Just because a packaged food gets a favorable nutrition rating doesn't necessarily mean it meets every recommendation for healthy eating. In fact, the same product might be considered healthy by one set of standards and unhealthy by another.
A new study published in BMJ Medicine found major differences in how packaged foods are evaluated in Britain. Depending on the standards used, researchers classified anywhere from about half to nearly all of the products they examined as unhealthy. The findings highlight how confusing food ratings can be and why a simple label doesn't always tell the whole story.
Researchers at University College London examined nearly 1,900 processed and ultraprocessed foods and drinks, comparing existing British food labeling systems with three new methods based on the country's dietary recommendations.
The differences were dramatic. Britain's traffic light labeling system, which uses green, amber and red symbols to show levels of fat, sugar and salt, flagged 48% of ultraprocessed products as unhealthy. Another system used to regulate food advertising identified about 58%.
But when researchers applied their own stricter standards, the percentage jumped to between 92% and 99%.
That doesn't mean the British government has declared nearly all packaged foods unhealthy. The higher figures came from new scoring methods developed by the researchers, not official government classifications. Those methods also haven't been tested to determine how well they reflect a food's actual effects on health.
So why such different results?
Some systems consider a food's overall nutritional makeup, allowing beneficial nutrients such as fiber and protein to balance higher amounts of sugar, salt or saturated fat. Others focus more strictly on whether a food exceeds certain nutritional limits.
Under the strictest approach tested, exceeding just one limit was enough for a product to receive an unhealthy rating.
That can lead to some surprising results.
Foods such as canned pasta in tomato sauce, packaged macaroni and cheese and fat-free probiotic yogurt weren't flagged by existing systems but exceeded limits under the researchers' new standards.
Meanwhile, foods such as nuts and whole fruit can receive less favorable ratings under certain labeling rules because of their naturally occurring fat or sugar, even though they're widely recommended as part of a healthy diet.
The examples illustrate why judging foods isn't always as simple as labeling them healthy or unhealthy.
The findings also add perspective to the ongoing debate over ultraprocessed foods. Many packaged products contain substantial amounts of added sugar, sodium or saturated fat, but not all processed foods are nutritionally alike. Processing alone doesn't tell us everything about a food's nutritional value.
There are important limitations to the study. The researchers applied recommendations intended for an overall diet to individual food products, which doesn't necessarily reflect how people eat. They also didn't evaluate minimally processed foods, so it's unclear how consistently the new standards would rate those products.
And because the study examined nutritional information rather than people's diets or health, it doesn't establish which rating system is most useful for making healthier choices.
Although the research focused on Britain, where food labeling differs from the United States, the broader issue is familiar to American shoppers navigating Nutrition Facts labels and health claims on packaging.
Those labels can be helpful, especially when comparing similar products. But a single rating can't capture everything that matters about what we eat, including portion sizes, nutritional benefits and how a food fits into our overall diet.
The research received support from the UK's National Institute for Health and Care Research, Medical Research Council and Rosetrees Trust. Several authors disclosed professional interests related to nutrition and food policy, including book royalties, consulting and speaking engagements involving ultraprocessed foods.