Fast food in the U.S. typically comes with extra salt, like it or not. A new study shows that the same products at fast food chains vary wildly in sodium content depending on what country you're served in.

An international team of researchers found U.S. fast food to be extra salty in a survey of 2,124 food items from fast food restaurants in Australia, Canada, France, New Zealand, the U.K. and the U.S. including Pizza Hut, Burger King, Subway, Domino's Pizza, Kentucky Fried Chicken and McDonald's.

The scientists found salt levels varied between food in the same category - turns out the average Pizza Hut sandwich is 70 percent saltier than the average Subway sandwich. Surprisingly, sodium levels also varied for the same company's product served across different countries.

For instance, the researchers found that McDonald's Chicken McNuggets contain 0.6 grams of salt per 100 gram serving in the UK, but contain nearly three times that amount -- 1.6 grams per 100 gram -- in the U.S.

Reducing salt levels in fast food could be an easy way to target health problems, but fast food companies often claim that their food processing technology cannot make lower-salt products, according to the authors.

But the researchers argued that producing food with less salt is not always a technical issue.

There is a clear opportunity for widespread reformulation of products toward the lower end of the range of salt content for most categories, the authors wrote. For example, a Big Mac in the U.K. contains 1 gram of salt per 100 grams, less than the 1.2 grams of salt per 100 grams for the same burger in the U.S.

Two of the authors have received funding from the World Health Organization to develop a tool for monitoring sodium content in foods, and one author is chair of the Australian Division of World Action on Salt and Health.

The scientists noted that their study is limited by the fact that their data came from the nutritional values reported on the companies' websites.

Although we believe most companies report correct nutritional values, this may not always be the case, the authors wrote.