TIME Diet/Nutrition

You Asked: Is It Bad to Eat the Same Thing Every Day?

Illustration by Peter Oumanski for TIME

You can get away with eating the same things on loop. But you have to be shrewd about the foods on your grocery list

Meal planning and prep is a pain—especially during the workweek. So it’s easy to fall into the habit of buying, making and eating the same foods day in and day out. Fortunately, that’s not necessarily bad news for your health.

For one thing, “More food variety universally leads to more food intake,” says Dr. Susan Roberts, director of the Energy Metabolism Laboratory at Tufts University.

Imagine a buffet of vegetable dishes versus one large bowl of salad. You’ll eat more from the buffet every time, Roberts says, since we’re “hard wired” for food variety. Unfortunately, that instinct kicks in even if you replace the healthy veggie buffet with its more realistic equivalent: junk food. For that reason, Roberts says trimming your mealtime array of food options is one way to control overeating.

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We have that hard-wired instinct toward food diversity for a good reason. “No one food has all the nutrients we need in the optimum amounts, so eating a variety of foods means you are much more likely to get enough of each one,” Roberts explains.

But how much variety is enough, and how much is too much? A study from Brigham and Women’s Hospital and the Harvard School of Public Health found women who regularly ate 16 or 17 items from a healthy list of foods—which included fruits, vegetables, whole grains, cereals like quinoa, fish, and low-fat dairy—enjoyed a 42-percent drop in death from any cause compared to women who ate fewer than nine of the foods on that list.

On the other hand, there’s some very preliminary research that suggests eating a varied diet may have some not-so-hot health effects when it comes to your microbiome. That’s the network of microorganisms that lives in your body and supports your digestive system, helps control your appetite and performs dozens of other essential functions.

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Typically, microbe diversity is a good thing when it comes to your gut. But, according to Dr. Daniel Bolnick, an ecologist at the University of Texas, “We’ve shown that in some animals, mixing foods actually reduces the number and variety of gut microbes.”

Bolnick says the takeaway at this stage isn’t that eating a wide variety of foods is bad, but rather that combinations of foods can do unexpected things. “If you know the effect of Food A and the effect of Food B, you can’t predict what will happen to the microbiome when you eat both,” he says. “There’s no question that, as a species, we eat a greater variety of things now then we used to. But whether that’s good or bad for us is still in question.”

So is it good or bad to eat the same stuff every day? If you’re thinking a bagel for breakfast, sandwich for lunch, and meat with potatoes and a salad for dinner, you’re surely going to be deficient in a number of the necessary nutrients your body needs to thrive, Roberts says.

But if you’re packing plenty of healthful, micronutrient-dense vegetables into your simple meal plan—at least six, Roberts advises—you probably don’t have much to worry about. Just be sure the vegetables you eat come in lots of colors, which tend to correlate with different nutrients. And stay away from starchy vegetables like potatoes, which don’t offer a lot of nutrient bang for your buck, she adds.

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Roberts says the following sample menu would offer pretty much everything your body needs even if you ate it every day: Greek yogurt with fresh fruit for breakfast, a spinach or kale salad with chicken and vegetables for lunch, a fruit-and-nut smoothie for a snack, and some kind of vegetable-and-brown-rice stir fry for dinner.

Of course, there are a thousand other ways you could structure your meals to get all the good stuff your body needs from just a few dishes. And you don’t have to restrict yourself to such a limited plan. The big takeaway here is you also don’t have to go crazy trying to fit a million exotic “superfoods” into your diet if you want to be healthy, Roberts says.

Consider this permission to be monogamous when it comes to your favorite healthy meals.

Read next: You Asked: What’s the Healthiest Sweetener?

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TIME Aging

You Asked: Can Smiling A Lot Really Cause Wrinkles?

Illustration by Peter Oumanski for TIME

The answer will make you frown (another expression that creates age lines)

Whether you’re talking, scowling or smiling, a groove forms on your skin the moment you move one of your facial muscles. That groove is perpendicular to the movement of the underlying muscle, explains Dr. Anthony Rossi, a dermatologist at Memorial Sloan Kettering Cancer Center. “For example, forehead grooves are horizontal because our forehead muscle pulls up,” Rossi says.

