TIME Diet/Nutrition

You Asked: Do Fruit Flies Come From Inside Fruit?

Illustration by Peter Oumanski for TIME

You might not love this answer—but getting rid of them is easy.

Fruit fly moms lay their eggs on everything, from just-starting-to-ripen fruit—like the kind you recently brought home from the market—to the small bits of old produce rotting in your kitchen garbage can, according to the University of Michigan. Even some vegetables, particularly old potatoes and onions, foster fruit flies.

That’s gross. Fortunately, if your fruit isn’t overripe or rotting, the fruit fly larvae and their proud parents haven’t yet burrowed their way deep inside your apples or pears, explains Dr. Gregory Courtney, an entomologist at Iowa State University. They’re just hanging out around the surface of your produce, waiting for the juices inside to start fermenting. (If the risk of pesticides or dirt never inspired you to wash your fruit, maybe the possible presence of fruit fly eggs will do the trick: washing produce rinses away the eggs before they’ve hatched, as long as the fruit is ripe and fresh.)

When the eggs hatch, the babies tunnel into your old bananas and tomatoes and lap up the bacteria and yeast they need to grow big and strong—and to produce hundreds more like themselves. Adult fruit flies likewise feed on the byproducts of the fermentation process, which are also found in wine, soda and everything else you’ve noticed the little buggers hovering around.

In cozy indoor temperatures, the whole birth to reproduction cycle lasts only a couple of weeks, Courtney says.

These insects tend to show up in large numbers in late summer and early fall because it’s the harvest season, and America is filled with the fruits of the earth. With those fruits come fruit flies. And that’s a good thing, Courtney stresses. “They’re not disease spreading, they’re just annoying,” he says. Also, they’re one of many insects that feed on decomposing food. We’d all be neck deep in rotting banana peels and apple cores without them.

But even if you appreciate the bugs’ utility around the compost or trash heap, you probably don’t want them buzzing through your kitchen or lounging on the rim of your wine glass. To get rid of them, Courtney says the best defense is the most obvious: banish all but the freshest produce from your countertops. “Bananas seem to be a big culprit, but that may just be because there are always bananas in my house,” he says.

Buy produce only as you need it, and keep ripe or overripe fruits and vegetables in your refrigerator. Make sure there are no old food scraps hanging out on your floors, countertops or trash. Keep your kitchen free of all those sources for a few weeks, and you’ll wipe out your local fruit fly population, Courtney says.

If a few weeks seems like too long to wait, the University of Nebraska—Lincoln offers a more aggressive solution: Fill a jar with an inch or two of warm water, a teaspoon of yeast and a small amount of sugar to activate the yeast. Take a plastic sandwich baggie, poke a small hole in one corner of it using a sharpened pencil and stick that corner inside the top of the jar. Now secure the bag around the rim of the jar with a rubber band.

The yeasty water will attract fruit flies, which will creep down the bag and through the hole but won’t be able to get back out. Clean out the jar and start over once a week until the fruit flies are gone. Just don’t dump the jar’s old contents in the garbage. The water will likely harbor many fruit fly eggs, so it’s best to dump it away from your house. If you toss it down the sink, run your faucet for a full minute to ensure the eggs are washed away, the UNL report advises.

Or you could just live with your fruit fly friends. They’re pesky, but they serve a purpose.

TIME Mental Health/Psychology

You Asked: Is Meditation Really Worth It?

Illustration by Peter Oumanski for TIME

Totally. Here's why

Updated Oct. 9, 2pm

First of all, understand that “meditation” is a catchall term for a lot of different mental activities, many of which have nothing to do with sitting cross-legged on the floor and saying om.

“There are thousands of different types of meditation,” says Dr. Andrew Newberg, a neuroscientist at Thomas Jefferson University Hospital and author of Words Can Change Your Brain. But while meditative practices come in all shapes and styles, Newberg says nearly all of them have at least one thing in common: They involve focusing your attention, a habit that’s been marginalized by our smartphone-tethered lifestyle of digital distraction.

“That focusing could be on a word or object or physical motion,” Newberg explains. “But regardless, the type of focusing involved in meditation activates the brain’s frontal lobe, which is involved in concentration, planning, speech and other executive functions like problem solving.” Studies have shown meditation can bolster all of these mental tasks. But the greatest benefits may spring from the interplay between your brain’s focus centers and its limbic system—a set of structures that manage your emotions and regulate the release of stress and relaxation hormones.

