It seems like every time you pick up the paper, you read about another new study that’s going to completely change everything we know about health. Sometimes it’s a new miracle food that’s supposed to prevent disease – or a food you eat frequently that you’re now being told to avoid completely. In other cases, the headlines blare that scientists have discovered the secret to losing weight, preventing cancer, or slowing the aging process.
However, in many cases, if you read the actual study, you find that its conclusions aren’t nearly as sweeping as the news stories suggest. In their pursuit of eye-catching headlines, media outlets often put too much stress on a single study, implying that it’s a complete game-changer when its actual findings are far from conclusive. And once a health claim is out there in the public sphere, it has a way of sticking around – even long after it has been debunked. Sometimes even reputable medical sources cling to outdated recommendations that have little evidence to support them.
Health myths can take a toll on your body – and on your wallet. In an effort to keep up with the latest health recommendations, you could end up shelling out big bucks for hot new super foods or exercise equipment that you don’t really need. Here’s a closer look at four particular health myths that you can stop worrying about today.
1. You Need Eight Glasses of Water Every Day
Everyone has heard the advice that you need to drink eight glasses of water a day to stay healthy. It’s widely repeated across the Internet, in newspaper and magazine articles, and even in health textbooks – often with an accompanying warning that drinks containing alcohol or caffeine don’t count toward this total, because they just dehydrate your body even more. This widespread belief has led many health-conscious people to shell out hundreds of dollars a year on bottled water, never leaving the house without a bottle of it in hand.
Where It Comes From
No one knows exactly where this advice originated. A 2002 paper in the American Journal of Physiology – Regulatory, Integrative and Comparative Physiology (AJP-RICP) dug into its origins and found that it might have been from a 1974 book written by nutritionist Fredrick J. Stare and Dr. Margaret McWilliams, which recommended consuming six to eight glasses of water every 24 hours. Another possible source was a 1945 recommendation by the Food and Nutrition Board of the National Research Council (FNB), saying that the average person needs 2.5 liters of water a day – about the same as 8 full glasses.
The problem is, neither of these sources actually says that all your daily water needs should come from drinking water. The 1945 FNB recommendation actually said that most of the water your body needs “is contained in prepared foods.” Similarly, Stare and McWilliams, in their book, said that your six to eight daily glasses of water could come from other beverages, such as “coffee, tea, milk, soft drinks, beer, etc.,” as well as from eating fruits and vegetables.
To some people, saying that coffee, tea, and soft drinks can provide hydration sounds odd, because these drinks often contain caffeine, which can increase the amount of urine your body produces. However, a 2003 paper published in the Journal of Human Nutrition and Dietetics, which analyzed medical studies spanning over three decades, found that this only happens over the short term, and only in people who have a large dose of caffeine – the equivalent of two or three cups of coffee – after going without any for several days or weeks. For regular coffee, tea, or soda drinkers, caffeine does not increase urine production. A 2014 British study published in PLoS ONE, an online scientific journal, confirmed this finding and concluded that for regular coffee drinkers, coffee consumed in moderate doses provides about as much hydration as water does.
No one is sure just how the advice to take in a total of 2.5 liters of water from all sources got warped into “drink eight 8-ounce glasses of water a day.” Most likely, it happened simply because this rule – sometimes abbreviated as “8 x 8” – was easy to remember. Nonetheless, there’s simply no scientific evidence to support it.
Dangers of Too Much Water
In fact, the AJP-RICP paper found, drinking too much water can actually be harmful. Drinking excessive amounts of water can lead to a life-threatening condition called hyponatremia – sometimes known as “water intoxication” – in which the level of sodium in your blood becomes dangerously low. If your body can’t remove the excess water fast enough, tissues throughout your body become swollen with water, causing symptoms ranging from headache and nausea to seizures, coma, and death. The AJP-RICP paper cites a couple of fatal cases of water intoxication in teens who had used the illegal club drug Ecstasy.
Drinking too much water is particularly likely to cause problems for athletes. When you sweat, your body loses salt as well as water, and replacing the water without also replacing the salt can throw your blood sodium level off balance – a condition called exercise-associated hyponatremia, or EAH. A 2015 paper in the Clinical Journal of Sport Medicine (CJSM) cited three fatal cases of EAH in high-school football players who drank massive amounts of water – as much as 16 liters, in one case – during sports practice in a misguided attempt to prevent muscle cramps.