When it comes to your smile, the largest of the lines that form are the “nasolabial folds”—those big parentheses of skin that arc downward from the sides of your nose to the corners of your mouth, explains Dr. Marc Glashofer, a New York-based dermatologist. Those folds appear every time you smile. And as you grow older, those happy-face grooves don’t fade away once you stop beaming, Glashofer says.

But don’t blame your smile. The real culprit is your skin’s diminishing elasticity.

Rossi calls the biological changes that hurt your skin’s rebound abilities “intrinsic aging.” These include breakdowns to the underlying structure of your skin due to factors like fat loss and muscle atrophy. Rossi says your genetic makeup also affects how your hide holds up to years of smiling. “We know different ethnicities age differently,” he says, adding that your skin’s natural melanin concentrations and oil production also play a role in how quickly your smile groves will start to leave their mark. Unfortunately, many of those variables are out of your hands.

But here’s one factor you can control: ultraviolet radiation exposure from sunlight. “This is actually the number-one cause of winkles,” Glashofer says. The more sun your skin soaks up, the more its connective tissue breaks down, leaving it less firm and less elastic.

For that reason, Glashofer and Rossi recommend the daily use of a sunscreen that guards against both UVA and UVB rays. Both dermatologists also advise keeping your skin well hydrated, which starts with drinking plenty of water. Rossi says H2O is a major component of your dermis—the layer of skin that houses many of the structural proteins that keep you looking youthful. He also suggests using a skin moisturizer, which helps your skin lock in water.

Retinol-based creams are also aces at fending off age lines, Rossi says. “They not only promote the formation of new skin cells, but they also increase collagen production, which improves the appearance of wrinkles and slows their formation,” he explains.

Of course, you could also try to limit your smiles. But you’d be forgoing the immune system-boosting, stress-lowering benefits of a good laugh. “I would never tell anyone to avoid smiling,” Glashofer says. “You are truly blessed to have an abundance of smiles in your life.”

Read next: You Asked: Does Laughing Have Real Health Benefits?

TIME Diet/Nutrition

You Asked: Are Cleanses Healthy?

Illustration by Peter Oumanski for TIME

Beware the detox deception

Skip the lemon water and extravagant juices. Peculiar potions and potables that claim to “detoxify” your body are just the latest reincarnations of snake oil.

“I always look for science to inform my recommendations,” says Dr. Joy Dubost, a dietitian, food scientist and spokesperson for the Academy of Nutrition and Dietetics. “But to date, there’s no solid science backing any of these cleansing or detox approaches for weight loss or health.”

Of course, the word “cleanse” has been applied to a huge range of diets, from those that replace one or two daily meals with fruit smoothies to the more extreme types that advocate drinking little more than spiced water for a week or longer. The extreme kind—those that could never permanently supplant a normal diet—don’t tend to have long-lasting effects.

Not only is the hard science on cleanse diets missing, but Dubost also says the premise underlying these drinks—that you can somehow flush your system of pollutants—doesn’t pass a basic sniff test. “Your body has built-in mechanisms for detoxification, including your liver, kidneys, and gastrointestinal system,” she says. “Swallowing some kind of solution isn’t going to further enable those organs, so the whole premise of detoxifying is inaccurate.”

“I’ve also never seen an explanation for what ‘cleanse’ or ‘detox’ diets are cleansing or detoxifying your body of,” Dubost adds. “I think the vagueness there may be part of the appeal.”

Put another way, if you’re eating a healthy diet packed with fruits, vegetables, whole grains and lean protein—the kind of sustainable diet that will help keep your weight down and lower your risk for many diseases—your body has no use for any radical detoxification measures. And if your diet is poor, pounding juice for a week isn’t going to do you any good.

“You’ll drop some water weight on these cleanses because you won’t be consuming very many calories,” Dubost says. “But that weight will come back when you start eating again.” The kind of severe calorie restriction associated with cleanse diets can also lead to muscle breakdown and feelings of extreme fatigue, as well as headaches, irritability, cramping and diarrhea.

