Is milk really good for your bones? Are all salty snacks unhealthy? Do you need to drink two litres of water per day? These are just some scientific food "facts" that aren't as concrete as you might think. We talked to a group of nutritionists and asked them to share the food myths they find most irritating and explain why people cling to them. Here's what they said.
Myth 1: Never Use Wooden Cutting Boards with Meat
This rule, one that I myself have repeated, comes from the notion that using a wooden cutting board will result in tiny scratches and cuts from your knife, and if you use that cutting board with meat -- especially raw meat -- that all those meat juices will settle into those tiny cuts in the board, and no matter how much you scrub, those germs won't be coming out. The point has even been made by people as esteemed as Alton Brown. The solution is to use plastic cutting boards, which can be dishwashed and sanitised and therefore must be safer, right?
Unfortunately, there's a great deal of research that disputes this notion. One of the most famous studies was conducted at the University of California: Davis, by Dean O. Cliver, Ph.D of the UC-Davis Food Safety Laboratory. His research points out that there's no significant antibacterial benefit from using a plastic cutting board over a wood one. He notes that even if you apply bacteria to a wooden cutting board, it's natural properties cause the bacteria to pass through the top layer of the wood and settle inside, where they're very difficult to bring out unless you split the board open.
Although the bacteria that have disappeared from the wood surfaces are found alive inside the wood for some time after application, they evidently do not multiply, and they gradually die. They can be detected only by splitting or gouging the wood or by forcing water completely through from one surface to the other. If a sharp knife is used to cut into the work surfaces after used plastic or wood has been contaminated with bacteria and cleaned manually, more bacteria are recovered from a used plastic surface than from a used wood surface.
Dr. Cliver's study tested ten different hardwoods and four different plastic polymers. In the end, the result was a very scientific one: if you want a plastic cutting board, anti-bacterial properties is no reason to buy one. If you want a wooden cutting board, bacterial infection shouldn't scare you away. Which is better? That's a different discussion, but ultimately it's more important that you take care to properly clean and disinfect whatever board you buy, regardless of what it's made of. Oh, and don't fall for plastic or other cutting boards that tout themselves as being coated or made with anti-microbial chemicals or materials, that's largely junk science as well.
Myth 2: Adding Salt to Water Changes the Boiling Point, Cooks Food Faster
This is one of those food myths that doesn't want to die. You'll hear it repeated by home cooks and professional chefs, but any first year Chemistry student (or in my case, a Physics student taking Applied Thermodynamics) will be able to show you how little the amount of salt you would add to a pot of boiling water in your kitchen actually alters the boiling point.
Yes, strictly speaking, adding salt to water will alter the boiling point, but the concentration of salt dissolved in the water is directly related to the increase in the boiling point. In order to change water's boiling point appreciably, you would have to add so much table salt (and dissolve it completely) that the resulting salt water would be nearly inedible. In fact, the amount of salt you're likely to add to a pot of water will only alter the boiling point of water by a few tenths of a degree Celcius at most.
So this is one of those food myths that rings of chemical truth, but only on scales that wouldn't applicable for cooking. One thing is for sure though, adding salt to your pasta water definitely makes the resulting pasta tasty.
Myth 3: Low Fat Foods Are Always Better For You
Alannah DiBona, a Boston based nutritionist and wellness counselor made this her number one food myth. She said:
"Without fat, the human body is unable to absorb a large percentage of the nutrients needed to survive. Additionally, fat deprivation prevents messages from being passed between neurotransmitters, resulting in all kinds of neural misfiring in the body! While good fats and bad fats do exist, the right fats in the proper amounts can actually aid in weight loss and cholesterol management."
The high-fat/low-fat food myth is one that's been around for a long, long time. Ultimately, it's more important to flip over the food you're about to buy and read the label, see what kinds of fats are in it, and then make an educated decision instead of immediately reaching for the low-fat version of whatever it is you're planning to buy, thinking it'll be healthier. In fact, many products that are "low-fat" are low in good fats as opposed to the bad ones, or substitute in other ingredients like sugars and sodium that you don't want more of in your diet.