MORE: The Mindful Revolution

“Studies suggests your body’s arousal system is calmed and the flow of stress-related hormones is reduced [by meditation],” Newberg explains. “There’s also a softening effect when it comes to emotional responses.” Just as weightlifting allows your muscles to lift a heavier load, working out your brain with meditation seems to fortify its ability to carry life’s emotional cargo. That stress-dampening effect has tied meditation to improved mood and lower rates of heart disease, insomnia and depression.

Newberg says there’s also some evidence that meditation quiets the area of your brain that manages your sense of self and your relationship to others. That may sound like a bad thing, but this quieting may help you feel more connected to others and less isolated within yourself, he says.

“Basically, meditation helps your brain get out of its own way,” adds Dr. Judson Brewer, a Yale School of Medicine psychiatrist.

Once you’re convinced meditation is worth a try, figuring out the right type for you is important, because the benefits tend to materialize only if you enjoy your practice enough to stick with it, Brewer says. Luckily, you have a lot of options—from Transcendental Meditation to Tai Chi. Even yoga counts, because it focuses your mind and blocks out distraction.

MORE: How Tai Chi Helps Fight Depression

Mindfulness is one style of meditation that’s exploding in popularity, largely because it can be done anywhere and anytime, Brewer says. “It’s mostly about being aware of your thoughts and not running after them in your mind,” he explains. Awareness is a wedge that, with practice, you can place between your thoughts and unhealthy emotional reactions, he says.

MORE: Can Yoga Ease Major Psychiatric Disorders?

That kind of vague, semi-abstract language can make meditation seem thorny and inaccessible, but it’s easier than you think. If you want a simple taste of meditation, Brewer suggests focusing your mind on your breath or a nearby object, refocusing it when it strays. “Your mind wanders, and you bring it back,” Newberg says. “That’s a mental push-up.”

Do enough mental push-ups, and you may be amazed at how strong your mind muscle can get.

TIME Research

You Asked: Is It Good or Bad to Take a Nap?

Illustration by Peter Oumanski for TIME

Snooze, or skip it?

You’re right to be confused. Even as a recent study linked napping to higher mortality, companies and colleges across the U.S. are installing nap rooms to boost productivity. Truly, it would be a dream to get some napping consensus.

But whether or not napping is right for you depends. “First of all, it’s important to ask yourself why you’re taking the nap,” says Dr. Sara Mednick, a psychologist at the University of California, Riverside and author of Take a Nap! Change Your Life. If you’re spending a big chunk of your day feeling sleepy and out of sorts, then your desire to snooze may be driven by stress, insomnia, sleep apnea or a hundred other slumber-disrupting health conditions, Mednick says.

“Daytime napping is an early indicator of underlying ill health,” adds Yue Leng, a University of Cambridge sleep researcher and coauthor of the study linking naps to higher mortality rates. Like Mednick, Leng suggests daytime drowsiness is likely a symptom of other health issues, not their cause.

Put simply, blaming naps for higher mortality rates is like blaming your doctor for heart disease; you’re more likely to see a doc if you have heart issues, but that doesn’t mean she’s to blame.

MORE: The Power of Sleep

Actually, naps are good for most people, Mednick says. Her research shows a nap—defined as daytime sleeping that lasts between 15 and 90 minutes—can improve brain functions ranging from memory to focus and creativity. “For some people, naps are as restorative as a whole night of sleep,” she adds. More research shows a quick nap can lower stress and recharge your willpower. And napping has also been linked to lower rates of cardiovascular disease and inflammation.

But all of these benefits depend on you getting a good night of sleep to begin with, Mednick stresses. Also, not everyone is a good napper. “Some people wake up from naps feeling like crap,” she says.

Genetics could explain why some people are nappers and some aren’t. But regardless of the explanation, there’s clearly a difference between the two groups. “People who aren’t habitual nappers tend to fall into very deep sleep during naps, and waking up from that leaves them feeling groggy,” Mednick explains. On the other hand, natural nappers—you know who you are—don’t plunge into deep slumber during their daytime snoozes, Mednick says. This allows them to wake up from naps feeling energized and alert, not discombobulated.