But what about those people who say they just feel amazing after completing a cleanse? Dr. Fabrizio Benedetti, a professor of neurophysiology at University of Turin Medical School in Italy, has written books about the placebo effect. “Feelings, perceptions, and a sense of well-being are very much influenced by placebos,” he says.

Benedetti cites a recent milkshake study from Yale University. During the study, researchers gave people a milkshake and told them it was either a 620-calorie “indulgent” shake or a 140-calorie “sensible” shake. Although all the milkshakes were identical, hunger-producing hormone levels plummeted in the “indulgent” milkshake sippers, but remained elevated among the “sensible” shake group. In other words, mind outweighed milkshake when it came to people’s hunger.

“We see placebo effects in the world of health science all the time,” Dubost says. “The mind is powerful, and I think it plays a big role for people who feel like going to diet extremes will offer them more benefits.”

All that said, Dubost admits she can see one potential benefit to cleanse diets. “Some people like ‘flipping the switch,’ or doing something extreme to kick start a new eating plan,” she says. If you know your diet isn’t great and you want to make a change, doing something a little over the top to initiate a hard break or “reset” from your old ways could put you in the right mindset to stick with a healthier eating routine, she says.

Like using the start of the New Year as motivation to change your life, initiating a cleanse for a few days before adopting a healthier well-rounded diet could have some psychological benefit, Dubost says. But again, that cleanse won’t be doing your health any favors.

“It’s amazing what people put their bodies through for a quick fix,” Dubost says. “If they’d put that kind of energy into a less-restrictive, more-sustainable diet, they’d have a lot more long-term success.”

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TIME toxins

You Asked: Are Hot Tubs Dangerous?

Illustration by Peter Oumanski for TIME

You’ve heard the rumors. The reality is probably worse.

Most men know that submerging their nether-parts in hot water can mean bad news for baby-making. And of course, the question of a hot tub’s water-to-urine ratio is a constant concern. But usual suspects aside, some very scary health issues have been linked to hot tub use.

“We call it ‘hot tub lung,’” says Dr. Cecile Rose, an environmental and respiratory health expert at National Jewish Health, a medical center in Denver. Rose is describing a type of lung inflammation that she and other researchers have linked to hot tubs. A specific kind of bacteria found in public water systems—called Nontuberculous mycobacteria—ends up in the mist produced when you switch on a tub’s bubbles.

“When you turn on the jets, this bacteria becomes aerosolized, and you inhale it,” Rose explains. Once it reaches your lungs, the bacteria can cause symptoms like fever andshortness of breath. If you continue to use your tub, the inflammation persists and worsens, and can cause lasting fatigue, weight loss and other more serious side effects. “A lot of doctors don’t ask if a person with these symptoms has been using a hot tub, and people become very sick,” Rose says. “If you keep using your tub, taking antibiotics or steroids won’t do any good.”

Even if you never use the bubble jets, you may still be at risk for so-called hot tub lung. “The jets are a very efficient delivery system, but that doesn’t mean turning them off is safe,” Rose adds. And no, you can’t just crank up your water supply’s chlorine and bromine disinfectant levels. Too much of those can lead to respiratory issues too, Rose adds.

More bad news: Mycobacteria aren’t your only unwelcome bathing buddies. Another type of bacteria called Pseudomonas can cause eye, ear and skin irritations, Rose says. She also mentions a germ called Legionella that can lead to Legionnaire’s disease—a severe form of pneumonia. Like mycobacteria, Legionella gets into your system through mist or steam inhalation, according to the Centers for Disease Control and Prevention (CDC).

“People with compromised immune systems—older adults, those with diabetes or on chemotherapy drugs—are most at risk, and the mortality rates associated with Legionnaire’s are actually quite high,” Rose explains.

That’s not all. A study in the Journal of the American Medical Association found the virus that leads to genital herpes can survive for hours on the plastic seats you’ll find in some hot tubs.

