Have you ever needed a quick, filling snack as you head to work or hit the gym? You’ve probably grabbed a protein bar.
These packaged foods have become synonymous with convenience—and with their wrappers touting their high protein levels, they’re often considered synonymous with nutrition, too. But a new paper casts doubt on the nutritional value of protein bars.
The study, published in March in Scientific Reports (Nature), revealed that many of the more than 1,600 bars tested didn’t contain as much protein as you might think. Moreover, the protein that most bars included wasn’t the best quality, which impacts absorption.
“This means that relying on these bars for your protein needs may not support muscle growth and maintenance as well as higher-quality sources,” Eliza Whitaker, MS, RDN, LDN, CDN, CYT, founder of Nourished Nutrition and Fitness, told Health.
Using data from an online consumer-generated database called OpenFoodFacts.org, researchers began with a list of approximately 4,600 protein bars, study author László Abrankó, of the Hungarian University of Agriculture and Life Sciences, told Health. Though the research team is based in Europe, around 46% of the entries initially studied were from the United States, he said, making it likely that at least some of the 1,641 bars ultimately tested are available in the U.S. market.
After finalizing the list of bars, the researchers divided them into groups based on the type of protein they used:
- Plant protein only, such as pea and rice protein
- Animal protein only, such as milk protein
- A mix of milk, egg, and soy protein
- A mix of milk, collagen, and soy protein
Researchers then ran the bars through a digestive simulation called Infogest, which analyzes amino acid composition and how much protein is truly absorbed by the body. Two key findings emerged:
- By the researchers’ benchmarks, many of the bars weren’t high in protein: While 81% of bars got at least 20% of their calories from protein, 19% did not, leading the authors to find that a good chunk of the bars weren’t high-protein sources. It’s worth noting, however, that this standard is higher than that put in place by the U.S. Food and Drug Administration (FDA), which considers sources of nutrients to be “good” and “excellent” if they contain at least a respective 10% and 20% of the Daily Value of that nutrient per serving, explained Monica Amburn, MS, RDN, LDN, senior director of food & nutrition at the International Food Information Council.
- The digestibility of some protein in bars was low: Digestibility scores for the protein bars varied widely, ranging from just 47% to 81%. Surprisingly, some of the lower-scoring bars contained animal protein or soy—both considered “high-quality” or “complete” proteins. “High-quality proteins contain all the essential amino acids the body can’t produce on its own,” explained Whitaker. “These proteins are often well-digested and absorbed, making them effective in supporting muscle repair, growth, and overall health.”
According to Abrankó, the poor digestibility of protein in the bars—even those made with complete proteins—was likely due to interactions with other ingredients. “We believe that other components present in the food product—such as dietary fiber or fat—may influence protein digestibility,” he said.
Because protein has become such a dietary darling, with nearly half of U.S. adults trying to consume more of it, it’s easy to lump all protein bars in the “healthy” category.
But the new study drives home an important truth: Nutrition quality can’t always be captured by an isolated component like protein, Abrankó said. Even if bars contain high-quality protein (such as milk, soy, quinoa, or buckwheat), that protein might not be fully digestible.
It’s also worth noting that protein bars are often highly processed. Mounting evidence indicates that a high intake of so-called ultra-processed foods may have deleterious health effects, like increased risk of obesity, cardiovascular disease, and type 2 diabetes.
On the other hand, Amburn stressed that protein bars fill a need for many groups of people. “For individuals with higher protein needs, protein bars offer a convenient option that provides a boost of protein in a small serving,” she said. “This can be incredibly helpful for individuals with suppressed appetites, such as those who may be taking weight management medications or those dealing with an illness.”
But even then, she said, bars shouldn’t be the only source of protein in a diet, but rather a supplemental source.
Protein choices like Greek yogurt, cottage cheese, hard-boiled eggs, jerky, nuts, and seeds offer high-quality proteins in a less processed form, Whitaker said. “These also provide additional nutrients such as calcium, healthy fats, and fiber.”
Want to choose a better-for-you bar? Though added ingredients may affect protein digestibility, it’s still smart to opt for bars with a higher protein content, Whitaker said, “ideally from animal sources like whey, casein, or milk, or from plant sources like soy or pea protein.”
She also encouraged looking for bars with low added sugar. Though the FDA does not currently have a specific threshold for “low” added sugars, it recommends 50 grams per day based on a 2,000 calorie daily diet and that less than 10% of total daily calories come from added sugar.
Whether or not bars supply as much high-quality protein as they say, they can be fine as an occasional snack. Just remember not to rely on them too much to supply your daily nutritional needs, Amburn cautioned. “Most protein bars are intended to be snacks or supplemental foods, which is acceptable in the context of a diverse diet,” she said. “It’s the overall quality of the diet that matters most.”
