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| Older adults consuming the Recommended Daily Allowance (RDA) of protein have a higher risk of losing muscle mass, said Wayne Campbell, Ph.D. during his Sept. 14 presentation about Zoom at UAMS.
Current recommendations are about 1 to 1.6 grams of protein per kilogram of body weight, preferably from meals with enough protein to stimulate muscle protein synthesis. As people age, the officially recommended dose for all adults may not be sufficient as they enter the later years of adult life.
Part of the Department of Dietetics and Nutrition’s 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 to April during each academic year, the lecture series is held on the second Thursday of the month, and videos from each webinar are posted on the department’s website.
Campbell is a professor in the Department of Nutritional Sciences at Purdue University in West Lafayette, Indiana. His lecture at the seminar was entitled “Dietary Protein Requirements and Effects on Aging Muscle: Perspectives from the Past, Present, and Future.”
“Research clearly shows that if you’re eating less than the RDA, then it’s not good for your muscles, whether it’s their morphology, metabolism, function or 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 following Campbell’s presentation. Hakkak asked him to comment on the suitability of high-protein diets for weight loss.
“If you lose weight through targeted energy restriction without exercise, on average you’ll lose about 25% muscle and about 75% fat,” Campbell said. “If you eat a higher protein diet, you can reduce that 25% probably down to 20%.”
He compared it to the results of a diet regimen and exercise. In a scenario where someone is losing around 25% lean mass due to calorie restriction, then exercise can reduce lean mass loss to as little as 10-12%.
“So if you’re doing strength training, you can almost completely negate that.” You know, if you had to choose just one, a higher protein diet or extra exercise, especially strength training to maintain lean mass and muscle, I would go for that exercise,” Campbell said.
When asked to compare the difference between animal and plant protein, he said that if one consumes less than the RDA for protein, then a vegetarian diet is inferior to an omnivorous diet in terms of changes in body composition.
However, Campbell said that if total protein intake was higher than the RDA, then the difference between the two protein sources was negligible.
At the beginning of his presentation, Campbell said that the topics of protein, muscle and aging have a long history of study and controversy. He asked his audience to put aside their own views and opinions during his lecture.
“I will be sharing information that will hopefully be scientifically based, but will also be contradictory in many cases,” he said. “It’s a bit of a journey from the past to the present and the future. Thinking about whether the science supports the current and future recommendations that will be made about muscle protein for older adults.”
Campbell reviewed the results of several different studies related to these issues and questions. He gave examples of three different studies using different methodologies that came up with very different dietary and protein intake recommendations for older adults.
Multiple factors can influence the health outcomes of their diet—chronological age, undiagnosed kidney disease, timing of protein intake with exercise, and qualitative differences between protein sources.
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