A significant amount of the American diet is made up of processed foods, and some processed foods are much higher in sodium and sugar than others.

Thankfully, there's a lot that a food's nutrition label can tell you in a matter of seconds if you use the 5/20 rule, one dietician says.

"You can use the daily value," says Jinan Banna, registered dietitian and professor of nutrition at the University of Hawaii.

"That's an easy way to know whether the food is generally high or low in a particular nutrient."

The 5/20 method requires checking the daily value percentages of nutrients like saturated fat, sodium and sugars, Banna tells CNBC Make It.

"The percent Daily Value shows how much a nutrient in a serving of food contributes to a total daily diet," according to the Centers for Disease Control and Prevention.

"The idea is, if [it's] 5% or less, then the food is generally low in that particular nutrient. If 20% or more, you can consider the food high [in the nutrient]," Banna says.

"So that's just a quick way to glance at the label and know if a food contains a little bit or a lot."

Banna notes that how often you should eat foods with sodium or sugar levels that exceed a 20% daily value depends on your own diet.

"There's no hard and fast rule because it really depends on the context of your diet, as to how much you should have," Banna says.

"And, of course, it's not necessary or desirable to eliminate sugar, saturated fat or sodium. We do include these in the diet, and they are part of a healthy diet."

She simply recommends being mindful and making sure "you're not routinely consuming foods that are very, very high in sugar or salt or saturated fat."

Want to stop worrying about money? Sign up for CNBC's new online course Achieve Financial Wellness: Be Happier, Wealthier & More Financially Secure. We'll teach you the psychology of money, how to manage your stress and create healthy habits, and simple ways to boost your savings, get out of debt and invest for the future. Start today and use code EARLYBIRD for an introductory discount of 30% off through September 2, 2024.

Plus, sign up for CNBC Make It's newsletter to get tips and tricks for success at work, with money and in life.