Another problem is that during vigorous exercise, the stress on your body reduces the rate at which you produce urine. A doctor interviewed in Scientific American explains that under normal circumstances, your body can produce a maximum of 800 to 1,000 milliliters per hour, so you can drink up to that amount each hour without becoming waterlogged. However, during exercise, your rate of urine production drops to as little as 100 milliliters per hour – so drinking 800 to 1,000 milliliters every hour could possibly lead to dangerous water buildup, even if you’re sweating profusely.
To be safe during exercise, you should drink no more water than your body is losing as you sweat. For instance, if you’re sweating 500 milliliters of water each hour, then that’s how much you should drink. But unfortunately, there’s no good way to measure how much water you’re losing through sweat, and so there’s no way to provide a clear, firm guideline about just how much water is reasonable to drink and how much is dangerous.
Fortunately, your body has a built-in mechanism for telling you how much water you need. It’s called thirst. Both the CJSM and the AJP-RICP conclude that relying on your natural “thirst mechanism” is the best possible guide to make sure you’re getting enough water and not too much. In other words, you can trust your body to tell you when it needs water and when it’s had enough.
Varying Water Needs
In 2006, the National Academies of Sciences, Engineering, and Medicine published a set of guidelines on nutrient needs for people in different age groups. It concluded that adult females typically need about 2.7 liters of water per day, while adult males typically need 3.7 liters. However, this does not mean that’s the amount of water you should actually try to drink. Rather, it’s the amount of water that a typical person needs to take in from all sources, including food and other beverages.
The Harvard Men’s Health Watch, commenting on these numbers, explains that the food and beverages in your normal daily diet supply at least 70% of your water needs. This means the amount you need to add by drinking water is no more than 810 milliliters per day for women and 1.1 liters for men. However, even this number is only a very rough estimate.
Many factors can affect your body’s need for water, including the following:
- Body Weight. The bigger you are, the more water you need. The Academies’ recommendation of 3.7 liters a day from all sources could easily be too much for a smaller-than-average man, and too much for a large one.
- Diet. If you eat a lot of fresh fruits and vegetables and drink plenty of fluids such as juice, milk, or soup, then your diet is probably supplying a lot more than 70% of your water needs. By contrast, if you eat a lot of prepared foods that are high in salt, you’re likely to need extra water to balance out this added sodium. A New York Times article about the rise in kidney stones among young children notes that a major factor is the increase in kids’ salt consumption.
- Exercise. As noted above, when you exercise, your body loses both water and salt through sweat. The Mayo Clinic says most people need an extra 1.5 to 2.5 cups of water to replace the fluids they lose from “short bouts of exercise,” and people who exercise longer and harder need to take steps to replace the lost salt as well.
- Climate. In hot weather, you sweat more, so you lose more water. Dry air also increases fluid loss because it sucks more moisture from your skin. In addition, living at high altitudes increases your breathing rate and urine production, which can also increase your fluid needs.
- Illness. Any disease that causes vomiting or diarrhea drains water from your body. Conditions such as bladder infections and kidney stones can also increase your fluid needs. On the other hand, other medical problems, such as heart failure and some types of liver or kidney disease, can slow down your body’s ability to produce urine, requiring you to drink less water.
- Pregnancy or Breast Feeding. Women need additional fluid when they are pregnant or nursing a baby. The Academies say pregnant women typically need 3 liters of water a day from all sources, and breast-feeding women need 3.8 liters.
Getting Enough Water
As you can see, there are so many different variables affecting your water needs that it’s impossible to give a simple, universal guideline. Instead, doctors recommend relying on – you guessed it – thirst. The Harvard Men’s Health Watch, the Mayo Clinic, and the AJP-RICP and CJSM studies all say that trusting your body’s natural thirst mechanism is the best way to make sure you get the right amount of water without going overboard.
There is plenty of other evidence, aside from these two studies, that thirst is the best way to guide your drinking. For example:
- A 1984 paper in Physiology and Behavior found that as long as people have free access to drinking water, they become thirsty and drink long well before they are actually dehydrated.