MORE: Pass The Pillow: “Google Naps” Is Google Maps for Places to Nap

For natural nappers, she says it’s “incredibly important” that you do catch your daytime ZZZs. “These people—and they probably account for about 40% of the population—tend to do really poorly if they don’t nap,” she explains. Without their much needed daytime shuteye, habitual nappers often reach for energy drinks, caffeine or other stimulants that perk them up but don’t recharge their cognitive batteries the way a short, healthy snooze would.

“For these people, skipping their nap is a huge productivity killer,” Mednick says, and that’s a compelling reason for employers and universities to provide nap spaces for employees and students.

While the length of an ideal siesta varies from person to person, 20 to 30 minutes is plenty for most. But up to 90 minutes—about the length of one full sleep cycle—could also be beneficial, Mednick says. She recommends trying different nap lengths to find the one that leaves you feeling the most refreshed.

If you’ve never been a napper but want to cash in on napping’s brain and health benefits, Mednick says you may be able to teach yourself to nap. The trick is to keep your daytime shuteye very short—no more than 15 minutes at first. This will prevent your brain and body from slipping into the deeper levels of slumber that leave you feeling foggy upon waking, she adds.

But if you’re just not a born napper, don’t sweat it. “Everyone’s different,” Mednick says. “If you feel good, whatever you’re doing is fine.”

TIME Aging

You Asked: Do Brain Games Really Improve Memory?

Illustration by Peter Oumanski for TIME

Unhand the crossword: it's not your golden ticket to a lifetime of quick wit and perfect recall

Games sure seem like a good way to work your brain out, but don’t put your stock in Sudoku. “They target very specific cognitive abilities, but they don’t transfer to clarity of thinking, problem solving, planning—all the complex skills that really matter,” explains Dr. Sandra Bond Chapman, chief director of the Center for Brain Health at the University of Texas at Dallas and author of Make Your Brain Smarter.

When it comes to keeping your brain real-world strong, research has shown–over and over again–two activities to be worth your time. The first is aerobic exercise, says Dr. Karen Li, head of Concordia University’s laboratory for adult development and cognitive aging.

By bolstering your cardiovascular fitness and blood circulation, exercise nourishes your brain with the nutrients and oxygen it needs to perform optimally, Li says. But physical activity offers more than just brain fuel. “Some brain regions and functions seem to benefit more than others,” she explains–specifically the frontal lobe, responsible for high-level skills related to complex processes like multitasking. “That tells us aerobic exercise helps the brain work more efficiently.”

Whether you enjoy running, speed walking, gardening or hiking, “as long as you sweat a bit and your heart rate goes up, that’s what your brain needs,” Li adds. Chapman agrees. “Skip the Sudoku and get out and exercise,” she says. (The Centers for Disease Control and Prevention recommends all adults get at least 150 minutes of moderate-intensity aerobic exercise a week.)

Along with physical activity, your brain needs mental stimulation to stay hale and fit. And when it comes to mental stimulation, novelty is important, Li explains. Here’s why: The more you use your mind to perform a task—whether it’s cooking your favorite dish or driving to the supermarket—the less effort your brain requires to complete that task. “If you feel like your brain’s on autopilot most or all of the time, that’s an indication that you need to increase the challenge a little bit,” she says.

One of the best ways to do that is to stay socially active, Li says. “Following and contributing to a conversation requires a lot of mental prowess.” Visiting intellectually invigorating places, like museums or cultural centers, and learning new skills are also great ways to keep your brain in shape. Even mixing in some variety when it comes to your favorite activities—like trying out a new recipe or cooking technique—will keep your mind off autopilot.

But there’s a catch. “It’s important that you feel genuine interest in these activities,” Li says. Practicing a foreign language for 30 minutes a day is a good way to challenge your brain, but if you feel meh about one day speaking fluent French, your mind won’t benefit as much as it would from something that truly excites or interests you.

