Potato chips. Pop-Tarts. Bottled water. If you’ve been to a grocery store recently, you’ve probably noticed that even the most unlikely products now come in protein-boosted versions.
Protein-maxxing — the social media-fueled trend of maximizing dietary protein at every opportunity — is showing no sign of slowing. That’s in part because the federal government has weighed in with nutrition guidelines that emphasize the consumption of meat and dairy and an increase in the recommended dietary allowance of protein by 50% to 100% over the previous RDA.
Do we really need all that protein? Should we be eschewing bread for a T-bone steak — or for Protein Slammin’ Pop-Tarts?
“Protein has gotten the kind of treatment that low-fat food did in the ’90s — the SnackWell’s phenomenon. We all have given protein a health halo,” said Marily Oppezzo, PhD, a dietician and instructor of medicine at the Stanford Prevention Research Center. “Protein intake is important. Just not as magical-fixer-fountain-of-instant-awesome as Instagram would tell you.”
We asked Oppezzo and other Stanford Medicine experts to help us break down protein fact and fiction — and get at the science behind conflicting dietary recommendations. Here are five key takeaways.
1. Protein intake fuels the creation of important bodily proteins.
While contradictory dietary advice might muddy the waters, it’s clear that we need protein in our diets. Broadly speaking, all food can be broken down into three macro-nutrients: carbohydrates, fat and protein. And, of course, many foods contain all three. But if you’re consuming a calorie, it has to come from one of those three sources.
Protein is essential for many things in our bodies. At its molecular root, dietary protein provides many of the building blocks we need to make our own bodies’ proteins, which in turn are used to build and carry out pretty much every bodily function imaginable.
“Protein can take the form of your muscles, your hair, your skin — everything has protein in it,” said Jonathan Long, PhD, an associate professor of pathology. “And you can’t get those constituents from fat or carbohydrates alone.”
Our bodies’ proteins — just the same as dietary proteins — are made up of strings of molecules called amino acids. There are 20 different amino acids, some of which we can synthesize from other compounds. But we must get nine of these, also called essential amino acids, from our diet. We simply can’t build them out of other components.
When you eat dietary proteins, your body breaks down those long strings of amino acids into their component parts, which it then uses to build new proteins your body needs. Imagine pulling all the beads off of a necklace and then using those beads to make new kinds of jewelry.
2. For some people, protein amounts are important for muscle retention.
Until just a few months ago, the federal RDA of dietary protein for adults was 0.8 grams per kilogram of body weight. For a 150-pound adult, that’s around 55 grams of protein a day, or the equivalent of an 8-ounce steak. The newly revised dietary guidelines instead recommend 1.2 to 1.6 grams per kilogram, raising that 150-pound person’s recommendation to 80 to 110 grams a day.
That’s quite a jump — so what actually changed with the science? Nothing, said Christopher Gardner, PhD, the director of nutrition studies at the Stanford Prevention Research Center.
Marily Oppezzo, Jonathan Long and Christopher Gardner
“Were we really off by that much? What new evidence became available to show that we were off by that much? There really isn’t any,” Gardner said. “Protein has become one of the single most heavily marketed products I’ve ever seen. Everything is marketed with protein in it.”
Oppezzo’s view is slightly more nuanced. She’s concerned about the protein intake of adults over 40 and the growing segment of the population taking medications to lose weight. For these two groups, there is evidence that eating more dietary protein than 0.8 grams per kilogram can help stave off some of the muscle loss that commonly accompanies aging and weight loss.
For those with a body mass index of more than 30, the calculation is a bit more complicated. Rather than using their actual body weight, they should use an “adjusted body weight,” Oppezzo said, because lean mass needs energy to build it and maintain it. For her clients who are actively losing weight, such as those taking a weight-loss medication, she advises 1.6 grams of protein per kilogram of the adjusted body weight. That’s because people eating a reduced calorie diet are at risk of muscle loss.
However, Oppezzo points out that resistance training is far more important than what you eat to maintain your muscles. One of her mentors, McMaster University nutrition researcher Stuart Phillips, PhD, likes to say that protein isn’t the cake, exercise is — protein is only a thin layer of frosting on the cake of resistance training.
“The biggest thing that stops muscle loss is strength training,” Oppezzo said. “What higher protein adds to that is pretty small potatoes.”
