Deborah Orr: Cut wheat, sugar and caffeine from your diet - along with enjoyment

One woman became convinced that the only foods she could safely eat were white sugar and lamb

We all know, of course, that staying lissome and lithe for ever is a central focus of Madonna's lucrative career, as well as her self-image, and that her good fortune in having the time and money to lavish on such ambitions stems largely from her good fortune in having shrewd intelligence and iron self-discipline.

For lesser mortals it's all a bit more difficult. I've been troubled for ages by the behaviour around food I've noticed among some of the most attractive middle-aged women I know. Slender, toned, with the boyish bodies of teenagers, they are never happier than when browsing through the shelves of health food stores like Fresh and Wild. Constantly absolutely starving, and ever on the look out for "healthy snacks", they're never actually on something as naff as a diet - though they might embark on a "detox". But they're never in much danger of putting on weight either, because virtually all food is off-limits due to its unhealthiness.

Cutting out sugar, caffeine, alcohol, wheat, gluten, yeast and dairy is usually just the start. According to the "detox guru" Dr Joshi, beloved of Gwyneth Paltrow, even tomatoes should be given the big heave because they promote acid in the stomach. Likewise, fruit should only be eaten two hours before or after other food (unless you suffer from candida, in which case it should never be eaten), and proteins shouldn't be eaten along with starches. Each day should start with a nice refreshing cup of hot water - with organic unwaxed lemon in if you defy the claims that citrus fruits are too acidic and can wait two hours for breakfast.

If this sounds somewhat cranky, you'll be relieved to learn that one dietary physician at least is ready to admit that it could even be dangerous. US doctor Steve Bratman suggests that people - particularly but not exclusively women over 30 - are becoming susceptible to a new sort of eating disorder that he calls orthorexia nervosa. Healthy eating, he says, can become pathological, and behaviour around food can become just as disruptive as any other sort of obsessive-compulsive behaviour. This may not yet be recognised officially as a medical condition. But there's certainly rather a lot of it about.

He describes one former patient of his called Andrea who turned up one day with asthma, and who was cured by him of a condition that she was using four medications to control with a few adjustments to her diet. By cutting out milk, wheat, soy and corn, Andrea got her symptoms under control. But she didn't stop there, and eventually became convinced that the only foods she could eat were white sugar and lamb.

Unable to exist on these foods alone, she drew up "a complex rotation diet, alternating grains on a meal-by-meal basis, with occasional complete abstention to allow her to 'clear'". Food came to dominate her life, to the point where, Dr Bratman concluded, "we started treatment, all she had was asthma. If she took her four medications, she also had a life. Now all she has is a menu. She might have been better off if she had never heard of dietary medicine".

It's dreadfully unfair (although it provides a nice picture) to single out Madonna as contributing to such problems. But the massive emphasis on faddy diets and the beration of women for being too fat (or too thin) are spawning new grown-up variations on mental illnesses that were bad enough when mainly confined to the young.

Too tough on gun crime?

No one seems tempted to leap to the defence of Carl Morgan, the So Solid Crew producer who was jailed for life this year after shooting dead "love rival" Colin Scarlett on a south London estate. But to me a 30-year-tariff, regardless of the rehabilitation this 24-year-old might achieve in prison, is much too harsh.

Judge Brian Barker explained that "gun use is the scourge of our streets" and that the message must be that "it will not be tolerated". Yet gun use is only one aspect of an extremely corrosive, much admired, complex street culture that is actually only bolstered by the routine imposition of rigorously hard-line sentencing.

Morgan's former musical colleague, Ashley Walters, was a few years ago sentenced to 18 months for possession of a loaded gun. Released early for good behaviour, his work now tends intelligently to challenge many of the self-destructive myths surrounding the urban scene. His approach will win many more hearts than the learned gentleman's.

Capitalist tricks and treats

One of the notable side issues in the resignation of David Blunkett was the early rush to assure everybody that buying shares was an entirely virtuous activity that all decent people were manfully engaged in. Blunkett himself was at pains to emphasise this in his resignation speech.

But even before he had taken the opportunity to advertise what a commitedly moral capitalist he was, his old friend and colleague, Helen Jackson, had been on BBC News 24 asking: "Who doesn't buy shares?"

Let's see. Socialists don't buy shares, but the days when Helen and David signed up to Clause Four are, oooh, a decade behind them. Scrupulous business journalists don't buy shares (even though the media is supposed to be such a hotbed of immorality compared to politics). People living hand to mouth don't buy shares. (Perhaps that's the very definition of social exclusion.)

And - I'm guessing now - people on incapacity benefit don't buy shares. Naughty them. It's not as if you have to be in tip-top condition to call your broker, is it? Perhaps that's what this whole paying the incapacitated in vouchers thing is about. Maybe if they were paid in vouchers that could only be exchanged for shares in FTSE 100 companies, disabled people could at a stroke be made both idle and economically active. I'm on to something, aren't I?

* I know we've already moved on, what with tonight's celebration of 400 years of religious hatred and the ruthless punishment of terrorists striking such a poignant note. But can I just say how much my boys enjoyed their evening of trick or treating? I know that many people feel that it's a horrible American scam. But when I was a child in Scotland, dressing up and trolling round the neighbourhood, when we really should be indoors, was a thrilling and memorable experience that turned the grim advent of early nightfall into sheer dark magic. The only bum note was that the pumpkins had sold out early, and the local florist bought up a few, cut very crude faces into them, then flogged them for £8.50. Is that the fault of the Americans too?