One of science’s main roles in society is to probe extraordinary claims, separate fact from fiction, and set the record straight. But it does not always succeed. Indeed, sometimes the exact opposite happens.

“Science” itself can sometimes take things out of context, and present half-truths which, repeated over generations, eventually come to seem like total certainties. These ideas do not necessarily take root because they are true, but because they sound good, seem like common sense, and often carry the authority of being linked to an eminent name.

When it comes to diet and health, this is all too common. I am not talking here about the fake news or outright hoaxes that proliferate on social media, but phrases and ideas with historical – and even academic – pedigree that have been mistakenly adopted as unquestionable truths.

1. Let food be thy medicine

One of the best-known examples is the phrase attributed to Ancient Greek philosopher and physician Hippocrates: “Let food be thy medicine and medicine be thy food”. While frequently attributed to him, there is no firm basis for this.

Despite its dubious origins being revealed years ago, the phrase continues to feature in articles and speeches – likely because it is shrouded in apparent wisdom.

2. You are what you eat

Something similar applies to the saying “you are what you eat”. Today it is often treated as an indisputable truth, but its original meaning was philosophical, not physiological. The phrase formed part of a reflection on the importance of the material dimension of human beings put forward by the 19th century German philosopher Ludwig Feuerbach, to challenge those who attached importance only........

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