Eating more protein than daily recommendations suggest may only benefit people who are cutting calories to lose weight or strength training to build more lean muscle mass, according to a new study.
The study also affirms that the recommended dietary allowance, of 0.8 grams of protein per kilogram of body weight per day—or 0.36 grams per pound—is adequate for most people. For example, an adult who weighs 150 pounds should eat 54 grams of protein a day, which could be three ounces of lean meat, three cups of dairy, and one ounce of seeds or nuts within a day.
“But here is the hard part for consumers: These findings support that most adults who are consuming adequate amounts of protein may only benefit from moderately higher protein intake when they are purposefully trying to change their body composition such as when dieting or strength training. The results are not meant to encourage everyone to increase their protein intake in general,” says Wayne Campbell, a professor of nutrition science, whose research integrates exercise physiology, geriatrics, and nutrition, especially protein.
“This research uniquely assesses whether adults benefit from consuming more protein than the current recommended dietary allowance,” says Joshua L. Hudson, postdoctoral research associate at Purdue University.
“This research was not designed to assess whether or not adults would benefit from consuming more protein than they usually consume. This distinction is important because the recommended dietary allowance is the standard against which to assess nutrition adequacy; however, most adults consume more protein than what is recommended.”
When people are in a neutral metabolic state—not losing weight or lifting weights—eating more protein does not influence their body composition any differently, including lean mass, which is consistent with the current recommended dietary allowances being adequate for generally healthy sedentary weight-stable people. This does not include adults with type 2 diabetes.
“And that is important because there is so much encouragement, advertising, and marketing for everyone to eat higher protein diets, and this research supports that, yes, under certain conditions, including strength training and weight loss, moderately more protein may be helpful, but that doesn’t mean more is needed for everybody at all times,” Hudson says.
Researchers screened more than 1,500 nutrition articles across journal databases to identify 18 studies with 22 intervention groups and 981 participants that addressed this topic. They selected studies based on specific factors including inclusion of healthy adults, protein intake, weight loss, and physical activity. The sources of protein researchers evaluated included lean and minimally processed meats, dairy, eggs, nuts, seeds, and legumes.
“This research is clinically more important for women and especially older women who are known to typically consume lower amounts of protein and should be maintaining a healthy bodyweight and regularly strength training,” Campbell says.
What do these findings mean for someone watching their weight during the holidays or planning New Year’s resolutions?
“If you are going to start losing weight, don’t cut back across all foods you usually consume, because you’ll inadvertently cut back protein. Instead, work to maintain, or even moderately increase, protein-rich foods. Then, cut back on the carbs and saturated fat-containing foods,” says Campbell, who studies how sources and amounts of protein—which is critical to building muscle mass—may be a part of adopting healthy eating patterns, including the Mediterranean diet and DASH diet.
These findings are general, and more evaluation is needed to determine effects on age and gender. This research does not apply to elite athletes or people who lost weight with bariatric surgery, nor does it relate to protein supplements.