Will your cell phone kill you?
Illustration: Jillian Takami

Is my microwave emitting death rays? Is bird flu still a threat? I do yoga, but should I also be lifting weights? You don't need to waste another second wondering and worrying. We've got the definitive answers right here.
1. Could my cell phone kill me?
It seems unlikely. But if you use your mobile phone a lot, consider getting an earpiece or putting your caller on speaker so you can hold the phone away from your head. The biggest study yet, in which Danish researchers tracked 420,000 cell phone users for up to 21 years, found no cancer risk, but much of the data was collected when cell phones were more of a novelty than a primary form of communication. In a smaller recent Israeli study of 1,726 people, heavy cell phone use raised the risk for salivary gland tumors 50 percent on the side on which the subjects usually held the phone (though the risk overall is still vanishingly small). The biggest threat, however, has nothing to do with cancer: Driving while talking on a cell phone puts you in the same league as a drunk driver. You're four to five times more likely to have an accident.

2. Will vitamin D save my life? Should I really be taking four times the recommended daily dose?
A growing body of evidence strongly suggests that vitamin D in high doses not only helps keep bones strong but also reduces the risk of colon, ovarian, and breast cancers, and diseases such as diabetes and multiple sclerosis. And many of us don't get enough because of a lack of exposure to sunlight (the sun triggers D's production in the skin) or diets that omit good sources (fatty fish such as salmon, mackerel, and tuna, and fortified milk and cereal). While the official daily dose for people age 51 to 70 is 400 IUs, most experts agree that they should aim for 800 to 1,000 IUs of supplemental D a day. But if you're under 50 and you consume the recommended 200 IUs (the equivalent of two glasses of milk daily) and get 10 to 15 minutes of sun exposure—without sunscreen—a day, a 400 IU supplement should do you fine.

3. Is it okay to cleanse your body by fasting from time to time?
As long as you are in good health, a brief liquid fast or cleanse is fine. But don't expect wonders—other than a sense of personal accomplishment, perhaps: Any physiologist will tell you that properly functioning lungs, liver, kidneys, and intestines do a fantastic job of keeping your body free of impurities without the help of fasting. If you do pursue a fast, always make sure to drink enough fluids to avoid dehydration.

4. Can I trust my tap water?
Sure. Unless you're on a private well, tap water comes from municipal treatment plants that are carefully monitored and better regulated than bottled water. (Some popular brands like Aquafina and Dasani are just that: tap water.) Very strict federal rules now require extensive filtering of the water supply, but minuscule amounts of chemicals and pharmaceuticals may still turn up. If you want to ensure you're drinking the purest water possible, consider adding a filter to your tap. For information on filters, go to NRDC.org/waterfilters.

5. Is my microwave giving me cancer?
No. Microwaving doesn't alter food in any way that could make you sick. All a microwave does is spur the water molecules in your food to move, and the friction of those molecules heats up your meal. The ovens do generate a tiny magnetic field, but there's very little evidence that such a field poses a problem for humans. What's more, there's an easy way to avoid any potential harm—step back when the oven is on.

6. How long am I contagious when I have the flu or a cold?
As long as you have symptoms. Your ability to spread these viruses remains until the last sniffle, says Bill Schaffner, MD, a physician and infectious disease expert at Vanderbilt Medical Center in Nashville. And you're contagious 24 hours before you first show symptoms.

How harmful is staring at the computer?
Illustration: Jillian Takami

7. Is it true that 48 hours after starting antibiotics I can't infect someone else?

Yes, in most cases, and provided you really had a bacterial infection, like strep throat, and not a viral one—against which antibiotics are useless, says Schaffner. But the bug may come back if you quit the drugs early; also, if you fail to complete the full prescription, the leftover bacteria could develop antibiotic resistance and the drugs might not work next time.

8. Is bird flu still a danger?
Yes. As of this writing, influenza A virus subtype H5N1—bird flu—has not made an appearance in the United States. But it still lurks in many parts of the world, particularly Asia and parts of Africa. What makes the virus so scary is its deadliness—it kills 50 to 80 percent of the people it infects. Currently, the virus is primarily passed from an infected bird to a human. "You're not going to get it because you're on the plane with someone who has it," says Richard V. Lee, MD, a physician and infectious disease expert at the State University of New York at Buffalo. Nor does cooked chicken pose a risk, since heat kills the virus. But influenza viruses can evolve rapidly, and despite some promising vaccine developments, if the H5N1 virus develops an ability to spread rapidly between people anytime soon, it could spell disaster.

9. How often do I really need to have my teeth professionally cleaned?
The answer depends on your habits at home, says periodontist Sally Cram, consumer adviser for the American Dental Association. Studies show it takes about three months for bacteria to take hold in the gums. Daily flossers who brush twice a day can get by with twice a year professional cleanings, but those who let things slide or have prior gum disease may need visits every two or three months. Diabetes, autoimmune diseases, and medications like antidepressants that dry out your mouth can also speed bacterial buildup and create a need for more cleanings, says Cram.