- A 2006 study in the Journal of the American Geriatrics Society found that healthy older men who drank an extra 1.5 liters of water per day showed no improvement in blood sodium levels, blood pressure, or quality of life compared to those who took a placebo medication and didn’t change their water intake.
- A 2013 study in Nephrology Dialysis Transplantation found that higher fluid intake did not improve kidney function or lower death rates and concluded that “specific fluid intake targets” – that is, telling the general public to drink a certain amount of fluid each day, rather than relying on thirst – are not helpful.
If you have any doubts about whether you’re drinking enough water, all you have to do is check yourself for signs of dehydration. Aside from thirst, these signs include:
- Infrequent Urination. Britain’s National Health Service says if you urinate less than three or four times a day, passing only a small amount each time, you could be dehydrated.
- Low Urine Volume. According to the Mayo Clinic, a well-hydrated person passes about 1.5 liters, or 6.3 cups, of urine per day.
- Dark-Colored Urine. If you’re getting enough water, your urine should be clear or light yellow, according to the Mayo Clinic.
- Dryness. Dehydration can make your mouth, lips, and eyes feel unusually dry.
- Other Symptoms. Headaches, dizziness, and tiredness are all signs of dehydration. Long-term dehydration can also lead to constipation.
Watching out for dehydration is particularly important for the elderly. The health publication Medical Daily notes that the body’s thirst mechanism can grow weaker with age, so older people should be extra careful to watch the signs and increase their fluid intake if needed. But for most people, thirst really is your best guide.
2. You Need at Least Eight Hours of Sleep Every Night
The number eight seems to be a popular one for health rules of all kinds. Ask any random person how much sleep you should get, and chances are they’ll say eight hours. This recommendation, like the one about drinking eight glasses of water a day, has been around for decades and shows up in all kinds of reputable health sources, from websites to books.
Where It Comes From
The eight-hour rule is more or less in line with the latest recommendations from the National Sleep Foundation, developed by a team of 18 leading scientists and published in 2015. These guidelines say that most healthy adults need between seven and nine hours of sleep per day.
However, the Foundation also stresses that this is only an approximation. According to its report, some adults can function perfectly well on as little as six hours of sleep, while others need up to ten to perform at their best. So rather than recommending a specific number of hours for everybody, the researchers advise paying attention to how you feel on different amounts of sleep and using that to figure out how much you personally need.
The Truth of the Matter
So the eight-hour rule is really just an approximation. However, there’s an increasing amount of evidence that it isn’t even the best possible approximation. Several studies published between 2002 and 2015 suggest that the ideal amount of sleep for most adults could actually be closer to seven hours than eight.
- Kripke, 2002. A 2002 study led by Dr. Daniel Kripke at the University of California San Diego, published in the Archives of General Psychiatry, tracked 1.1 million cancer patients over a six-year period. Kripke and his team found that the patients who slept around seven hours a night – specifically, between 6.5 and 7.4 hours – had lower mortality rates than those who got either less or more sleep.
- Kripke, 2011. Dr. Kripke also led a 2011 study published in the journal Sleep Medicine. Kripke’s team monitored the sleep habits of 450 women with an average age of 67.6 years over a period of a week, then checked in with them again 10 years later. The study found that the women who slept at least 5 hours a night and no more than 6.5 hours were least likely to die during that period.
- Lumos Labs, 2013. A team of researchers at Lumos Labs – home of the website Lumosity, a web-based platform to help people improve their mental acuity – studied how more than 200,000 people performed on tests of spatial memory, matching, and arithmetic after varying levels of sleep. The study, published in the journal Frontiers in Human Neuroscience, found that performance on all three tests tended to increase with more sleep – but only up to the seven-hour mark. Beyond that point, the more sleep people got, the more their performance dropped.
- Journal of Clinical Sleep Medicine, 2014. Many people believe that our fast-paced modern world interferes with people’s natural sleep patterns. To test this theory, a team of researchers conducted an experiment in which five healthy adults spent two months in “a Stone Age-like settlement.” They lived in huts with no electricity, running water, or other modern conveniences, and they had to gather and prepare all their own food. The study, published in the Journal of Clinical Sleep Medicine, found that people living in these conditions did, in fact, fall asleep earlier and sleep longer than they did in their normal lives. However, the amount of time they actually slept during the experiment only ranged from 6 to 9 hours, averaging around 7.2 hours.
