and now I'm an epidemiologist.

And nobody really knows what epidemiology is.

Epidemiology is the science of how we know in the real world

if something is good for you or bad for you.

And it's best understood through example

as the science of those crazy, wacky newspaper headlines.

And these are just some of the examples.

These are from the Daily Mail. Every country in the world has a newspaper like this.

It has this bizarre, ongoing philosophical project

of dividing all the inanimate objects in the world

into the ones that either cause or prevent cancer.

So here are some of the things they said cause cancer recently:

divorce, Wi-Fi, toiletries and coffee.

Here are some of the things they say prevents cancer:

crusts, red pepper, licorice and coffee.

So already you can see there are contradictions.

Coffee both causes and prevents cancer.

And as you start to read on, you can see

that maybe there's some kind of political valence behind some of this.

So for women, housework prevents breast cancer,

but for men, shopping could make you impotent.

So we know that we need to start

unpicking the science behind this.

And what I hope to show

is that unpicking dodgy claims,

unpicking the evidence behind dodgy claims,

isn't a kind of nasty carping activity;

it's socially useful,

but it's also an extremely valuable

explanatory tool.

Because real science is all about

critically appraising the evidence for somebody else's position.

That's what happens in academic journals.

That's what happens at academic conferences.

The Q&A session after a post-op presents data

is often a blood bath.

And nobody minds that. We actively welcome it.

It's like a consenting intellectual S&M activity.

So what I'm going to show you

is all of the main things,

all of the main features of my discipline --

evidence-based medicine.

And I will talk you through all of these

and demonstrate how they work,

exclusively using examples of people getting stuff wrong.

So we'll start with the absolute weakest form of evidence known to man,

and that is authority.

In science, we don't care how many letters you have after your name.

In science, we want to know what your reasons are for believing something.

How do you know that something is good for us

or bad for us?

But we're also unimpressed by authority,

because it's so easy to contrive.

This is somebody called Dr. Gillian McKeith Ph.D,

or, to give her full medical title, Gillian McKeith.

(Laughter)

Again, every country has somebody like this.

She is our TV diet guru.

She has massive five series of prime-time television,

giving out very lavish and exotic health advice.

She, it turns out, has a non-accredited correspondence course Ph.D.

from somewhere in America.

She also boasts that she's a certified professional member

of the American Association of Nutritional Consultants,

which sounds very glamorous and exciting.

You get a certificate and everything.

This one belongs to my dead cat Hetti. She was a horrible cat.

You just go to the website, fill out the form,

give them $60, and it arrives in the post.

Now that's not the only reason that we think this person is an idiot.

She also goes and says things like,

you should eat lots of dark green leaves,

because they contain lots of chlorophyll, and that will really oxygenate your blood.

And anybody who's done school biology remembers

that chlorophyll and chloroplasts

only make oxygen in sunlight,

and it's quite dark in your bowels after you've eaten spinach.

Next, we need proper science, proper evidence.

So, "Red wine can help prevent breast cancer."

This is a headline from the Daily Telegraph in the U.K.

"A glass of red wine a day could help prevent breast cancer."

So you go and find this paper, and what you find

is it is a real piece of science.

It is a description of the changes in one enzyme

when you drip a chemical extracted from some red grape skin

onto some cancer cells

in a dish on a bench in a laboratory somewhere.

And that's a really useful thing to describe

in a scientific paper,

but on the question of your own personal risk

of getting breast cancer if you drink red wine,

it tells you absolutely bugger all.

Actually, it turns out that your risk of breast cancer

actually increases slightly

with every amount of alcohol that you drink.

So what we want is studies in real human people.

And here's another example.

This is from Britain's leading diet and nutritionist in the Daily Mirror,

which is our second biggest selling newspaper.

"An Australian study in 2001

found that olive oil in combination with fruits, vegetables and pulses

offers measurable protection against skin wrinklings."

And then they give you advice:

"If you eat olive oil and vegetables, you'll have fewer skin wrinkles."

And they very helpfully tell you how to go and find the paper.

So you go and find the paper, and what you find is an observational study.

Obviously nobody has been able

to go back to 1930,

get all the people born in one maternity unit,

and half of them eat lots of fruit and veg and olive oil,

and then half of them eat McDonald's,

and then we see how many wrinkles you've got later.

You have to take a snapshot of how people are now.

And what you find is, of course,

people who eat veg and olive oil have fewer skin wrinkles.

But that's because people who eat fruit and veg and olive oil,

they're freaks, they're not normal, they're like you;

they come to events like this.

