Is wearing a hat the key to staying warm when the temperature plummets? Do you wish you could use more than 10 per cent of your brain? Have you switched to waxing your legs because shaving made the hair grow back faster and thicker? Is it a struggle for you to drink the recommended eight glasses of water a day?
Every day, you hear or think things about your body and health that are not true. Maybe these ideas are simply unproven. Or maybe these ideas about your body and how to keep it healthy have actually been shown scientifically to be false.
And yet we still see these things on TV, read them in magazines or hear them from our friends. Even your doctor may have told you one of these myths.
One of the dirty little secrets in the practice of medicine is how little of what we doctors do is actually proven. People assume that if doctors recommend something then it must be correct. To know something is true, however, requires scientific research, and good research requires time and money. Although there are millions of people and billions of pounds invested in scientific research, there just isn’t enough to go around to answer every question; especially since the focus of modern research is usually on the most serious problems and the most advanced drugs and procedures.
Often when a doctor tells you to do something, it’s just his best guess. And that’s okay. A good doctor builds on his training, experience and knowledge to give you his best advice, so most of the time this medical advice will be useful and helpful. However, another doctor may give you different advice. Who’s right? How do you know whom to trust?
If this is happening with important medical issues, what about those things that are less critical – the things your mother warned you about? Or the things your friends told you they saw on TV, or even the stuff you read in popular health books?
The fact is that often we just don’t know what’s true. That’s where the idea for this book came from. Many things you believe about your health, things you were told as a child, are simply unproven. Again, that’s okay, but these ideas should not be given the same weight and credence as those that are proven. It’s in our best interest to understand where these unproven beliefs came from, and then judge for ourselves whether they are useful.
Some of these myths have actually been studied. So we can look at what the studies say and make a judgement. How do we decide whether to trust scientific studies? We are both doctors and researchers. In our professional lives, we spend a great deal of our time teaching people, from parents to other doctors, how to understand health research. As researchers, we strive to maintain a sense of fairness in our work; we are careful not to make any decisions before the experiments are complete. Therefore we are able to accept whatever the science tells us, regardless of what we might have believed before. We want to give you a crash course in health research and scientific studies so that you can understand how science helps us decide whether a belief is right or wrong. As part of this crash course, we suggest a quick look at the section Boring Research Terms That You Might See in This Book. We don’t want you to believe something is a myth just because we said so. We want you to understand why we said so.
The best possible type of study is what the scientific world calls a ‘randomized controlled trial’ (see the Boring Terms section.) In these studies, people are secretly given one of two or more treatments. In the best research, no one involved in the study knows which person is getting what treatment. By looking at what happens to people in this kind of study, we can tell what effect the treatment or situation caused. Randomized controlled trials are the only way to prove causation. You should be sceptical when anyone tells you something has been ‘proven to work’ or ‘proven to cause’ something unless the outcome was a result of a randomized controlled trial. But these types of trials are pretty rare in the medical world because they are expensive and complicated. Sometimes they are even unethical. You have probably heard tobacco companies say that smoking has never been proven to cause cancer. This is because there has never been a randomized controlled trial of smoking and cancer. And there never will be. Can you imagine anyone approving a study that secretly forced some people to smoke so that we could see if they got cancer? That would be crazy! And wrong!
When we simply can’t get a randomized controlled trial, we have to look at the next best thing. Through other types of studies, called epidemiological or cohort studies, we can look at ‘associations’. An association is a relationship one thing has with something else. Association and causation are not the same. While we can’t prove that smoking causes cancer, there is an overwhelming amount of evidence that smoking is associated with cancer. With evidence that reveals an association between smoking and cancer, we can’t say we are 100 per cent sure that smoking causes cancer, but we are as close to being sure as we are ever going to get. The scientific studies that tell us about associations usually involve big groups of people (the bigger, the better), where we can best see if these people have certain things in common (like smoking and getting cancer).
Many of the myths in this book have this type of evidence stacked against them. Maybe there aren’t any randomized controlled trials to dispel the myth, but there are large epidemiological or cohort studies that point to that answer. When scientific evidence for or against something builds up, we argue, you should believe the science. In this book, you will always see us argue on the side of science.
Keep something else in mind as you read this book: that you cannot prove a negative. Although we can tell you that something has never, ever happened in the history of the world, we cannot offer definitive proof that this thing won’t ever happen. This does not mean you should expect it to happen. It is not logical to believe that something is true or that something is going to occur only because there is no absolute proof that it is false.
For instance, in the history of the world, no one has ever been born who could fly. We can’t prove, or say with 100 per cent certainty, that someone won’t be born tomorrow who can, but it is really, really, really unlikely. So it’s okay for us to say, even without absolute proof, that people can’t fly.
In this book, we will examine a lot of beliefs about your body and your health. We will lay out the science as best we can, based on everything we can find in medical and scientific literature. We will argue that you should decide what to believe based on the evidence or lack thereof.
What really concerns us are those myths which great randomized controlled trials have already disproved and which people still believe. This is frustrating, because the jury is in – there won’t and shouldn’t be any more studies. All the research indicates that the myth is untrue, but people just don’t want to accept that.
We know that people don’t like to hear that they are wrong (Aaron especially – he always thinks he is right). Discovering that something you believed is not true can be disturbing and unsettling. When we published the first of these myths in the British Medical Journal in December 2007, we were shocked at the strong reactions it provoked. Some people just can’t let a myth go.
Some of you will read this book and still refuse to accept what the studies show you to be true (or false). We have provided extensive references for those of you inclined to investigate further. You may be surprised not only by the scarcity of evidence supporting some of your beliefs but also by the volume of evidence disproving others. We tried to show you everything; we included all the evidence we could and told you when there was none.
Keep an open mind. More often than not, this book will make your life easier. Moreover, it will give you a number of smart answers for your mother.