TIME Diet/Nutrition

You Asked: Why Can’t I Eat Raw Meat?

Illustration by Peter Oumanski for TIME

Well, you could. But you’d be rolling the dice.

Sushi restaurants are nearly as rampant as Starbucks stores. So why is raw fish okay to consume, while raw beef, pork and other land animals are typically not on the menu?

For one thing, the parasites and bacteria that set up shop in raw animal meat are different and more dangerous than the ones you’d find in raw fish, says Dr. Robert Tauxe, deputy director of the Division of Foodborne, Waterborne and Environmental Diseases within the Centers for Disease Control and Prevention (CDC).

From salmonella and parasitic E. coli to worms, flukes, and the virus hepatitis E, Tauxe says the creepy crawlies that may inhabit raw meat tend to be more harmful to humans than the microorganisms you’d find in raw fish. “Perhaps it’s because our bodies are more closely related to land animals than to those of fish,” he explains.

The way animals are slaughtered and packaged also has a lot to do with their health risks, says Dr. Eugene Muller, a microbiologist at Framingham State University in Massachusetts. “Parasites and bacteria tend to come from an animal’s gut, not its muscle,” he says. If your butcher nicks open an animal’s intestines, any harmful microorganisms released could contaminate all the meat the butcher is preparing.

Packaged ground beef is particularly likely to house sickness-causing bacteria or parasites, says Dr. Lee-Ann Jaykus, professor of food science at North Carolina State University. That’s because a single package of ground beef could contain meat from dozens of cows, Jaykus says. “One contaminated animal could corrupt dozens of batches,” she explains. For that reason, she advises never eating hamburger that’s red or rare in the center.

Both Muller and Jaykus say whole cuts of beef are less risky because they come from a single animal. “Anything harmful lives on the surface of the meat, not inside the muscle,” Muller says. “So if you like your steak very rare, just searing the outside will likely kill anything harmful.”

Jaykus agrees, but says you have to watch out for something called “mechanically tenderized meat,” which involves puncturing the beef with small needles or blades to make it more tender. She says many restaurants and grocery stores sell meat that’s undergone this process because it improves the texture of cheaper cuts like sirloin or round. “This process can force contaminants into the muscle tissue where searing the outside won’t kill them,” she says. “You don’t see this at high-end steakhouses, but it’s an issue with steaks purchased for home cooking and in some restaurants.”

Most of these concerns and caveats also apply to lamb, pigs, chickens and other land animals—though Muller says pigs and chickens tend to carry some harmful microorganisms you don’t find in cows or sheep. “But I don’t think many people really want to consume raw pig or raw chicken,” he adds.

Fish is a different story. Setting aside the differences between fish and mammals when it comes to the number, type, and frequency of potentially dangerous organisms they may harbor, fish tends not to be ground or mixed. That lowers the likelihood of a single disease-carrying salmon or tuna contaminating others, Jaykus says.

Also, any raw fish you consume at a sushi restaurant are caught in colder waters and frozen before you eat them. “This kills the encysted worms and other parasites,” Tauxe says. Unfortunately, freezing doesn’t kill parasitic E. coli and many of the harmful microorganisms you’d find in meat, Muller says.

With raw fish, oysters and other uncooked seafood, you’re taking a risk, Muller says—though not nearly as big a risk as eating that bloody tenderloin or tartare.

Read next: The 50 Healthiest Foods of All Time (With Recipes)

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TIME Aging

The World’s Oldest Person Is Totally Chill About Turning 117

Misao Okawa, the world's oldest Japanese woman poses for a photo with her great-grandchild Himaki and grandchild Takako Okawa on her 117th birthday celebration at Kurenai Nursing Home on March 4, 2015 in Osaka, Japan.
Buddhika Weerasinghe—Getty Images Misao Okawa, the world's oldest Japanese woman poses for a photo with her great-grandchild Himaki and grandchild Takako Okawa on her 117th birthday celebration at Kurenai Nursing Home on March 4, 2015 in Osaka, Japan.