They are posh, they're wealthy, they're less likely to have outdoor jobs,

they're less likely to do manual labor,

they have better social support, they're less likely to smoke --

so for a whole host of fascinating, interlocking

social, political and cultural reasons,

they are less likely to have skin wrinkles.

That doesn't mean that it's the vegetables or the olive oil.

(Laughter)

So ideally what you want to do is a trial.

And everybody thinks they're very familiar with the idea of a trial.

Trials are very old. The first trial was in the Bible -- Daniel 1:12.

It's very straightforward -- you take a bunch of people, you split them in half,

you treat one group one way, you treat the other group the other way,

and a little while later, you follow them up

and see what happened to each of them.

So I'm going to tell you about one trial,

which is probably the most well-reported trial

in the U.K. news media over the past decade.

And this is the trial of fish oil pills.

And the claim was fish oil pills improve school performance and behavior

in mainstream children.

And they said, "We've done a trial.

All the previous trials were positive, and we know this one's gonna be too."

That should always ring alarm bells.

Because if you already know the answer to your trial, you shouldn't be doing one.

Either you've rigged it by design,

or you've got enough data so there's no need to randomize people anymore.

So this is what they were going to do in their trial.

They were taking 3,000 children,

they were going to give them all these huge fish oil pills,

six of them a day,

and then a year later, they were going to measure their school exam performance

and compare their school exam performance

against what they predicted their exam performance would have been

if they hadn't had the pills.

Now can anybody spot a flaw in this design?

And no professors of clinical trial methodology

are allowed to answer this question.

So there's no control; there's no control group.

But that sounds really techie.

That's a technical term.

The kids got the pills, and then their performance improved.

What else could it possibly be if it wasn't the pills?

They got older. We all develop over time.

And of course, also there's the placebo effect.

The placebo effect is one of the most fascinating things in the whole of medicine.

It's not just about taking a pill, and your performance and your pain getting better.

It's about our beliefs and expectations.

It's about the cultural meaning of a treatment.

And this has been demonstrated in a whole raft of fascinating studies

comparing one kind of placebo against another.

So we know, for example, that two sugar pills a day

are a more effective treatment for getting rid of gastric ulcers

than one sugar pill.

Two sugar pills a day beats one sugar pill a day.

And that's an outrageous and ridiculous finding, but it's true.

We know from three different studies on three different types of pain

that a saltwater injection is a more effective treatment for pain

than taking a sugar pill, taking a dummy pill that has no medicine in it --

not because the injection or the pills do anything physically to the body,

but because an injection feels like a much more dramatic intervention.

So we know that our beliefs and expectations

can be manipulated,

which is why we do trials

where we control against a placebo --

where one half of the people get the real treatment

and the other half get placebo.

But that's not enough.

What I've just shown you are examples of the very simple and straightforward ways

that journalists and food supplement pill peddlers

and naturopaths

can distort evidence for their own purposes.

What I find really fascinating

is that the pharmaceutical industry

uses exactly the same kinds of tricks and devices,

but slightly more sophisticated versions of them,

in order to distort the evidence that they give to doctors and patients,

and which we use to make vitally important decisions.

So firstly, trials against placebo:

everybody thinks they know that a trial should be

a comparison of your new drug against placebo.

But actually in a lot of situations that's wrong.

Because often we already have a very good treatment that is currently available,

so we don't want to know that your alternative new treatment

is better than nothing.

We want to know that it's better than the best currently available treatment that we have.

And yet, repeatedly, you consistently see people doing trials

still against placebo.

And you can get license to bring your drug to market

with only data showing that it's better than nothing,

which is useless for a doctor like me trying to make a decision.

But that's not the only way you can rig your data.

You can also rig your data

by making the thing you compare your new drug against

really rubbish.

You can give the competing drug in too low a dose,

so that people aren't properly treated.

You can give the competing drug in too high a dose,

so that people get side effects.

And this is exactly what happened

which antipsychotic medication for schizophrenia.

20 years ago, a new generation of antipsychotic drugs were brought in

and the promise was that they would have fewer side effects.

So people set about doing trials of these new drugs

against the old drugs,

but they gave the old drugs in ridiculously high doses --

20 milligrams a day of haloperidol.

And it's a foregone conclusion,

if you give a drug at that high a dose,

that it will have more side effects and that your new drug will look better.

10 years ago, history repeated itself, interestingly,

when risperidone, which was the first of the new-generation antipscyhotic drugs,

came off copyright, so anybody could make copies.

Everybody wanted to show that their drug was better than risperidone,