If museum visits or learning new languages doesn’t float your boat, Chapman offers an alternate way to fire up your idling brain. “Challenge yourself to think in top-down, complex ways as you go about your day,” she recommends. When you watch a television show or read an article (like this one), pause once you’ve finished to really dissect the information you’ve just encountered. “Zoom out, then zoom in,” Chapman says. Start as broadly as you can (this is a health article) and work your way down (about the brain) until you’ve gotten to the nitty gritty—things like themes or lessons you could take away from what you’ve just seen or read (surely, too numerous to list).

“People take in a lot of information—probably more than we ever have before—but it’s not making us smarter because we’re not spending much time making sense of it,” Chapman says. “Try to push yourself out of your mental comfort zone by asking what about the information matters.”

This is especially important for older retired adults who aren’t faced with the everyday intellectual challenges presented by work or school. “We’re all going to be living longer,” Chapman says. “Along with aerobic exercise, engaging your brain in complex ways is absolutely necessary to keep your mind sharp in the second half of life.”

TIME Exercise/Fitness

You Asked: Should I Eat Before or After a Workout?

Illustration by Peter Oumanski for TIME

Experts answer the great exercise question of our time

Short answer: Both.

Long answer: How and when to fuel your body is the same for all exercisers to some extent, but your routine may warrant a few nutritional tweaks, says Dr. Nancy Cohen, head of the department of nutrition at the University of Massachusetts.

“In general, you’ll want to eat a meal high in carbs and protein and low in fat roughly three to four hours before you exercise,” Cohen says, whether you’re trying to shed pounds or build muscle. Carbohydrates supply your body with the glycogen it needs for your yoga session, gym visit, or jog. Skimp on carbs, and your muscles will sputter when called on to perform, she says.

If you’re trying to lose weight, it may seem weird and counterproductive to eat a carb-heavy meal before you hit the gym. But complex carbohydrates like beans, lentils, whole grains and starchy vegetables will provide exercise fuel plus nutrients and fiber. Unlike refined carbohydrates—things like white bread, cookies, soft drinks, or many pre-packaged foods—complex carbs won’t expand your personal equator or supercharge your appetite, research shows.

Cohen recommends avoiding fat in your pre-workout meal because it slows down your digestion. But eating protein supports your muscles. “During and after exercise, your muscle cells break down and rebuild,” Cohen explains. The right proteins contain the amino acids your muscles need to complete that cellular rebuilding process.

Complete protein packages include animal sources like chicken or lean beef, since they have all those amino acids, Cohen says. Grains like quinoa and bulgur as well as beans and some vegetables also contain protein, though probably not the “complete” kind. But if you eat a variety of those food sources, you can skip the meat and still get all the amino acids you need, she adds.

As for post-workout food, Cohen suggests eating or drinking more protein an hour or two after lifting weights for bodybuilders and athletes. But despite what you’ve heard, it’s not necessary (or healthy) to pound a massive protein shake the second you stop pumping iron.

According to Dr. Rob Danoff, an Aria Health System physician with a focus on sports medicine and nutrition, your body—and especially your kidneys—can only synthesize so much protein. Research suggests roughly one gram of protein per kilogram of body weight is plenty to maximize muscle growth. By that measure, for a person who weighs 175 pounds, 80 grams of protein all day is enough.

One large chicken breast or cut of red meat can contain 60 grams of protein or more, so slamming a huge protein shake after a workout will only inundate your kidneys with protein it can’t handle and your muscles don’t need, Danoff says. Apart from the risk of kidney damage, there’s evidence that overloading your body with protein can contribute to an imbalance in the acidity of your blood, which in the long run could lead to bone weakening. “It’s a myth that we need all this protein,” Danoff says. “More isn’t always better.”

In your workout-food focus, don’t forget water. If you exercise first thing in the morning, Cohen says dehydration is a big concern because you’ve probably passed much of the night without a sip of H2O. “Your whole cellular metabolism is dependent on fluid,” she says. And everything from your workout performance to your mood and mental acuity will suffer if you’re parched.

TIME You Asked

You Asked: Why Do Mosquitoes Always Bite Me?

Illustration by Peter Oumanski for TIME

You’re covered with itchy red welts while your friends seem blissfully unbitten. What’s the deal with that?

First of all, it’s not in your head. Mosquitoes really do prefer some people to others, says Dr. Jonathan Day, a medical entomologist and mosquito expert at the University of Florida. And that time your grandmother told you your skin was just sweeter? There’s some truth to that, Day says. “Some people produce more of certain chemicals in their skin,” he explains. “And a few of those chemicals, like lactic acid, attract mosquitoes.” There’s also evidence that one blood type (O) attracts mosquitoes more than others (A or B).

