Imagine you’re standing in the grocery store, comparing boxes of cereal. One has less sugar. Another offers extra protein. A third has a reassuringly low calorie count. Which is the “healthiest” option?
If you’re like most shoppers, you’ve learned to look for certain numbers on a nutrition label and to avoid others. But according to the new book Food Is Medicine by cardiologist and Tufts University professor Dariush Mozaffarian, that approach may be leading you astray. Nutrition labels offer useful information, but they can also encourage us to focus on individual nutrients while overlooking a more important question: What kind of food are we actually eating?
Here are five ways to better decipher the mysteries of your food packaging, based on the eye-opening explanations you'll find in Food is Medicine.
1. Low-calorie doesn't always mean healthy
For decades, many of us have been taught to think of calories as something to minimize, full stop. But calories are a measure of energy, not a verdict on a food's virtues. “On their own, they do not define a food’s healthfulness,” Mozaffarian writes.
Consider nuts, olive oil, and avocados. Though these foods are relatively calorie-dense, they provide beneficial fats and other nutrients. Meanwhile, a low-calorie snack made primarily from refined starches, sweeteners, and additives may offer considerably less nutritional value. As Mozaffarian writes, “Three hundred calories of leafy greens and olive oil, beans or nuts, or yogurt and fruit is better for your health than 200 calories of an ultraprocessed product formulated from starches, sugars, preservatives, and additives.”
The takeaway? Don't automatically choose the product with the lowest number. Instead, think about what those calories contain — or don’t — such as fiber, beneficial fats, and vitamins and minerals.
2. Sugar-free doesn't mean free of sugar-like substances
Added sugar is indeed worth avoiding. But eating only foods with no added sugar listed on the label isn't a foolproof way to build a healthier diet.
For example, when we eat white flour or purified starches, we metabolize them in ways that are similar to the way we metabolize sugar. But you’d never know that from the information on the label, since these ingredients don't appear in the nutrition facts as “sugar.”
“A rigid pursuit of zero sugar can mistakenly absolve sugar-free products laden with ultraprocessed grains, refined starches, and artificial sweeteners,” Mozaffarian points out.
Look for ingredients like wheat flour, rice flour, corn starch, or other refined starches to make sure you’re avoiding them — but bear in mind that not all carbohydrates are inherently bad. Whole grains, beans, fruits, and vegetables contain carbohydrates within a more complex food structure, often alongside fiber and other beneficial nutrients.
3. A high-protein label can hide some unsavory truths
Protein has become one of the food industry's favorite selling points. It's splashed across yogurt cups, snack bars, and even desserts. Of course, protein is essential, and getting enough is important. But a prominent protein claim doesn't tell you everything about a product's nutritional quality. As Mozaffarian puts it, “It’s not safe to assume that the new wave of adding acellular proteins to ultraprocessed foods makes them any healthier.”
Some packaged foods achieve their high protein numbers by adding isolated proteins, such as whey, soy, or pea protein. Those ingredients aren't necessarily harmful, and some have legitimate nutritional benefits. But that doesn’t mean the entire product is “healthy,” because a protein bar can still contain refined starches, added sugars, and numerous additives. A plain yogurt, a handful of nuts, or beans may offer protein as part of a broader package of nutrients.
4. Fat isn't automatically the enemy
The low-fat era taught consumers to treat fat as something to categorically avoid, ushering in a vast market for fat-free cookies, snack foods, and other products that often compensated for reduced fat with additional sugar or refined starch.
But fat is not inherently good or bad. Nuts, seeds, olive oil, and avocados contain fats that can be part of a healthy diet. Only “highlighting calories, total fat, or saturated fat doesn’t just miss the mark; it can misdirect people away from wholesome, naturally calorie- and fat-rich foods and toward ultraprocessed slop,” writes Mozaffarian.
Instead of choosing a product simply because it's low-fat, consider the type of fat (you’ll want to look for the unsaturated kind, which naturally occurs in many healthy foods) as well as the overall ingredient list.
5. The ingredients list may tell you what the nutrition facts panel can't
“Unfortunately, much of what’s required on the label — calories, total fat, saturated fat, carbohydrate, sugars, protein, vitamins, minerals — does little to help people navigate opaque products,” writes Mozaffarian.
In other words, while the nutrition facts panel gives you standardized numbers for nutrients, it doesn't fully explain how a food is made or how its ingredients fit together. A product can be fortified with vitamins or loaded with added protein and still be highly processed. Those additions may improve aspects of its nutritional profile, but they don't automatically make the entire product a healthy choice.
The ingredients list can provide additional context. Ingredients are generally listed in descending order by weight, so the first few entries tell you a lot about what the product contains. Look for recognizable whole-food ingredients when possible, and pay attention to how much of the product consists of refined grains, starches, sweeteners, and other highly processed components. No single ingredient is a definitive test of whether a food is healthy, but the overall pattern can be revealing.
Ultimately, the goal isn't to find a perfect label or eliminate every packaged food from your diet. It's to make choices based on a fuller understanding of what you're eating. A food's healthfulness can't always be reduced to a single number. And sometimes, the product that looks best on the front of the box isn't the one that does the most for your health.