Misao Okawa was born on March 5, 1898

The world’s oldest person has lived through two World Wars and the invention of the first airplane, but it doesn’t seem like a long time to Misao Okawa.

“It seemed rather short,” Okawa said on Wednesday, the day before her 117th birthday, the Associated Press reports. When Okawa was asked about the secret to her longevity, she said nonchalantly, “I wonder about that too.”

Okawa was born in Osaka on March 5, 1898 and was recognized as the world’s oldest person by Guinness World Records in 2013. She has slowed down in recent months but still eats well and is healthy, according to her Osaka nursing home.

She married her husband, Yukio, in 1919, and has three children, four grandchildren and six great-grandchildren. Her husband died in 1931.

Japan has more than 58,000 centenarians, more than any other country in the world.

Read next: 13 Secrets to Living Longer From the World’s Oldest People

[AP]

Read next: Europe’s Oldest Woman Says Being Single Helped Her Live to 115

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TIME medicine

4 Things to Know About Zinc And Your Cold

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Zinc can help treating a cold, but it doesn't prevent

Zinc is often touted as a way to fight the common cold. But while research suggests it does work, there are some caveats. Tod Cooperman, MD, president of the independent testing group ConsumerLab.com, provides the scoop:

Zinc helps treat—not prevent—a cold

Popping zinc within 24 hours of the start of symptoms helps shorten your sniffle, according to a 2013 Cochrane review. The authors say significant effects were seen at doses of at least 75 mg (the equivalent of three or four lozenges) per day, taken as long as your cold lasts. How does it work? The theory, according to the Mayo Clinic, is that zinc may keep cold viruses from multiplying and taking up residence in your nose and throat. But don’t bother taking it just to take it; there’s no evidence it’ll actually prevent a cold.

Read more: Best and Worst Foods to Eat When You’re Sick

Pick a lozenge, not a spray

Back in 2009, the U.S. Food & Drug Administration warned against using zinc gel sprays and nasal swabs after receiving more than 130 reports of people losing their sense of smell after using these products. (The manufacturer pulled the products from store shelves, though they claim no link has been established.)

Though you can no longer buy zinc nasal spray, it’s still available as a throat spray, which might be problematic, according to Dr. Cooperman. “If you spray it into your throat it can still go up your nose,” Dr. Cooperman says.

The best way to go is still the good old lozenge. Just make sure you suck—not crunch—it: “It needs to dissolve slowly to be effective so it can coat your throat,” explains Dr. Cooperman.

Read more: Best and Worst Exercises to Do When You Have a Cold

Not all lozenges are created equal

In order for a lozenge to provide enough zinc to be effective, it needs to contain between 13 and 23 milligrams, Dr. Cooperman says. Yet only two of the four lozenges Consumer Lab tested—Cold-Eeze Homeopathic Cold Remedy and Nature’s Way Zinc—provided enough. (There are other brands of zinc they didn’t test.)

Read more: 14 Reasons You’re Always Tired

You can’t pop ’em like candy

The safe upper limit for zinc in adults is 40 milligrams per day, as determined by the Institute of Medicine. While it’s okay to exceed that 40mg limit for three to five days (or roughly the length of a cold), you still don’t want to down the lozenges like crazy. At most, only take one every three hours if you’re sick, and limit yourself to one a day if you’re healthy: “Too much zinc can actually depress your immune system,” explains Dr. Cooperman.

Read more: How to Stop a Cold In Its Tracks

This article originally appeared on Health.com.

TIME Research

New Hormone Discovered That Curbs Weight Gain, Diabetes Just Like Exercise

“This represents a major advance in the identification of new treatments for age-related diseases such as diabetes”

Scientists have discovered a new hormone that mimics the health benefits of exercise by normalizing the metabolism and slowing the weight gain caused by fatty diets.

Appearing in the scientific journal Cell Metabolism on Tuesday, the study found the newly discovered MOTS-c hormone increases insulin sensitivity, allowing the body to more effectively process glucose sugars, according to a press release from the University of Southern California.

