TIME public health

You Asked: Is My Air Conditioner Killing Me?

You Asked Air Conditioner Killing Me
Illustration by Peter Oumanski for TIME

It can be unhealthy for you—and it’s certainly bad for the planet. It could also save your life.

In the summer, many of us can’t bear to live without it, but even so, cool air is a modern luxury that sometimes seems to freak people out.

“We had forms of heating for a very long time before we ever had air conditioning,” says Dr. Stan Cox, senior scientist at The Land Institute in Salina, Kansas, and author of Losing Our Cool: Uncomfortable Truths About Our Air-Conditioned World. Cox points out that as recently as the 1960s, only 12 percent of Americans had some kind of AC in their homes. While heat was an absolute necessity for people to live in cold climates, Cox says, air conditioning is more of a newcomer on the climate-controlled front.

And research suggests that a little freaking out is warranted. “If you have a badly maintained or badly designed AC system, whether it’s in your home or office or vehicle, it can become contaminated and potentially harmful,” says Dr. Mark Mendell, an epidemiologist with the California Department of Public Health.

Mendell studied the health effects of air conditioning systems while with the U.S. Department of Energy’s Lawrence Berkeley National Laboratory. He says worsening asthma problems and allergies are two health issues that can stem from contaminated AC units. He also mentions an ominous-sounding phenomenon: sick building syndrome.

“We started seeing it in the 70s and 80s,” Mendell says. “People in office buildings started saying the building was making them sick.”

He says sick building syndrome was associated with a range of seemingly unrelated symptoms: nasal congestion, breathing problems, headaches, fatigue and irritated skin. His own research has linked AC systems in office buildings to many of those same symptoms.

“The most likely explanation is that there may be some microorganisms growing in the system that may have some subtle effect on certain people,” Mendell says. “But it’s not clear how many people are sensitive to this or how big of a problem it is.”

Unlike heating systems, the process of cooling hot air creates a lot of moisture and condensation, which must be channeled away, Mendell explains. If your AC system does a bad job of this, whether due to poor maintenance, damage or shoddy design, it can become a breeding ground for bacteria and fungi. To protect yourself, he says, your best defense is a well-maintained and routinely serviced AC unit. (HVAC repairmen, you owe this guy!)

But Mendell is also quick to point out that AC has been firmly linked to many health benefits. “Outdoor air pollution is common in urban environments, and especially in heavy traffic,” he says as just one example. “AC filters out the particles in outdoor pollutants.”

Exposure to airborne pollution particles can raise your risk for hospital admissions and premature death due to cardiovascular issues, says Dr. Michelle Bell, a professor of environmental health at Yale University. Bell’s research found the use of well-maintained AC use lowered a person’s risk for these health complications. “Use of central air conditioning causes less outdoor air pollution to penetrate indoors compared to open windows,” she says.

Both Bell and Mendell also say that during intense heat waves, AC saves lives.

If this seesawing between AC’s benefits and risks feels disorienting, you’re not alone. “Anyone who does research on these systems will admit there’s still a lot of things we don’t know,” Mendell says.

What isn’t in doubt, though, is air conditioning’s very real and harmful impact on the planet.

“The headline issue is its contribution to greenhouse warming,” says Cox, the Land Institute environmental researcher. Indoor heating has long been a bigger contributor than AC to the accumulation of harmful greenhouse gasses, Cox says. But the U.S. population’s southward shift has allowed AC to catch up—and maybe draw even.

Despite his concern for the planet, Cox says that AC can be life saving and beneficial. But he takes issue with what he calls our “lavish” use of any climate control conveniences. Setting our thermostats a bit higher in summer and a little lower in winter would benefit the environment without affecting anyone’s health, he says.

In fact, a little thermal discomfort could be good for you. People tend to eat more and gain more weight when the temperature is perfectly cozy, Cox says. “When we’re a little cold or a little warm, our metabolism runs faster,” he says. Research backs him up: One recent study found exposure to cold temps—enough to make you shiver—may increase your body’s stores of healthy, energy-burning brown fat.

Cox adds that your body can adapt to a range of temperatures. (This is why you break out the shorts and T-shirts on that first 65-degree spring day, but the same thermostat reading in autumn sends you hunting for jeans and sweaters.) So if you can cut out the heat or cold for a week or two, your body will often acclimate to temperatures you found unpleasant at first—and easing up a bit on the AC will make the planet thank you, too.

TIME Mental Health/Psychology

You Asked: Do I Worry Too Much?

You Asked Do I Worry Too Much
Illustration by Peter Oumanski for TIME

Frequent fretting is unproductive and not so hot for your health.