- Current Biology, 2015. Another study, published in the journal Current Biology, looked at the sleep habits of people in actual pre-industrial societies in Tanzania, Namibia, and Bolivia. The researchers found that people in these societies typically fall asleep a few hours after sunset and wake before sunrise, sleeping anywhere from 5.7 to 7.1 hours in between. They also take naps during the day only occasionally – on about 7% of the days in winter and 22% of the days in summer.
The bottom line is, there’s nothing unnatural about sleeping for six or seven hours rather than for eight, as long as you can function on that amount. Instead of relying on a hard-and-fast rule, you should listen to your body.
If you feel just fine on seven hours of sleep, then stick with that amount. On the other hand, if you’re not sleeping well, you rely on caffeine to get through the day, or you ever feel drowsy while driving, these are all signs that you need more shut-eye.
3. Eggs Are Bad for Your Heart
Eggs are a great, cheap source of protein. Just one large egg has about 6 grams of protein – about as much as an ounce of lean beef or chicken. But based on food prices from the Bureau of Labor Statistics, lean beef currently costs around $5.50 a pound ($0.34 per ounce) and boneless chicken breasts are $3.25 a pound ($.20 per ounce). By contrast, a dozen eggs cost just $2.33, or $0.19 each.
On top of that, eggs are fast and easy to fix and incredibly versatile. You can cook them in lots of different ways – boiled, fried, scrambled, poached – and use them in nearly any recipe, from salads, to stir-fries, to soups. Yet many people are passing up – or at least cutting back on – this cheap, convenient food because they’ve been told it will increase their risk of heart disease.
Where It Comes From
The egg’s bad reputation is based mostly on its cholesterol content. A bit of background: cholesterol is a waxy, fat-like substance found in all your body’s cells. And, to some extent, that’s a good thing – your body needs cholesterol for growth, digestion, and producing hormones and vitamin D.
The problem is that too much cholesterol in your bloodstream can cause a buildup, known as plaque, inside your arteries. In turn, this can lead to heart disease and a host of related problems, such as heart attack and stroke. People with high levels of blood cholesterol – especially the type known as low-density lipoproteins (LDL), or “bad” cholesterol – are at a higher risk for heart disease. So far, all this is pretty much accepted fact in the medical community.
But when you look at the causes of high blood cholesterol, matters get a little murkier. Some of the cholesterol in your body, called called dietary cholesterol, comes from the the foods you eat. Because of this, the American Heart Association (AHA) has long recommended keeping your intake of dietary cholesterol to no more than 300 mg per day. And since a single egg yolk has 187 mg, the AHA has generally advised people to limit the number of whole eggs they eat.
However, most of the cholesterol in your blood is produced inside your body. Nutritionist John Berardi, writting for HuffPost Healthy Living, says the average person produces one to two grams of cholesterol every day. Even the AHA admits in its dietary guidelines that saturated fat, which triggers LDL production, has a much greater impact on your blood’s LDL levels than dietary cholesterol does. Nonetheless, the AHA says limiting dietary cholesterol is still a good idea – especially since many foods high in cholesterol have a lot of saturated fat as well.
A 2012 study published in the journal Atherosclerosis added more fuel to the concerns over egg consumption. It found that patients who ate more eggs were more likely to have artery-clogging plaque. The authors of the study went so far as to claim that regularly eating egg yolks was two-thirds as dangerous as smoking.
The Truth of the Matter
The 2012 study was controversial and generated a lot of negative letters to the editor, some with titles like, “Putting eggs and cigarettes in the same basket; are you yolking?” One problem was that although the study showed a link between egg consumption and plaque buildup, it did not necessarily show that the eggs were actually at fault. AHA cardiologist Gordon Tomaselli, writing for Prevention, notes that there are many factors the study didn’t look at, such as what else the participants ate or how much they exercised.
Other doctors and nutritionists point out that although egg yolks are high in dietary cholesterol, they also have other nutrients that can actually help prevent heart disease. For example, egg yolks are high in unsaturated fats, including the omega-3 fatty acids that experts say are essential for heart health. They’re also a good source of vitamins A, D, E, and B12.
