This is Everyday Science with Clare Wilson, a subscriber-only newsletter from The i Paper. If you’d like to get this direct to your inbox, every single week, you can sign up here.

Hello and welcome back to Everyday Science.

I am back from a holiday in Cyprus, where I spent most of the time lazing around and having delicious food and drink.

Highlights were traditional Greek breakfasts of halloumi, ham, olives and fresh bread, with main meals such as moussaka, and – my favourite – a dish of succulent and intensely flavoured roast lamb called kleftiko.

A fellow hotel guest said that we didn’t need to feel guilty about the Cypriot food, because the Mediterranean diet is known for being healthy.

A Mediterranean eating pattern – based on cuisines from countries such as Greece, France, Spain and Italy – is certainly widely advocated by dietitians and doctors in several countries.

Holes in logic

But there are some problems with this school of thought. They include that the scientific evidence supporting it is weak, and that what is currently claimed to be a Mediterranean diet doesn’t resemble what is eaten by most people in such countries, either now or traditionally.

I’m not advising anyone ignores NHS guidelines, nor their doctor’s advice, but it seems worth exploring if there are holes in the logic behind such widespread dietary recommendations.

The idea of the Mediterranean diet stemmed from several studies going back to the 1960s that suggested better heart health is seen in people who eat more fish, olive oil, fruit and vegetables, and whose alcoholic drink of choice is wine, rather than beer or spirits.

This chimed with accumulating evidence that diets low in saturated fat – found in red meat, eggs and dairy products – are best for the heart.

It was later bolstered by the idea that there seem to be more people living to extreme old age in certain parts of Greece and Sardinia – the so-called Blue Zones.

And it was posited as the explanation for the “French paradox” – the finding that people in France have a low rate of heart disease yet eat a lot of saturated fat. Perhaps the fish and olive oil cancelled out the butter and red meat.

The NHS’s official diet advice, called the “Eat well guide”, doesn’t mention the word Mediterranean, but many NHS sources have Mediterranean diet advice sheets saying that this approach is best for the heart.

Such guidelines usually advise eating a heavily plant-based diet, with plenty of fruit and vegetables, and getting protein mainly from pulses such as beans and chickpeas. We can have moderate amounts of lean meats like fish and chicken but red meat is a no-no.

Starchy foods like bread, pasta and rice should be wholegrain versions. Dairy products should be low fat, like skimmed milk and low-fat yogurt. Olive oil should replace other oils and fats.

Fish is a major feature of the Mediterranean diet (Photo: hxyume/Getty)

But if you think about this for a few moments, it doesn’t make sense.

Yes, the countries of southern Europe eat more fish and olive oil than the UK – but they are not renowned for their vegetarian cuisine.

A vegetarian friend tells me she found it almost impossible to get meat-free meals in restaurants in Spain, and a quick search of chat forums shows she is not the only one.

Think about the dishes that Italy, Portugal, France and Greece are famous for, and many of them involve red meat. Cyprus’s lamb kleftiko is a case in point. (Apparently, the secret is to marinate a leg of lamb in lemon juice, olive oil and herbs overnight before roasting it in a parcel of foil.)

It’s not just about the meat. The delicious home-made bread from these countries are most commonly made with white flour. These cuisines don’t stint on their cheeses, and we are not talking low-fat versions, either. The name we give to yogurt with the highest fat content? Greek yogurt.

To try to get to the bottom of it, I spoke to Dr Fumiaki Imamura, a scientist from the Medical Research Council’s epidemiology unit at the University of Cambridge, which has produced much research on the benefits of the Mediterranean diet.

Dr Imamura conceded that the plant-based Mediterranean diet so commonly recommended these days isn’t the same as traditional diets in those countries.

He said health bodies have changed their views because of accumulating evidence that diets low in saturated fat and high in vegetables are best for the heart. So agencies now advise a modified version of the original Mediterranean diet that we could think of as “healthy-Mediterranean”. “This is not the authentic Mediterranean diet,” he said.

The Mediterranean diet is said to be good for heart health (Photo: ljubaphoto/Getty)

In fact, it is hard to define a single authentic Mediterranean diet, because over 20 countries border this body of water with quite different cuisines, he said. The region includes countries such as Spain, Turkey, Croatia, Algeria and Morocco, representing “huge diversity”, said Dr Imamura.

This might explain why different diet gurus can recommend some very different eating patterns while all claiming these represent the Mediterranean diet.

Another problem is that the evidence for a plant-based, low-saturated-fat diet comes mainly from “observational” studies, which can give biased results. That’s because people who follow healthy-eating advice tend to be healthy in other ways, for instance, taking more exercise and avoiding smoking.

This reliance on observational studies is why the whole field of nutrition science is renowned for producing contradictory findings from one week to the next. And why NHS healthy eating advice has changed over time (for instance, when it comes to trans fats and low-carb diets).

The best kind of medical evidence is a kind of research called a randomised trial, which can avoid biases. For the Mediterranean diet, there have been three such trials, but all were planned and begun around two decades previously and used diets based on the original Mediterranean concept, not the current chiefly plant-based version.

In one of the most widely cited trials, called Predimed, people on the Mediterranean diet were told to eat white meat instead of red, but not to reduce total meat. So this does not really support the plant-protein ethos of the current Mediterranean diet advice.

The conclusion from the Predimed trial was that those on the Mediterranean diet had fewer heart attacks and strokes than the comparison group, who were on a low-fat diet. But low-fat has long been the foundation of NHS diet advice because it is thought to aid weight control – also very important for heart health.

In the Predimed trial, incidentally, people were also advised that, unless they were teetotal, they should have at least seven glasses of wine a week, as a minimum. That starkly contradicts the current NHS mantra that there is no safe level of alcohol.

Could we at least salvage the core principle of the original Mediterranean diet, that avoiding red meat is good for the heart? Sorry, even that is up for debate. A review of all other randomised trials of cutting down on red meat found the approach has little or no effect on heart health (or cancer rates).

I can’t help concluding that the whole of nutritional science is one big contradictory mess!

I’ve also written

As growing numbers of people are using weight loss jabs such as Wegovy and Mounjaro, doctors are learning more about their long-term effects. Some of them may be a natural consequence of weight loss, while others have come as more of a surprise.

I’ve been reading

I’m a die-hard fan of the novelist William Boyd, so his latest paperback Gabriel’s Moon was among my holiday reading. Set in the 1960s, it’s about a travel journalist who is reluctantly drawn into a web of espionage and violence.

As always with Boyd, the characters and the dialogue are so well written they sweep you along and leave you believing everything really could have happened.