Blame the hot water temperature for most of these health hazards. Just as you enjoy a toasty soak, bacteria and germs thrive in the cozy comforts of warm water, Rose says. A report on Legionella from the CDC says higher water temperatures make it more difficult to maintain the proper disinfectant levels required to kill off the microscopic creepy crawlies that can make you ill.

That doesn’t mean all hot tubs are sickness-spreading cesspools. If you own your own tub, and you’re rigorous about cleaning it frequently, changing the water and checking its disinfectant levels, you can probably breathe easy. (Literally.) But when it comes to public pools, you might be taking a risk every time you slide down into those invitingly frothy bubbles.

TIME Diet/Nutrition

You Asked: What’s the Healthiest Sweetener?

Illustration by Peter Oumanski for TIME

Why sweet and good-for-you might not go together

You’ve heard sugar is bad news. But what about all those low-cal or no-cal substitutes? And organic honey! That has to be healthier, right?

“Honey, table sugar—doesn’t matter. It’s all sucrose, and your body metabolizes it the same way,” says Dr. Robert Lustig, a pediatric endocrinologist at the University of California, San Francisco. Lustig is also board president of the Institute for Responsible Nutrition, and presenter of “Sugar: The Bitter Truth”—a much talked about YouTube lecture that lays out the perils of the sweet stuff.

Apart from its high calorie content, which contributes to weight gain and obesity, sugar messes with your body’s insulin responses, Lustig says. Heart disease, diabetes and fatty liver disease have all been linked to the types of insulin issues sugar provokes.

“Sugar also binds to proteins in your body and causes damage,” he says—the same kind that browns fruit left out on your kitchen countertop. “We’re all browning. That’s part of aging,” Lustig explains. “But sugar causes you to brown seven times faster.”

There’s more to say on the subject of sugar and your health, but the bottom line is that too much sugar is bad for you, and most Americans consume way more than they should. “Your liver can process roughly six to nine teaspoons a day without significant issue,” Lustig says. “The average American consumes 19.5 teaspoons a day.” And while honey may contain antioxidants or compounds that, on their own, may offer some benefits, “The sucrose in honey is still sucrose,” Lustig adds.

Unfortunately, when it comes to artificial sweeteners and other sugar alternatives—from stevia to sucralose—the health picture grows foggier, not clearer. “Some people believe that, because some artificial sweeteners have no calories, they have no consequences,” says Dr. Yanina Pepino, research assistant professor in medicine at Washington University in St. Louis. “But we know that’s not true.”

Pepino’s research has demonstrated that sweet tastes—even those produced by non-caloric sweeteners—have the power to ramp up your body’s insulin responses. She says there’s also data suggesting non-caloric sweeteners contribute to the development of metabolic disorders and type 2 diabetes.

MORE: Should I Drink Diet Soda?

More new research has hinted that artificial sweeteners may mess with your gut’s microbes, the tiny organisms that live in your digestive system and help manage the ways your body breaks down and processes the stuff you eat. Like opening Pandora’s box, Pepino says any changes to the gut’s microbiota may lead to widespread negative health consequences.

“When it comes to sugar substitutes, we just don’t know enough,” she says—a sentiment Lustig repeats over and over again. And not knowing makes choosing between sugar and sugar alternatives a thorny proposition.

While some new sweeteners may claim to be healthier than others, the fact is they’re simply newer, so there’s not as much known about them, Lustig says.

In the end, both he and Pepino agree there’s only one right answer if you’re watching out for your health: Limit the amount of sweet stuff in your diet.

“I know people won’t like that answer, but that’s the only one I can give,” Pepino says. “There’s just no way to say one is better than another without a lot more data.”

TIME Research

You Asked: What’s the Best Way to Whiten My Teeth?

Illustration by Peter Oumanski for TIME

Pearly whites are just a dentist’s visit away, but they’ll cost you

Like a shiny new watch or a sparkling personality, white teeth are an ornamentation. Both men and women are attracted to a bright white smile, concludes a study in the journal PLOS One. Additional research has shown job applicants with white teeth are more likely to be hired than yellow-toothed applicants.