As human beings, our ability to predict trouble—and outwit it—is one of those cerebral superpowers that set us apart from birds and beasts. But nonstop worrying can be crippling to your life and your immune system.

“Just having a thought about some potential bad thing that might happen—everyone has those,” says Dr. Michelle Newman, director of the Laboratory for Anxiety and Depression Research at Pennsylvania State University. “But if you have difficulty stopping the worry once it starts, that’s one of the ways we define what’s called pathological worry.”

Newman, who is also editor of the journal Behavior Therapy, cites more characteristics of out-of-control worrying, like fixating on things over which you have no control—or which have a low probability of happening—and “catastrophizing” them. Worrying about a loved one who’s driving and picturing the horrible ramifications of an accident is one example; imagining a string of events that might lead to your losing your job and your home is another.

Anxiety is a related feeling that often goes hand in hand with worrying. While it can be a little tricky to separate the two, Newman says the technical difference is that worrying is “verbal-linguistic” while anxiety is “physical.” If you feel tense or on edge while thinking about your job security or your child’s long car trip, you’re experiencing both worry and anxiety. Feel those emotions “more days than not” for a period of six months, and you meet the American Psychiatric Association’s criteria for a diagnosis of generalized anxiety disorder, or GAD. Basically, you’re a chronic worrier.

“I like to say that chronic worry is a process looking for content,” Newman says. “You’ve gotten into the habit of looking for something to be concerned about, and you always find it.”

That’s bad news for several reasons. First and foremost, incessant worrying and anxiety can increase your blood pressure and heart rate and has been linked to an elevated risk for cardiovascular disease. “Anxiety can also over-activate your immune system,” says Dr. Wesley Moons, formerly of the University of California, Davis, and now CEO of his own consulting firm, Moons Analytics.

While at UC Davis, Moons and his graduate student Grant Shields found that people who reacted to stressful situations with anger experienced a smaller immune system response than those who reacted with anxiety. Shields says the sorts of immune system responses his research linked to anxiety could hurt the body’s ability to fight off infection or disease and have been tentatively linked to higher mortality rates.

“That’s not to say getting angry is a healthy reaction to stress,” Moons adds. “But in terms of your immune system, anxiety appears to trigger some different and potentially more detrimental responses.”

But isn’t there a benefit to lots of worrying? After all, if your mind is tackling contingencies and potential threats, you can act now to prevent them—right?

Unfortunately, Newman refutes this idea. “Mostly worrying becomes a process unto itself that doesn’t lead to problem solving or helping you in any way,” she says. If you’re worrying about something, she says, you’re not taking steps to address the source of your worry, if that’s even possible.

When you boil it down, worry is really a failure to live in the moment, Newman says. Activities that attempt to anchor your mind to the present—including yoga and meditation—may help combat incessant worrying. Exercise, massage and other things that alleviate physical tension are also helpful, she says.

Another great way to reign in your worrying is to set aside a specific time and place for it. Select a spot you can get to easily every day, but that isn’t a place where you normally spend time, Newman advises. (A quiet bench in your backyard, maybe, or a chair in your guest room.) Your goal is to give yourself 20 or 30 minutes a day in that space, devoted only to worrying. “The rest of the day, you tell yourself you aren’t going to worry because you will at that time and place,” Newman explains. “The idea is that by isolating your worry, you can control it.”

She says that focusing on a favorite relaxing setting—your “happy place”—also has proven worry-reducing benefits. “Close your eyes,” she says. “Try to vividly picture that place—the sights and smells and sounds you would feel and hear.” Hopefully the place that you see is worry-free.

TIME Cancer

You Asked: Can Deodorant Give You Cancer?

You Asked Deoderent Cancer
Illustration by Peter Oumanski for TIME

There may be reasons to worry—though hard proof remains elusive.

If you’ve seen the 1989 film Batman—the one with Michael Keaton and Jack Nicholson—you’ll recall that the Joker terrorizes Gotham City by slipping toxic chemicals into cosmetics: while no single item is lethal, combining deodorant with shampoo and lipstick could kill you.

It’s hard not to think of that movie while chatting with toxicologists who study the potential risk of deodorant and antiperspirant ingredients, especially parabens and aluminum. However, according to the American Cancer Society’s website, there is no “clear” or “direct” link between parabens or aluminum and cancer. The National Cancer Institute site says “more research is needed.”

The FDA, for its part, says “FDA believes that at the present time there is no reason for consumers to be concerned about the use of cosmetics containing parabens. However, the agency will continue to evaluate new data in this area. If FDA determines that a health hazard exists, the agency will advise the industry and the public.

But “absence of evidence is not evidence of absence,” says Dr. Philip Harvey, editor-in-chief of the Journal of Applied Toxicology.

