Professor Ruopeng An at the University of Illinois studied eight years of health data from around 18,000 adults in the US.
She found that while people who ate at restaurants did consume more healthy nutrients - including vitamins, potassium and omega-3 fatty acids - than their counterparts who visited fast food outlets, they actually took in more sodium.
Eating fast food increased the amount of sodium people consumed per day by an average of 300mg, while restaurant dining added 412mg.
The American Heart Association recommends that Americans consume less than 1,500 mg of sodium a day.
Dining in restaurants meant that people took in, on average, 58mg of extra cholesterol a day, compared to people who ate home-cooked meals, while people who ate fast food consumed an extra 10mg. Visitors to restaurants consumed a little less saturated fat than diners at fast food joints – 2.46mg as opposed to 3.49mg – but on average, visitors to both types of eatery consumed 10g more total fat than people eating dinner at home. Overall, the study found that people who ate outside the home ended up consuming about 200 additional calories.
“People who ate at full-service restaurants consumed significantly more cholesterol per day than people who ate at home," said Professor An.
"This extra intake of cholesterol, about 58 milligrams per day, accounts for 20 percent of the recommended upper bound of total cholesterol intake of 300 milligrams per day.