The 13 Biggest Nutrition and Food Myths Busted
Behind most food and nutrition myths, there's a kernel of truth. We separate the science from the silliness.
When I was a teenager, I steered clear of chocolate. Not because of the calories or even the fat (which was considered the ultimate evil back in the '70s). It was because I had read, somewhere, that chocolate caused acne-and the last thing I wanted was zits. Years later, I was relieved to learn that studies had unequivocally shown there was no connection between chocolate and skin problems, and that some types of chocolate, in fact, may even be good for you.
So it was jarring when I recently heard a mom urge her daughter to get a vanilla ice cream cone instead of a chocolate one, saying, "Chocolate gives you acne, you know."
Why do some nutrition myths die and others keep bouncing back, even in the face of what seems to be incontrovertible evidence? "Let's face it, myths and misinformation are much more seductive than the truth," says Keith-Thomas Ayoob, Ed.D., R.D., professor of pediatrics at Albert Einstein College of Medicine in New York. A balanced diet, enough sleep and regular exercise are usually the best course for fighting diseases and staying healthy, he notes, "and that just isn't as interesting to people."
In reality, the most persistent nutrition myths are those that contain at least a kernel of truth-and some "myths" help us get to real dietary wisdom that actually might help our health. Here's a cold, hard, science-based look at some of the most oft-repeated ones and what really is the truth behind them.
1. "Eggs are bad for your heart."
Eggs do contain a substantial amount of cholesterol in their yolks-about 211 milligrams (mg) per large egg. And yes, cholesterol is the fatty stuff in our blood that contributes to clogged arteries and heart attacks. But labeling eggs as "bad for your heart" is connecting the wrong dots, experts say. "Epidemiologic studies show that most healthy people can eat an egg a day without problems," says Penny Kris-Etherton, Ph.D., R.D., distinguished professor of nutrition at Penn State University.
How? For most of us the cholesterol we eat-in eggs or any other food-doesn't have a huge impact on raising our blood cholesterol; the body simply compensates by manufacturing less cholesterol itself. The chief heart-disease culprits are "saturated and trans fats, which have much greater impact on raising blood cholesterol," notes Kris-Etherton. Seen through that lens, eggs look more benign: a large egg contains 2 grams of saturated fat (10 percent of the Daily Value) and no trans fats.
But before you celebrate with a three-egg omelet, consider the American Heart Association's diet and lifestyle recommendations, which Kris-Etherton helped write: Limit your cholesterol intake to less than 300 mg daily-less than 200 mg if you have a history of heart problems or diabetes or are over 55 (women) or 45 (men). "If you do the math, that works out to less than an egg a day for this population-more like two eggs over the course of the week," she notes. "Eggs can fit in, as long as you make room for them in the rest of what you're eating."
2. "High-Fructose Corn Syrup (HFCS) is worse for you than sugar."
Though consumers who fill their shopping carts with products labeled "No HFCS" might feel otherwise, the idea that high-fructose corn syrup is any more harmful to your health than sugar is "one of those urban myths that sounds right but is basically wrong," according to the Center for Science in the Public Interest, a Washington, D.C.-based nutrition and health advocacy group.
High-fructose corn syrup was created to mimic sucrose (table sugar), so its composition is almost identical to sucrose's (55 percent fructose, 45 percent glucose; with sucrose the ratio is 50:50). Calorie-wise, it's a dead ringer for sucrose. And in studies that compare the effects of HFCS with other sweeteners, HFCS and sucrose have very similar effects on blood levels of insulin, glucose, triglycerides and satiety hormones. In short, it seems to be no worse-but also no better-than sucrose, or table sugar.
"The debate about HFCS and sucrose [table sugar] is taking the focus off the more important question," says Kimber Stanhope, Ph.D., R.D., a researcher at the University of California, Davis, who has studied the sweetener extensively. "What we should be asking is ‘What are the effects of all sugars (HFCS and sucrose) in the diet?'"