Dr. Philippa Darbre, an oncologist at the University of Reading in the U.K., has published more than 30 research papers on those substances found in underarm deodorant and other personal care products. She says that many of these ingredients are concerning on their own. But the health risks of each may be greater—and more difficult to identify—when you consider the complex chemical cocktails that form when they combine.

For example, her research has detected parabens—a category of chemical that acts as a preservative in some underarm and personal care products—in women’s breast tissue, though how those parabens got there and what happens when they are in breast tissue is unknown.

In Darbre’s experiments, combining different parabens with human cells creates activity that may contribute to the development of cancer. But attempts to find these links in humans—as opposed to in petri dishes—have produced inconsistent results. One 2002 study found no correlation between underarm product use and breast cancer; a 2003 study did find ties. Darbre says both studies have flaws and leave many important questions unanswered.

Like Darbre, Harvey has looked into the ways cosmetics interact with your body. He says wiping these chemicals under your arms and on the sides of your chest or breasts “could provide a route of almost direct exposure to underlying tissue containing estrogen receptors.”

Both parabens and aluminum are “estrogenic” chemicals—meaning they interact with your body’s hormones or cells in ways similar to estrogen. That’s concerning, because excess estrogen plays a role in promoting the growth of cancer cells, according to the National Cancer Institute. While many experts think cosmetic chemicals like parabens have only “weak” estrogenic activity, Harvey doesn’t agree. He says, “It is often quoted that parabens are thousands of times less potent than estrogen in terms of their estrogenicity. This can be misleading and ignores actual exposures.”

Harvey says his own calculations suggest these cosmetic chemicals may “significantly add to estrogenic burdens.” Because of that, he says he questions the wisdom of including any chemical with known hormonal activity in your personal care regimen.

But until he and other researchers are able to explain—and demonstrate—the ways these chemicals cause health problems, no regulatory changes are likely.

That’s because unless a chemical is proven harmful, regulators allow you to eat it, smoke it, brush with it or slather it on your body. Finding that proof of harm is a difficult, costly and time-consuming proposition. Darbre says researchers can’t simply mix some human cells and some chemicals in a test tube and watch for cancer to pop up.

So where does that leave deodorant and antiperspirant users? Largely in in the dark, Darbre says. “People want a simple fix,” she says. “Unfortunately it is not simple.”

Until more is known, consumers are in a bind. “Avoiding certain publicized chemicals is only the tip of the iceberg,” she says. Darbre says she switched to a twice-daily regimen of underarm cleaning with soap and water. (“No one has yet complained!” she jokes.) Frequent pit scrubbing may seem unnecessarily laborious—or just plain weird. But if you’re concerned about the chemicals you rub on your body, regular bathing might seem like an attractive alternative.

TIME Exercise/Fitness

You Asked: Is It Better to Sleep In Or Work Out?

Peter Oumanski for TIME

Sleep and exercise are both vital. But if you can’t seem to fit in both, you can sometimes substitute a little of one for a little of the other.

When it comes to your health, there are few absolutes. But that’s not the case with sleep and exercise. You need both, period.

“I couldn’t choose between the two,” says Edward Laskowski, MD, a resident and professor of physical medicine at Mayo Clinic. “Sleep and exercise are like food and water.”

Not only are both necessary, but it’s difficult to get healthy doses of one without the other. “When you look at the research, regular physical activity is important for high-quality sleep, and high-quality sleep is important for physical performance,” says Cheri Mah, a sleep medicine researcher at Stanford University and the University of California, San Francisco.

But when pressed to choose one that’s more important, Mah grudgingly decides on sleep. “Sleep is foundational,” she says. While specific needs vary from person to person, she says most of the scientific literature suggests adults need a minimum of seven hours of good sleep every night. “Lots of individuals think they can operate on less, but when you test them, you find they’re not performing at their best,” Mah says. “They get used to feeling tired, and they think that’s the norm.”

Sleep is the base on which a healthy mind and body stand, she explains. From your immune function to your mood, energy, appetite and dozens of other health variables, if that base is wobbly, your health will suffer.

But let’s assume you’re getting your seven-plus hours every night. Can you sacrifice some zzzs a few times a week in order to fit in regular exercise? Yes, but with caveats, says Dr. Phyllis Zee, director of the Center for Circadian and Sleep Medicine at Northwestern University.

Regularity is very important for sound, restorative sleep. Mess around too much with your sleep and wake schedule, and all of your body’s circadian rhythms can be thrown out of whack. Not only will you feel sleepy at odd hours, but you may also struggle to fall asleep at night, and your appetite and energy will fluctuate in unhealthy ways, Zee says.

