Almost half of Scotland’s councils have served up pizzas which, unknown to the primary school pupils, contain powdered seaweed from the Isle of Lewis.
Seaweed flavouring is much healthier because it contains just 3.5% sodium compared with table salt, which is 40% sodium.
The makers of the pizzas bake the seaweed powder into the base so that youngsters are none the wiser.
“It’s health by stealth.”
The approach - known as “stealth nutrition” - has proved a big success in dinner halls across Scotland.
The “healthy” pizzas are made by Scottish firm Eat Balanced, which has Glasgow University professor of nutrition, Mike Lean, on board as an advisor.
Katie Sillars, marketing director, said: “We’re taking on the likes of McCain’s. Instead of salt we use a really nutritious powdered seaweed from the Isle of Lewis.
“We use it instead of salt - it bakes down into the base. We hide it.”
She added: “One thing we’ve have problems with is that if you promote it as a healthy product. The cooks say, ‘Oh, they just won’t eat it’.
“It’s health by stealth.”
Professor Lean said: “Having done it with pizzas we can do it with other things.
“There’s a big problem with salt and fat, and not enough fruit and vegetables. There are ways of incorporating that.”
East Renfrewshire Council is one of 15 councils to trial the Pizza Power Kids products.
A spokeswoman said: “We recently tried the pizza with some of our primary pupils and had a very positive response.
“It is now our intention to move all our primary schools over to this new pizza.
“With any new dish, feedback from our pupils is essential and if it is felt that the dish is not well received then we will move back to the original option.”
East Lothian, Moray, Argyll and Bute, Aberdeen City, South Ayrshire, Fife, East Ayrshire, North Ayrshire, Clackmannanshire, Edinburgh, Glasgow, Dundee, Perth and Kinross, and Angus have all trialled the pizzas.
The seaweed provides essential iron, zinc, vitamin B12 and iodine.
Seaweed has become a popular ingredient in artisan breads in recent years. And St Andrews ice cream parlour Janettas Gelateria also launched seaweed ice cream this summer, at £1.60 a scoop.
Last month, the Scottish Government was accused of failing to tackle the obesity crisis plaguing the nation.
Figures from 2014 showed one in six (17 per cent) children aged between two and 15 are "at risk of obesity", with another 14 per cent classed as being "at risk of overweight".
Children who eat too much salt are also more likely to suffer high blood pressure and cardiovascular disease as adults.