Insulin is a hormone that is used to move glucose sugars from food into the blood stream; resistance occurs when levels are high for a long period of time — commonly from a poor diet — which increases the body’s tolerance to the hormone and can lead to type 2 diabetes.

The new MOTS-c hormone targets muscle tissue and reverses age-dependent and diet-related insulin resistance.

“This represents a major advance in the identification of new treatments for age-related diseases such as diabetes,” said Dr. Pinchas Cohen, senior author of the study.

Researchers injected the new hormone into lab mice eating high-fat foods that usually lead them to become obese. The injection suppressed the weight gain and also reversed the insulin resistance caused by their diet.

While tests were only administered on mice, the necessary mechanisms are present in all mammals, humans included.

Read next: 5 Non-Diet Factors That Can Affect Your Weight

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TIME Addiction

Heroin-Related Deaths Have Quadrupled in America

New federal data reports bad news for America's heroin problem

Heroin-related deaths quadrupled in the U.S. within just three years, according to new federal data.

The new report from the National Center for Health Statistics (NCHS) shows that from 2010 to 2013, drug-poisoning deaths involving heroin increased fourfold, from 0.7 deaths per 100,000 people to 2.7 deaths per 100,000 people. The rate was about four times higher among men than among women in 2013.

Heroin-related drug-poisoning deaths have increased in all age groups, races and ethnic groups, the data show. Every region in the U.S. also experienced an increase, and the Midwest experienced the biggest jump.

One reason for the spike is America’s growing painkiller problem. The NCHS released another report last month showing that significantly more people over age 20 are using opioids. The number of people who used a painkiller stronger than morphine increased from 17% to 37% from the early 2000s to about a decade later.

CDC/NCHS, National Vital Statistics System, Mortality.

People who are hooked on painkillers may make the switch to heroin since it’s cheaper and doesn’t need a prescription, according to Dr. Andrew Kolodny, the chief medical officer of the Phoenix House, a national nonprofit drug and alcohol-rehabilitation organization. Both drugs come from the opium poppy and therefore offer a similar high. “We are seeing heroin deaths sky rocketing because we have an epidemic of people addicted to opioids. There are new markets like suburbs where heroin didn’t used to exist,” says Kolodny. (He was not involved in the research.)

MORE Why You Don’t Know About the Heroin Vaccine

Prior data from the Centers for Disease Control and Prevention show that painkillers are a growing problem. In 2014, the CDC reported that physicians wrote 259 million painkiller prescription in a single year — the equivalent of a bottle of pills per American — and almost 50 Americans die every day from a prescription-painkiller overdose. The agency recommends that states run prescription-drug prescribing databases to track overprescribing and consider policies that reduce risky prescribing practices.

As states and the White House struggle to tackle opioid addiction, some experts are skeptical about whether such efforts are enough to solve the problem. “We are dealing with the worst drug epidemic in our history,” says Kolodny. “There’s no evidence it’s plateauing.”

Read next: Ohio Steps Up Fight Against Heroin Deaths

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TIME Exercise/Fitness

How to Get Kids to Exercise More

Getting children to encourage their peers to exercise may be the best way to inspire kids to stay more active, according to new research presented at a meeting of the American Heart Association. The finding introduces a wrinkle in current recommendations that parents play a key role in encouraging children to exercise.

“For a child to be active, they have to really enjoy the activity,” says Stephen Daniels, a professor at the University of Colorado School of Medicine. “We have to find activities they like and settings that promote activity, so this really helps us understand how to do that and emphasizes the fact that having friends involved can be a big motivator.”

The study, which relied on interviews of more than 100 children of various ages, found that kids enjoyed working out more when they did it with friends. Children also got over typical excuses, like not having the right equipment or not being good at, when accompanied by their friends. Though children clearly like exercising with friends, less than half of kids actually do it, according to the study.

