WSMoreOrLess: Can we trust food surveys?
More or Less
BBC
4.6 • 3.7K Ratings
🗓️ 11 March 2016
⏱️ 9 minutes
🧾️ Download transcript
Summary
Stories about what foods are good and bad for you, which foods are linked to cancer and which have beneficial qualities are always popular online and in the news. But how do experts know what people are eating? Tim Harford speaks to Christie Aschwanden, FiveThirtyEight’s lead writer for science, about the pitfalls of food surveys. She kept a food diary and answered nutrition surveys and found many of the questions were really hard to answer – how could she tell all the ingredients in a restaurant curry; and how many tomatoes did she eat regularly over the past six months? Presenter: Tim Harford Producer: Charlotte McDonald/Wesley Stephenson
Transcript
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| 0:00.0 | This is the short edition of More or Less, first broadcast on the BBC World Service. |
| 0:05.0 | Hello and welcome to More or Less on the BBC World Service. |
| 0:09.0 | We're your weekly guide to the numbers that surround us in the news and in life, and I'm Tim Harford. |
| 0:15.0 | There's a lot of rubbish written about food, how much we eat, what's making us fat, and what is giving us cancer. |
| 0:21.0 | A lot of this research looks like it's based on scientific method, but how robust is it really? That's a question that Christy Ashwondon decided to ask. She's the lead science writer at the website 538.com and she decided to go back to the first principles of nutrition science and the surveys used to gather data about what we eat. |
| 0:43.0 | It turns out that if you want to study relationships between what we eat and diseases and other health outcomes, |
| 0:50.0 | you have to start by figuring out what it is that people are eating. |
| 0:53.0 | And so what's done is something called the food frequency questionnaire. |
| 0:57.0 | It's a very detailed questionnaire that asks people |
| 1:00.0 | very specific questions about the foods they eat and the frequency that they eat them. |
| 1:04.0 | So did you eat that pie? Come on be honest, did you really eat that pie? |
| 1:08.0 | When did you eat the pie? How far back does this go? Or is this just a kind of generally how many pies do you eat kind of |
| 1:14.3 | questionnaire? Why don't I give you a sample question here Tim? |
| 1:17.4 | Sure. In the last six months how often did you eat tomatoes? In the last six months? In the last six months? |
| 1:22.8 | In the last six months that's right. |
| 1:24.8 | Would you say once a week twice a week, four times a week? |
| 1:29.1 | I don't want a quibble but I'm already wondering what you mean by tomatoes. |
| 1:32.3 | Or as we say tomatoes. So if I make a |
| 1:36.0 | parmesiana melonzane thing baked in the oven with a tomato passata or just some chopped tomatoes. Is that using |
| 1:45.4 | tomatoes or are you just talking about like a salad tomato, a whole tomato that I |
| 1:49.5 | just pop in my mouth and eat? Well that's's a really good question, isn't it? |
| 1:53.7 | So I took the FFQ, as did two of my colleagues at 538, and then we also recruited some readers |
... |
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