Say you typically go to bed around 11:00 p.m. and rise at seven. Zee says the midpoint of your night would land near 3 a.m. As long as you’re maintaining your seven-to-eight-hour average and that midpoint lands between 2 a.m. and 4 a.m., Zee says you’re fine skipping a half hour of sleep a few days a week in favor of a morning run or gym visit.

Not fine: Rising two hours early to attend a morning yoga class or to fit in a lengthy bike ride.

“Even on weekends, you want to keep that regularity of when you go to bed and when you get up,” Zee stresses. Your body doesn’t understand what a weekend is, so it doesn’t react well if you stick to one schedule during the workweek and adopt a radically different schedule on Saturdays and Sundays. The same goes for your workout days.

But if you’re falling short of your seven hours a night, Zee, Mah and Laskowski all say the same thing: It’s time to reorganize your schedule in a way that makes room for both adequate sleep and regular exercise.

There may be some exceptions for people with insomnia or those who can’t seem to sleep at night. For them, rising at the same time each day and incorporating regular exercise might help alleviate sleep woes, even if it means sacrificing a little sack time in the short term.

But for the rest of us, making time for sleep and exercise can come down to cutting out activities that aren’t as important.

“Almost everyone could forgo 30 minutes a day of internet or TV time,” Mah says. Both the CDC and American Heart Association recommend a minimum of 2.5 hours of moderate-intensity aerobic exercise every week. Along with your seven-plus hours of sleep, those are you bare-minimum goals when it comes to healthy rest and physical activity.

“There are so many unique benefits that each have, it’s hard to pull them apart,” Laskowski says. “The real danger is when you only make adequate time for one of them.”

TIME Diet/Nutrition

You Asked: Can I Scrape Mold Off of Food and Eat It?

Can I eat moldy food
Illustration by Peter Oumanski for TIME

Believe it or not, you can eat food with fuzz. But only when it comes to certain stuff.

Nobody wants to waste food. So when you see something hairy in your cream cheese or suspicious spots on your bread, it’s tempting to scrape the mold away and chow down. But in most cases—including the two just mentioned—munching moldy food is a bad idea, says Kristin Kirkpatrick, a registered dietitian and wellness manager at Cleveland Clinic.

Kirkpatrick says that when visible mold is present, its tentacles—called “threads”—have likely penetrated deep into your food, contaminating even those parts that appear to be mold-free.

The health risks of mold exposure are many. “Mold can produce toxic substances, called mycotoxins,” says Katie George, a clinical dietitian at the University of Kansas Hospital. These toxins can cause respiratory problems, allergic reactions and illness. George says aflatoxin, a specific type mycotoxin found in nuts and grains, can even be cancer-causing.

Mold is usually easy to spot. It often appears as a blue or green discoloration, which can grow a hairy coat if left long enough, Kirkpatrick says. If you’re examining foods in jars—things like pasta sauce or salsa—it’s best to check the underside of the lid and rim of the container for suspicious growths.

Just don’t sniff your foods, Kirkpatrick warns, which could lead to you inhaling mold spores. If you’re worried about mold but don’t see any growths, use common sense. “If the food doesn’t look the way it normally would, and especially if it seems moisture-soaked, toss it,” Kirkpatrick says.

The exceptions: Hard block cheeses like parmesan, cheddar or Swiss. “With those, the mold generally won’t penetrate deep into the product,” Kirkpatrick says. But don’t start scraping, which can release mold spores into the air or allow them to spread to your countertops or other foods. The only safe way to remove that mold is to cut away an inch of cheese all the way around the spot, she says. “You’ll probably cut away some safe parts, but that’s a good rule of thumb.”

A similar rule applies to some super-dense meats, like hard salami or cured ham. If mold is present, Kirkpatrick says you can cut it away and still enjoy these meats. But again, avoid scraping.

She also advises tossing the moldy bits in your trash—not your sink, where they could release spores or be splashed onto nearby countertops or dishes. Be sure not to use the same knife to prepare food that you used to remove the mold, too.

If you want to cut down the risk of mold in the first place, make sure you keep the inside of your fridge clean, George says. If bits of food or spilled condiments sit for weeks or months, the mold they harbor could spread to other foods—even fresh stuff. She also recommends keeping every food covered in your refrigerator to avoid cross-contamination.

Also, toss any prepared foods—things like casseroles or dinner leftovers—after two days. “Forty-eight hours is probably pretty conservative,” Kirkpatrick says. “But why take the chance?” Playing it safe is especially important for people with weakened immune systems, she says.

Her final piece of advice is probably your best course of action when it comes to moldy food: “When in doubt,” she says, “throw it out.”

