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There have been many misconceptions about the human body that have been passed down through the years, such as that eating carrots can improve your eyesight. Various authors have methodically dispelled these myths. Photo: Shutterstock

Busted: five myths about the human body, from larger private parts in men with big feet to only using 10 per cent of your brain

  • Many misconceptions and inaccuracies regarding the human body exist, such as the idea that a flatlining heart can be restarted again with a defibrillator
  • That eating carrots can help you see in the dark and that your appendix serves no purpose are two other medical fallacies that have been accepted as fact

Of all the myths propagated about the properties of the human body, those about our brains are the ones most in need of being dispelled, says British children’s book author Paul Mason, whose most recent title is Hair-raising Human Body Facts.,

“I still hear people saying, ‘You only use 10 per cent of your brain, you know?’” says Mason. The 2014 Hollywood film Lucy starring Scarlett Johansson is among media productions to have touted this false idea.

“It’s complete nonsense, just as the idea that having a big brain makes you more intelligent: Albert Einstein’s brain was completely average-sized,” he adds.
Mason, who also wrote You Can Fill a Swimming Pool with Your Spit: The Fact or Fiction Behind Human Bodies, is a swimming coach too. The inspiration for his Body Bits series, he says, comes from a habit of using random body facts to distract swimmers when they’re training hard.
“I might tell them that they can’t really be out of breath: the airways in their lungs are so long that they’d stretch halfway across North America. And the smallest kids always like to hear that they have the exact same number of muscles as Adam Peaty, the world 100m breaststroke champion,” he says.

He is not the only writer to have published books that separate the real from the ridiculous, the facts from the falsities. Dr Sarah Schenker wrote Myth-busting Your Body: The Scientific Facts Behind the Headlines, Drs Aaron Carroll and Rachel Vreeman published Don’t Cross Your Eyes … They’ll Get Stuck That Way!: And 75 Other Health Myths Debunked, and Bill Bryson’s latest chart-topper, The Body: A Guide for Occupants, takes us on a tour of everything that makes us human.

Bill Bryson turns his wry gaze onto the human form

Understanding the very essence of our physical selves has long captivated writers – which isn’t surprising given how astonishing our physiological composition is. As Bryson notes, people’s belly buttons have been found to contain 2,368 species of bacteria; over a lifetime our hearts exert the equivalent energy in their daily pumping to that needed to force a one-tonne weight 240km (150 miles) into the air, and; if you strung a single person’s DNA end to end, it would stretch beyond the planet Pluto.


Our bodies are such incredible vessels that it is perhaps not surprising that sometimes our imaginations run a little wild and we get caught up in myth and legend and forget to separate what’s real from what’s not.

Here are five common body myths busted; they are outed in a number of books, including the succinctly titled Everything You Know About the Human Body is Wrong, by science writer Matt Brown and illustrator Sara Mulvanny.

It’s a myth that having a big brain makes you more intelligent. Photo: Shutterstock

1. We only use 10 per cent of our brains

As Mason observes, this is nonsense. It is clear from scans and imaging that we engage all regions of our brains at some point during the day.

The myth dates back to at least the early 20th century – long before brain scans and MRIs were available – so it seems the figure was plucked from thin air.

A doctor applies a defibrillator to a patient’s chest. Photo: Shutterstock

2. A flatlining heart can be restarted with a defibrillator

No, it can’t – even though every medical drama show you’ve ever watched has led you to believe otherwise.

When the heart monitor shows a flat line, this suggests an absence of electrical activity. Applying an electric shock will not help – that would be like trying to jump-start a car with no battery. Defibrillators work by stopping a heartbeat that is out of whack. They cannot start a stopped heart. Electric shocks only work if the heart has some electrical activity – a “shockable rhythm” which shocking with a defibrillator may help to reset.
The appendix is a reservoir for healthy, helpful bacteria. Photo: Shutterstock

3. The appendix has no known function

The appendix has had a bad rap for years – it’s whipped out with such ease and we do not apparently suffer when it’s gone. But it must have a point, otherwise, why would it have been in situ in the first place? The appendix, it is now known, is a reservoir for healthy, helpful bacteria.

Microbes that help us fight disease are stored there. During childhood, the appendix also makes white blood cells and antibodies to fight infections. And even when it’s removed it can serve a useful purpose as a spare part: surgeons have adapted it as a replacement for diseased urine ducts.

The cover of Hair-raising Human Body Facts, by Paul Mason.

4. Carrots improve your night vision

“Eat your carrots. They’ll help you see in the dark.” Who wasn’t told that by their parents as a child, in a bid to get them to eat more veg? Carrots do, indeed, contain high levels of vitamin A, which helps to support night vision, but it will not improve eyesight.


The carrot eating/eyesight myth apparently originated during the second world war. The success of British pilots who intercepted enemy planes was explained away by the Royal Air Force as their having better night vision – on account of a healthy diet of carrots. It wasn’t, of course; the RAF relied on superior, secretive radar technology. But that in itself may be another legend.

There is no correlation between a man’s foot size and the size of his penis. Photo: Shutterstock

5. Men with big feet have larger genitals

Men with large feet, so the myth goes, have big you-know-whats, too.


London hospital urologists have done studies on this and discovered that the theory does not stand up. In a study published in 2002 in the journal BJU International, they measured the stretched penile length of 104 men and compared it with their shoe size.

Penis size: the long and the short of it

They found no correlation. What they did discover was that the average stretched penile length is 13cm (five inches), while the average male UK shoe size is nine.