CHICAGO, March 25 (Xinhua) — A 10-week muscle-building and dietary program involving 50 middle-aged adults found no evidence that eating a high-protein diet increased strength or muscle mass more than consuming a moderate amount of protein while training.
In a study of the University of Illinois (UI), the researchers assessed participants’ strength, lean-body mass, blood pressure, glucose tolerance and several other health measures before and after the program.
They randomized participants into moderate- and high-protein diet groups. To standardize protein intake, the researchers fed each person a freshly cooked, minced beef steak and carbohydrate beverage after every training session. They also sent participants home with an isolated-protein drink to be consumed every evening throughout the 10 weeks of the study.
The moderate-protein group consumed about 1.2 grams of protein per kilogram of body weight per day, and the high-protein group consumed roughly 1.6 grams per kilogram per day. The researchers kept calories equivalent in the meals provided to the two groups with additions of beef tallow and dextrose.
The researchers also analyzed gut microbes in fecal samples collected at the beginning of the intervention, after the first week – during which participants adjusted to the new diet but did not engage in physical training – and at the end of the 10 weeks.
The researchers hypothesized that getting one’s protein from a high-quality source like beef and consuming significantly more protein than the Recommended Dietary Allowances would aid in muscle growth and strength in middle-aged adults engaged in resistance training. But at the end of the 10 weeks, they saw no significant differences between the groups. Their gains in strength, their body fat, lean body mass, glucose tolerance, kidney function, bone density and other “biomarkers” of health were roughly the same.
The only potentially negative change researchers recorded is between the groups involved alterations to the population of microbes that inhabit the gut. After one week on the diet, those in the high-protein group saw changes in the abundance of some gut microbes that previous studies have linked to negative health outcomes. The researchers found that their strength-training intervention reversed some of these changes, increasing beneficial microbes and reducing the abundance of potentially harmful ones.
The study, posted on UI’s website on Thursday, has been published in the American Journal of Physiology: Endocrinology and Metabolism. Enditem