frequently a woman is pregnant, the more monthly menstrual cycles she endures. With each perioda jolt of estrogen causes cells in the uterus and mammary glands to begin multiplying, duplicating their DNA—preparing for the bearing and the nursing of a child that may not come. Each menstrual cycle is a roll of the dice, an opportunity for copying errors that might result in aneoplasm. Estrogen (along withasbestos,benzene,gamma rays, andmustard gas) is onthe list of known humancarcinogens published by the federal government’sNational Toxicology Program.
    Women these days are also exposed to more monthly doses of estrogen because they are beginning to menstruate at much earlier ages,possibly increasing the risk of breastcancer.A few scientists blame the change onbisphenol A—a chemical in plastic bottles that mimics estrogen—buta more widely accepted explanation involves nutrition. With more food to eat, girls mature more rapidly, accumulating fat, and that may serve as a signal that the body is healthy enough to begin ovulation. Over a centurythe age ofmenarche, whenmenstruation begins, has dropped in the Western world from about seventeen to twelve. At the same time women are spending less of their fertile life either pregnant or nursing a child.Lactation also appears to hold estrogen in check. The result of all this is that a teenager today may have already experiencedmore menstrual cycles than her grandmother did during her entire life.
    There are other risks in being female.Hormone therapies, administered during menopause or pregnancy, have been associated with some cancers. Andobesity, especially in older women, can increase estrogen along with cancer risk. But none of this is straightforward. Strangely enough, excess body fat can actuallyreduce the chances of premenopausal women getting breast cancer. And whileoralcontraceptives may slightly raise the odds for cancer of the breast, they appear to reduce the risk of gettingovarian andendometrial cancer. Nancy wasn’t using birth control pills and she was far from beingoverweight, but she worried, just a little, about another factor: the wine we liked to have with dinner.Alcohol might also tip the hormonal scales and has been associated for entirely different reasons with digestivecancers. Snuffed out by alcohol, epithelial cells lining the esophagus must be replaced—more DNA to be duplicated, more chances forerror. There is evidence linking alcohol toliver cancer, but more certain isthe risk fromhepatitis viruses or long-termexposure toaflatoxin, a poison produced by funguses that can invade peanuts, soybeans, and other foods.
    You could live your life with a calculator.Consuming two or three drinks a day might increase breast cancer risk by 20 percent. That is not as bad as it sounds. The chance thata woman between the ages of forty and forty-nine will get the cancer is 1 in 69, or 1.4 percent. Alcohol consumption would raise that to 1.7 percent.Even tallness is a risk factor. (Nancy was just five foot three.) An analysis of data from theMillion Women Study found that every four inches over five feet increased cancer risk by 16 percent. A clue to the mechanism may be found inEcuadoran villagers with a kind ofdwarfism calledLaron syndrome. Because of a mutation