Snack bars, yogurts, ice cream, even bottled water: it seems like food makers have worked out ways to slip extra protein into just about anything as they seek to capitalize on a growing consumer trend.
Today, protein-fortified foods and protein supplements form a market worth tens of billions of US dollars, with fitness influencers, as well as some researchers and physicians, promoting high-protein diets as the secret to strength and longevity. Protein is undeniably essential, but how much people really need is still a topic of debate.
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On the one hand, most official guidelines recommend a minimum of close to one gram of protein per kilogram of body weight per day, or the equivalent of about 250 grams of cooked chicken (which contains around 68 g of protein) for an adult weighing 70 kilograms. On the other hand, a growing narrative in wellness circles encourages people to eat more than double that amount. Many scientists fall somewhere in the middle and take issue with some of the advice circulating online.
“It’s really frustrating because there isn’t evidence to support the claims that they’re making,” says Katherine Black, an exercise nutritionist at the University of Otago in Dunedin, New Zealand, referring to the super-high protein recommendations often shared on social media. What research does show is that protein needs can vary from person to person and can change throughout a lifetime. And people should think carefully about what they eat to meet those needs. “On social media, it’s like everyone’s worried about protein, putting protein powder into everything,” she says.
Health authorities can help to guide people’s dietary choices on the basis of the latest research. The next Dietary Guidelines for Americans, a document that advises on what to eat for maintaining a healthy lifestyle, is due to come out by the end of this year. But its recommendations, which have tended to be broadly influential, might be changing.
Calculating protein needs
Researchers have been trying to estimate how much protein people need for more than a century. In 1840, chemist Justus von Liebig estimated that the average adult required 120 grams of protein a day, on the basis of a group of German workers’ diets. Later, scientists started to use nitrogen to calculate protein requirements. Protein is the only major dietary component that contains nitrogen. So, by measuring how much of it people consume and the amount they excrete, researchers could estimate how much the body uses.
Since the 1940s, this nitrogen-balance method has been used to determine the Recommended Dietary Allowances (RDA), a set of nutrient recommendations developed by the US National Academies of Sciences, Engineering, and Medicine.
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