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Higher Protein Intake Doesn’t Improve Muscle Strength in Middle Aged Adults

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Higher Protein Intake Doesn’t Improve Muscle Strength in Middle Aged Adults

Among middle-aged adults who took part in a strength training program, eating more protein didn’t lead to any improvements in muscle strength or mass, according to a new study published in the American Journal of Physiology: Endocrinology and Metabolism.

As the study authors point out, resistance training is well accepted as a strategy to help adults maintain muscle strength and mass as they get older. For this study, they were interested in whether two different levels of protein supplementation — representing a moderate or high protein intake — had an impact on muscle-related outcomes in a group of 50 middle-aged adults, ranging in age from 40 to 64, who took part in a 10-week resistance training program. There were three exercise sessions each week, after which each participant was randomly assigned to consume either 15 or 30 grams of protein from lean beef. Each participant also consumed an identical amount of protein later in the evening.

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As noted in a HealthDay article on the study, members of the moderate-protein group were also instructed to keep their overall protein intake to the U.S. government’s recommended daily allowance of 0.8 grams for every kilogram (2.2 pounds) of body weight. In reality, though, based on diet records that all participants kept, members of the moderate-protein group ended up eating about 1.0 grams of protein per kilogram of body weight. Members of the high-protein group, on the other hand — which received the larger protein supplements — ended up eating a daily average of 1.6 grams of protein per kilogram of body weight.

But despite their higher protein intake, members of the high-protein group gained no more muscle mass or strength than those in the moderate-protein group by the end of the 10 weeks. They also showed no differences in overall body composition, such as having more or less body fat, or blood markers related to glucose control, kidney function or cardiovascular health. This means that while consuming more lean beef seems to have had no measurable harmful effects, it also led to no measurable health benefits.

These results show, the researchers wrote, that eating more protein than recommended amounts doesn’t appear to make strength training any more effective or beneficial — in contrast to the longstanding myth that eating more protein helps you build muscle. While this is true up to a point, most American adults already get the protein they need for optimal muscle growth and maintenance. When the body takes in more protein than it needs for muscle maintenance, it converts that extra protein to stored energy, which is then treated no differently from stored energy from carbohydrate in your diet.

So if you’re looking to boost your muscle mass or strength, how and when you work out — along with other lifestyle factors like sleep, stress and overall nutrition — are likely to be more important factors than how much protein you eat, once you reach basic daily recommended levels.

Want to learn more about exercising with diabetes? Read “Add Movement to Your Life,” “Picking the Right Activity to Meet Your Fitness Goals” and “Seven Ways to Have Fun Exercising.”

Living with type 2 diabetes? Check out our free type 2 e-course!

Quinn Phillips

Quinn Phillips

Quinn Phillips on social media

A freelance health writer and editor based in Wisconsin, Phillips has a degree from Harvard University. He is a former Editorial Assistant for Diabetes Self-Management and has years of experience covering diabetes and related health conditions. Phillips writes on a variety of topics, but is especially interested in the intersection of health and public policy.

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