How much water should we drink a day? Can a contact lens go missing in my brain? Is eight glasses of water a day too much?
These are the questions medical doctor and senior editor at the Atlantic James Hamblin gets all the time.
So he set out to answer the top questions about bodily functions in a series of videos and now a book, If Our Bodies Could Talk: A Guide to Operating and Maintaining a Human Body. It's a field guide to the fascinating world inside our skin.
Speaking to RNZ’s Jesse Mulligan, Hamblin says there’s a lot of misinformation in the medical world, which affects daily decisions in people’s lives.
He says the concept of ‘false equivalence’ is often used to confuse facts, where one side of the matter is overly represented in a debate.
“In the mid-20th century it was becoming clear that smoking caused cancer and yet the tobacco industry would try to advocate by having, you know, one expert on every panel who would say ‘no, we don’t know yet, we just don’t know, the science isn’t clear’ and you’d see a lot of TV shows saying OK here’s one person who thinks that smoking does cause cancer and one who thinks that it doesn’t… as though it were just a matter of opinion.”
He says a lot of people want quick answers in regard to their health.
“Should I be avoiding gluten? How many hours should I be sleeping? Just tell me!”
Hamblin says he can relate - when it comes to auto-mechanics and investing, he wants straight forward answers too, - but he says humans are complex.
“It becomes very difficult to make any recommendation that is, you know, absolutely valid for all people in all situations.”
He answers a range of questions in the book, including confirming a contact lens cannot get lost in your brain, and why men have nipples.
“That got me to this interesting idea of why we treat nipples so differently in culture when they are the same organ.
“That we all have this thing and men are, in most parts of the world, allowed to go out on beaches and no one gives it a second though when they’re shirtless and the opposite is true for women.
“Why this really passionate double standard?”
Hamblin says the claim that carrots can give people better eye sight has turned out to be false, unless you’re deficient in vitamin A.
“Just because a little bit can save you from blindness, doesn’t mean the more you take, the sharper your vision will get.
“More does not mean better.”
That’s a constant theme throughout the book, he says, as people often attempt to mega-dose on things.
But that just results in expensive urine, he says, as if you eat an even moderate diet you’re not going to be deficient in vitamins.
“People tend to think that when they’re taking these supplements that they don’t need to eat quite as well.
“There are just inherent properties in a plant-based diet that we have not been able to reduce into a pill.”
When it comes to alcohol, he says there’s a clear message in ‘the dose makes the poison’.
While alcoholism is clearly associated with shrinkage of the brain and early cognitive decline, he says the healthiest populations in the world often have alcohol in their diet.
In answer to the question of how much sleep we should have, he says the average of all the studies comes out somewhere around 7.5 hours.
“For some people 7.5 might not be enough, and for others it might be too much, and this so-called population of short sleepers that get by on much, much less and so there certainly seems to be a genetic, hereditary element to how much sleep our bodies require.”
He says people who require less sleep are often believed to have stronger character.
“And it’s just not, it’s almost like treating taller people as though they were just simply more dedicated to growing.
“It’s not a sign of strength to forgo that sleep, it’s more like you’re doing harm to yourself, you’re putting yourself at risk.”
The idea of drinking eight glasses of water a day is where physiology meets behavioural science, he says.
“It is an arbitrary number, but giving people a concrete goal is more effective than telling them they need to drink more water.”
He says the point of the book is to not stress about the golden answer to the way we should be living, as that can be stressful in itself.
“We do know things but there’s a lot that we don’t and there’s not one perfect answer for the way that we should be doing things.
“You can kind of be happy with what’s working for you.”