In the supermarket these days, packaged foods brandishing health, nutrition or environmental claims are easier to find than foods with less-cluttered packaging. And if you’re among the growing number of shoppers who seek out healthier items on store shelves, these labels can end up guiding your purchasing decisions. But a study posted in March 2017 in the Journal of the Academy of Nutrition and Diabetes found that certain nutrition claims are no guarantee you’re dropping the most nutritious option into your grocery cart.

After examining the data from more than 80 million food beverage purchases by more than 40,000 households, researchers concluded that items featuring low-content claims, such as “low-calorie,” “low-sugar,” “low-fat” or “low-sodium” were often not more nutritious than counterparts making no such claims.

One reason is that standards of comparison are often unclear: low-sugar in relation to what? Another reason is that one nutrient never tells the complete story. A “reduced-fat” peanut butter may have 25% less fat than a full-fat version, but it will often be higher in sugar, and the calorie difference may be negligible. What’s more, the fat stripped away is the heart-healthy unsaturated kind.

In the end, “reduced” or “low” claims are about only one nutrient and don’t reflect the whole nutritional picture of a product. So decide on the best food or drink based on information presented in the ingredient list and on the Nutrition Facts panel—not the essentially meaningless front-of-package hoople