Seattle-based Registered Dietician Andy Belatti also called out this particular myth. He said, "A good intake of healthful fats is beneficial for cardiovascular health. Prioritise mono-unsaturated fats (avocados, olives, pecans, almonds, peanuts) and omega-3 fatty acids (hemp seeds, chia seeds, sea vegetables, wild salmon). Virgin coconut oil and dark chocolate (80 per cent cocoa or higher) also offer healthful fatty acids. Many low-fat diets are high in sugar and refined carbohydrates (i.e.: white flour), which are increasingly becoming linked to increased rates of heart disease."
Myth 4: Dairy Is The Best Thing For Healthy Bones
When I asked Andy Belatti about the most stubborn food myths he's encountered, he noted that too many people confuse "dairy" with "calcium", assume they're the same thing, and think that dairy is the best thing for healthy and strong bones. He explained, "Dairy contains calcium, but so do dark-leafy greens. Milk is fortified with vitamin D, just like all milk alternatives. Additionally, bone health goes beyond calcium and vitamin D. Vitamin K is important for bone health (dark leafy greens have it, dairy doesn't). Magnesium (present in foods like almonds, cashews, oatmeal and potatoes, but missing in dairy products) also plays an important role in bone health."
Ultimately, if you're concerned about bone health, you should make sure to get enough calcium in your diet, and while milk and cheese are good sources of it, they're by no means the only sources. It's important -- and can be just as healthy -- to branch out and make sure you're eating dark leafy greens instead of just chugging down milk. Even the Harvard School of Public Health points out that milk isn't the only, or even the best, source of calcium, as does the University of Missouri's Nutrition "mythbusters". If you're looking for good sources of calcium and Vitamin D, consider collard greens, mustard greens, kale and bok choy instead of milk.
Myth 5: Everyone Should Drink 2L or 8 Glasses of Water Every Day
This myth is a holdover from a poor attempt by a number of doctors who wanted to wage an ill-researched campaign against sodas and sugary drinks. Their hearts were in the right place, but the fact of the matter is that there's no uniform rule for how much water a person should drink in a given day. Alannah DiBona explains, "Water's been touted as the cure for all sins, and in some ways, it's true -- proper hydration is necessary for just about anything body and mind-related. However, sixty-four ounces [1.9L]per day isn't going to always be the right number for you."
My old nutritionist explained to me that I should try to drink my body weight in ounces of water, divided in half. She noted that's a good guideline for most people, but also noted that it's a goal -- not a rule. When I asked her whether there would be real health benefits from it, she explained that it's not going to make my body work better or somehow stave off disease magically, but it will give me energy, prevent dehydration, get me up away from my desk and walking to the water cooler and she pointed out that often our bodies interpret thirst signals as hunger. It's anecdotal, but I have to admit that drinking more water made me feel better by leaps and bounds.
While it's important to hydrate, it's not important to stick to an arbitrary rule defining how you hydrate, or how much you drink, or even where you get it, although water is obviously the best source of, well, water. "Nutrition is an individual science, and there will be days when your body and mind require less than the average recommendation," DiBona explains. "Remember that water is available to you through all liquids, fruits and vegetables, and that the mark of proper hydration is very light yellow-colored urine."
Myth 6: High-Sodium Foods Taste Salty, So Avoid Salty Snacks
Andy Belatti pointed this one out when we spoke, and it's especially important for people who are managing their salt and sodium intake because they're at risk for hypertension or diabetes. While new research indicates that low-sodium diets may not be better for your heart, they definitely reduce your chances of high blood pressure or type II diabetes. The trouble with managing sodium though, is that not all high-sodium foods taste salty when you eat them.
"While surface salt (the type on pretzels and salted nuts) is noticeable, stealth sodium (that which is added during processing) is harder to taste. This is why many people don't realise that a Dunkin' doughnuts corn muffin contains as much sodium as nine McDonald's Chicken McNuggets," Belatti explains.
This fact is a testament to the importance of reading nutrition labels when you shop, and why it's important to look up nutrition information for your favourite foods at restaurants or fast-food eateries either on the web or in-store when you're out for lunch or dinner. Sodium can lurk in strange and surprising places. Check out the National Heart, Lung, and Blood Institute (at the NIH) for more tips on reducing your sodium intake and what to watch out for.