3. Maybe there wasn’t a protein intake problem to begin with.
The difference between the old and new dietary guidelines could be moot, because Americans are eating plenty of protein already. According to the National Health and Nutrition Examination Survey, adult men in the U.S. are eating around 90 to 100 grams of protein a day, and women are getting 65 to 75 grams. That’s already in line with the new recommendations.
Some people think that the old RDA was a suggested minimum and that more protein is always better. But that’s a misconception, Gardner said. In the 1980s, scientists calculated adults’ protein needs through controlled diet studies in which they measured everything that went in and everything that came out.
The outcome of those studies is known as the estimated average requirement for protein, and it’s only 0.66 grams per kilogram. To make sure they were meeting the needs of the entire U.S. population, they set the RDA 20% higher. That 0.8 grams per kilogram was designed to meet the needs of 98% of American adults, Gardner said, so it shouldn’t be viewed as a minimum to “beat.”
4. With all the protein talk, we might be neglecting fiber.
While overconsuming protein likely isn’t harmful on its own, it’s important to look at where that extra protein is coming from, Gardner said. If it’s from red meat, as the new dietary guidelines emphasize, folks might be consuming unhealthy levels of saturated fat.
And if we fill up on steaks and protein shakes, we’re not eating enough fiber and other nutrients found primarily in plant-based foods. National surveys show that, unlike for protein, only 5% of Americans are meeting the RDA for fiber, which is critical for gut health and reducing the risk of cardiovascular and other chronic diseases.
“There are all kinds of antioxidants that can lower inflammation and prevent cancer, and those don’t come in meat and cheese and protein bars,” Gardner said.
There are plenty of foods that have both fiber and protein, Gardner said, such as beans and other legumes and whole grains. Unfortunately, these aren’t the foods Americans typically turn to when increasing their protein intake.
Mila / Adobe Stock
“Americans hardly eat any legumes,” he said. The average American eats less than 10 grams of legumes per day. “There’s plenty of room to increase that and get your fiber, your antioxidants, and your plant protein, and have enough.”
5. There’s no such thing as incomplete protein.
If there’s one protein myth that Gardner wishes would die already, it’s the fable of the incomplete protein. For years, common nutrition advice has posited that plants contain so-called incomplete proteins, while animal proteins are complete. If you’re getting most of your protein from beans and legumes, the advice goes, you need to pair them with certain grains at the same meal to make up the difference.
That’s bupkis, Gardner says. Plant proteins are not missing any of the 20 amino acids, although legumes have slightly less of one of those 20 than do animal proteins. If a person was eating only legumes and no excess protein, that lower amount of the single amino acid might be a problem. But that’s not the reality of the American diet.
“If you need 50 grams of protein a day and you got only 50, then you’d have to be careful that it’s the right kind. But most Americans eat 80, 90, 100 grams of protein a day,” Gardner said. “At that point the distribution doesn’t have to be perfect, because you have so much extra.”
Gardner and his colleagues published a paper in 2019 debunking the incomplete protein myth: They compared amino acid distributions in several different animal and plant foods and found that they’re nearly identical. A recent study even found that a vegan diet works just as well for muscle building as does an omnivore diet.
Oppezzo notes a few other protein myths, namely that you can’t absorb more than a certain amount of protein at once, so it needs to be evenly distributed throughout your daily meals. While you might find it easier to eat 25 grams of protein in three meals than 75 grams all at once, studies have shown that there’s no real difference in how your body metabolizes protein by doing so. For older adults, however, splitting the protein among multiple meals can help ensure they get enough protein because, as we get older, we may need more protein within a given meal to trigger muscle protein synthesis.
It’s also not the case that you have to mainline protein immediately after strength training, she said. It’s true that there is a so-called anabolic window after exercise, a period when your muscles are repairing themselves and can more easily incorporate protein from your diet. But that window is around 24 hours, so just eat your normal meals for the rest of the day and don’t worry about downing a post-workout protein shake at the gym.
And finally, eating more than the RDA can have its drawbacks — even if it’s not coming from a box of protein-packed Pop-Tarts.
“I don’t think a high-protein diet is necessarily bad, but what are you not eating?” Oppezzo said. “Are you missing out on the fiber, vitamins, phytochemicals and antioxidants that vegetables, fruits, whole grains and nuts provide?”
