Walk down the aisles of any grocery or convenience store and pick up a package. Somewhere on it is a food label listing nutrition information.

Labels include the federally mandated Nutrition Facts Label; the simplified front-of-pack Facts Up Front label; the American Heart Association’s Heart-Check mark; Guiding Stars, developed by the Hannaford grocery chain; and the for-profit and now defunct NuVal tag. Foods can also carry simpler labeling claims such as “fat free” or “low sodium,” or provide total calorie counts.

Such labels don’t come just from the food industry. They also represent a “soft” approach for the government to educate consumers about healthy eating and to shift industry toward making healthier products.

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Those goals are important. Diet-related diseases are major contributors to poor health, lost productivity, premature death, and rising health care costs around the world. Cardiovascular disease, a large proportion of which is linked to unhealthful eating, costs the U.S. an estimated $316 billion a year. Diabetes, another diet-related disease, costs the nation $327 billion. Add up the costs of all obesity-related conditions and it’s a whopping $1.4 trillion a year. These burdens are overwhelming the pocketbooks of families, private businesses, and governments; undermining military readiness; and contributing to poorer health among lower income Americans.

Although labels have graced food packaging for decades, it’s not entirely clear if they influence consumer choices or food industry practices. To examine their impact, we pooled the findings of 60 studies that included 111 interventions that tested foods with and without labels. There were 2 million observations of people or their purchases across 11 countries. As we and other colleagues recently reported in the American Journal of Preventive Medicine, food labeling had some effects on consumer choices: They reduced the intake of calories by 6.6 percent, total fat by 10.6 percent, and other generally unhealthy choices by 13 percent. They also increased vegetable intake by 13.5 percent. There was little evidence, however, that food labels affected the intake of total carbohydrates, protein, saturated fat, or sodium, nor did they influence consumption of fruits, whole grains, or other healthy options.

When we evaluated the potential for food labels to motivate food companies to make changes to their products, we found that labels reduced the amount of harmful trans fat in food by 64 percent and the amount of sodium by 8 percent. Yet they appeared to have little effect on total calories in food or the amounts of saturated fat, dietary fiber, or other healthy or unhealthy components, although relatively few studies looked at these endpoints.

The bottom line is that food labels appear to work to shift consumer or industry behavior for a few dietary targets, but not for many others.

For consumers, they seem to work best for simpler and widely understood metrics such as calories, total fat, and products labeled as “unhealthy,” but not for more complex and perhaps poorly understood nutrient targets. Labels also appear to nudge food companies to reduce major industrial additives like trans fat and sodium, but do not appear to influence industry formulations for more complex targets such as nutrients that are intrinsically in food, like saturated fat or dietary fiber.

Too few studies were available for us to assess the effect of food labels on added sugars, a new addition to the U.S. Nutrition Facts Label.

Of note, while our research shows that food labels can influence some consumer and industry choices, there wasn’t enough evidence for us to evaluate the effects of labels on health outcomes. For example, food labels may have helped reduce the intake of total fat, but it’s become clear from other research that lowering total fat has little health benefit, especially when consumers cut back on healthy fats and replace them with refined carbohydrates.

Studies that looked at the effect of labels on calorie intake generally assessed only a single meal, and it’s not clear if a 6.6 percent reduction in calories in one meal will translate into reduced calories over the course of a week, month, or year, and eventually into health outcomes. That said, if mandatory calorie labeling in restaurants reduced the calorie choices for people across numerous meals in different venues over time, the cumulative effect could be significant. Such long-term effects, however, haven’t been well evaluated.

Efforts to improve and expand food labels around the world are underway. These include visually simple traffic light symbols or even black-box warning labels. Unfortunately, many of these systems cover just a few nutrients, often don’t account for processing, and frequently exclude beneficial factors such as healthy fats, probiotics, or polyphenols.

The NuVal shelf tag, a for-profit health scoring system that at its peak was featured in more than 1,600 grocery stores in 31 states, has been removed from U.S. markets as it was eventually deemed “fatally flawed.” The Choice logo, launched in 2006 in The Netherlands, faced a similar fate: With mounting criticism, the Dutch government ordered it to be replaced by a cellphone app.

In our results, the specific type of food label did not seem to make a big difference on either consumer or industry responses. Perhaps it’s the general presence — or absence — of key information that matters to consumers and industry, rather than fancy designs or scoring.

At the end of the day, food labels may be most useful for generally raising awareness among consumers and the food industry about what nutrients should be measured and highlighted in food. To be effective, this means focusing on the most relevant list of nutrients, obtained from the best modern evidence for effects on health.

Unfortunately, too many labels today focus on outdated targets like total fat, total calories, and total saturated fat, rather than more holistic assessments of foods that incorporate healthy components such as fruits, vegetables, nuts, or beans or the extent of processing, giving lower scores for highly refined and rapidly digested foods and higher scores for minimally processed and slowly digested foods.

To solve the nutrition crisis in the U.S. and around the world, we need smarter labels as well as smarter supportive policies that can together make healthy eating the easier, cheaper, more widely available choice.

Dariush Mozaffarian, M.D., is a cardiologist and dean of the Tufts Friedman School of Nutrition Science and Policy. Siyi Shangguan, M.D., is an internal medicine attending physician at Massachusetts General Hospital and a former research assistant at the Friedman School.

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