Epidemiologic studies show that consuming large amounts of added sweeteners-primarily in sodas and other sweetened drinks-is associated with greater risk of fatty liver disease, insulin resistance, heart disease and type 2 diabetes. And it's not just the extra calories they provide that may be hurting us; research by Stanhope and others suggests that fructose itself in added sugars may be hazardous to our health too. One problem is that our bodies weren't designed to handle a large amount of fructose at a time, she notes, because we wouldn't have come across it in our food supply. "If you look at what nature provided for humans to eat, we only had fructose in whole fruit, in amounts that are relatively dilute." Problems arose when we learned how to turn foods-which contain fiber, water and other nutrients-into pure sources of sugars (e.g., refining sugarcane into table sugar).
But the associations between sweetener consumption and disease don't implicate just HFCS, which despite its name contains only a little more fructose than sucrose does, Stanhope emphasizes. It's the sheer amount of the sweet stuff we consume that matters or, to put it another way, it's the dose that is the problem. Too much honey, agave syrup or dehydrated cane juice would likely cause the same health problems.
"The American Heart Association recently recommended that women consume no more than 100 calories a day in added sugars [6 teaspoons]; men, 150 calories [9 teaspoons]," Stanhope notes. Our current intake, however, hovers around 355 calories per day. "The U.S. population isn't anywhere close to [the AHA's] goal."
3. "Carbohydrates make you fat."
Contrary to the theories of the low-carb/no carb manifesto, Dr. Atkins' Diet Revolution, first published in 1972 (and the similar books that followed), there's nothing inherently fattening about carbohydrates, says Jean Harvey-Berino, Ph.D., R.D., chair of the department of nutrition and food sciences at the University of Vermont and co-author of The EatingWell Diet (Countryman, 2007). "It's eating too many calories, period, that makes you fat."
There's no question that loading up on sugary and refined-carbohydrate-rich foods, such as white bread, pasta and doughnuts, can raise your risk of developing health problems like heart disease and diabetes. But if you cut out so-called "good-carb" foods, such as whole grains, beans, fruits and vegetables, you're missing out on your body's main source of fuel as well as vital nutrients and fiber. What's more, for many people, a low-carb diet may be harder to stick with in the long run.
When a handful of major studies recently compared low-carb diets with low-fat diets and other approaches to losing weight, notes Harvey-Berino, they found that in the first few months, those following the low-carb diets tended to lose slightly more weight. "That's because low-carb diets are more restrictive," she explains. "Anything that limits your choices will help you lose weight initially." But after a year or as much as three years, weight-loss differences between the diets tend to even out. One recent report noted that although there was a greater weight loss initially, low-carb dieters tended to regain more weight by the end of three years when compared with low-fat dieters.
But Harvey-Berino acknowledges that low-carb eating can help many people manage their weight-especially if you're "one of those people who has a hard time staying in control when you eat carbohydrate-rich foods." No matter how you slice it, the best diet is one you can stick to, she adds. "If you can stick with an Atkins-like regimen, then go for it."
4. "A raw-food diet provides enzymes that are essential to healthy digestion."
"Raw foods are unprocessed so nothing's taken away; you don't get the nutrient losses that come with cooking," says Brenda Davis, R.D., co-author of Becoming Raw: The Essential Guide to Raw Vegan Diets (Book Publishing, 2010). But the claim by some raw-food advocates that eating raw boosts digestion by preserving "vital" plant enzymes, Davis explains, just doesn't hold water. "Those enzymes are made for the survival of plants; for human health, they are not essential."
It's true that heating a food above 118°F inactivates plant enzymes, "since enzymes are proteins and proteins denature [break down] with heat," explains Andrea Giancoli, R.D., a Los Angeles-based spokesperson for the American Dietetic Association. "But those enzymes are denatured-and thus inactivated-when they reach our stomachs. Our stomach acids are designed to break down proteins very efficiently." If associated with living microorganisms (such as those in fermented foods like sauerkraut), plant enzymes might reach the small intestine intact, adds Davis, "but their overall contribution to human digestion appears minimal."