Of course, encouragement to exercise by peers only worked if the peers were, in fact, encouraging. If you’re not picking the right peer group, it could backfire in a way,” Daniels says. “I think finding kids and friends who will be non-judgmental who really are there for the fun of the activity and not there to criticize, etc. is an important part of this.”

Overall, the study found that feeling self-conscious, low enjoyment, health concerns, a lack of self-discipline and a lack of energy were the most common impediments to children’s exercise.

TIME public health

You Get the Flu Way Less Than You Think

Instead of twice each winter, you might actually get the flu twice every 10 years

If it seems like you’re constantly getting the flu, you might be blaming the wrong bugs. A new study published in PLOS Biology suggests that after age 30, people generally only get the flu about twice a decade.

Researchers from Imperial College London looked at a single blood sample from 151 people in southern China and examined their flu antibody levels to the current strain of flu, as well as several historical strains prevalent over the last 40 years. They then estimated how many times people were infected and what happened to their antibodies at different points in their lives.

Young people got the flu more often, about once every other year. That might be because young people socialize more, the authors write. But once they hit age 30, rates flattened out; adults got the flu about twice every 10 years.

“A lot of people say once or twice a year they’ve got the flu, and that’s very unlikely to be true,” says Dr. Steven Riley, senior author of the study and reader at the Medical Research Council Centre for Outbreak Analysis and Modelling at Imperial College London. Sometimes flu can be mild—you may not even know you have it, but your sky-high antibody levels indicate otherwise, Riley says.

Though Riley is cautious to overinterpret the findings, the data was able to estimate infection rates across many years, which may one day prove valuable in vaccine applications, he says. “You could certainly think that down the road, this type of analysis would lead to a more sophisticated vaccine protocol—possibly the frequency with which you vaccinate and the doses with which you vaccinate could be optimized,” he says. “We can’t say what those optimal regimes would be based on this paper, but these nicely reproducible patterns suggest that that’s a good avenue to look for in the future.”

TIME Diet/Nutrition

The Weird Benefit of Eating Salty Food

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Too much salt can lead to heart disease, but there may be a healthy side to salt that hasn’t been appreciated — until now

If you’re an average American, chances are that you’re eating too much salt. But the latest research — which, the scientists stress, is still in its early stages — hints that there may be some benefits to salt that have gone unnoticed. Salt, it seems, may be an ancient way for the body to protect itself against bacteria.

Reporting in the journal Cell Metabolism, Jonathan Jantsch, from the University of Regensburg in Germany, says that salt may be an effective way to ward off microbes. In a series of studies using both mice and human cells, he and his colleagues found that levels of sodium go up around an infection site, and that without salt, bacteria tend to flourish and grow better.

MORE Older Adults May Be OK to Eat More Salt Than Previously Thought

The discovery came about by accident, after Jens Titze, the study’s senior author, noticed that mice who had been bitten by their cage mates showed higher levels of sodium in their skin than those who were wound-free. Jantsch decided to find out whether the salt had something to do with the infection-fighting functions of the immune system.

He and his team conducted a series of experiments in which they subjected mouse and human cells to high levels of sodium chloride, and watched the immune cells activate. They also fed mice diets that were low and high in sodium, and then infected them with Leishmania major. The mice fed the higher amounts of sodium showed stronger immune responses to the wounds, and cleared their infections faster than the mice eating less salt. In fact, Jantsch speculates that certain skin cells may transport sodium preferentially to sites where bacterial populations are high in order to create another barrier preventing the microbes from entering deeper into the body.

That opens the possibility that salt may be an unrecognized contributor to the immune system, and possibly a remnant from the days before antibiotics, when mammals, including humans, needed some allies in the fight against microbes. After all, salt has been used for centuries to preserve food from spoiling in bacteria’s presence, so it makes sense that evolutionarily, sodium might have also been co-opted by the body in a similar way. “I really think salt is an unappreciated factor of immunity,” says Jantsch.