Unfortunately, your genes dictate your blood type and the chemical makeup of your birthday suit. Genetics also determine several other factors that could make you an object of blood-sucking affection for your local mosquito population, Day says. Maybe the most important: Your metabolic rate, or the amount of carbon dioxide (CO2) your body releases as it burns energy.

Mosquitoes use CO2 as their primary means of identifying bite targets, Day says. Why? “All vertebrates produce carbon dioxide, so what better way could there be for a mosquito to cue in on a host?” And while it’s true that you can moderate your metabolic rate through diet and exercise, you can only change your metabolism so much, Day says.

“Pregnant women and overweight or obese people tend to have higher resting metabolic rates, which may make them more attractive to mosquitoes,” he explains. Also, drinking alcohol or physically exerting yourself raises your metabolic rate—and also your appeal to winged biters, he adds. (Exercising before grabbing a beer and heading outside = asking for trouble.)

While CO2 detection is the primary technique mosquitoes and other blood-sucking bugs use to spot hosts, they also rely on secondary cues to differentiate you from cars, decaying trees, and other CO2-producing objects. And you can control some of those secondary cues, Day says.

For example: Dark clothing is more attractive to mosquitoes than light oufits. Why? “Mosquitoes have problems flying in even a slight wind, and so they keep close to the ground,” Day explains. Down there, they spot hosts by comparing your silhouette to the horizon. Dark colors stand out, while light shades blend in, he says. At the same time, lots of motion distinguishes you from your surroundings. So if you’re moving around a lot or gesturing, you might as well be shouting, “Hey, mosquitoes! I’m right here, ladies!” (Only the females bite, Day says.)

Obviously, you’re not going to spend the summer sitting stock-still in a white suit. So what are the best ways to avoid itchy bites? Day recommends protective clothing, which doesn’t mean baggy jeans and long-sleeved sweatshirts. “Lots of the lightweight, breathable fabrics made for athletes or fishermen are woven tightly enough to protect you from bugs,” he says.

If your summer style isn’t negotiable—or for those parts of your body you can’t cover up—Day recommends a mosquito repellant with 15% DEET. Just make sure to follow the label’s instructions for safe application. “Spray it into your hands and then rub it on your skin to avoid inhaling it,” he says. “That’ll protect you for around 90 minutes.”

Also, mosquitoes usually feed at dawn and dusk when the wind tends to die down and the humidity rises, Day explains. If you can stay indoors at those times, you’ll avoid bites. A good fan pointed in your general vicinity will also do a great job of keeping the bugs away. “Mosquitoes can’t fly in a breeze faster than 1 mile per hour,” Day says.

If all that fails, hug a bite-free buddy. Maybe some of his mosquito-repelling skin chemicals will rub off on you.

TIME Aging

You Asked: Can Computers Really Ruin My Eyes?

Illustration by Peter Oumanski for TIME

You spend most of the day staring at a computer, and your tablet or smartphone lull you to sleep at night. What does all that digital screen time do to your eyes?

From sore eyes and blurred vision to headaches, doctors have a catch-all term for any screen-induced discomfort: “Computer vision syndrome,” says Dr. Joshua Dunaief, an ophthalmologist and macular degeneration researcher at the University of Pennsylvania. Dunaief says the specific causes of computer vision syndrome (CVS) are numerous, from improper reading glasses to an overly bright screen. But in most cases, any eye issues you’re experiencing stem from two root issues. Either your eyes are dried out, or they’ve become too fatigued to see properly.

“There are tiny muscles inside your eyeball that change the shape of your eye’s lens in order to bring whatever you’re seeing into focus,” Dunaief explains. After hours of sitting in front of your computer screen, those muscles can grow tired from focusing on a single fixed point. “In some cases, those muscles become so fatigued that your eyes can no longer focus,” Dunaief adds. He says research has also shown that when reading or working online, people tend to blink less. That can lead to dry eyes, tearing, or a burning sensation, he says.

