DEAR DR. ROACH: I am 40 and have been diagnosed with three separate primary cancers in my life. My genetic testing came back normal. I am wondering if there are any dietary changes I can make (other than a standard healthy diet) for prevention? -- T. W. ANSWER: I can understand why you would want to do anything you can to prevent future cancers given your history. Most cancers are, essentially, bad luck. You ran across something to cause cancer at the wrong time. That could be environmental (there are many carcinogens -- cancer-causing chemicals -- in the air, water and soil). Your DNA might have been hit by a gamma ray from the cosmos (literally), or you might have been affected by radiation in building materials. There is no way, unfortunately, to protect yourself 100% from cancer. There are dietary factors that protect against cancer. A diet rich in fruits, vegetables, legumes, nuts and whole grains has been shown to reduce cancer risk. Processed meats, including smoked meats, increase cancer risk and should be avoided. The jury is out on red meat, but meat cooked at very high temperatures is clearly carcinogenic. While this is a standard healthy diet, it’s not what most North Americans eat. If it were, there would be a whole lot less cancer and heart disease. DEAR DR. ROACH: My wife, 68, always feels cold. She has mentioned this several times to her primary care physician, and the physician checks her blood to see if an increase in thyroid medication is warranted. The reading always comes back in the normal range, and the problem is not mentioned again until the next appointment. Meanwhile, my wife is uncomfortable most days of the week. Is it possible that an increase in medication is warranted, even though her blood is normal? Might it be that normal for my wife is different than normal for other people? She has been on thyroid medication for at least 30 years, but this chilliness did not begin until she started warfarin after a heart valve replacement with a metal valve. We keep our house at 69 degrees Fahrenheit during the day in winter. She dresses warmly. She is approximately 50 pounds overweight. -- S. B. ANSWER: It’s not uncommon for people to feel cold at levels where most people are comfortable. It’s particularly common in middle-aged and older people. Although low thyroid levels are certainly a cause for being cold, your wife’s doctor needs to be very careful not to overdo it. Without the exact thyroid numbers, I can’t give specific advice, but the thyroid level doesn’t have to be much higher than the normal range before the risk of cardiac arrhythmias, especially atrial fibrillation, starts to go up. That is a significant potential problem in a person with a prosthetic valve. There are other medical causes for feeling cold, especially anemia, which should also be checked. DEAR DR. ROACH: A friend of mine who is a physician has recommended cobra venom for my arthritis. Have you heard of this? -- M. G. ANSWER: Cobra venom has been used in traditional Chinese medicine and in Ayurvedic medicine for many years, and there is evidence in animal models of effectiveness. Clinical trials in Western medicine, some dating back to the 1940s, have generally failed to show a benefit of snake venoms in arthritis, although (perhaps surprisingly) there was not much toxicity. I have read some promising research, but in absence of good data, I can’t recommend it. .