MORE New Dietary Guidelines: Cut Salt and Sugar, Eat More Fish

If that’s the case, then it may be possible to take advantage of salt-based dressings, for instance, to improve wound healing. Burn patients may benefit the most, since their skin, the first line of defense against microbes, is compromised. And for those with hyperactive immune responses, dialing down the concentration of sodium at specific areas might also be helpful. “We are interested in how this works, because it can have broad applications,” says Jantsch. “We can possibly target and boost sodium in situations where we need more salt if it’s deficient, and lower it in situations where there is salt overload and hypertension.” Already, some companies have produced wound dressings with enhanced sodium concentration as a way to help infections heal faster.

MORE Salt Doesn’t Cause High Blood Pressure? Here’s What a New Study Says

He stresses, however, that the results don’t mean high salt diets are now healthy — or advisable. His studies, even in mice, haven’t worked out exactly how salt in the diet affects the body’s ability to recruit the nutrient to fight infections. And to get the bacteria-fighting effect, the mice were fed a diet that was extremely high in sodium — 4%, compared to the average mouse chow which is only 0.2% to 0.3% sodium. “There is overwhelming data that tells you a high salt diet is detrimental to the heart,” he says. “We used one animal approach to look at the beneficial role of salt. So I would be hesitant to draw any conclusions for humans at this stage.” He and others are already setting up more experiments, however, to study how salt might become the next weapon in fighting infections.

MORE FDA Wants to Limit Your Salt Intake. Is That a Good Thing?

Read next: 11 Bad Habits That Bloat You

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TIME Diet/Nutrition

5 Non-Diet Factors That Can Affect Your Weight

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Weight control is influenced by more than your daily calorie intake

For years I’ve heard experts say, “Weight loss simply comes down to calories in versus calories out.” But throughout my years as a practitioner, that simple philosophy hasn’t rung true. I’ve seen clients break a weight loss plateau after increasing their calorie intake—swapping processed “diet” food for whole, nutrient-rich clean foods and changing up their meal balance and timing.

I’ve also found that stressed-out, sleep-deprived clients have a more difficult time losing weight, which has been backed by numerous studies. And now, research shows that a number of other lifestyle and environmental factors also play roles in influencing metabolism and weight control.

Here are five on my radar, and tips for combating them.

Artificial additives

Just-released animal research from Georgia State University found evidence that artificial preservatives used in many processed foods may be associated with metabolic problems, such as glucose intolerance and obesity. In rodents genetically prone to inflammatory gut diseases, the chemicals led to an increase in the severity and frequency of metabolic problems. Scientists believe the effects are due to changes in gut bacteria. When chemicals break down the mucus that lines and protects the gut, unhealthy bacteria come into contact with gut cells, which triggers inflammation, and as a result, changes in metabolism.

Combat it: This is preliminary research, but even more of a reason to read food labels and eat clean. When buying anything that comes in a box, bag, or jar, read the ingredient list first. My philosophy is that it should read like a recipe you could whip up in your own kitchen. For more info check out my previous post What Is Clean Eating?

Read more: 16 Ways to Lose Weight Fast

Shift work

Researchers from the University of Colorado at Boulder found that people who work the night shift burn fewer calories during a 24-hour period than those who work a normal schedule. The difference can lead to weight gain, even without an increase in calories. In other words, when you throw off your body’s circadian rhythm, your normal diet can suddenly become excessive due to a metabolic slowdown. This parallels research which found a relationship between body clock regulation, gut bacteria, and metabolism. When mice received gut bacteria from jet-lagged humans, they gained significant amounts of weight and had abnormally high blood sugar levels.

Combat it: If you work when most people are sleeping, or you travel through different time zones, seek out nutrient-rich foods that help boost satiety, increase metabolic rate, and regulate hunger, including fresh veggies and fruit, beans and lentils, nuts, ginger, hot peppers, and good old H2O. For more tips check out my previous post 9 Natural Appetite Suppressants That Actually Work.

