A. Parke Wilde, PhD, an associate professor at Tufts’ Friedman School, responds: “Most food labels are fairly accurate most of the time, and yet this remains an important question, because there are exceptions you should know about.
“Under federal law, a food label is ‘misbranded’ if it is false or misleading. The consequences can be severe. For most food products, the Food and Drug Administration (FDA) is responsible for enforcing rules against misbranding. For some products, such as meat and poultry, it is USDA’s Food Safety Inspection Service (FSIS) that is responsible. These two agencies sometimes lack sufficient budget resources to vigorously monitor the marketplace, but they do crack down when falsehoods are brought to their attention.
“However, in some circumstances, labels may be less accurate. First, even on basic label elements such as the Nutrition Facts panel, the companies are allowed some margin of error. Second, for certain labeling facts that are difficult to verify by scientific testing, it may be easier for companies to cheat. For example, nongovernmental organizations that have tested seafood have reported finding mislabeling of seafood varieties. Third, labeling claims that are difficult to define may be more misleading than labeling claims about simple scientific facts. For example, while a ‘sugar-free’ claim is clearly either true or not true, a labeling claim that a product is ‘natural’ is notoriously difficult to regulate.
“In short, some labeling claims are more accurate than others. In your example of ‘sugar-free’ labeling, a company that lied would run a terrible risk that a competitor would notice, leading to a formal complaint and perhaps a lawsuit, so I would expect that sugar-free labels by major brands are accurate.”