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Muscle Up to Some Protein Every Day

ARS Researchers Explore How Regular Protein Consumption Can Ward Off Disability in Older Adults

A man reaching for a grocery item on a shelf

A man selects groceries at Purcell Nutrition Services in Purcell, OK. It is important, especially for older people, to ensure they consume enough protein in each meal. (Photo by Don Hamilton for USDA).

What should we be eating? Meat? Plant-based foods? The Mediterranean Diet? With all the competing claims out there, it can be hard to know what to put on our plates. Luckily, there is at least some agreement among those who study nutrition: we all need protein.

“Because protein is found in all cells of the body, it is important for the structure, function, and regulation of the body’s tissues and organs as well as a healthy immune system,” explained Dr. Shanon Casperson, Research Biologist and Lead Scientist with ARS’s Grand Forks Human Nutrition Research Center (GFHNRC), in Grand Forks, ND. “Without adequate protein intake, the body will break down its existing skeletal muscle to get what it needs to maintain critical metabolic functions; this becomes especially important for older adults during times of illness or injury.”

That’s why Casperson, along with GFHNRC Director Dr. James Roemmich and collaborators at North Dakota State University, set out to examine the association of eating protein and health outcomes among older adults. In particular, they examined whether eating enough protein might be correlated with functional disability – that is, injuries and impairments that interfere with a person’s ability to complete the ordinary functions of daily life – among older Americans. To do so, they used dietary recall data – what people remembered about what they had eaten – from adults who were at least 60 years old. The data was collected between 2007 and 2016 as part of the National Health and Nutrition Examination Survey, a broad survey designed to assess the health and nutritional status of adults and children in the United States.

“Research shows that older adults need about 0.54 grams per pound of body weight per day,” said Casperson. “However, most older adults do not consume this amount of protein. In fact, about 40% of older adults do not consume even the recommended dietary allowance (RDA) of about 0.37 grams per pound per day.”

A plate containing a chicken leg and couscous.

A healthy meal should contain protein, along with other important nutrients. Pictured: Chicken with Veggie Couscous. (Photo courtesy of USDA Food and Nutrition Service)

In results published in the Journal of Health and Aging, the researchers found that not only was the amount of protein consumed correlated with preventing impairment, but the timing was significant as well. “As we age, our skeletal muscle becomes resistant to the anabolic effect of dietary protein,” said Casperson. “Research has shown that there is a threshold for the amount of protein that needs to be consumed to optimally stimulate muscle protein synthesis. This threshold is 25-30 grams at each meal.”

The source of the protein is also important: Some foods can get people to the protein threshold much faster than others. “You only need to eat 4 ounces of a lean meat such as beef, chicken, and pork, or 1 cup of cottage cheese to reach the 25-30-gram threshold,” said Casperson. However, “You need to eat 2 cups of beans to get the same amount of protein. Additionally, most plant-based proteins are not complete, and must be paired with other foods; this is why beans are typically paired with rice, which can further [increase] the amount of food that needs to be consumed.”

The findings provide an important foundation for future research. Because the study relied on self-reported data from participants, Casperson noted that more robust clinical trials are needed. Additionally, she added, the researchers would ultimately like “a more comprehensive understanding of the role plant-based proteins play in the preservation of functional capacity in older adults.”

For now, though, the health benefits of consuming proteins are clear, especially for older adults.

“It is important to make a conscious effort to consume an adequate amount of protein every time they eat for healthy aging,” Casperson said. – by Kathryn Markham, ARS Office of Communications.


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