Read more: Best Superfoods for Weight Loss

Weight criticism

University College London researchers found that over a four-year period, people who experienced weight discrimination or “fat shaming” gained weight, while those who did not shed pounds. Another study from Renison University College at the University of Waterloo found that over five months, women with loved ones who were critical of their weight put on even more pounds.

Combat it: You may not be able to control the type or amount of support you receive from others, but there are effective techniques for improving your personal mindset. For example, practicing mindfulness meditation has been shown to help reduce stress, lower hunger hormones, and prevent weight gain. In a study published in the Journal of Obesity, this practice led to a greater loss of belly fat, without following a calorie-counting diet. I teach it in my private practice and I devoted an entire chapter to meditation in my upcoming book, Slim Down Now($20, amazon.com). If you’re a newbie, check out UCLA’s online classes.

Read more: 11 Reasons Why You’re Not Losing Belly Fat

Environmental chemicals

It may seem odd for a nutrition professor to study flame retardants. But one such professional at the University of New Hampshire found that these substances—which are found in everything from furniture to carpet padding and electronics—trigger metabolic and liver problems that can lead to insulin resistance, a major cause of obesity. Compared to a control group, rats exposed to these chemicals experienced dramatic physiological changes. In just one month, levels of a key enzyme responsible for sugar and fat metabolism dropped by nearly 50% in the livers of rats exposed to flame retardants. According to the researcher, the average person has about 300 chemicals in his or her body that are man made, and we’re only beginning to understand the possible effects.

Combat it: You can’t eliminate your exposure to synthetic substances, but you can limit it. You can now find natural products in nearly every shopping category, including cosmetics, cleaning supplies, toys, and household goods. For help, check out resources and guides from organizations like the Environmental Working Group.

Read more: Get a Flat Belly in 4 Weeks

Genetics

It’s no surprise that we take after our parents when it comes to body type, but new research shows that the type of bacteria that live in our digestive systems are also influenced by genetics. That’s an important finding, because more and more research indicates that gut bacteria are strongly connected to weight control. Scientists at King’s College London found that identical twins had a similar abundance of specific types of gut bacteria, compared to non-identical twins. This indicates that genes strongly influence bacteria, since identical twins share 100% of their genes, while non-identical twins share about 50% of their genes. They also found that the presence of a specific type of bacteria was most influenced by genetics, and that type strongly correlated with leanness. In fact, transplanting this bacteria to the digestive systems of mice caused the animals to gain less weight than those that did not receive the bacteria.

Combat it: You can’t change your genetics, but there’s a great deal of research now about how you can transform your good gut bacteria. The top strategy: avoid artificial and processed foods, and load up on a variety of whole, plant-based foods, including vegetables and fruits, whole grains, beans and lentils, and fermented foods like kimchi and sauerkraut. For more about how to eat more plant-based foods, check out my previous post 5 Delicious Pasta Alternatives.

Cynthia Sass, MPH, RD, is Health’s contributing nutrition editor, and privately counsels clients in New York, Los Angeles, and long distance. Cynthia is currently the sports nutrition consultant to the New York Rangers NHL team and the Tampa Bay Rays MLB team, and is board certified as a specialist in sports dietetics.

This article originally appeared on Health.com.

Read next: 7 Reasons Why You’re Working Out and Still Not Losing Weight

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TIME Diet/Nutrition

4 Superfoods You Might Be Overeating

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You can have too much of a good thing, even when it may be the healthiest food of all

When it comes to diet, you can totally have too much of a good thing. Even the healthiest foods, in big quantities, may have side effects. And today, with our increased zeal for superfoods, the risk of overdosing on certain power eats has multiplied. Here are my top culprits—plus how to stay balanced.

Kale

For nutrients and antioxidants per calorie, few foods compare to kale. But our current obsession with this leafy green may be overkill: Kale’s appearance on U.S. restaurant menus jumped nearly 400 percent from 2009 to 2013. And the number of new kale products introduced globally more than tripled between 2007 and 2012, per Innova Market Insights.