While you’re not powerless to combat these problems (more on that in a minute), Dunaief says these issues are typically short-lived—meaning they go away within a few hours if you abandon your computer. But are there any serious, long-term dangers associated with digital screens?

“Possibly,” Dunaief says. “There’s evidence that bright light can damage your retinas irreversibly. That might mean staring at a computer screen that is very bright could damage your eyes.” He says there’s also some experimental evidence indicating regular exposure to computer-strength light could be damaging in similar ways.

Sitting too close to your computer screen (or holding your cell phone very near to your face) could also potentially lead to some vision problems, explains Dr. Joan Portello, an associate professor and researcher at the State University of New York School of Optometry. “A lot of people don’t realize this, but when you’re viewing something really close, that’s when your eyes are working the hardest—much harder than when you’re looking at something far away,” Portello explains.

Both she and Dunaief say there’s some evidence that students who spend many hours hunched over textbooks tend to become nearsighted. (Some Chinese schools have started employing metal desk bars to keep kids from lowering their heads too near to their study materials.) “Kids who play outside a lot tend to have better distance vision,” Portello adds. “And heavy computer use could turn out to cause some similar issues to this close textbook reading.” Like Dunaief, Portello says it’s too early to say how bad long-term computer use is for your eyes.

One thing is crystal clear: Computers aren’t going anywhere. So what can you do to safeguard your sight? First and foremost, proper eyewear is essential—especially if you’re older than 40, when reading small print tends to become troublesome for most people, Dunaief says. “Your reading glasses aren’t made for your computer,” he explains. Ditto for your regular spectacles. “An optometrist can fit you for glasses made specifically for computer use that will make things easier on your eyes.”

Dunaief also recommends dimming your computer screen and moving it as far away from your eyes as comfort and readability allow. Enlarging the font, closing blinds, and turning down the lights in your office to prevent glare can also help keep your eyes safe, he explains.

Portello says eye drops or artificial tears can help, as long as you consult with your eye doctor first about which type will work best for you. She also recommends sticking to the 20-20-20 rule. “Every 20 minutes, look away from your screen at something 20 feet away for 20 seconds,” she advises. Why? This gives your eye muscles a rest and helps ward off fatigue and strain. Focusing on something even farther away is just as good, she adds. “And while you’re at it, try to blink as much as you can to keep your eyes moist.”

TIME Mental Health/Psychology

You Asked: What’s the Best Bedtime?

Illustration by Peter Oumanski for TIME

The earlier the better? 11 PM? Sundown? Sleep experts say it’s not that simple. But there is a time range you should shoot for if you’re questing for a perfect night’s sleep

Every hour of sleep before midnight is worth two after midnight. Your grandparents (and great grandparents) probably adhered to that creaky adage. “The mythology is unfortunate, because there’s no pumpkin-like magic that occurs,” says Dr. Matt Walker, head of the Sleep and Neuroimaging Lab at the University of California, Berkeley. And while nothing special happens to you or the quality of your sleep at the stroke of midnight, many do wonder: What’s the best time to go to bed?

Walker says your sleep quality does change as the night wears on. “The time of night when you sleep makes a significant difference in terms of the structure and quality of your sleep,” he explains. Your slumber is composed of a series of 90-minute cycles during which your brain moves from deep, non-rapid eye movement (non-REM) sleep to REM sleep. “That 90-minute cycle is fairly stable throughout the night,” Walker explains. “But the ratio of non-REM to REM sleep changes.”

He says that non-REM sleep tends to dominate your slumber cycles in the early part of the night. But as the clock creeps toward daybreak, REM sleep muscles in. That’s significant, because some research has suggested that non-REM sleep is deeper and more restorative than lighter, dream-infused REM sleep—though Walker says both offer important benefits.

What does this have to do with the perfect bedtime? The shift from non-REM to REM sleep happens at certain times of the night regardless of when you go to bed, Walker says. So if you hit the sack very late—at, say, 3 AM—your sleep will tilt toward lighter, REM-heavy sleep. And that reduction in deep, restorative sleep may leave you groggy and blunt-minded the next day.