10. Do the plastic bags from my dry cleaner contain toxic chemicals?
The plastic bag isn't dangerous, but the chemical residues it traps in your clothing might be, says Sarah Janssen, MD, an expert with the Natural Resources Defense Council, an environmental advocacy group. That smell your dry-cleaned clothes give off is perchloroethylene (perc), a chemical the state of California classifies as a potential carcinogen. Reduce your exposure by removing the bag and hanging the clothes outside—or in your bathroom with the window open or the fan on—to air. Don't leave bagged clothes in a hot car: The heat accelerates perc's release, and could make the air in your car toxic, says Janssen.

11. Are the new birth control pills that eliminate your periods really safe?
Yes. There's no evidence that suppressing your period is dangerous. The periods you get on the regular Pill aren't real anyway, because the hormones prevent your uterus from building up the thick lining that's normally shed during menstruation. One reason the Pill's inventors included the off week was to mimic the normal menstrual cycle in the hope that the Pope might bless the Pill. Needless to say, he didn't.

12. Will staring at a computer all day make me blind?
No. A marathon computer session is like a long hike. "If you walk long enough, your legs will be tired, but that doesn't mean you've permanently damaged them," says ophthalmologist John C. Hagan III, MD, a spokesperson for the American Academy of Ophthalmology. Focusing on a computer screen—a fixed distance—will leave your eye muscles tired and stiff, he says, plus you tend to blink less. The antidote: Look up from the computer screen every so often and focus on something 20 or more feet away, then blink briskly four or five times.

Is tuna bad for you?
Illustration: Jillian Takami

13. Can diet soda kill me?

If you mean, could it give you cancer, the answer is probably not. Diabetes? Unlikely. Osteoporosis? Maybe. And it seems possible that the drinks are related to weight gain. Recent research suggests that having several diet drinks a day can weaken bones and is linked to weight gain, though the causes are very murky. Respected nutritionist Marion Nestle, PhD, author of What to Eat and Food Politics, has this to say: "I so prefer real sugar. The other sweeteners are all chemical and all artificial, and I'm not aware of much real evidence that they help people cut calories." A study published this year indicates just the opposite: In rodents, at least, there's evidence that the substitutes interfere with the body's ability to register how many calories it's taking in—which could lead to overeating.

14. Flu shots—should I or shouldn't I?
Yes, absolutely. Although the CDC does not say everyone needs a flu shot, it does recommend them for enough people (due to health risks, age-related concerns, and other factors) that about 82 percent of the total U.S. population qualifies. Even if you don't, you'd be best off getting in line. According to flu expert Trish Perl, MD, a professor of medicine at Johns Hopkins University, "it usually prevents you from catching the flu, but even if you do get sick, your symptoms won't be as severe." More important, it prevents you from spreading the flu to others who might be at risk for developing a fatal case. (About 25 percent of people who have the flu don't even realize it.)

15. Is there any surefire way to stave off Alzheimer's disease?
Sadly, no. The closest scientists have come was a vaccine against synapse-destroying beta-amyloid deposits, a hallmark of the disease. But human trials were stopped abruptly a few years ago when some volunteers developed severe brain inflammation. Still, studies suggest that you can take steps to help your brain—from staying intellectually, socially, and physically active (exercise raises levels of a brain chemical called BDNF that encourages the growth of new brain cells) to eating more fruit, veggies, and salmon.

16. I have to stop eating tuna, swordfish, and salmon, right?
Swordfish, yes. But for most other fish, the benefits of wise consumption outweigh the risks, according to a landmark study in the Journal of the American Medical Association. Swordfish contains high levels of mercury; canned albacore (white) tuna has more mercury than canned light tuna, which is why the Environmental Protection Agency recommends that women of childbearing age eat no more than six ounces of albacore per week. Though salmon does not pose a mercury risk, it may have PCBs (industrial compounds). Limit servings of farmed salmon to one a month; enjoy wild-caught four or more times a month. To learn which seafood is lowest in contaminants and isn't overfished, visit OceansAlive.org.

17. When should I see a doctor about...

...a backache?

See a physician immediately if the back pain keeps you from sleeping; you also have numbness in your leg, foot, groin, or rectal area; you also have fever, chills, nausea, vomiting, stomachache, weakness, or sweating; you've also lost control of urination or bowel movements; you've been in a car crash or other accident; you have a history of cancer. Otherwise, try over-the-counter pain relievers, alternating heating pads with ice packs, and a day or two of rest followed by gentle exercise for two to three weeks before making an appointment.

You'll want to call after two weeks of a burning sensation in the middle of your chest or abdomen—or sooner if you have other signs of gastroesophageal reflux disease such as a dry cough or trouble swallowing despite using an over-the-counter antacid or reflux medicine.

...a fever?
Go to the emergency room if you also experience stomach pain, nausea, or vomiting (it could be appendicitis); severe headache, neck stiffness, drowsiness, vomiting, and light sensitivity (possibly meningitis); you feel faint and confused after spending time outdoors in hot weather (signs of heatstroke). Call your doctor right away if you have one or more of the following: a fever above 103 degrees; bloody diarrhea; a red rash or red streaks on your arm or leg; an earache; painful urination; sore throat; muscle and joint pain; back pain. If two days of an over-the-counter fever reducer (like aspirin or ibuprofen) doesn't bring down your temperature—or if you're also vomiting—it's time for professional help. Call in two weeks if you have a persistent low-grade (101 degrees or less) fever that doesn't go away.