From whitening toothpastes and over-the-counter strips to dental office procedures, all tooth-whitening measures employ hydrogen peroxide to clean away stains. “The only differences are the concentrations of hydrogen peroxide employed and how they’re held against your teeth,” explains Dr. Matt Messina, an American Dental Association spokesperson who practices dentistry in Cleveland.

Of course, cost is also a factor. Starting with the least-potent (but least-expensive) whitener, Messina says toothpastes contain 1% to 1.5% concentrations of hydrogen peroxide. “That’s adequate to clean surface stains,” he says, “but it won’t penetrate your tooth enamel.” The enamel tends to hold the deepest, hardest-to-remove blemishes—that patina of black coffee or red wine that gradually accumulates on your smile like vehicle pollution on the sides of old brick buildings.

So if your teeth are seriously stained, a whitening toothpaste alone won’t get the job done—no matter how hard you brush. (In fact, brushing forcefully can damage your gums and is never advisable, Messina warns.)

Over-the-counter gels or strips are the next level up on the hydrogen-peroxide/price spectrum. “They’re usually in the 6% to 10% range, ” Messina says. At these concentrations, the hydrogen peroxide can penetrate microscopic holes and fissures in your enamel to bubble away stains.

While over-the-counter options can be very effective, Messina says the key is to apply them evenly and keep them on as long as directed. “I usually recommend the strips over the gels because they stay in place,” he explains. If the strips or gel are applied incorrectly, your teeth could look unevenly white. Gum irritation is also possible, he says.

But remember this important caveat: whitening agents do not work on caps, crowns or fillings. If you’ve had some dental work done, you should speak with your dentist before you whiten your teeth to be sure the results will look uniform, Messina says.

Another step up in both cost and potency is dentist supplied “tray-and-gel systems,” which contain hydrogen peroxide in the 10% to 15% range and can cost several hundred dollars. After custom fitting your mouth with a mold, your dentist supplies a take home tray and whitening gel for you to use at home. “The custom tray ensures the gel is evenly applied, and it can produce some pretty impressive results,” Messina says.

The final and most expensive option is settling into your dentist’s chair for a series of 10- to 15-minute whitening treatments. With hydrogen peroxide concentrations as high as 35%, these treatments can make your smile a dozen shades brighter, Messina says. They can also run you more than $1,000. “Whitening is a strictly cosmetic procedure, so it’s almost never covered by insurance,” Messina says.

So how white should you go? That’s really a personal preference thing, Messina says. While some people want their teeth as white as possible, the same PLOS One study mentioned above found that people with “natural” looking teeth scored just as highly in terms of attractiveness when compared to people with ultra-bright white smiles.

It’s also possible to over-whiten your teeth, Messina says. “If you whiten excessively, the tooth enamel can actually become translucent, which can make the teeth look blue or gray.” That’s not harmful in the long-term, but blue teeth isn’t a hot look.

While über-white teeth may not be any healthier than stained chompers, Messina says he thinks there are dental health benefits associated with a whiter smile. “I’ve found people who’ve had their teeth whitened are better at brushing and flossing,” he says. “When you’re proud of something, you take better care it.”

Read next: You Asked: Is Sleeping In a Cold Room Better For You?

TIME Research

You Asked: What Is My Poo Telling Me?

you-asked-poop
Illustration by Peter Oumanski for TIME

Your excrement is illuminating

Some say you are what you eat. But really, you are what you poop. “Not only does stool tell you about the health of your diet, but it shows you how your body’s digestive system is handling the foods you eat,” says Dr. Anish Sheth, a Princeton-based gastroenterologist and author of What’s Your Poo Telling You?

From hemorrhoids to cancer, diseases grave and small often show up first in your feces, Sheth says. And in recent years, health experts have learned your excrement also contains a wealth of information about your microbiome, the world of microscopic organisms that live and support your body’s many internal systems.

Put simply, your poop is a window to your health—even if you don’t consider the view all that appealing.

