The fast food industry has gotten knocked for selling high-fat, high-sodium and high-sugar fare, a major contributor to the bourgeoning obesity and diabetes epidemics.

Many chains have responded by offering salads, wraps and fresh fruit alongside their burgers, pizzas and fries. New York City and in the U.K. have instituted "voluntary" salt-reduction programs for food makers; in response some companies claim to be cutting back on the sodium as much as they can. But due to their high-volume production, these large multi-national corporations can't cut the salt much further, they have contended, because it is not "technically feasible" with their current food processing processes.

A new study of more than 2,100 dishes in six countries finds, however, that the same fast-food chain will serve up vastly different quantities of salt depending on the country it is slinging burgers (or pizza or subs or drumsticks) in.

Perhaps not surprisingly, the U.S. dishes from six chains (Burger King, Domino's, Kentucky Fried Chicken, McDonald's, Pizza Hut and Subway) generally contained more salt (both per overall serving and per 100 grams of food) than the same menu items in Australia, France, New Zealand and the U.K.

A Big Mac, for example, has 2.6 grams of salt in the U.S. versus 2.1 grams in the U.K. Chicken nuggets have an even wider disparity: a serving of about six nuggets contains 1.5 grams of salt in the U.S. and less than half of that in the U.K. (0.6 g). The findings were published online April 16 in the Canadian Medical Association Journal.

"Although some differences are to be expected," the study authors note, "there is a clear opportunity for widespread reformulation of products toward the lower end of the rang of salt content." And because companies are always in the process of reformulating their products anyway, a pinch less salt should not be a big disruptor.

These authors and other researchers advocate for a slow, mandatory reduction in salt content for all, which, they contend, consumers likely won't even notice.

Doctors recommend that adults eat less than 2.4 grams of salt each day—about one teaspoon. The authors of the new paper, led by Elizabeth Dunford of the University of Sydney, found that menu items often contained many times that amount in a single serving, including salads with 7 grams of salt, sandwiches with 8 grams, and a pizza with 10 grams—four days' worth of salt in a single serving.

Of course salt, is not the only thing keeping us from staying slim and healthy. Americans on the whole eat far too many processed carbohydrates and excess fats. And a large meta-analysis published last year suggested that there was little proof that cutting back on salt would lower the chance that a person would suffer from stroke, heart attack or death. Another 2011 study noted that the balance of sodium and potassium might be more important for heart health than sodium levels alone.

But the new findings do show that McDonald's is able to build a healthier burger after all. In fact in some countries, it's already flippin' 'em.