That’s unfortunate news for nightshift workers, bartenders, and others with unconventional sleep-wake routines, because they can’t sleep efficiently at odd hours of the day or night, Walker says. “The idea that you can learn to work at night and sleep during the day—you just can’t do that and be at your best.” Your brain and body’s circadian rhythms—which regulate everything from your sleeping patterns to your energy and hunger levels—tell your brain what kind of slumber to crave. And no matter how hard you try to reset or reschedule your circadian rhythms when it comes to bedtime, there’s just not much wiggle room. “These cycles have been established for hundreds of thousands of years,” Walker explains. “Thirty or 40 years of professional life aren’t going to change them.”

When it comes to bedtime, he says there’s a window of a several hours—roughly between 8 PM and 12 AM—during which your brain and body have the opportunity to get all the non-REM and REM shuteye they need to function optimally. And, believe it or not, your genetic makeup dictates whether you’re more comfortable going to bed earlier or later within that rough 8-to-midnight window, says Dr. Allison Siebern, associate director of the Insomnia & Behavioral Sleep Medicine Program at Stanford University.

“For people who are night owls, going to bed very early goes against their physiology,” Siebern explains. The same is true for “morning larks” who try to stay up late. For either type of person—as well as for the vast majority of sleepers who fall somewhere in between—the best bedtime is the hour of the evening when they feel most sleepy.

That means night owls shouldn’t try to force themselves to bed at 9 or 10 if they’re not tired. Of course, your work schedule or family life may dictate when you have to get up in the morning. But if you can find a way to match your sleep schedule to your biology—and get a full eight hours of Z’s—you’ll be better off, she adds.

Both she and Walker say your ideal bedtime will also change as you age. While small children tend to be most tired early in the evening, the opposite is true for college-aged adults who may be more comfortable going to bed around or after midnight. Beyond college, your best bedtime will likely creep earlier and earlier as you age, Walker says. And again, all of this is set by your biology.

Siebern suggests experimenting with different bedtimes and using sleepiness as your barometer for a best fit. Just make sure you’re rising at roughly the same time every morning—weekdays or weekends. It’s fine to sleep an extra hour on your days off. But if you’re getting up at 6:30 during the workweek and sleeping until 10 on weekends, you’re going to throw off your sleep rhythms and make bedtime more challenging, she says.

TIME Diet/Nutrition

You Asked: Is Coffee Bad For You?

Illustration by Peter Oumanski for TIME

For years, your morning joe got a bad rap from health experts. But newer research suggests coffee may actually be good for you—if you follow the rules

“I gave up coffee” is a refrain of the health conscious. But should it be? The idea that coffee is a dangerous, addictive stimulant springs mostly from 1970s- and 1980s-era studies that tied the drink to higher rates of cancer and heart disease, explains Dr. Rob van Dam, a disease and nutrition expert at Harvard School of Public Health who has examined coffee and its health effects. According to van Dam, that old research didn’t do a great job of adjusting for a person’s cigarette habit or other unhealthy behaviors.

But newer, better-designed research paints a more benign picture of your favorite eye-opener. Van Dam and his colleagues analyzed health and diet data on roughly 130,000 adults spanning 24 years. They found no evidence that drinking coffee increases your risk of death from cancer, cardiovascular disease, or other causes. That was true even for people who knocked back 48-ounces of coffee a day. In fact, there was some indication that regular coffee drinkers might enjoy a slight drop in mortality risk, van Dam says.

The idea that your java could actually deserve a health halo would have shocked doctors a few decades ago. But van Dam’s study is only one in a wave of new research sure to please coffee fans. Coffee has been linked to lower rates of type-2 diabetes, a reduced risk for some cancers, and protection against Parkinson’s disease. Other research links coffee to improved memory, mood and energy levels.

The drink could even help shield you from a deadly form of skin cancer. How? The caffeine in coffee may interact with a type of “repair gene” that plays a role in the development of basal cell carcinoma, says Dr. Jiali Han, a disease researcher at Indiana University, Indianapolis, who coauthored the coffee-and-skin cancer study. Han says it’s also possible that coffee’s antioxidant compounds could account for the drink’s anti-cancer benefits—an explanation you’ll come across a lot when reading about coffee’s benefits.