The first thing to consider when assessing your stool (a practice Dr. Sheth heartily advocates) is consistency, both in terms of physical attributes and regularity. “The ideal stool,” Dr. Sheth says, “has been described as a single soft piece.” You’re looking for something log-ish but not too firm, he continues. Imagine dispensing soft serve ice cream into your toilet, and you’ll have the general, somewhat less delicious idea.

This type of stool indicates you’re getting plenty of water and fiber in your diet. An absence of either can produce firmer, broken-up, difficult-to-expel feces or constipation, Sheth says. How hard you have to push is also important, he adds. Ideally, you should “evacuate” your waste with almost zero effort and feel as though you’ve fully emptied yourself.

Of course, everyone has the occasional bout of diarrhea or too-firm poo. But Sheth says neither should worry you much if it happens just once or twice before you’re back to normal. If a week passes without you passing healthy-looking stool, you should speak with a doctor. Even if you’re taking a number-two every day, hard or broken-apart poop is a sign that your diet is probably too low in fiber or water, which can lead to all sorts of gastrointestinal (GI) tract issues, Sheth says.

The color of your feces is also important. If it appears black or tarry, that may be evidence of blood. “The darker the stool, the higher up in your GI tract the blood is likely coming from,” Sheth says. He explains that blood emanating from ulcers or stomach problems will darken as it passes through your digestive system.

If you see maroon or dark red hues or streaks in your poop, that could mean inflammation, colitis, or certain intestinal cancers, Sheth explains. Bright red blood often indicates hemorrhoids or problems localized very near your anus.

Even the buoyancy of your bowel movements can reveal concerns. If your poop usually floats, that may signal an issue with your body’s ability to absorb fat, which in turn might mean your pancreas is having problems, Sheth says. Some particularly bad odors could also be red flags for health issues, although you probably wouldn’t know them if you smelled them. “Some doctors can identify certain GI diseases just by the distinct smell, although people who don’t diagnose them all the time wouldn’t be able to,” Sheth explains.

To keep your poop and your health in top form, Sheth recommends a diet than includes, again, plenty of fiber. “The average American gets about nine grams of fiber a day, when you need 25,” he says. He recommends lots of whole grains, fruits, vegetables, legumes and seeds like flax or chia. “Throw those in a daily smoothie,” he suggests. “And look before you flush!”

TIME

You Asked: Should I Go Paleo?

you-asked-paleo-diet-healthy
Illustration by Peter Oumanski for TIME

It’s more than a diet; it’s a way of life. Just ask a Paleo person.

The Paleo premise seems tantalizingly sensical: For hundreds of thousands of years, human beings ate and lived in ways that bear little resemblance to our modern modes of existence. It stands to reason that our bodies and minds haven’t had time to adapt, and that the unhappy consequences are stress, obesity, disease and a general feeling that, well, our primitive ways were probably preferable.

The solution, according to Paleo proponents, is a return to our roots. From aligning your sleep schedule with the rise and fall of the sun to exercising like your ancient ancestors—barefoot running, climbing, lifting heavy stuff—there are countless ways to channel your Paleolithic predecessors. And for most people, “going Paleo” starts in the kitchen.

Eating a Paleo diet involves consuming lots of lean meat, as well as eggs, fruits, some nuts, seeds and vegetables—basically, the kinds of foods humans were forced to subsist on for most of history. Dairy, grains, beans and all other foodstuffs unavailable in cave-dwelling days are verboten. So are foods with added hormones and artificial additives like processed sugars.

MORE: What’s Right and Wrong About Eating Like a Caveman

Proponents of the Paleo diet claim miraculous gains in energy, mental acuity, physical strength and general health. But naysayers point out the diet is expensive, difficult and probably not sustainable. (There are 7 billion people on Earth, and there’s only so much meat to go around.)

But what does the research show? Several studies have compared Paleo-style diets to the average American diet and found, unsurprisingly, that Paleo pounds our standard fare. Among the Paleo crowd, weight fell off faster, body composition improved and both blood pressure and blood sugar scores tacked toward healthier numbers, found one paper from the University of California San Francisco.

