Last night's viewing - The Food Hospital, Channel 4; The Case, BBC1

I've had a weird allergy to Channel 4 dieticians ever since I unwisely swallowed a Gillian McKeith programme without reading the small print first. Even the sight of one can make me breathless and sweaty now, so I approached The Food Hospital with some caution.

"I passionately believe in the science of food as medicine and I want the public to know about it," said Lucy Jones, the series' resident dietician. Which is all very well but for the fact that "passionate belief" doesn't prove anything at all. The best procedure, I thought, was to follow some advice Bear Grylls once offered on how to find out whether jungle fruit is poisonous: nibble a tiny sample and then wait to see whether you get an adverse reaction before eating the whole thing. And the essential verdict is that it seems to be harmless – one of those programmes that helps Channel 4 with its public-service remit, but also allows the viewer to squat in a consultation room and gawp at the unwell.

How much good it will do, I'm not sure. The simple proposition is that improved diet can achieve results just as good as expensive medicines, and that even when it can't, symptoms can be improved. But when it comes to the prescriptions The Food Hospital doles out, there doesn't seem to be anything terribly sophisticated in the advice. Poor Lauren, who has polycystic ovaries and hirsutism (she has a beard ), was hauled into a consulting room lined with tasteful monochrome pictures of broccoli and told to give up eating sausages and cheese and replace them with pulses, vegetables and fruit. Oh, and they thought it would be a good idea if she did some exercise too. Harvey, a little boy who suffered from terrible migraines, was given slightly more specific advice about avoiding foods that might trigger his attacks. But then with Chris, who has type two diabetes, we were back to common sense. An exclusive diet of petrol-station pies and confectionery, it turns out, isn't very good for you. Who'd have thought it?

It's to the programme's credit, though, that they undermined the idea of any fast-track way to guzzle your way to better health. Dr Pixie McKenna, who we usually encounter peering at a scrofulous set of genitals in Embarrassing Bodies, gently undermined the idea of the "super-food" – a marketing ploy designed to get us to pay more for blueberries – and pointed out that nearly all fresh fruit is super if the alternative is a Twix bar and a packet of pork scratchings. And then Lauren, Harvey and Chris returned to demonstrate – visibly in the case of Lauren and Chris – that you really can achieve quite a lot in a short time if you're prepared to stick to the diet.

Chris had given himself an incentive by downloading photographs of gangrenous toes on to his mobile, a reminder of what awaited him if he strayed from the straight and narrow (very narrow, in his case, at just 800 calories a day). The food that had gone into them had achieved some of this, I'm sure, but not nearly as much as the food that hadn't gone into them. The truly effective medicine was personal determination. Perhaps Channel 4 could follow up with "Will Power Hospital".

Lovers of courtroom drama will be able to gorge themselves over the next couple of weeks. Peter Morgan's The Jury starts next week on ITV1 and in the meantime there's The Case, running on five consecutive afternoons this week with the trial of a man accused of murdering his terminally ill partner. Ruthie Henshall plays the chambers' harpy in a way that suggests she's worried about reaching the upper circle, but she's less conspicuous than she might normally be because everything in The Case is a touch melodramatic. And if the Did He Do It plot isn't enough to keep you hooked there's a Will They Do It teaser involving the lead barrister and his ambitious young junior.