Scientists. They've been at it again. This week a study was published in Archives of Neurology showing that adoption of the “Mediterranean diet” makes recall-sufferers “less likely” to develop dementia. “By adding oily fish and lots of fruit and vegetables to our shopping baskets, we can help reduce the risk,” Rebecca Wood, chief executive of the Alzheimer's Research Trust, said.

This means that Alzheimer's and dementia now join cholesterol levels, cardiovascular disease, blood pressure, weight-loss and diabetes, plus prevention of cancer and stomach ulcers, as things being defeated by the world's smuggest shopping list: fruit, vegetables, oily fish, wholegrains, olive oil and a modest amount of wine. Someone should release a song with those lyrics - it would be like Here Come the Girls, but with veg. A smash hit. They'd use it to soundtrack features on healthy living. Not that we need a song listing the diet, of course. We all know what it consists of. It's what all the celebrities who do “My Fridge” features in the Sunday newspapers pretend they eat, while hiding all the Reggae Reggae Sauce and gin.

As you will note, the Mediterranean diet is very different from “the UK diet” - tea, Kit Kats, Rennies, WKD and a loaf done four ways (toast, sandwich, fried with an egg, fried without an egg.) Or, indeed, “the New York diet”, which - to judge from sitcoms - consists merely of a gigantic leafy bunch of celery in a large, brown paper bag, placed on a worktop while quick-fire dialogue about sexual dysfunction happens around it.

But you know what? As the Mediterranean diet has slowly gained credit for everything from making Sophia Loren's jugs to discovering the quark, I have harboured an increasing suspicion. No single dietary regime can be responsible for all this, surely? If we look at the strongest force on Earth - gravity - it just keeps us stuck to the ground. That's all it does. And it's gravity! Frankly, I doubt tomatoes are more powerful than gravity. You don't have to use booster rockets to escape the force of the avocado. If you did, the veg aisle of Waitrose would be carnage.

No. Of course it's not the diet. None of the evidence stacks up. That's not the key bit of “the Mediterranean diet”. It's the Mediterranean, isn't it? That's where most of these people who are eating the diet are living. Because these are the real contributory factors:

1) People of the Mediterranean do not have to put on upwards of 15 kilos of clothes every time they leave the house. You know when Arctic explorers moan: “Polar bears, temperatures below minus 50, the grinding loneliness and fear - that's the easy bit. It's dragging the sledge laden with supplies that's the difficult bit. That's what reduces your distance to a mere 400 yards a day.” Although it is a more-than-fair point, when it comes down to it they're not really burdened with much more equipment than the average British family in February, going to return some library books. Hats, coats, gloves, scarves, umbrellas, wellingtons, ear-muffs, leg-warmers - and we haven't even begun to list the soul-sapping litany of vests, under-jumpers, over-jumpers, second cardigans, tights and jumbo-cord blouses that must go on first.

In the Mediterranean, meanwhile, a body simply rises from its bed, puts on one or two delightfully inconsequential cotton items, and walks out of the door, into the sunshine. There are no furious, hour-long searches for a missing mitten. No mentally trying to reconcile the two thoughts, “I am a desirable and sexual woman” and “I am putting on a pair of quilted long johns”.

Essentially, those in warmer climates live in a benign world, climatically suited to human beings - something that we cannot truthfully say about, for instance, Lanarkshire or Bedford. They never have to face an unhappy truth: “I'm about to go out into an environment that wants to kill me with dampness, and/or a wind straight off the Urals.” These melancholy thoughts are easily going to add up to hypertension, let alone cancer. Personally, I feel I carry every thermal vest I've ever worn inside my arteries.

2) An advertising industry still in the relative Dark Ages. Greece, Turkey, Cyprus, Italy - if they've got something to sell you, nine times out of ten they'll just lovingly place it between the breasts of a pretty lady, write the word “WOW!” underneath it, and, ipso facto, poster campaign. There are no tricks. There are no surreal bamboozlements.

Here, on the other hand, we have advertising that works as some manner of psychological befuddlement-maze, plotted by Escher. Instance: the most popular advert of the moment shows two terrifying, saturnine children with mild electric shocks being applied to their foreheads to a disco beat. And that's “about” Cadbury's chocolate.

I'm sorry but, long-term, that's just too weird for the human brain. We're still basically wired up to do little more than chase moose across the plains and pick nits off each other - and suddenly we're having to deal with some manner of visual lysergia in the ad-break in Corrie? No wonder we get dementia. Those Guinness ads alone will probably see half of us wandering down corridors, naked, wailing “I'm looking for Auntie Pam's magic bookcase!” by the time we're 50.

3) People in the Mediterranean hate cats. Marauding hordes of scraggy strays fill the streets of the Mediterranean, and why? Because people in the Med view cats, quite correctly, as rubbish, midget failure-lions, riddled with disease and vermin. In the UK, on the other hand, we look at that CV - and invite the creatures into our houses, for meat and catnip. One day, we will discover that cholesterol is caused by kittens, and a revolution will occur.

4) Banana boats. You don't get banana boats in this country. The sight of five people, straddling a gigantic yellow dirigible, being towed by a man in a rusty speedboat smoking a fag, is sadly absent from the docks of Liverpool, Newcastle and Portsmouth. Clearly this is to our detriment. Every person that does have this sight as a cheerful backdrop to everyday life has a life-expectancy of 942, universally limber buttocks, and hearts so healthy they could power windmills with them.

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