Myth 7: Eating Eggs Will Jack Up Your Cholesterol
A number of you took me to task on this one the last time I insinuated that eggs may not be healthy, and rightfully so. Alannah Dibona cleared this one up once and for all, and notes: "More often than not, a person diagnosed with high cholesterol will go out of his or her way to avoid eggs, which is really unnecessary. The body's cholesterol levels are influenced by certain saturated and trans-fats; eggs contain very little saturated fat (1.5g of fat per large egg) and absolutely no trans-fat. Depriving yourself of an egg means foregoing 13 naturally-occurring vitamins and minerals (and a really delicious breakfast option)."
Ultimately, eliminating eggs from your diet because you're concerned about cholesterol will do absolutely nothing for you, and instead may actually be harmful because you're missing out on the health benefits they have. The Harvard Medical School agrees, as does the Mayo Clinic, although they take a more metered approach to the issue, and suggest that if you love eggs, eat the whites and not the yolks. Both agree that even though the yolks have a lot of cholesterol, very little of it actually makes it into your bloodstream, where it matters.
Myth 8: Searing Meat Seals In Juices
19th century German chemist Justus von Liebig was one of the first people to propose that by applying very high temperatures to meat you would create a "sealed" layer of cooked meat through which liquid inside the meat couldn't escape. Ever since then, the mantra has been repeated over and over again, specifically in reference to dry heating cuts of raw meat.
The trouble is that Liebig's experiment compared the liquid and nutrients from a piece of meat submerged in cold water which was gradually heated in that water and simmered in the cooking liquid with a dry piece of meat applied to an extremely hot surface. When considered this way, you can see why Liebig thought that searing meat "sealed in juices", because the resulting meat was juicier than the meat that was essentially boiled to death.
However, in the book On Food and Cooking, Harold McGee finally makes a direct comparison between a seared piece of meat and an un-seared piece, both cooked with identical methods. The result was that the seared piece of meat actually retained fewer juices than the un-seared piece, and at the very least the searing did nothing to preserve the moisture inside the meat.
This debate is still one that rages today. There are plenty of people who think that searing meat does result in moister meat, while others dispute it. In reality, the best thing about searing meat is that when applied to high heat, the surface of the meat undergoes the Maillard Reaction, which results in some delicious browning on the surface of the meat. At the end of the day, you should definitely sear your steaks -- not because it "locks in juices", but because it's tasty.
Myth 9: Aluminium Foil and Cookware Is Linked to Alzheimer's Disease
If you haven't heard this one in a while, good -- it was repeated often in the late 80s and through the 90s, and even though it's fallen out of fashion (largely because it's just not true) there are still a lot of people who believe it. This myth has its roots in research from the 1960s and 1970s that showed elevated levels of aluminium in the brains of Alzheimer's patients. The hyperbole alarm was subsequently sounded, and for years people were warned off of aluminium pots and pans, and even aluminium foil to store food.
Since those studies however, a great deal of research has been done into what possible connections aluminium may have with Alzheimer's Disease, and at best has failed to show any substantive link or connection between aluminium and risk for Alzheimer's Disease. At worst there have been conflicting results. Most experts at this stage believe any aluminium absorbed by the body is processed by the kidneys and urinated out, and it does not pose a threat for Alzheimer's Disease.
Myth 10: Don't Eat After 6, 7, 8pm
Both Andy Belatti and Alannah DiBona called this myth out in different ways. Andy went right for its throat, noting that it is "A silly weight-loss gimmick. What matters is what you're eating throughout the day. Food eaten after 7pm does not magically turn to fat. This is also a ridiculous 'tip' for someone who goes to bed at midnight or 1am. This tip often 'works' because people end up reducing their total caloric intake."
