Does your body run best on 8 glasses of water a day? Not necessarily. Everyone has different fluid needs. The weather--both temperature and humidity--plays a part. So does your size, gender, and level of activity.
Sometimes this health claim is more specific. Some say 8 glasses of water helps with weight loss. That wasn't true of 38 overweight and obese teens though, who were asked by researchers to drink more water for six months. Others claim that drinking extra water beyond what you're thirsty for helps hydrate or smooth skin, reduces headaches, or helps flush more toxins from kidneys. These claims were carefully reviewed and found untrue: "There is no clear evidence of benefit from drinking increased amounts of water," the researchers concluded. Instead, drinking when thirsty is good enough for most people.
Eggs pack lots of cholesterol compared to other foods. Cholesterol in the blood is strongly related to heart disease and heart attacks. So eating lots of eggs should be bad for your heart, right? It seems true, but most nutritional studies say otherwise.
As many as one egg per day does not raise your risk of cardiovascular disease—which can lead to heart attack—for people with normal cholesterol. That could be because eggs have other heart-protecting properties beyond cholesterol. It may also be because eating cholesterol is only weakly associated with raising cholesterol in your blood. Whatever the reason, your egg habit probably won't harm your heart.
More than 40 years ago, alarm bells were being rung in the health world relating to antiperspirants and dementia. Researchers found higher ratios of aluminum in the brains of Alzheimer's patients. There were fears that the aluminum that temporarily plugs your sweat ducts could raise risks of neurological problems. But over time no evidence has emerged to support this. Instead, it seems that Alzheimer's shrinks your brain, leaving a higher concentration of aluminum behind. And it seems the aluminum in an antiperspirant is barely absorbed by your skin. In other words, aluminum in the brain seems to be a consequence of Alzheimer's, and not a cause, and antiperspirants probably do not raise any risk of dementia, including Alzheimer's.
It was poorly understood science that started the Alzheimer's scare, but a chain email was responsible for convincing lots of women in the 1990s that their antiperspirant was raising their risk of breast cancer. The email falsely claims that antiperspirant traps harmful chemicals inside your body. It turns out all your underarm deodorant blocks are sweat and body salt--your urine and feces remove the more harmful chemicals. And there is no truth to this medical myth--the American Cancer Society says there is no link between antiperspirants and breast cancer.
You may have heard this one from your mother: "Don't go outside with wet hair or you'll catch cold!" With all due respect to Mom, that isn't how colds are spread. If you go outside in cold weather, with or without wet clothes or hair, you stand no greater risk of catching cold. Colds come from viruses, and viruses can be spread regardless of the weather.
Why do colds and flus become so common in the winter then? It's true that there is a "cold season" and a "flu season" that lasts from about October to May. But why? One theory is that cold weather forces people indoors where cold and flu viruses spread more easily in a closed space where people are clumped together.
Vitamins seem healthy in principal. They are full of the nutrients that let our bodies fight disease, let our cells grow, and let our organs do their work. So taking a daily dose of vitamins seems beneficial, right? Not so fast. Vitamins aren't harmless. Taking supplements of beta-carotene and vitamins A and E have been linked with an increased death rate. What's more, well-nourished adults don't get any disease-fighting benefit or any other benefit from taking extra vitamins. Most Americans get all the vitamins they need from their diets, and extra isn't helpful.
Even so, lots of health-conscious adults are taking multivitamins. The supplemental use of vitamins has risen from about 40% of the adult population in the early 1990s to more than half today. Lots of people take their vitamins "just in case," but many doctors say money spent on multivitamins is wasted. "The multivitamin-as-insurance-policy is an old wives' tale and we need to debunk it," nutritionist Dr. Miriam Nelson said.
All that being said, some people should take supplements. Your doctor can advise you if you are pregnant or face a particular health problem that would benefit from them. But if you're generally healthy, multivitamins won't do anything to help--and may actually harm--your health. Nutritionists agree that the healthiest way to get vitamins into your body is through fruits and vegetables.