What about the claim by some raw-foodistas that our bodies have a limited lifetime supply of enzymes-and that by eating more foods with their enzymes intact, we'll be able to spare our bodies from using up their supply? "The reality is that you don't really have a finite number of enzymes; you'll continue to make enzymes as long as you live," says Davis. Enzymes are so vital to life, she adds, "the human body is actually quite efficient at producing them."
5. "Your body can't use the protein from beans unless you eat them with rice."
Proteins-which our bodies need to make everything from new muscle to hormones-are made up of different combinations of 20 amino acids. Thing is, our bodies can make only 11 of these amino acids; we must get the other nine from food. Animal-based protein-rich foods like eggs and meat provide all nine of these "essential" amino acids, but nearly all plant foods are low in at least one. Experts used to say that to get what your body needs to make proteins, you needed to pair plant-based foods with complementary sets of amino acids-like rice and beans. Now they know that you don't have to eat those foods at the same meal. "If you get a variety of foods throughout the day, they all go into the ‘basket' of amino acids that are available for the body to use," says Winston J. Craig, Ph.D., R.D., nutrition department chair at Andrews University in Berrien Springs, Michigan.
6. "Calories eaten at night are more fattening than those eaten early in the day."
Dr. John Foreyt: "Calories are calories are calories, and it doesn't matter what time you eat them. What matters are the total calories you take in." John Foreyt, Ph.D., is the director of the Behavioral Medicine Research Center at Baylor College of Medicine.
7. "I have a weight problem because I eat foods like wheat or dairy that my body can't process."
This theory is, in fact, "illogical," says Marc Riedl, M.D., assistant professor of clinical immunology and allergy at UCLA. The inability to "process" foods, he notes, "would mean the foods are not metabolized and calories would not be absorbed." This would lead to weight loss, not gain, he notes.
"This is an example of how the term ‘food allergy' has become misused and distorted to be associated with anything unpleasant surrounding eating," says Riedl. "There is no scientific evidence that a food allergy causes weight gain." Of course, cutting out whole categories of foods will probably help you lose weight, simply because it takes so many choices off the table.
8. "Radiation from microwaves creates dangerous compounds in your food."
"Radiation" might connote images of nuclear plants, but it simply refers to energy that travels in waves and spreads out as it goes. Microwaves, radio waves and the energy waves that we perceive as visual light all are forms of radiation. So, too, are X-rays and gamma rays-which do pose health concerns. But the microwaves used to cook foods are many, many times weaker than X-rays and gamma rays, says Robert Brackett, Ph.D., director of the National Center for Food Safety and Technology at the Illinois Institute of Technology. And the types of changes that occur in microwaved food as it cooks are "from heat generated inside the food, not the microwaves themselves," says Brackett. "Microwave cooking is really no different from any other cooking method that applies heat to food." That said, microwaving in some plastics may leach compounds into your food, so take care to use only microwave-safe containers.
9. "Microwaving zaps nutrients."
This is misguided thinking, says Carol Byrd-Bredbenner, Ph.D., R.D., professor of nutrition at Rutgers University in New Brunswick, New Jersey. Whether you're using a microwave, a charcoal grill or a solar-heated stove, "it's the heat and the amount of time you're cooking that affect nutrient losses, not the cooking method," she says. "The longer and hotter you cook a food, the more you'll lose certain heat- and water-sensitive nutrients, especially vitamin C and thiamin [a B vitamin]." Because microwave cooking often cooks foods more quickly, it can actually help to minimize nutrient losses.
10. "You crave certain foods because you're deficient in one of the nutrients they provide."
Nope-unless you're a deer or moose. (In the spring, those animals are attracted to "salt licks"-mineral deposits that supply nutrients they need.) Human food cravings tend to be more about satisfying emotional needs, says Marcia Pelchat, Ph.D., a researcher at the Monell Chemical Senses Center in Philadelphia. "Cravings tend to occur when your diet is restricted or boring, or when you know that you can't have something," says Pelchat. "If it's forbidden, you usually want it more."
