8 Nutrition and Fitness Myths Debunked by Science

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Whether you’re reading information from a popular website or receiving an e-mail from a friend that sounds like it could be credible, be skeptical. Many of these nutrition and fitness myths started from a single-source, but once they went viral they were treated like facts. Here, we debunk seven of the myths on the Internet. Know other myths? Share them in the comments section below.

1. MYTH: It Takes 21 Days to Break a Bad Habit (or to Form a New One)

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Many popular self-help gurus claim that it will take 21 days to break or form a habit. But the truth is, there is no magical timeframe for making lasting changes. Some people can pick up a new habit (like eating more veggies) in just a few days. Others may take weeks or months. A study published in the European Journal of Psychology found that making new habits (like eating a piece of fruit daily) took an average of 66 days. However, there were wide variations. The authors found the adaptation time was a function of the specific habit, as well as the individual. If you’re trying something new, like daily exercise, give yourself time to make it a routine. It may not happen overnight – or in 21 days!

Related: STUDY: How Are Habits Formed

2. MYTH: Oil Lubricates Your Joints

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Can oil lubricate your joints? Well maybe, but not in the way that you might think. There are some studies showing that omega-3 fatty acids, commonly found in fatty fish like salmon, as well as walnuts and flaxseed, may help ease joint pain. Omega-3 fats don’t actually lubricate the joints in our bodies the way that you would grease a creaky door. Instead, omega-3s are believed to reduce inflammation which may lessen pain. A recent review of multiple studies on fish oil and joint pain found that participants who took fish oil supplements reported reduced morning stiffness, less joint swelling and pain, and a decreased need for anti-inflammatory drugs to control their symptoms.

Related: 17 Reasons Why You Probably Need More Omega-3s

3. MYTH: Muscle Can Turn to Fat (and Vice Versa)

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Muscle and fat tissue are entirely different, and they cannot morph into one another. “This is like saying that lead can turn into gold,” says Ed Ingebretsen, an American College of Sports Medicine-certified personal trainer. What really happens when you stop exercising is that your muscle mass declines. How you gain weight is by eating more calories than you burn off, and this becomes a lot easier to do when you have lost highly metabolic muscle tissue that helps to keep your body running like a V8 engine instead. Bottom line: Stay active. If you stop exercising, be sure to eat less to avoid weight gain.

Related: The Claim vs. The Facts on Muscle Turning to Fat

4. MYTH: Canola Oil is Made from Rapeseed (And Is Toxic!)

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Many people think that canola oil comes from the rapeseed plant, but it actually comes from the pressed seeds of the canola plant. While Rapeseed oil does contain very high levels of erucic acid (a compound that in large amounts can be toxic to humans), canola oil contains very low levels of erucic acid. Misinformation about canola oil may stem from the fact that the canola plant was developed in the 1960s through traditional plant crossbreeding with rapeseed to reduce the erucic acid and glucosinolates contained in the rapeseed oils. While canola oil is not, by definition, genetically modified, as of 2010 90% of canola crops are genetically modified (GMO) to make them more resistant to pesticides. To avoid GMOs always look for organic and expeller pressed canola oil (mechanically extracted at a temperature of 120F vs. chemically).

5. MYTH: “Juice Cleanses” Are The Best Solution for Long-Term Weight Loss

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From celebrities to personal trainers, there’s no shortage of people advocating juice “cleansing.” For most healthy people, occasional short juice cleanses, won’t cause harm, however you may feel hungry and tired. If you really want to do you body a favor, get regular exercise, sleep, and eat a healthy, balanced diet.

Related: Should You Try a Juice Cleanse? (LIVESTRONG Editor’s Experience)

6. MYTH: Some Foods, Like Celery, Have Negative Calories

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When something sounds too good to be true, it probably is. A “negative calorie food” may sound great, but unfortunately there is no such thing. The myth of “negative calories,” stems from the notion that some foods will burn more calories than they provide. The faulty logic of this urban legend rests on the idea that the thermic effect of food (TEF), i.e. the amount of energy required to digest some foods, can give certain foods less-than-zero calories. Celery, apples, and limes and are among those touted to be negative calorie foods. Sadly, there are no negative calorie foods. The TEF generally ranges from 10%-20% of the calories in a food. So let’s say a celery stalk has 7 calories. Even if we assume a 20% TEF, that still means your left with about 5.5 calories.

7. MYTH: Fresh Produce Is Always Better Than Frozen

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Produce found in the freezer section might have as much --and maybe even more --nutritional value than fresh produce. But because frozen fruits and vegetables are picked within hours of harvest, essentially “locking in” their vitamins and minerals, in many cases they are nutritionally equal or superior to their fresh counterparts. This makes sense when you consider that fresh picked produce can spend several days or even weeks in transit or in storage prior to consumption, possibly losing key nutrients along the way. A healthy diet can include both fresh and frozen produce.

Related: Which Produce to Always Buy Organic (Even If You’re on a Budget)

8. MYTH: Cut Onions Harbor Bacteria That May Cause Food Poisoning

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Have you heard this myth before? Many of us had not. According to a viral email going around sliced raw onions are a “magnet for bacteria” and should not be stored in the refrigerator even for brief periods. Not true. In fact, according to the National Onion Association, cut onions can be refrigerated in a sealed container and used for up to seven days. The only feasible way onions can be a problem is if they are contaminated through poor handling. Be sure to wash your hands, use clean cutting boards and knives when cutting any produce as you can cross-contaminate foods.

Related: Is It True That Onions Absorb Bacteria?

What Do You Think?

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Had you heard of any of these myths before? Does it surprise you that they were debunked? Are there any other nutrition and fitness myths that we left out that you think we should tackle in an upcoming piece?

The romaine scare is officially over — here's how to stay safe in the future

credit: istock istock
1 of 10

Whether you’re reading information from a popular website or receiving an e-mail from a friend that sounds like it could be credible, be skeptical. Many of these nutrition and fitness myths started from a single-source, but once they went viral they were treated like facts. Here, we debunk seven of the myths on the Internet. Know other myths? Share them in the comments section below.


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