...a sore throat?
See a doctor immediately if you have one or more of the following: a fever of 101 degrees or higher; dehydration; difficulty swallowing or breathing; tender or swollen lymph glands in your neck; pus in the back of your throat; a red rash that feels rough, with increased redness in the skin folds; a persistent cough. Call after three days if you also have body aches, headache, cough, or runny nose.

...abdominal pain, diarrhea, vomiting?
You'll need emergency treatment if you have one or more of the following: a fever above 102 degrees; tender abdomen; bloody diarrhea or black stools; sudden sharp pain that starts under your ribs and moves to your groin; backache; bloating and severe cramping; or you're pregnant and have abdominal or pelvic pain or vaginal bleeding. Call your physician right away if you're in constant pain and have vaginal discharge or a burning feeling when you urinate; traveler's diarrhea that doesn't respond to over-the-counter medicines; or are taking a new medicine that seems to be causing diarrhea.

...muscle and joint pain?
Get your internist or general practitioner on the phone immediately if you have a fever; red or swollen skin over the muscle; severe pain that has no obvious cause; a tick bite or rash; or if you recently started a new prescription or changed doses of a drug you've been taking. Otherwise, give rest and pain relievers three days to work before making a call.

18. Is liposuction worth it?
Yes—but only to resculpt stubborn bulges after weight loss. It won't get rid of cellulite, and it's a bust for keeping you slim: In one study from the University of Texas Southwestern Medical Center, 43 percent of people who'd had lipo put the fat back on, mostly because they didn't adopt a healthy diet or exercise.

19. What's a sure way to stay cancer-free?
There isn't one. The ugly truth is, some people who do everything right get cancer anyway. Still, bad habits worsen your odds. Tobacco use causes about one in three cancers overall, and diet, inactivity, and obesity contribute to another third of cases, says Peter Greenwald, MD, PhD, director of the division of cancer prevention at the National Cancer Institute.

20. Do I really need to lift weights? Isn't yoga enough?
Yoga can build muscle, exercise physiologists say, as long as your muscles burn a little; poses like downward dog require you to lift and shift your own body weight. It's less clear whether yoga can build or maintain bone density—a benefit weight lifting confers—simply because it hasn't been studied. If your current yoga sessions don't feel challenging, or if your bones are thinning, consider adding strength training to the weight-bearing exercise (walking, for example) that you're already doing for your bones. (You are already doing it, right?)

21. Do self-tanners cause cancer?
Nope. The faux glow is delivered by dihydroxyacetone (DHA), which only interacts with dead surface cells on the skin to create a color change that simulates a tan for five to seven days. However: "Although self-tanners do not cause cancer, they generally don't give any protection against UVB or UVA, so it's still important to use sunscreen to prevent aging, sun damage, and skin cancer," says Oanh Lauring, MD, a dermatologist at Mercy Medical Center in Baltimore.

22. Skip exercise when I have a cold, right?
Not necessarily. "If the symptoms are above the neck, like a runny or stuffy nose, sneezing, or sore throat, exercising should pose little or no risk," says Cedric X. Bryant, PhD, chief science officer for the American Council on Exercise in San Diego. "In fact, mild to moderate exercise has been shown to help boost immune system function." But if your symptoms include body aches, chest congestion or tightness, and a hacking cough, workouts should be postponed.

23. Shouldn't everyone get the shingles vaccine?
Not yet. "The vaccine has been studied only in relatively healthy people over age 60," says Stephen K. Tyring, MD, PhD, clinical professor of dermatology at the University of Texas Medical School at Houston. "There's no problem with healthy people under 60 receiving the vaccine, but insurance companies won't pay for the shot, which usually runs at least $150." People with weak immunity—those with cancer or HIV—should avoid this vaccine. A recent study Tyring co-authored suggests that if a blood relative has had shingles, you could be at higher risk and may want to consider the vaccine.

24. Is it true that aluminum-based antiperspirants are dangerous?
There's no evidence, according to the National Cancer Institute, though you wouldn't know it from the persistent Internet and e-mail rumors. Aluminum-based compounds such as those in antiperspirants can be absorbed by the skin and may behave like cancer-promoting estrogen in the body. But no one can say whether antiperspirants lead to a buildup of aluminum in breast tissue, or if that would trigger the breast cell changes that may lead to cancer. Aluminum-free alternatives are out there, though their effectiveness is questionable.

25. What's the best superfood?
Sorry; there isn't one. Forget the latest news on supposedly magical treats like blueberries, chocolate, emu meat, or red wine. Researchers often get their amazing results by isolating a substance in the food and then injecting it into cells in a petri dish or administering amounts to rats that far exceed what you could realistically get in your diet. Yes, these foods are healthy—but only as part of an overall sound diet. Don't let that news dismay you; it should be freeing. You don't have to track the latest food craze—just eat right and in sensible portions. Phew; that sure makes things easier.
As a reminder, always consult your doctor for medical advice and treatment before starting any program.


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