Furthermore, there are a variety of studies showing that dietary cholesterol really doesn’t have that much impact on your heart health. Current Opinions in Clinical Medical Care points out that in most people, the amount of cholesterol in their diets has little or no impact on their blood cholesterol. It also notes that eating eggs tends to shift the type of LDL in the bloodstream to a form that’s less likely to clog the arteries. A 2012 study in the same publication examines disease statistics and finds that there is no link between at all between cholesterol intake and heart disease rates.
Some studies even find that eating eggs can improve heart health. A controlled study from 2013, published in Metabolism, looked at a group of people with metabolic syndrome – a combination of risk factors that increases the risk of heart disease, diabetes, and stroke. Patients were put on a moderately low-carb diet that included either three whole eggs a day or an equivalent amount of egg substitute. The patients who ate whole eggs, including the yolks, saw greater improvement in their blood cholesterol levels and bigger drops in insulin resistance, a precursor to diabetes.
In light of these new findings, the Harvard School of Public Health now says that eating eggs in moderation is fine for most people. However, the same article notes that certain groups of people are better off limiting their egg consumption. People who have diabetes, or who have difficulty controlling their total blood cholesterol and LDL levels, should limit themselves to just three egg yolks per week. For everyone else, one whole egg per day – plus as many egg whites as you like – should be no problem.
4. Standing at Work is Better Than Sitting
If you work in an office, it’s possible you have a few coworkers who have suddenly started using standing desks. Some people do this by using improvised stands to raise the levels of their monitors and keyboards, while others invest in specially designed standing desks that can cost hundreds or even thousands of dollars. But many people think the high cost – along with the discomfort of standing all day – is worth it, because they’re convinced that sitting is a threat to their health.
Where It Comes From
Fears about the dangers of sitting arose out of a series of medical studies between 2012 and 2015 that focused on the risks of being sedentary, or inactive. First came a 2012 paper in Diabetologia that analyzed the findings of 18 earlier studies and concluded that more time spent sitting was linked to a higher risk of diabetes, heart disease, and death from all causes. Then a 2013 paper in the American Journal of Preventive Medicine examined the behavior of more than 92,000 older women over a 12-year period and found that the women who spent most time sitting – more than 11 hours per day – also had the highest risk of death from heart disease and cancer.
In 2014, researchers at the British Journal of Sports Medicine did a study trying to find the link between physical activity and the length of the body’s telomeres – structures that protect your cells from damage. The shorter your telomeres are, the higher your risk for all the diseases related to aging, including obesity cancer, diabetes, heart disease, and stroke. The researchers in this study announced that the biggest threat to the telomeres was time spent sitting; participants who reduced their sitting time lengthened their telomeres far more than those who exercised more.
Following up on this, a January 2015 study in the Annals of Internal Medicine announced that sitting still for long periods of time increases the risk for heart disease, diabetes, cancer, and premature death. Even people who got plenty of exercise at other times showed some negative effects from prolonged sitting – although the risks weren’t as high for them as for people who weren’t physically active.
In the wake of these studies, a rash of headlines declared that sitting was “the new smoking.” Sales for standing desks spiked. Steelcase, a leading manufacturer of standing desks, told Mother Nature Network that sales for its non-seated desks had increased five-fold between 2008 and 2013.
Risks of Standing
Unfortunately, in many cases, the cure workers adopted for sitting too long was worse than the disease. Standing for hours at a time isn’t just tiring; it actually poses long-term health risks of its own.
In 2002, the journal Work published a review of 17 studies on the dangers of prolonged standing, where “prolonged” was defined as more than 8 hours. This meta-study found that standing for this long is linked to a host of medical problems, including back and foot pain, miscarriage or premature birth in pregnant women, and chronic venous insufficiency (CVI). This is a condition in which the veins in the legs don’t work effectively, causing blood to pool in these veins.
CVI can lead to pain, swelling, skin ulcers, and varicose (swollen and enlarged) veins. A Danish study from 2005, published in Occupational and Environmental Medicine, found that workers who spend at least 75% of their workday on their feet were 75% more likely to be hospitalized for varicose veins. The authors concluded that standing at work was responsible for more than 20% of all cases of varicose veins in people of working age.
