A new BBC2 documentary, Eat to Live Forever, with food critic and presenter Giles Coren, looks at three extreme diet regimes thought to push the very limits of life expectancy.
He tries the calorie-restriction diet, the Palaeo diet (aka the Stone Age diet, eating the same foods as our Palaeolithic ancestors), and a fruitarian diet.
But while he’s busy wondering which dietary secret will mean we live longer, we can get busy looking at the opposite end of the spectrum – which dietary hazards will mean you live shorter.
And the main life-cutting cupboard culprits (some obvious, some not so) are…
A diet high in red meat can shorten life expectancy, according to researchers at Harvard Medical School, whose 2012 study of more than 120,000 people suggested red meat increased the risk of death from cancer and heart disease. Scientists found that adding an extra portion of unprocessed red meat to the daily diet increased the risk of death by 13%, of fatal cardiovascular disease by 18% and of cancer death by 10%.
The risks appeared even higher for processed meat consumption - 20% increased overall risk of death, 21% increased risk of death from heart problems, and 16% for cancer mortality.
The experts aren't saying you need to cut red meat out altogether, But it's best to make sure you don't eat more than the recommended 70g a day – the equivalent of a medium portion of shepherd's pie and a rasher of bacon.
A small amount of salt is essential for the body to function normally, but the campaign group Consensus Action on Salt & Health (CASH) says adults need just 1g per day. Most adults currently consume 7g-10g/day, but CASH warns that a high salt diet can contribute to high blood pressure, stroke, heart disease, stomach cancer, kidney disease and obesity - all conditions we know can shorten your life!
Scientists have warned the levels of sugar that many of us consume without a second thought could be harming our life expectancy. Tests on mice at the University of Utah in the US found that when mice ate a regular diet with 25% extra sugar - the equivalent of three cans of cola per day for humans - females died at twice the normal rate. And studies of humans with type 2 diabetes, characterised by high blood-sugar, show they're at higher risk of conditions including high blood pressure and high cholesterol which can lead to heart disease, and kidney problems.
A handful of dried fruit such as raisins can contain five teaspoons of sugar - that's almost your daily recommended allowance. In addition some fresh fruits, often apples, have extra sugar added to them - a handful of that “healthy snack” can be over 200 calories, contain four teaspoons of sugar and 15g of fat.
Weight loss surgeon Dr Sally Norton, founder of the diet-free weight loss programme Vavista.com, warns that fruit juice often contains a large amount of sugar, and there can be as much as seven teaspoons in a glass of orange juice, which is the daily recommended limit.
Fruit juice is, however, still better than fizzy drinks as it contains some goodness, and Dr Norton advises: “If you do want juice then it's better to juice your own as you can ensure there's no added sugar or nasty preservatives, unlike some shop-bought varieties.”
Supermarket salads may contain dressing which is often high in sugar and fat, warns Dr Norton, so read labels carefully.
A healthy start to the day? The answer is probably no, says Dr Norton. These supposedly healthy breakfast choices can be 25% sugar, leaving you with plummeting blood-sugar by mid-morning.
Eat to Live Forever will be aired on BBC2 on March 18 at 9.30pm.