Another long-term study from Sweden saw similar health gains after comparing a meat-centric Paleo plan to a carb-heavy Nordic diet. In particular, triglycerides—a type of blood fat that raises your risk for heart disease—plummeted among the Paleo dieters, the Swedish study shows.

MORE: Can the Paleo Diet Help You Lose Weight?

But not so fast. “I do not believe there is anything magical about the Paleolithic diet,” says Caroline Mellberg, a doctoral researcher at Sweden’s Umeå University and coauthor of the Swedish study, in addition to several others that have looked into the viability of a Paleo-style diet. While she doesn’t dispute the diet’s benefits, she says her team’s findings aren’t surprising when you consider all the foods you have to ditch when you stick to a Paleo-inspired menu.

“Most unhealthy food items are excluded, and no empty calories are allowed,” she explains. Take out the crap from any diet, and she says you’d likely see many or all of the same health benefits.

MORE: How To Be A Modern-Day Caveman

Other nutrition experts say there just aren’t any research-backed reasons to drop dairy, legumes and grains, and that doing so might have unintended health consequences. “These foods provide many nutrients that have been shown over and over again to be beneficial for optimal health,” says Stephanie Maxson, senior clinical dietitian at the University of Texas MD Anderson Cancer Center.

Maxson is quick to add that she thinks Paleo diets can be healthy. Her point—and one that many others have also argued—is that the extremes Paleo diets prescribe are unnecessary. “Dieting is tough,” Maxson says. And when it comes to a meal plan that restricts you to a slim cluster of food groups, your chances of staying with it are just as small, she says.

If you’re in the market for a healthy diet, you might want to consider Paleo for its impressive health benefits—but only if you’re also ready to take a caveman club to most of your current kitchen, too.

Read Next: Are All Calories Created Equal?

TIME

You Asked: Is Sleeping In a Cold Room Better For You?

Illustration by Peter Oumanski for TIME

Here's the sweetest spot on the thermostat

Ask any insomniac about the perils of a hot pillow: When you’re trying to sleep, your brain loves the cold. Wearing a cooling cap helped insomniacs snooze almost as well as people without sleep problems, found a study from the University of Pittsburgh School of Medicine, and there’s also some evidence that yawning helps your brain offload heat before bedtime.

In fact, there’s lots of evidence for the cooler camp. A drop in your core temperature triggers your body’s “let’s hit the sack” systems, shows research from the Center for Chronobiology in Switzerland (and a lot of other places.) Some new research from the National Institutes of Health also suggests that sleeping in a cool room could have some calorie-burning health benefits. Healthy men who spent a month sleeping in a cool (but not cold) 66-degree room increased their stores of metabolically active brown fat, says Dr. Francesco Celi, chair of Virginia Commonwealth University’s division of endocrinology and metabolism. “Brown fat” may not sound very desirable, but it actually helps your body burn calories and dispose of excess blood sugar, he explains.

“We found that even a small reduction in bedroom temperature affects metabolism,” Celi says.

So if you want a healthy night’s sleep, crank down the thermostat, right? Unfortunately, it may not be that simple—when it comes to all of your below-the-neck parts, things aren’t so straightforward.

In Celi’s brown fat experiment, the men slept under thin sheets. What if you’re the type who likes a cozy down comforter? “Sorry, that won’t work,” Celi says, adding that some evidence points to shivering as the mechanism that brings on the increase in brown fat his team observed. His experiment didn’t keep tabs on sleep quality. So while the cold may be good for your metabolism and brown fat stores, you may be paying for those benefits with a night of fitful sleep.

That possibility is supported by research from Dr. Eus van Someren and colleagues at the Netherlands Institute for Neuroscience. While a dip in core temperature before bedtime flips on your brain and body’s “time for bed” switches and helps you fall asleep, Someren’s research shows that keeping your skin temperature “perfectly comfortable” is important when it comes to maintaining deep, restful slumber.

Your level of “perfect comfort” is quite individual. But if you’re cold enough to be shivering, you’re not sleeping deeply, Someren says. His research shows that older adults in particular may benefit from warmer skin temperatures during sleep. In fact, both his work and more research from France suggest skin temps in the range of 90 degrees (!) may be optimal.