Standing for long periods can also lead to long-term heart and circulatory problems. A 2000 paper in the Scandinavian Journal of Work, Environment & Health, linked prolonged standing to an increased risk of atherosclerosis, or blocked arteries, which in turn can increase the risk of heart attack and stroke.
The same researcher who published that paper went on to work on two others that were presented at the 4th International Conference on Work Environment and Cardiovascular Diseases in 2005. One of these found that spending a lot of time “in an upright posture” at work increased the risk of hypertension, or high blood pressure, by as much as 20 years of aging. The second found that prolonged standing at work increased the risk for atherosclerosis by the same amount as smoking, high blood pressure, or high cholesterol.
Sitting Plus Exercise
Some more recent studies appear to contradict the findings about the dangers of sitting at work. These studies suggest that prolonged sitting isn’t necessarily all that bad for you, as long as you’re also getting some exercise.
For instance, a 2014 study of nearly 17,000 Canadian adults, published in the in the Official Journal of the American College of Sports Medicine, found that those who spend the most time standing had a 33% lower risk of dying from any cause over a 12-year period than those who stood the least. However, this difference vanished for people in the study who met Canada’s recommendations for physical activity – at least two hours of exercise per week. The people who got this amount of exercise had no increased mortality risk, even if they spent the rest of their time sitting.
An October 2015 study in the International Journal of Epidemiology reached a similar conclusion. Researchers looked at the behavior of more than 5,000 healthy, active people in Britain over a 16-year period and found that those who spent the most time sitting during the day were no more likely to die during this time than those who sat the least. The study’s authors noted that the participants in this study spent nearly twice as much time walking each day as the average Brit and suggested that their activity level might be protecting them from the harmful effects of sitting. They concluded that it makes sense to look at recommendations for sitting and recommendations for physical activity as two sides of the same coin, rather than treating sitting time as a separate risk factor.
The Best Way to Work
Based on the research above, it seems clear that standing still all day isn’t really any better for you than sitting still. A better approach is to find more ways to be active – both on the job and off it.
Health experts interviewed by US News and World Report recommend several ways to move more throughout the day:
- Switch Positions. Changing from sitting to standing frequently is better than spending the whole day either standing up or sitting down. Alan Hedge, a professor of Design and Environment Analysis at Cornell University, says changing your position in this way “completely eradicates” the health risks of sitting – as well as the risks of standing.
- Fidget. Sitting isn’t necessarily the same as sitting still. Ken Tameling, an economic seating expert from Steelcase, says “micromovements” like tapping your foot or shifting your weight are much better for your body than staying fixed in one position.
- Take Breaks. Hedge notes that it’s harder to concentrate on some types of work – such as tasks that require fine motor skills – while you’re standing up. So if you have trouble focusing on your work while standing, go ahead and sit – but only for 30 to 90 minutes at a time. Make a point of getting up periodically to move around, stretch your legs, and get your blood flowing.
- Do Exercises. Standing in one position at your desk isn’t particularly good exercise. Instead, find ways to fit some real activity into your workday. You can take the stairs instead of the elevator, take a walk on your lunch break, do squats while you’re heating up your lunch, do leg lifts under the desk, or just walk around the halls in between stretches of work.
The best way to protect yourself against health myths is to use your common sense. If a health article recommends doing something that just doesn’t sound right – like telling you to drink water when you’re not thirsty, or to spend your whole day in an uncomfortable position – don’t just assume that it must be good advice because it comes from “experts.”
Instead, look a little deeper and see what’s behind the recommendation. You might discover that the health headline is actually overstating or oversimplifying the results of a single study – or maybe even that there never was a study to back up the advice in the first place. And even if the basic science is sound, digging deeper could reveal that the “rule” actually comes with some exceptions or caveats. For instance, you might discover that some people really do need eight hours of sleep, but the amount needed varies from person to person – or that standing can be better than sitting, but you shouldn’t do either one for hours at a time.
And when in doubt, remember that in health matters, moderation is often the best approach. Even things that are undeniably good for you – like sleep or drinking water – are better if you don’t go overboard. And even things that can be bad for you at high doses – like egg yolks or inactivity – can be harmless, or even helpful, as long as you keep them within reasonable limits.
What other health myths have you heard?