Children's meals at popular fast food chains around the world vary wildly in the amount of salt they contain.

The difference is so extreme that in some cases, the amount of salt varies by as much as the equivalent of 10 packets of crisps.

One children's meal alone had nearly twice the recommended amount of salt children should consume in a day.

The research, conducted by World Action on Salt and Health (WASH), tested the same meals at fast food restaurants around the world - including McDonalds, KFC and Burger King.

Scroll down for video

Salty: KFC popcorn chicken and fries in Costa Rica have the same salt content as more than 10 packets of ready salted crisps

As this map shows, the salt content of KFC Popcorn Nuggets kids meal varies considerably around the globe

SALT CONTENT FOR KFC POPCORN NUGGETS KIDS MEAL COUNTRY SALT IN GRAMS Costa Rica 5.34

United States 4.28 Germany 3.30 Canada 2.6 South Africa 1.97 Australia 1.86 United Kingdom 0.9 Based on the countries where details of salt content was provided for this meal

Overall, 37 countries were examined and 387 food choices.

Too much salt can raise blood pressure, which increases the risk of health problems such as heart disease and stroke

The maximum recommended salt intake for children aged four to six is 3g a day and 5g for seven to 10-year-olds.

The most anyone should consume is 6g of salt per day.

The researchers found the widest variation was the KFC Popcorn Nuggets kids meal which contained as much as 5.34g in Costa Rica, more than five times the amount as the same meal in the UK.

It means if a child ate that meal twice a month for a year in Costa Rica, they would consume 18 teaspoons of salt more than a child in the UK.

The US was another bad offender, coming shortly behind Costa Rica with 4.28g.

The analysis also revealed that eight out of 10 meals contain more than 1g of salt per serving.

Overall, the UK performed better than most countries.

Scroll down for video

Varied: McDonald's cheeseburger and hamburger meals contained far more salt in Turkey than the US

For example, a Burger King children's meal burger and fries contains 1.06g of salt compared to Colombia, where the meal contains 4.82g.

And the UK's Subway Kids Pak turkey sub contains 1g, compared to Germany which topped the charts at 1.5g.

It was also rated lowest of all for its KFC popcorn nuggets and fries meal, which measured at 0.9g of salt per serving.

COSTA RICA'S LOVE OF SALT Costa Rica’s salt intake is so high it introduced a national plan to reduce salt consumption across the population in 2011. High salt diets are a major cause of raised blood pressure in the area. High blood pressure raises the risk for cardiovascular disease, kidney disease and death. Since then, a programme by Canada’s International Development Research Centre (IDRC), aims to continue to lower the region’s salt intake. In a report, the IDRC says the key barriers to reducing consumption include lack of information on the level of salt in processed and packaged foods, lack of consumer awareness about salt and its health effects, and the lack of standardised nutrition labelling. Advertisement

The UKs McDonald's Chicken McNuggets Happy Meal also had the lowest at 0.78g with Turkey coming top with 2.4g and Venezuela the next highest with 1.7g.

WASH said that too much salt in childhood habituates youngsters to the taste of salt, and puts up blood pressure, which leads to strokes and heart failure.

The group is calling for all food manufacturers to universally reduce the salt content of their products, to help achieve the target of 5g salt a day.

It comes as rising numbers of children are being treated in hospital for high blood pressure over concerns they are eating too much salt.

Admissions have trebled in the last ten years and include almost 400 children under five.

Nutritionist and international programme lead at WASH Clare Farrand, said: 'The fact that these fast food chains are able to produce less salty children's meals in some countries means they can do the same in all countries, and should immediately.

'All children, regardless of where they are from, should be able to enjoy the occasional meal out as a treat, without putting their health at risk.'

WASH chairman, Professor Graham MacGregor, of Queen Mary University of London, said the more salt you consumed as a child, the more likely you are to have serious health issues in later life.

Disparity: As this chart reveals, the amount of salt can be nearly double, depending on the country

'This can include high blood pressure, increased risk of stroke, heart disease, osteoporosis and kidney disease. That's why it's vitally important children do not get used to the taste of salt,' he said.

The survey also found only 233 out of 387 children's food choices had complete nutritional information to allow comparison of salt contents.

WASH is calling on all fast food restaurants to provide this for parents.

With over half of all meals (53 per cent) containing more than half a days' worth of salt for a four to six-year -old (1.5g), WASH is calling for all food manufacturers to universally reduce the salt content of their products, to help us achieve the global maximum target of 5g salt per adult per day.

Ms Farrand said the levels found here were particularly worrying given the age of diners.

'A six year old should not be having more than 3 grams of salt in an entire day so we are talking about half its allowance coming in a single burger,' she said.

'This is the age when taste preferences are programmed for life so it's really important children are not encouraged to eat salty meals.

'We are still playing catch up in the out-of-home sector so there is still work to do.'