You've probably heard that skipping breakfast makes it tougher to lose weight. Is that true? Probably not. Though some evidence seems to point that way, that evidence has been criticized for bias, including misrepresenting its own data and the scholarship of other researchers.
The argument for breakfast-as-weight-loss-cure goes like this: if you eat in the morning, you won't be as hungry during the day and you will eat fewer calories at night while your body is least active. Studies have shown that it doesn't much matter, though, when you get your calories. For the most part your body treats a calorie like a calorie whether you eat it at night or in the morning.
There is one study that found some health difference between skipping breakfast and skipping dinner, however. In that study, subjects who skipped breakfast had evidence of elevated inflammation in their blood. This could potentially be a reason to eat breakfast in the morning, but breakfast health benefits haven't been conclusively proven. Another study found that people lost weight if they switched their routine, either from starting a new breakfast routine or by starting to skip breakfast. In both cases, dieters who changed the time when they usually ate their calories lost more weight.
Many people believe that if they see green after blowing their nose, it's time to go to the doctor for an antibiotics prescription. Are you protecting your health this way? Not really. To understand this, it helps to know how antibiotics work.
When you take an antibiotic, you help your body fight a bacterial infection--and only a bacterial infection. Most colds are caused by viruses, though. Antibiotics are completely useless against viruses. Unfortunately, the color of your mucus does not indicate bacterial infection, as the more likely cause--a virus--can produce green mucus, too.
If green mucus doesn't mean you need antibiotics, what does? Here are a few signs you may have a bacterial infection:
- Your high fever isn't improving.
- Your mucus looks thick and white like pus.
- You've been sick for more than 10 days.
- Your symptoms are severe and they don't get better with standard cold remedies.
You and your kids are enjoying a boisterous Halloween party full of candy and other sweets. As the night moves on, they won't settle down and just don't listen when you say it's time to leave. Sound familiar? A lot of parents would attribute this unruly behavior to the sugar their kids just ate. But sugar doesn't seem to do anything to promote hyperactive behavior in kids.
This myth continues because it depends on who you ask. When parents were instructed to add or remove sugar from their children's meals, these parents thought they saw their kids' behavior change. They reported links between sugar and hyperactivity. That may be because of a popular diet in the early 1970s called the Feingold Diet, which called on parents to remove sugar and other food additives to help calm their children. That diet has been discredited, but many parents now expect restless kids after feeding them sugar. When researchers are the ones observing, though, they can't find any difference between sugared-up kids and kids without.
In one study, kids were chosen who were supposedly sensitive to sugar, along with regular kids. Researchers gave the kids sugar and two sugar substitutes to see how these different chemicals changed their behaviors. What they found was that there weren't any significant differences between any of the kids. That would seem to put this myth to rest, but the idea that sugar causes hyperactivity persists.
You may not be thrilled to use a public toilet, but for the most part, you need not fear catching any diseases from one. To understand why, it helps to remember that disease-causing microbes are everywhere. You can find them on your keyboard, on doorknobs, on money, and even on your smartphone. Yes, they're probably on the toilet seat too, but which one do think is cleaned more often--a toilet or your phone? Which one do you hold closer to your face? Compared to other objects you touch every day, the toilet is not a significant source of disease-carrying microbes.
One myth that needs to be quashed is the one about sexually transmitted infections (STIs). Can you really catch an STI from a toilet seat? Almost certainly not. These diseases survive and spread from skin-to-skin contact, and once they hit cold porcelain they are soon dead. There has never been a single reported case of an STI transmitted by sitting on a toilet seat.
All the same, there are a few more common microbial diseases that may be spread from toilet seats. The good news is that the risk is nearly eliminated just by washing your hands. Those diseases include E. coli, Strep, and Staph microbes, as well as the microbes (viruses) responsible for colds and flu. But remember--these disease-causing microbess need a way into your body, and merely resting on your skin won't cut it. Most need to contact your mucus membranes--your eyes, nose, or mouth--to do any damage. So if you avoid touching your face before washing your hands, chances are you'll be just fine.
You might be irritating others with these popping noises, but cracking knuckles won't give you arthritis. That popping noise comes from bubbles bursting in your joint fluid.