TIME Research

You Asked: Are Self-Tanners Safe?

You Asked: Should I Use Spray Tanner?
Illustration by Peter Oumanski for TIME

These products are safer than sun exposure—but only if you avoid the sprays.

To bake, or to fake? It’s a classic tanning conundrum. Sitting under the sun causes skin damage and cellular changes that raise your risk for skin cancer, and even among adults under 40, melanoma rates are on the rise.

“In order to get a natural tan from ultraviolet light, your skin has to be injured,” says Dr. Darrell Rigel, a clinical professor of dermatology at New York University. You know this, and you worry about it. But unlike ultraviolet rays, sunless self-tanners don’t mean you have to damage your skin. “These products contain an ingredient that stains the outermost layer or your skin,” Rigel says.

In most cases, that ingredient is dihydroxyacetone (DHA). When it combines with amino acids in your skin, DHA causes a browning reaction—the same type of reaction that occurs when you make toast or grill meat, explains Dr. Adam Friedman, director of dermatologic research at Montefiore-Albert Einstein College of Medicine.

That may sound scary. But the browning only takes place in your skin’s “stratum corneum”—the topmost layer composed of dead cells, Friedman says. “Our bodies make a form of this stuff,” he adds, referring to DHA. “So I’m not concerned about it from as safety standpoint. When used topically, I think it’s the only safe way to have a tan appearance.”

For anyone who’s read up on self-tanners, Friedman’s statements may raise eyebrows. A few years ago, a much-cited report from ABC News raised concerns about spray-tanning salons and the risks of inhaling DHA and other self-tanning ingredients. Subsequent research supported the idea that inhaling spray-on tanning chemicals could potentially raise your risk for asthma, chronic obstructive pulmonary disease (COPD) or cancer.

“Stretched flat, your lungs are the size of a tennis court,” says Dr. Reynold Panettieri, a professor of pulmonary medicine at the University of Pennsylvania. “So inhaling these self-tanning agents could have all sorts of potential health consequences.”

But what about self-tanners you spread on your skin? The ABC News report cited Food & Drug Administration data suggesting that small amounts of DHA might seep through your skin and into your bloodstream. If true, that could also raise health concerns. But since that FDA data came to light, follow-up studies have failed to find evidence that DHA penetrates your skin’s protective barriers.

Dr. Rigel was one of several experts who voiced concern to ABC News following their DHA investigation. But when it comes to DHA in lotions, Rigel says his concerns have since been assuaged. “There’s no data to show that DHA is harmful when applied topically,” he says. “Pregnant women and children may want to avoid it just as a precaution, but this is benign stuff.”

Panettieri agrees. “Based on what we know today, DHA is really pretty safe when applied to the skin correctly,” he says. Correct application means avoiding the sensitive skin around your eyes and on your lips, as well as cuts or abrasions—more reasons to be wary of spray-on options. Panettieri says rubbing DHA into very thin or broken skin could let it enter your system. “Even if DHA got beyond the skin, any risk is hypothetical,” he’s quick to add.

Both he and Rigel say that compared to the well-established risks of sun exposure, topical self-tanning lotions are a safer option. Friedman agrees, and says his only concern is that some people might have an allergic reaction to DHA or other ingredients in self-tanners—a risk that comes with almost any cosmetic.

But Friedman adds one big warning: Self-tanners do not offer your skin any protection from sun damage. “Some people think these self-tanners act like sunscreen,” he says. “They don’t.” In fact, some research suggests DHA may actually increase the amount of damage your skin sustains from sun exposure.

Of course, new research could always surface new risks. And not as much is known about less-common tanning chemicals. But for now, if you’re craving a little color, self-tanning lotions with DHA seem to be your safest option.

TIME Healthcare

You Asked: Why Are My Teeth So Sensitive?

You Asked: Why Are My Teeth So Sensitive?
Illustration by Peter Oumanski for TIME

Sometimes teeth are just touchy. But certain sensitivities are signs of trouble.

You feel it when you sip a hot drink or bite into a cool dessert: an ache, an acute stab of pain. Even a sharp breath of cold air might trigger a twinge. “Any tooth sensitivity is trying to tell us something,” says Dr. Matt Messina, an Ohio-based dentist and spokesperson for the American Dental Association. “It may be easy to treat, but something is still causing it.”

For dentists, the most common (and least alarming) sensitivity is an all-over reaction to very cold stimuli, Messina says. Especially if that cold-induced pain is short-lived, you probably don’t have reason to worry. But if the pain is persistent and confined to a specific tooth or area of your mouth, that’s a problem. “That’s often the sign of a micro-crack, a degraded filling or a cavity,” Messina says.