He's right: this myth comes from a half-scientific understanding of how digestion works. The idea is that if you eat too late and go to bed on a full stomach, your body's metabolism will slow down and instead of burning the food you just ate, you'll turn it all into fat and gain weight. That statement is only partially true, and isn't universal for all people. While it's true your metabolism slows down when you go to sleep, it doesn't stop, and you still churn through the food in your stomach, albeit slower. If your diet, exercise and activity habits mean that a meal is more likely to metabolise into fat because you sit at a desk all day, eating it at 5pm versus 7pm isn't going to change that.
In reality, what really happens for the people who swear by this trick is that they don't wind up eating breakfast the following morning on top of a stomach full of food, and that they've blocked off areas of their night when they're not consuming food -- as opposed to someone who would be tempted to have a late-night snack. In essence, they're just eating less overall. This myth is so popular that the ADA has a page dedicated to debunking it.
Belatti also makes the point that if you're the type of person who's up very late, setting an arbitrary time to stop eating at night isn't going to help you lose weight, it's just going to make you skip a meal. DiBona had something specific to say about meal skipping, and how dangerous it can be: "Just several years ago, I remember reading in Cosmopolitan magazine that skipping breakfast or lunch following a "night of indulgence" could aid in one's efforts to lose weight. The editors couldn't have been more wrong. If a meal is skipped, the body begins a process of metabolic slowing commonly referred to as 'starvation mode.'" She continued, "Additionally, surges of hormones then encourage overeating at the next meal, resulting in a higher caloric intake at the day's end. Keeping one's blood sugar balanced with small meals and snacks throughout the day is a much more successful approach for weight maintenance and mental alertness."
Bonus Myth: Wine Has Health Benefits, Beer and Liquor Do Not
Cheers, everyone: while studies outlining the health benefits of wine make for great headlines, it's commonly accepted that in addition to the antioxidants in wine, all alcohols -- when consumed in moderate doses -- can raise the body's levels of HDL, or the "good cholesterol". Alannah DiBona explains: "Wine (as well as beer, liquors, and all types of alcohol) in moderate doses raise the body's levels of HDL, or good cholesterol, which protects the heart against the plaque build up that may cause strokes and heart attacks. As Europeans have proved for centuries, 1 to 2 alcoholic beverages per day helps to reduce the risks of heart disease."
While we're not going to tell you to go out and develop an alcohol problem in the name of good heart health and lower cholesterol, a glass of wine or a couple of beers can actually reduce your risk for heart disease when combined with a good diet and exercise. Just be careful of the calories you intake when drinking alcohol-that bottle of wine or six-pack of beer isn't calorie-free, you know.
How to Debunk Your Own Food Myths
Some of the most persistent food myths are the ones that are considered common knowledge, or the ones that have been long disproven but were trumpeted loudly when they were "discovered" but never formally rebutted so much when they were debunked. If there's anything I learned in my years as a scientist and a student, it was to always keep an open mind. Not so open that your brains fall out, mind you, but open enough that you're willing to challenge your own deeply held beliefs in the light of new evidence that contradicts them.
Keeping an open mind is only part of the battle however: you also need to seek out and pay attention to reputable sources of information when you're reading about or researching food or nutrition science. Also, don't ever hesitate to seek out peer-reviewed scientific studies and research to prove or disprove a point.
It's all too easy on the internet to demand someone produce a study when they present an idea you disagree with-it's another thing to look for it yourself, or to similarly concede when they do so, instead of simply finding a new vector of attack.
One last note: common sense reigns king: if some tip or magical diet truism seems too good to be true, or too simple to be uniformly true for all people, it probably is.
These myths just scratch the surface, and are only a few of the long lists of food myths that Alannah Dibona and Andy Belatti suggested. There are plenty where these came from, and we cover a lot of them here at Lifehacker when they come up. For example, our own Melanie Pinola took note when research from the USDA showed alcohol doesn't "burn out" during cooking the way many people think it did.
What are some of your favourite food myths that desperately need debunking? Share your thoughts in the comments below.
Andy Bellatti, MS, RD is a Seattle-based Nutritionist and the author of the nutrition blog Small Bites. Alannah Dibona, MA, MS, is a Boston-based nutritionist and wellness counselor, and the woman behind mindbodysportconsulting.com.
This story has been updated since its original publication.