Women I know are whipping up a green juice (many of which contain far more kale than they could eat in one sitting concentrated into 16 ounces) in the morning, having kale salad for lunch and snacking on kale chips at night. The potential side effect? Kidney stones. Kale contains oxalate, which can bind with calcium to form stones. While other foods (like spinach) are higher in oxalate, megadoses of kale could make it a problem for those susceptible to stones.

The best balance: Choose a kale-rich green juice or a big kale salad per day. On days you have whole kale, you can still do green juice; just make one with a low-oxalate ingredient like cucumber and a variety of other vegetables.

Read more: 13 Healthy Kale Recipes

Sushi

One of the simplest (and yummiest) ways to get the recommended twice-weekly servings of ocean fare is to hit the local sushi joint. But plenty of busy women overrely on it.

While sushi does offer lean protein and heart- and brain-protective omega-3s, mercury in fish (from pollution) is a real concern. And it can be easy to OD on it via sushi, per a recent study. Researchers at Rutgers University interviewed 1,289 men and women about their sushi intake and tested fish samples. Among the tuna, eel, salmon and crab, tuna had the highest levels of mercury. Researchers estimated that mercury exposure for people who ate seven sushi meals consisting mostly of tuna per month exceeded the EPA’s recommendations. The scary part: Symptoms of mercury overexposure (vision issues, tingling fingers and muscle weakness) may not show up for months, or even at all.

The best balance: A good sushi option is a brown rice California roll; it’s made with crabmeat, so it’s fine twice a week. It’s best to limit bigger fish like certain types of mackerel and tuna, which tend to have more mercury—particularly if you’re pregnant, planning to get pregnant or nursing.

Read more: 10 Fish You Should Avoid (and Why)

Fortified foods

If you shop for cereals, energy bars, orange juice and bottled water, you’ve probably seen labels bragging about added nutrients. Check those labels carefully, however. Some cereals boast 100 percent of the daily value (DV) for many vitamins and minerals. While fortification helps ensure that you’re not lacking in nutrients like vitamin D, ingesting a total day’s worth of zinc, iron, B vitamins and more from one product ups your likelihood of getting a surplus. This is especially true if you take supplements or have more than one fortified food a day. If you want a boost, buy brands fortified with no more than 50 percent of the DV for any nutrient.

Consistently going far above the daily allowance can push you toward your tolerable upper intake level (UL), the point at which good nutrients can become dangerous. One European study suggested that people who ate large amounts of dairy could exceed the UL for calcium when adding things like calcium-fortified orange juice and oatmeal. Passing the daily 2,500-milligram limit regularly can cause constipation and kidney problems. Too much zinc may reduce immune function and HDL (good) cholesterol levels.

The best balance: Skip products that pack 100 percent of your DV for any one nutrient. Consume plenty of whole foods instead.

Read more: The 20 Best Foods to Eat for Breakfast

Seaweed

Once only health food staples, chips, spice concoctions and salad mixes made of sea plants like nori and kombu are now in the grocery. You can also find this power green—which has been linked to heart health—in sushi rolls and seaweed salads. The problem? Seaweed is often super rich in iodine. Too much can lead to thyroid problems, which can cause weight fluctuations. In one study, a 39-year-old woman was diagnosed with hyperthyroidism after downing tea that contained kelp for four weeks.

The best balance: I generally recommend that clients get their kelp fix safely by stopping at one fresh seaweed salad (in addition to sushi) once a week. Steer clear of the teas, unless prescribed by a doc, and keep seaweed snacks to one serving a day. If you notice fatigue or weight changes, though, cut them out completely.

Read more: 19 Signs Your Thyroid Isn’t Working Right

Cynthia Sass, MPH, RD, is Health’s contributing nutrition editor, and privately counsels clients in New York, Los Angeles, and long distance. Cynthia is currently the sports nutrition consultant to the New York Rangers NHL team and the Tampa Bay Rays MLB team, and is board certified as a specialist in sports dietetics.

This article originally appeared on Health.com.

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