I'M a celebrity, do as I say. But according to scientists, we should not be taking any notice of the dafter claims made by some of the people who regularly adorn the pages of magazines and tabloid newspapers.

Sarah Beeney, Stella McCartney, Gwyneth Paltrow, Nicole Kidman and Gillian McKeith are among those who have been criticised by the charity Sense About Science.

The first two came in for a hammering for talking out of turn about chemicals in make-up and skincare products. Gwynnie was blasted for claiming that her macrobiotic diet could help her avoid cancer, which runs in her family.

Meanwhile Nicole was criticised for supporting the Nintendo-based Dr Kawashima's Brain Training game, which experts say has not been proved to improve cognitive function.

As for "Dr" Gillian McKeith, her obsession with people's poo and pronouncements on diet have rendered many a doctor or dietitian almost speechless.

Sense About Science has distributed pamphlets to VIP clubs and restaurants, management agencies and publishers across the UK listing some of the stars' statements and scientists' views. A telephone number is included so that the celebs can check their facts with a scientist before pronouncing.

Dr Dominic Williams, a pharmacologist at Liverpool University, was irritated by Stella McCartney's comments on skin products. She claimed many contained the same chemicals as the antifreeze you put in your car and 60 per cent could be absorbed through the skin.

Yet, as Dr Williams told the Daily Echo, the chemical, propylene glycol, is actually very safe.

"All it is is a moisturiser. It gets moisture from the air and can be used in make-up," he explained.

"It is possible for things to be absorbed through the skin into the bloodstream, but generally in such small quantities that it doesn't matter.

"Propylene glycol is even a registered food additive, approved by the US Food and Drug Administration. It's metabolised to lactic acid, which is easily excreted."

He pointed out that everything, whether natural or man-made, was made up of chemicals, making a nonsense of Sarah Beeney's endorsement of chemical-free make-up and moisturisers.

Dr Williams is also sceptical about celebrity-backed detoxing, a regular feature of New Year newspaper and magazine spreads.

"The liver can far and away cope with all these chemicals the body is being subjected to, so a lot of these detox diets don't really have any effect," he said.

"It's definitely not the case that natural always means better. There is a particular type of liver cancer brought about because of a chemical produced by a organism living in wheat."

However, one celeb who has managed to get it right is chef Jamie Oliver. "He mentioned a chemical found in chillis which speeds up the metabolism," said Dr Williams.

"A trial in Japan found that that eating a breakfast containing this chemical, capsaican, resulted in an increase in energy expenditure."

Sense About Science has 1,400 scientists committed to counteracting the damage and improving public debate. Director Tracey Brown said: "There is a real problem when people present things as though they are scientifically grounded."

Its campaign is backed by illusionist Derren Brown, and Professor John Toy of Cancer Research UK, who said: "Celebrities often have a real effect on how members of the public view issues, particularly health and lifestyle. They have a major responsibility to be well informed before they make statements endorsing particular treatments of products so as not to mislead people."

  • Smart Health Choices, by Professor Les Irwig, Judy Irwig, Dr Lyndal Trevena and Melissa Sweet, is a guide to making sense of health advice, wherever it comes from. It is published by Hammersmith Press at £12.99.