But before you start swigging your java by the gallon, van Dam warns that there remain reasons to be careful. There’s evidence that pregnant women might want to limit morning caffeine fix because of an admittedly small correlation between coffee intake and miscarriage. (There is research showing that moderate coffee drinking is perfectly safe, making it a judgment call for expecting moms.) There are also reports hinting that people with cholesterol issues may have more problems if they drink some kinds of coffee. Compounds called cafestol, present in coffee beans, appear to raise LDL cholesterol—though paper filters eliminate most of those compound, making it more of a concern with French press and espresso-style brews. And of course, if you’re drinking so much that you’re unable to sleep or your heart races, that’s a bad thing too, van Dam adds.

But if you’re in good shape and enjoy coffee? “For most people,” van Dam says, “black coffee is a healthy, non-caloric beverage choice.” And it should go without saying that the benefits conferred to coffee do not extend to mocha-flavored “coffee drinks” or other sugar-loaded concoctions.

“Coffee is a highly complex beverage with hundreds of compounds,” van Dam says, which means it affects people differently. Van Dam doesn’t recommend people who don’t already drink the stuff start now, but if you love it, can tolerate it, and it isn’t messing with your sleep? Bottoms up.

TIME Diet/Nutrition

You Asked: Can Water Go Bad?

Illustration by Peter Oumanski for TIME

Does drinking old water make you sick?

That depends, says Dr. Kellogg Schwab, director of the Johns Hopkins University Water Institute. As soon as you take a sip, your lips and mouth introduce microorganisms into your H2O. Combined with the ambient temperature in your home or office, and sunlight streaming into your windows, those microorganisms could start to multiply pretty quickly, Schwab says.

“If you have clean water in a clean glass, you’re fine for a day or two,” he says, adding that almost all tap water in the U.S. contains chlorine additives that will kill small communities of microorganisms. But if you’ve ever swigged a sip of day-old water from bedside your bed or on your desk and wondered why it tastes funny, that’s because after about 12 hours it goes flat and, as carbon dioxide from the air interacts with the H2O in your glass, it slightly lowering its pH. “But it’s most likely safe to drink,” Schwab adds.

He says reusing the same dirty glass day after day will raise you risk of exposure to some unfriendly bacteria—especially if someone else is sipping from your vessel and mixing his or her mouth microorganisms with yours. But assuming you grab a new cup every few days? “You’re probably not going to have a problem,” Schwab assures, adding that, “This is far from the top of the list of public health concerns.”

One possible exception: Touching the rim of your glass with dirty fingers—especially if you (or whoever unloaded the dishwasher) forgot to wash up after using the bathroom. There are lots of different sickness-causing bacteria in human waste, and if you handle your glass with dirty hands, those bacteria could make their way into your water, Schwab warns.

But what about that plastic water bottle on the floor of your car? Heat and plastic are a bad combination, he stresses. “A chemical called bisphenol-A, or BPA, along with other things used to manufacture plastic can leach into your water if the bottle heats up or sits in the sun,” he explains. BPA is a hormone disruptor that research has tentatively linked to several health hazards, including heart disease and cancer. Schwab says the types of plastic used for bottling water aren’t meant to be washed or refilled, so use them once and recycle them. Or better yet, use refillable containers made of metal or glass.

When it comes to storing water for long periods, the answer is “Yes,” your H2O can certainly become unsafe to drink, says Zane Satterfield, an engineer scientist with the National Environmental Services Center at West Virginia University. “Most experts will tell you tap water has a shelf-life of six months,” Satterfield says. “After that point, the chlorine dissipates to the point that bacteria and algae start to grow.” That growth will speed up if you store your water in a warm or sunny spot—or in a glass container that hasn’t been thoroughly washed or sealed, he adds.

If you’re a doomsday hoarder with giant vats of pre-packaged water in your basement, you should know that will last at least a year. But after 12 months you’re best off swapping out what you have for fresh stores, Satterfield advises. “You’ll see that some of the water will evaporate during that time, which is proof that the plastic isn’t impermeable,” he explains.

If you want to play it safe when it comes to water that’s been stored for long periods, Satterfield says adding a few drops of plain, unscented bleach and waiting 30 minutes will make your water safe to drink. (Specifically, that’s four drops per gallon, he adds.) Good to know in case of an apocalypse—zombie or otherwise.

Your browser, Internet Explorer 8 or below, is out of date. It has known security flaws and may not display all features of this and other websites.

Learn how to update your browser