Is salt bad for you?

episode

More or Less 27 min 4 speakers 4 chapters transcribed 2 months ago

▲ 0

Transcript

jump: chapters · speakers · find in transcript

Transcript

Transcript generated automatically by AI and may contain errors.

What is the main topic discussed in this episode?

Unknown 0:00

Thanks for downloading the More or Less podcast from BBC Radio 4. Here's Tim Harford.

Tim Harford 0:05

Hello and welcome to More or Less. Whether you love numbers or just want to be friends with them, we're the programme for you. And as always, we'll be turning to the numbers for insights about the news and, more importantly, the world. Later, we'll ask whether zero-tolerance policing really works.

Unknown 0:22

We call it Newton's Law of Crime. What goes up must come down and what goes up the most tends to come down the most.

Tim Harford 0:30

And we'll ask whether it's possible to predict the future height of growing children.

Unknown 0:34

The best predictor of what height an individual is going to be is the height they are in childhood.

Tim Harford 0:39

But first, let's talk about the most delicious condiment in existence, salt. Last month, a Daily Express headline declared... Now salt is safe to eat. And that sentiment was echoed in the, I think it's fair to say, more academically-minded Scientific American magazine, which said... It's time to end the war on salt. The zealous drive by politicians to limit our salt intake has little basis in science. These and similar reports cited a Cochrane collaboration review which, in its own words, set out to assess whether advice to cut down on salt in foods altered our risk of death or cardiovascular disease. The Cochrane Collaboration is a highly respected network of researchers which evaluates the evidence for medical interventions.

Tim Harford 1:25

Their review was a meta-analysis of seven studies, each of which was a Randomised Controlled Trial, or RCT. RCTs are considered to be the best kind of study for medical research, and the plain English summary of the Cochrane Review itself does seem to support the Daily Express headline writer.

Ben Moody 1:43

Cutting down on the amount of salt has no clear benefits in terms of likelihood of dying or experiencing cardiovascular disease.

Tim Harford 1:52

All this might surprise you. Haven't public health bodies been telling us to eat less salt for years? In Britain, NICE, the National Institute for Health and Clinical Excellence, wants people to reduce their intake of salt to six grams per day per adult by 2015. and to 3 grams per day by 2025, from over 8.5 grams a day at the moment. So has the Cochrane Collaboration paper really challenged this advice? The paper was published in the American Journal of Hypertension, which is edited by Dr Michael Alderman. Dr Alderman thinks it has.

Unknown 2:27

Well, I think it's important because they attempted to assemble all of the available randomized clinical trials. That's the highest level of evidence for medical interventions. They were only able to find seven, and in analyzing those as a group in a process called meta-analysis, they were unable to find sufficient evidence to determine whether or not reducing sodium intake, which is the issue, would be safe or beneficial.

Tim Harford 2:57

We spoke to Rod Taylor, one of the authors of the Cochrane analysis, and he very clearly said he thinks people should cut down on their salt and this shouldn't be interpreted as meaning that salt is harmless.

Unknown 3:11

I mean, what do you think about that? Well, I mean, I think everybody's entitled to their opinion and I think the fact of the matter is that the findings of the analysis were there's not evidence of harm or benefit. You know, when you're talking about going from the 3,500 milligrams a day that we in the United States and Great Britain eat now down to levels of 2,300 or 1,500, that's cutting it by more than half. It seems to me that there has to be really solid, powerful, overwhelming, robust information that this is going to be beneficial and safe.

Tim Harford 3:47

I'm going to be talking to Professor Graham McGregor. He's been using mathematical modelling and he reckons that cutting down salt intake could save many thousands of lives. I mean, do you dispute the methods he's using?

Unknown 3:59

Those models, of course, have been used for years and years. And it's traditionally in science, that's a technique. We say, as Professor McGregor and others have done, Since we know that reducing sodium intake by half will lower average blood pressure by a couple of millimeters of mercury, and we know that a difference of a couple of millimeters of mercury in a population will prevent so many reduced deaths by so much, they believe it's inevitable that a salt reduction of this amount will save those lives.