Those conditions, all of which require a dentist’s attention, become more probable if the tooth or area is also sensitive to heat and biting pressure. “If you have reactions to all three—cold, hot, and biting pressure—we could also be talking about some sort of infection in the tooth,” Messina adds.

If you’re dealing with an all-over ache, your gums—not your teeth—may explain your pain. Exposing your gums to irritants or harsh treatment makes them recede. And when they do, they leave exposed the tender roots near the base of your teeth. “Your roots don’t have the same quality of protective enamel as your crowns, so they’re more sensitive,” says Dr. Eugene Ko of the University of Michigan’s department of oral pathology.

Brushing too forcefully, chewing tobacco or allowing the buildup of plaque can all cause your gums to “run away” from your teeth, resulting in temperature sensitivity, Messina says. If you think gum recession might be the cause of your sensitivity, Ko says you may be able to look in a mirror and spot the issue. “The margin where your teeth and gums meet: there may be a change in color, almost like water elevation marks during a drought.”

Of course, there are many more reasons for temperature-sensitive teeth. Those include the excessive use of mouthwash or whitening products, dead or dying nerves, tooth grinding, recent dental work or serious gum issues like gingivitis or periodontal disease. Messina also says eating lots of acidic foods—things like soda, sports drinks, sour candy or citrus fruits and juices—can lead to a loss of tooth enamel that renders your teeth sensitive to temperature.

Apart from ditching those foods, Messina advises carefully reading and following instructions when using whiteners, mouth rinses, or other dental hygiene treatments. “More is not always better,” he warns.

When it comes to brushing, apply gentle pressure with a soft-bristle toothbrush. “You’re trying to massage you teeth all the way to the junction where they come together with your gums,” Messina says. “You should not be scrubbing like you would tub grout.” If changing your brushing technique doesn’t do the trick, he says switching to a sensitive-teeth toothpaste can help. “These contain a chemical agent that fills tubules in teeth and blocks sensitivity,” he says.

No matter what, you should mention the temperature issue to your dentist during your next visit. “Big problems often start out as sensitivities,” Messina says. “The solutions are often simple, but only if we address the problem early.”

TIME Mental Health/Psychology

You Asked: Are My Devices Messing With My Brain?

You Asked: Are All My Devices Messing With My Brain?
Illustration by Peter Oumanski for TIME

Yes—and you're probably suffering from phantom text syndrome, too.

First it was radio. Then it was television. Now doomsayers are offering scary predictions about the consequences of smartphones and all the other digital devices to which we’ve all grown so attached. So why should you pay any attention to the warnings this time?

Apart from portability, the big difference between something like a traditional TV and your tablet is the social component, says Dr. David Strayer, a professor of cognition and neural science at the University of Utah. “Through Twitter or Facebook or email, someone in your social network is contacting you in some way all the time,” Strayer says.

“We’re inherently social organisms,” adds Dr. Paul Atchley, a cognitive psychologist at Kansas University. There’s almost nothing more compelling than social information, he says, which activates part of your brain’s reward system. Your noodle is also hardwired to respond to novel sights or sounds. (For most of human history, a sudden noise might have signaled the presence of a predator.) “So something like a buzz or beep or flashing light is tapping into that threat detection system,” he explains.

Combine that sudden beep with the implicit promise of new social info, and you have a near-perfect, un-ignorable stimulus that will pull your focus away from whatever task your brain is working on. And while you may think you can quickly check a text or email and pick up that task where you left off, you really can’t.

“Every time you switch your focus from one thing to another, there’s something called a switch-cost,” says Dr. Earl Miller, a professor of neuroscience at Massachusetts Institute of Technology. “Your brain stumbles a bit, and it requires time to get back to where it was before it was distracted.”

While this isn’t a big deal if you’re doing something simple and rote—making an omelet, say, or folding clothes—it can be a very big deal if your brain is trying to sort out a complex problem, Miller says.

One recent study found it can take your brain 15 to 25 minutes to get back to where it was after stopping to check an email. And Miller’s own research shows you don’t get better at this sort of multitasking with practice. In fact, people who judged themselves to be expert digital multitaskers tended to be pretty bad at it, he says.

“You’re not able to think as deeply on something when you’re being distracted every few minutes,” Miller adds. “And thinking deeply is where real insights come from.”

There seems to be an easy solution to this: When you’re working on something complicated, switch off your phone or email.

That could work for some people. But there’s evidence that as your brain becomes accustomed to checking a device every few minutes, it will struggle to stay on task even at those times when it’s not interrupted by digital alerts. “There’s something called ‘phantom text syndrome,’ ” Atchley says. “You think you hear a text or alert, but there isn’t one.”

