For years now, I’ve kept a little log in my planner tracking my water intake each day. I aim to drink eight glasses because I’ve always believed it to be the guideline for healthy water intake. If I’m being honest, however, I’ve never struggled with being dehydrated. It’s just something I’ve felt like I should do as a part of trying to be a healthy person. Lately, this little checklist has started to feel like more of a burden in my busy life than a key to healthy living. At the end of the day, after taking care of three young kids and working from home as a freelance writer has swallowed up most of my time, my water log is more often than not just one more task I’m not checking off my to-do list. So recently I actually stopped trying to track how much water I drink each day. I drink when I’m thirsty and leave it at that. But what does science have to say about my dismissal of my old health-seeking habit? 
When it comes the things we believe about the body, it’s easy to oversimplify or believe things about the ways they function that are simply untrue—and how much water we need each day is just one myth we’ve all fallen for. Even though most of the myths are pretty harmless, some ideas we have about our bodies can actually keep us from making the right decisions about how to care for ourselves. So, do you have an adequate understanding about how the body works? Let’s clear up those lingering untrue “facts” once and for all.
1. The Truth About Water Intake
When it comes to how much water we aim to drink each day, eight glasses has long been touted as the gold standard. But how accurate is the belief that everyone should drink 64 ounces of H2O each and every day?
That much water is far too much for those people and can overwhelm their systems.
The fact of the matter is, a one-size-fits-all rule is often too simple. Each person has different needs, and this definitely applies when it comes to water intake. 
“Drinking eight glasses of water a day is not only not necessary for most people most of the time; it’s actually a very bad idea for the elderly or anyone who has a heart condition or kidney impairment. That much water is far too much for those people and can overwhelm their systems,” explains Dr. David Belk, internal medicine doctor and healthcare blogger. So just how much water should you aim to drink each day? You might not like the answer, but water intake should vary person to person, day to day. The activities that fill your day, like working out or working outside, along with the environment you live in influence your body’s need for fluids according to Valentina Olivadese, holistic nutritionist and owner of Valiant Nutrition. There is good news, though! You don’t have play a guessing game, because your body will tell you when it’s time to pour a glass. The body is great at communicating its needs, especially if you are a generally healthy person. Instead of aiming to drink a certain number of ounces of water each day, just pour yourself a glass whenever you body tells you it’s thirsty, instructs Dr. Fayne Frey, board-certified dermatologist.
2. The Truth About When You Should Stop Eating
Many dieters and health enthusiasts hold strong to the belief that food eaten after a certain time each night will contribute to weight gain. Even well-respected publications like Runner’s World advise their readers to stop eating right after dinner if they want to lose weight.
Late-night eating is usually mindless and happens at the end of the day when a person ate too little.
As it turns out, though, there is hardly an ounce of truth to this claim, according to Dr. Lisa Doggett, a board-certified family physician who says that the act of eating late at night is not what causes weight gain. Instead, it is eating more calories that can land you in trouble. So, yeah, that late-night PB&J might be causing you to gain weight, but it’s the calorie count, not the timing, that deserves the blame. 
Additionally, Olivadese suggests that late night eating and weight gain may have a more complicated relationship than we assume. “This myth is so widespread because late-night eating is usually mindless and happens at the end of the day when a person ate too little. Feeling famished makes us more likely to eat whatever we can find and to eat to the point of feeling stuffed. This cycle of starvation and bingeing can affect weight over time by causing stress and … preoccupation,” she says. When in doubt, trust your hunger and feed your body healthy options in small portions, no matter what time of day hunger strikes.
3. The Truth About How Much of Your Brain You Use
Maybe like me, the first time you heard the statement that humans only use 10 percent of our brain power, it was coming from a self-improvement guru. Their solution was simple: Learn to use more of your brain, become a better person.
Most of our brain is continuously active, though we are unaware of much of what our brain does all day.
It’s not bad advice at first glance, but dig a little deeper and you’ll learn that it’s based on a widely accepted falsehood about the human brain. The idea that we only use a very small percentage of our brain couldn’t be further from the truth. 
“Most of our brain is continuously active, though we are unaware of much of what our brain does all day. Even when we’re sitting and doing nothing, our brains are busy regulating our heart rate, body temperatures, blood pressures, posture, etc.,” shares Belk. And even when we aren’t paying close attention to what’s going on in our brain, it is working hard to process what is going on around us using the information it takes in through the senses. Each part of our brain is so important that even a small stroke that affects only one spot in the brain may be debilitating, according to Belk. “That we only use 10 percent of our brain is an urban myth that was never based on any scientific evidence whatsoever,” he concludes.
4. The Truth About Your Baseline Body Temperature
Feeling a little clammy? Don’t automatically assume something is up just because the thermometer isn’t reading 98.6 degrees.
It’s not even all that common for a healthy person to have a temperature of 98.6 degrees.
Even though most people hold pretty strongly to the belief that 98.6 degrees is the baselines temperature for humans across the board, it’s less of a rule and more of a guideline, according to Belk. “In fact, it’s not even all that common for a healthy person to have a temperature of 98.6 degrees Fahrenheit. A person’s body temperature will vary by one to two degrees throughout the day with an average of around 98 degrees and only occasionally crossing 98.6 degrees,” he explains. 
Instead, we should look for a range of temperatures within certain limitations. Most healthy people will find that their temperature changes by small amounts but falls somewhere between 97 and 99 degrees.
5. The Truth About What Shaving Does to Your Hair
As a preteen, I was told more than once to put off shaving my legs as long as possible because once I started, my hair would grow in dark and thick. I mostly ignored that advice, but I’ve always wondered if there is any truth to the idea that shaving makes your hair grow thicker. Frey was quick to set the record straight. Hair does not grow faster or thicker if it has been shaved. In fact, because the nature of hair fibers, which are made of a protein called keratin, it’s impossible for shaving to have any effect on their structure.
The dead hair shaft cannot send information about being cut to the hair follicle.
“The visible portion of the hair that is cut has no biological activity. Since the dead hair shaft cannot send information about being cut to the hair follicle, the site of hair growth, growth continues as usual,” says Frey. The fact that this belief is a myth isn’t new information, either. According to Frey, in 1928 a forensic anthropologist by the name of Mildred Trotter published conclusive findings that shaving does nothing to the color or texture of hair and it certainly doesn’t speed up growth. 
And, while we’re at it, the same goes for trimming your nails. “Similarly, clipping a fingernail, also made of keratin, does not cause the fingernail to grow any slower or faster because it was trimmed,” adds Frey.
6. The Truth About Detoxing
After every holiday, we’re barraged with advertising for detox diets. The idea behind each diet is that the body needs help clearing all the junk we eat out of our systems. But just how much truth is there to the claims that there are pounds of waste trapped in the human body? And does detoxing really help?
Our livers are incredible machines, they help detoxify the world around you.
“Our bodies are not dirty vessels and the concept of detoxing is off base…our livers are incredible machines, they help detoxify the world around you,” explains Elizabeth Trattner, an integrative medicine practitioner.
So many women come to see me saying, ‘I ate so much and now I have to detox.’
Although we are exposed to more chemicals than previous generations, regular detoxes are needless according to Trattner, who suggests skipping juicing and just eating the whole fruit instead. 
Trattner does help some of her patients detox, but these are people who have been exposed to dangerous chemicals or have genetic conditions that prevent their livers from clearing heavy metals. “So many women come to see me saying, ‘I ate so much and now I have to detox.’ Seriously, just eat [healthy foods] and you’re good to go.” she advises.
