Nutrition Seminar Speaker: Protein Intake, Exercise Key to Fighting Muscle Loss in Older Adults

By Ben Boulden

Current recommendations are about from one to 1.6 grams of protein per kilogram of body weight, preferably from meals with sufficient protein to stimulate muscle protein synthesis. As people age though, the officially recommended allowance for all adults may not be sufficient as they enter the later years of adult life.

Part of the Department of Dietetics and Nutrition Seminar series, Campbell’s presentation was the first in the series to be approved for continuing education credit for physicians, nurses, pharmacists, physician assistants, registered dietitians and athletic trainers. From September through April during each academic year, the series features a lecture on the second Thursday of each month, and video recordings of each webinar are posted on the department’s website.

Campbell is a professor in the Department of Nutrition Sciences at Purdue University in West Lafayette, Indiana. His seminar presentation was titled “Dietary Protein Needs and Influences on Muscle with Aging: Views from the Past, Present, and Future.”

“Research clearly shows that if you’re eating less than the RDA, then that is not good for your muscles, whether or not its morphology, the metabolism, the function or the physiology,” Campbell said.

Reza Hakkak, Ph.D., chair of the Department of Dietetics and Nutrition in the UAMS College of Health Professions, opened a question-and-answer session after Campbell’s presentation. Hakkak asked him to comment on the advisability of high-protein diets for weight loss.

“If you are losing weight by purposeful energy restriction without any exercise, on average, you are going to lose about 25% of your lean body mass  and about 75% as fat mass,” Campbell said. “If you eat a higher protein diet, then you can cut that 25% probably down to about 20%.”

He contrasted that with the results from a regimen of diet and exercise. In a scenario in which someone is losing about 25% of lean mass from calorie restriction, then exercise can reduce the loss of lean mass down to about 10 to 12%.

“So, if you’re doing strength training, you can almost completely negate it. You know, if you only had to pick one, higher protein diet or extra exercise, particularly strength training for preservation of lean mass and muscle, I would go with the exercise,” Campbell said.

When asked to compare the difference between animal and vegetable proteins, he said if a person is consuming less than the RDA for protein, then a vegetarian diet was inferior to an omnivorous diet as far as body composition changes were concerned.

However, Campbell said if total protein intake was above the RDA, then the difference between the two sources of protein was negligible.

Early in his presentation, Campbell said the topics of dietary protein, muscle and aging have a long history of study and controversy. He asked his audience to put their own perspectives and opinions to the side during his lecture.

“I’m going to be sharing information that hopefully will be scientifically sound, but it will also be in many cases contradictory,” he said. “It’s a bit of a journey from the past to the present and future. Of thinking about whether or not the science supports the recommendations that are currently and into the future will be made regarding protein for muscle for older adults.”

Campbell reviewed the results of several different studies relevant to those issues and questions. He gave the examples of three different studies using different methodologies that came up with very different recommendations as to diet and protein intake for older adults.

Multiple factors can influence the health outcomes of their diets — chronological age, undiagnosed kidney disease, timing of protein intake with exercise and qualitative differences between sources of protein.