While phantom texts can afflict adults, Atchley says this phenomenon is pretty much universal among people under the age of 20—many of whom wouldn’t recognize a world that doesn’t include smartphones. Even if you don’t hear phantom alerts, you may still find yourself reflexively wanting to check your device every few minutes for updates, which disrupts your concentration regardless of whether you ignore that impulse.

Your ability to focus aside, a 2014 study appearing in the journal PLOS One found that people who spend a lot of time “media multitasking”—or juggling lots of different websites, apps, programs or other digital stimuli—tend to have less grey matter in a part of their brain involved with thought and emotion control. These same structural changes are associated with obsessive-compulsive disorder, depression, and anxiety disorders, says that study’s first author, Kepkee Loh, who conducted his research at University College London.

Atchley says more research suggests lots of device use bombards your brain’s prefrontal cortex, which plays a big role in willpower and decision-making. “The prefrontal cortex prevents us from doing stupid things, whether it’s eating junk food or texting while driving,” he explains.

He says this part of the human brain isn’t “fully wired” until your early 20s—another issue that has him worried about how a lot of device use may be affecting children and adolescents.

So what’s the antidote? Spending time in nature may counteract the focus-draining effects of too much tech time, shows research Atchley and Strayer published in 2012. Meditation may also offer focus-strengthening benefits.

Strayer says putting your phone on silent and setting your email only to deliver new messages every 30 minutes are also ways to use your devices strategically and “not be a slave to them,” he adds.

Of course, there are plenty of benefits associated with the latest and greatest technologies. Ease and convenience of staying in touch with friends is a big one. But many open questions remain when it comes to the true cost of our digital distractions.

“Imagine Einstein trying to think about mathematics at a time when part of his brain was wondering what was going on with Twitter,” Atchley says. “People make incredible breakthroughs when they’re concentrating very hard on a specific task, and I wonder if our devices are taking away our ability to do that.”

TIME Pain

You Asked: Do High Heels Actually Damage My Feet?

You Asked: Do High Heels Actually Damage My Feet?
Illustration by Peter Oumanski for TIME

Yep. And the damage doesn’t end at your toes.

High heels hurt. If you’ve worn them (I have not) then you probably know this already. But are high heels also bad for you? A 2014 survey from the American Podiatric Medical Association—composed of the nation’s top foot and lower-leg docs—found heels were far and away the most common cause of foot pain among women.

Unsurprisingly, much of that pain comes from contorting your foot into a steep “plantarflexed” position, concludes a study from the Journal of Applied Physiology. Like standing on your tiptoes for hours, that high-heeled posture may lead to painful muscle fatigue and strain injuries, the authors of that study say.

Calluses, blisters, bunions, and ingrown nails are all common among high heel wearers, adds Dr. Rodney Stuck, division director of podiatry at Loyola University Chicago. The higher the heel, the more trouble you’re likely to run (or walk) into, Stuck says.

But the most significant risks of your high-heel habit may begin higher up your leg. According to research from the U.K. and Austria, lots of time spent walking in heels actually changes the structure of the muscles and tendons in your calves—and not for the better.

High heels lead to shorter muscle fibers and a toughening of the Achilles tendon, says Dr. Marco Narici, a professor of clinical physiology at the University of Nottingham (and coauthor of that study). Narici says these muscle changes reduce your ankle’s range of motion, and contribute to your risk for strains and sprains. Stuck says these sorts of muscle adaptations may also up your risk for other lower-body injuries. A sore ankle or leg you blamed on running may actually have more to do with your high heels, he says.

More research shows walking in heels puts a great deal of force on your kneecaps. This force can lead to the early onset of osteoarthritis, says Dr. Constance Chu, a professor of orthopedic surgery at Stanford.

Chu says this risk increases among heavier women. “Combining walking in very high heels for long periods of time every day with obesity and aging would be a perfect storm for knee osteoarthritis, as well as foot, back, and other joint problems,” she says.

Of course, tossing your stilettos is the one surefire way to dodge all these potential health hazards. But if you’re not willing to part with your pumps, Chu says lower heels lowers your risk. For formal or work events when you feel heels are a must, she recommends wearing flats beforehand and changing into your heels only when you’ve arrived at your destination. “Taking time to sit and move the knees through a full range of motion may also be helpful,” she says.

Loyola University’s Stuck also suggests standing against a wall or with one foot on a step and stretching your feet for a few minutes every day.

But don’t swap your heels for flip-flops. An Auburn University study found the way those loose summer sandals shorten your gait and force you to grip with your toes may lead to all sorts of heel, ankle, and sole problems.

Feet sure don’t have it easy.