That doesn't make this habit harmless, though. If you regularly crack your knuckles, you are putting yourself at risk of swollen hands. Chronic knuckle-crackers are also more likely to lose some of their grip strength.
Consumers like natural foods, and the food industry knows this. Foods such as ice cream, potato chips, and soda can be found labeled "organic" or "natural" on grocery store shelves. Does this make them healthier? Not necessarily. Salt is natural, and so are many toxins. Describing a food as "natural" doesn't tell you enough to make a healthy choice.
To know if a food is healthy, you have to check the label. Even foods with organic or natural ingredients can be full of saturated fat, sugar, and other sources of empty calories.
Natural things aren't necessarily healthier. But of course a lot of them are. Healthy eaters skip over processed foods--often full of artificial chemicals--and fill their grocery carts with wholesome fruits, vegetables, and whole grains.
Vaccines have been under fire. Fear of vaccines has led many parents to delay them or avoid them altogether in the treatment of their children. Are the fears justified? Can vaccines cause harm?
Vaccines, like any other medication, can cause side effects. These are almost always minor, such as a small red bump developing where the needle went in. Rarely allergies are triggered by vaccines, and doctors and nurses are trained to look for them. It's not a bad idea to keep an eye on your child for signs of allergic reaction for a few days after vaccination.
The downside to the shot is a little inconvenience. The upside is protection from extremely dangerous and often deadly diseases. Diseases like polio, measles, and whooping cough have been successfully controlled by vaccines, but outbreaks have been seen now that vaccine scares are on the rise. Don't believe the fear. For the protection of all children, it is wisest and best to have yours vaccinated.
What do microwaves and cell phones have in common? They both emit energy, also known as radiation. What do they have to do with cancer? Not much. Some inventions that emit energy can damage DNA and raise cancer risks, such as x-ray machines. Similarly, the UV light that radiates from the sun can cause skin cancer. But not all energy-emitting things harm your DNA. Your own body, for instance, radiates energy to create warmth.
To understand why x-rays can damage DNA but smartphones and microwaves can't, you need to know something important about radiation. Radiation can be either high-energy or low-energy. It all exists on what's called the electromagnetic spectrum. High-energy radiation like x-rays and the gamma rays that are propelled from nuclear explosions can damage your DNA. However low-energy radiation, including the kind that comes from smartphones and microwaves, is not powerful enough to harm DNA.
Even so, research is ongoing as to whether cell phones or cell phone towers cause tumors or other forms of cancer. Some think that even without damaging your DNA, the radio waves emitted to send your cellular signal could harm you. However, the American Cancer Society says there is "very little evidence" of harm from cell phone towers. When it comes to the phones themselves, "evidence... is limited, and more research is needed."
When you hear the word "bacteria," does it make your skin crawl? Those tiny single-celled organisms are responsible for some terrible diseases, including tuberculosis, syphilis, and cholera. Sounds like you wouldn't want to be anywhere near bacteria, right? There's a problem though--there are more bacterial cells in your body than human cells.
How can we live with bacteria every day if they're so harmful? Well, the harm depends on the bacterium. While there are some nasty bacterial infections to watch out for, most bacteria we contact are either neutral or beneficial to human life. Sometimes we can even harm our bodies by killing off the bacteria that live inside, many of which help us by digesting our food and performing various other functions. For that reason, many doctors recommend probiotic foods like yogurt carefully timed during a course of antibiotics.
Homeopathy is the practice of mixing a tiny amount of a drug or herb into water in an attempt to reverse the drug or herb's effects. Homeopathic practitioners believe water can retain the "memory" of a drug in this way. It's been practiced since the 1700s, a time when modern medicine frequently killed its patients, and at that time the relative harmlessness of homeopathy (the cures were essentially water) led many to assume it worked.
Scientists have now studied homeopathy hundreds of times. They've reviewed the evidence from these studies over a dozen times in metastudies. The result? They all "failed to provide strong evidence in favor of homeopathy," according to physician and trained homeopath Edzard Ernst, who wrote a review of the metastudies.