There is one nutrient deficiency that's clearly associated with cravings in humans: iron. But instead of longing for iron-rich liver or steak, people severely deficient in iron stores tend to crave things like ice cubes, clay or even cement. Researchers don't know what causes this strange, rare condition, called "pica," but some suspect that a lack of iron might somehow affect the body's appetite mechanisms.
11. "Grazing on mini meals throughout the day keeps your metabolism stoked and helps you control your weight better than eating fewer, larger meals."
Our metabolisms rev up slightly each time we eat, as our bodies process what we've consumed. So by having many mini meals instead of fewer, larger ones, we shift our metabolism into a higher gear more often-and burn a few more calories. But "the calorie difference is so small it doesn't add up to a hill of beans," says John Foreyt, Ph.D., director of the Behavioral Medicine Research Center at Baylor College of Medicine in Houston. That said, snacking between meals may help some dieters by keeping them from getting overly hungry and eating too many calories when they finally sit down to dinner. But probably for just as many others, "each meal is an opportunity to lose control," says Foreyt. Bottom line: Choose the eating pattern that works best for you.
12. "It's important to fast periodically, to cleanse toxins from your body."
The truth: Your body has its own elegantly designed system for removing toxins-namely, the liver, kidneys and spleen. There isn't any evidence that not eating-or consuming only juice-for any period of time makes them do this job any better. Source: Keith-Thomas Ayoob, Ed.D., R.D., of Albert Einstein College of Medicine
13. "Anyone can benefit from a gluten-free diet: it can give you more energy and even treat autism."
With more and more gluten-free products cropping up in supermarkets, it's easy to think their benefits might stretch beyond the audience for whom they're intended: people with celiac disease and gluten intolerance. Celiac disease is an autoimmune condition in which the body can't digest gluten, a protein found in wheat, rye and barley; it's marked by damage to the small intestine that leads to deficiencies because nutrients can't be absorbed. A blood test is used to diagnose celiac disease. Gluten intolerance, on the other hand, may be diagnosed when abdominal distress, and sometimes fatigue, regularly occurs after consuming gluten-and celiac disease has been ruled out. If you don't have a medical reason for following a gluten-free diet, "there's probably no benefit," says Tricia Thompson, R.D., a Massachusetts-based dietitian and founder of glutenfreedietitian.com.
When people with celiac disease or gluten intolerance go gluten-free, "they do feel better and more energetic," adds Thompson, "but that's only because they were feeling so sick before." Those without a medical need to avoid gluten shouldn't expect such results, she adds.
(If you suspect you have trouble with gluten, don't self-diagnose. It is much more difficult to get a definitive medical diagnosis of celiac disease if one stops eating gluten.)
When it comes to autism, however, the case isn't so clear-cut. Many children with autism have gastrointestinal problems, and some parents report that their children's autism symptoms improve when they follow a gluten-free diet that usually also eliminates casein, a protein found in milk. (The son of celebrity mom Jenny McCarthy is perhaps the most famous example.) But objective clinical studies haven't shown that the diet works. Most recently, in May, University of Rochester researchers reported the results of a well-designed (double-blind, placebo-controlled), four-month study of 14 preschoolers with autism. They found that a strict gluten-free, casein-free (GFCF) diet had no discernable effects on autistic behavior patterns, attention, sleep and other symptoms.
Indeed, a consensus report published last year in the journal Pediatrics noted that "available research data do not support the use of a casein-free diet, a gluten-free diet, or combined gluten-free, casein-free diet" for people with autism spectrum disorders. But that doesn't rule out trying diet therapy, says Timothy Buie, M.D., a pediatric gastroenterologist at Harvard Mass General Hospital in Boston and lead author of the report. "At the minimum, these kids merit a nutrition consultation with a registered dietitian to determine if there's an underlying problem."