If that sounds nuts to you, consider the fact that thin pajamas, plus a sheet and blanket, could crank up your skin temperature to that 90-degree range—even if your room of slumber is only 65 degrees, Someren says. On the other hand, if your bedroom is too chilly or your blankets aren’t thick enough, blood vessels in your skin can narrow, locking in heat and upping your core temperature to a point that your sleep is disturbed, he explains.

Add in a sleeping partner, and things get even more complex; while you may yearn for a heavy down comforter, your spouse might prefer a thin sheet. “Temperature regulation is a tricky thing,” Someren says.

That’s a lot of bedroom science, but here’s the bottom line: keeping your head nice and cool is conducive to good sleep. To achieve that, set your thermostat somewhere around 65 degrees, research suggests. And layer up until you feel the Sandman creep closer.

TIME Mental Health/Psychology

You Asked: Does Laughing Have Real Health Benefits?

Illustration by Peter Oumanski for TIME

Your body could use a belly laugh

It may not be the best medicine. But laughter’s great for you, and it may even compare to a proper diet and exercise when it comes to keeping you healthy and disease free.

That’s according to Dr. Lee Berk, an associate professor at Loma Linda University in California who has spent nearly three decades studying the ways the aftershocks of a good laugh ripple through your brain and body.

Berk says your mind, hormone system and immune system are constantly communicating with one another in ways that impact everything from your mood to your ability to fend off sickness and disease. Take grief: “Grief induces stress hormones, which suppress your immune function, which can lead to sickness,” he says. Hardly a week goes by without new research tying stress to another major ailment.

Why mention stress? “Because laughter appears to cause all the reciprocal, or opposite, effects of stress,” Berk explains. He says laughter shuts down the release of stress hormones like cortisol. It also triggers the production of feel-good neurochemicals like dopamine, which have all kinds of calming, anti-anxiety benefits. Think of laughter as the yin to stress’s yang.

Thanks largely to these stress-quashing powers, laughter has been linked to health benefits ranging from lower levels of inflammation to improved blood flow, Berk says. Some research from Western Kentucky University has also tied a good chuckle to greater numbers and activity of “killer cells,” which your immune system deploys to attack disease. “Many of these same things also happen when you sleep right, eat right, and exercise,” Berk says, which is why he lumps laughter in with more traditional healthy lifestyle activities.

Berk has even shown that laughter causes a change in the way your brain’s many neurons communicate with one another. Specifically, laughter seems to induce “gamma” frequencies—the type of brain waves observed among experienced meditators. These gamma waves improve the “synchronization” of your neuronal activity, which bolsters recall and memory, Berk says.

How does laughter accomplish all this? That’s where things get murky, says Dr. Robert Provine, a neuroscientist at the University of Maryland, Baltimore County and author of Curious Behavior: Yawning, Laughing, Hiccupping, and Beyond.

Provine calls himself a “reserved optimist” when it comes to laughter’s health-bolstering properties. “One of the challenges of studying laughter is that there are so many things that trigger it,” Provine explains. For example, you’re 30 times more likely to laugh around other people than when you are by yourself, he says. Social relationships and companionship have been tied to numerous health benefits. And so the social component of laughter may play a big part in its healthful attributes, Provine adds.

Here’s why that matters: If you’re going to tell people they should laugh to improve their health, there may be a big difference between guffawing on your own without provocation, watching a funny YouTube clip or meeting up with friends who make you laugh, Provine says.

“That doesn’t mean the benefits aren’t real,” he adds. “But it may not be accurate to credit laughter alone with all these superpowers.”

But even for researchers like Provine who aren’t ready—at least not yet—to coronate laughter as a panacea, he doesn’t dispute the benefits associated with a hearty har har. He only questions science’s current understanding of the underlying mechanisms.

“When we laugh, we’re in a happy place,” he says. “That’s always a good thing.”

Read next: Is It Good Or Bad To Take A Nap?

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