Read next: These High-Tech High Heels Change Color With the Click of an App

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TIME Diet/Nutrition

You Asked: Do I Have a Gluten Allergy?

You Asked: Do I Have a Food Allergy?
Illustration by Peter Oumanski for TIME

What you eat could be the cause of your headaches, joint pain, sluggishness or dozens of other ailments. Or maybe not.

People tend to conflate the terms allergy, intolerance, and sensitivity when they talk about food-related reactions, and especially gluten. The first two refer to well-understood digestive disorders with predictable symptoms, says Dr. Robert A. Wood, division chief of allergy and immunology at Johns Hopkins.

If you have a true allergy, your immune system produces antibodies designed to protect you from something it sees as a threat—be it nuts or shellfish. Even a little nibble can cause cramping or stomach pain, a runny nose, skin rashes, or swelling and breathing issues, Wood says.

An intolerance is an inability to properly digest or absorb specific foods or nutrients, often due to a lack of one or more digestive enzymes. (For example, people who are lactose intolerant don’t have the enzymes required to break down lactose.) This inability can lead to gastrointestinal problems like stomach pain, vomiting or diarrhea. Wood says food intolerances, unlike allergies, tend to be “dose dependent”—meaning the more of the food you eat, the worse you feel.

Take gluten, a type of protein found in grains like wheat, rye and barley. When it comes to gluten-related health concerns, says Dr. Alessio Fasano, director of the Center for Celiac Research at Massachusetts General Hospital, roughly 1% of the population has celiac disease—a condition that causes a sufferer’s immune system to attack the small intestine whenever gluten is present. A smaller percentage of people, maybe 0.5%, have a related wheat allergy. “We can verify each of these through blood tests and screening,” Fasano adds. Blood tests are the first step in identifying the underlying condition; to get a definitive diagnosis, a gut biopsy is usually required. For people with these conditions, cutting gluten or wheat is an absolute necessity.

But unlike allergies and intolerances, food sensitivities occupy a gray zone. Like an allergy, they may be related to immune reactions. But they’re poorly understood and symptoms are hard to pin down, says Fasano. “If you believe reports, a food sensitivity could cause a stomachache one time, then a headache, then joint pain or even cognitive problems,” Fasano says.

Because the mechanisms underlying sensitivities aren’t known, Fasano says there’s no way to test and validate them. That ambiguity has led to a lot of confusion and disagreement among researchers, while creating ideal conditions for spurious health “experts” to push food elimination diets that may do more harm than good, he says.

Eliminating gluten is the most common (and some would say trendy) example of this, Fasano says. Some estimates suggest a third of Americans are trying to avoid or altogether ditch gluten. “There’s this misconception that gluten-free foods are healthier or somehow linked to weight loss,” Fasano says. “But for most people, going gluten-free probably will not be beneficial.”

There may be another category of people who suffer from a sensitivity to wheat or gluten. Some popular books have suggested, in the words of Grain Brain author David Perlmutter, that gluten “represents one of the greatest and most under-recognized health threats to humanity.” But there’s not much data to support such claims. Fasano says what data there is point to stomach or abdominal pain as the most common symptom of gluten sensitivity, followed by skin conditions like eczema. While foggy thinking and fatigue are tied to gluten, there’s no agreed-on explanation for these symptoms, Fasano says.

Aside from celiac disease, Johns Hopkins’s Wood says that the medical science community is so convinced gluten isn’t a major health issue that there’s very little funding or interest in studying the subject further. “I think the bulk of people avoiding gluten are avoiding it unnecessarily,” he says. “Most doctors or people who’ve looked into it think it’s more of a lifestyle choice than a valid health issue.”

And when people claim to feel healthier after ditching wheat or gluten? “Lots of junk foods and snack foods contain gluten,” Fasano says. Some estimates show one-third of all grocery store items contain gluten—many of them the additive-stuffed, overly processed packaged foods nutritionists would love for you to eighty-six from your diet. “If you cut out those things, of course you’ll feel better,” Fasano says. “But it’s not because your body has a problem with gluten.”

While he doesn’t believe gluten is the health villain many have made it out to be, Fasano says food-related reactions are common, from gastrointestinal issues like stomachaches or cramps to non-GI issues like headache and joint pain. Fruit, beans, alcohol and many other common foods have been linked to symptoms of allergy or intolerance.

If you feel certain foods, including gluten or wheat, may be triggering pain or another type of physical reaction, Fasano recommends visiting a gastroenterologist or an expert dietitian—someone who can help you identify the source of your problem without putting you at risk for a nutritional deficiency.

“You wouldn’t take antibiotics or insulin without seeing a doctor first,” he says, “and you should take the same precautions when it comes to making changes to your diet.”

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