A New Zealand nutrition expert has attacked carb-cutting diet fads endorsed by Hollywood celebrities in a highly regarded medical journal.
Writing in British medical journal The Lancet, University of Otago medicine and human nutrition lecturer Jim Mann said there was a lot of uncertainty and a great deal of rubbish written about appropriate dieting.
"Our dietary guidelines permit a wide range of diets - including the Mediterranean, Nordic, Japanese - but to radically limit carbs and say 'you've got to have a Paleo diet' or some other similar kind of approach, or the Atkins diet - this is absolute nonsense," he said.
"You have people recommending a whole range of things, making a whole range of claims and furthermore saying that what we have said for some time about healthy nutrition, for example: reduce saturated fat, increase the amount of dietary fibre in your diet - people are saying that is incorrect."
Prof Mann wrote the article at the request of The Lancet to counter such misinformation and uncertainty.
"What we're saying in this editorial is that the dietary guidelines that exist in New Zealand and internationally - by every authoritative agency in the world - are actually right. Those basic principles of nutrition still hold."
Prof Mann warned that fads encouraging people to avoid carbohydrates were not only misleading but potentially dangerous.
People were cutting such foods out because they were told they led to diabetes and obesity, he said, but quality carbohydrates actually protected against diabetes, colon cancer and heart disease.
The real problem was refined carbohydrates and sugars, said Prof Mann.
"If you cut out the good carbs you are depriving yourself of fibre-rich carbohydrates.
"Too much rice and potatoes is not particularly beneficial but there's no reason why you shouldn't eat them."
Such carbohydrates are rapidly digested and broken down into glucose, Prof Mann said, and it should be brown rice that was eaten.
He emphasised the best carbohydrates were foods containing whole grains, such as wholegrain bread, or vegetables that were colourful rather than white.
"Some 'wholegrain' products are not necessarily as wholegrain as you'd want them to be," he said.
"I'd encourage people to eat bread with proper wholegrain, using stoneground wholemeal flour or porridge using wholegrain oats."
Prof Mann said wholegrain oats required slightly longer cooking than ground up oats.
Barley could also be used in recipes requiring whole grains, and getting a spectrum of carbohydrates provided a lot of other critically important nutrients, Professor Mann said.