Homeopathic treatments continue to be sold in pharmacies and supermarkets, even though they are often little more than water. They don't need to prove their effectiveness to be placed next to other medicines. This may change, however, as the FDA has introduced new rules making it tougher for homeopathic remedies to find a place next to scientifically proven medicine on drug store shelves.
Can your blood type lead you to a weight loss cure? A diet book came out in 1996 claiming it can. It proposed several diets depending on a person's ABO genotype. It took 18 years, but researchers put this idea to the test. The results probably won't make your heart beat faster.
The researchers studied 1,455 people. They found that the specific diets may have healthy results, but that was true no matter what blood type you have. For example, participants who followed the "type-O diet" were basically following a low-carb meal plan, and the same benefits from that type of diet could be expected for anyone. Since it didn't matter what the dieters' blood types were, this large study served to debunk the whole concept, marking diet based on blood type a health myth.
Does your body need a cleanse to flush itself of toxins? The idea is appealing. If you could rid your body of bad chemicals that would give you more energy, mental focus, or better sleep, wouldn't you do it? There's also something satisfying about taking bad things out of your body, especially if you're told it will cure another health problem. So does detoxifying your body work?
For doctors to know if a detoxification therapy works, they need to know two things. First, they need to know what toxin is being removed from the body. Second, they need to know how it will be removed. A group of scientists reviewed 15 products that claim to detoxify your body. The products ranged from face scrubs to bottled water. Most of the companies selling these products simply renamed ordinary processes like cleaning or brushing, calling them "detoxifying." For example, one of those face scrubs "detoxified" dirt and makeup--exactly what you would expect any facial scrub to do. The investigators said these companies could neither explain how they removed toxins nor what "toxins" their products were designed to remove. In other words, they simply used "detox" as an advertising buzzword.
So if a product claims to cleanse your colon, chelate your kidneys, or help you sweat out toxins, think twice before purchasing. Legitimate detoxification happens in a hospital, and usually only when something has seriously gone wrong, like in patients with heavy metal poisoning or medical treatment of an alcoholic.
Many products claim to improve or "boost" your immune system in some way. But they tend to be fuzzy on the specifics. You should ask yourself, "What part of the immune system does it boost?" Your immune system is a complex series of processes involving antibodies, certain proteins, parts of your blood (including white blood cells), and much more. When a product simply says it "boosts immunity," but doesn't say how, that should raise a red flag.
What's more, there are ways your immune system can be elevated that would be harmful to your body. One of the most important aspects of your immune function is inflammation, the natural process your body enacts to fight off bacteria, viruses, and anything in your body that your cells don't recognize as a part of your body. Activating your inflammatory response is one way a product can boost your immune system, but it would also be boosting your risk of stroke, heart attack, and other health problems.
Your best shot at improving your immune response is to follow the health basics: get plenty of sleep, exercise regularly, and eat healthy foods. Even in these areas, research is ongoing and plenty of controversy remains.
If you only used 10% of the brain, does that mean you could remove 90% and be fine? People who support this common claim say that if you were able to use the rest of your mental power you could unlock tremendous abilities hiding deep within. The only trouble? It's not at all true.
It could be that 1930s rat studies led to this idea. In these studies, parts of rats' brains were removed and the rats could still perform basic tasks. But that was only a specific portion of the rodents' brains, and the rats may have had other deficiencies that weren't tested.
Wherever the myth came from, it remains a myth. Brain scans clearly show that no matter what activity you do, your brain is active and engaged. Sure, some parts of the brain are "turned on" for some activities more than others, but there aren't any areas that aren't used.
How long should you wait to swim after eating? Advice to wait after eating has been around for at least 100 years, usually with the warning that you will cramp up if you swim too soon. Fortunately for young swimmers everywhere, there is no truth to this common health myth.
But what if you do get a cramp while swimming? Even if a full stomach won't cause it, you could pull a muscle while you swim or get a charley horse. Cramping won't cause you to slip under the water as long as you don't panic. If you do start to cramp while you swim, tighten and relax the cramped muscle until the cramp works its way out.
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