Do older adults have impaired protein digestion and absorption?
During ageing, muscle and strength are progressively lost. This process of losing muscle with age is called sarcopenia.
One of the underlying mechanisms of sarcopenia is a lower anabolic response to protein ingestion. However, it is not fully understood why older adults are less responsive to protein.
In this study from our lab, we combined data from all our previous studies using intrinsically labeled protein. Intrinsically labeled protein is a special type of protein that we produce for research, that allows us to follow it throughout to body to measure its absorption for example. This allowed us to make all kind of interesting comparisons, such as differences in protein digestion and absorption between young and older adults.
For young adults, 51% of ingested protein ends up in the blood following digestion and absorption. For older adults, this was only 45%.
Therefore, less of the ingested protein may become available for muscle tissue in older adults. This may suggest that older adults need to consume slightly more protein to compensate.
A few important details. First, our data do not suggest that always ~50% of protein is taken up into the circulation. The exact percentage of protein that is absorbed will be determined by a variety of factors, such as the amount of protein ingested, the type of protein, and the time period over which you measure digestion.
Second, our method specifically measures protein absorption into the circulation. The total amount of protein absorption from the gut is way higher (>90%), but a large part of that protein is taken up into gut tissues and not released into the circulation. So our data do not imply that half of your ingested protein is wasted!
In conclusion, protein digestion and absorption into the circulation is lower in older compared to younger adults.
Go to the next infographic in the protein series:
Elderly need more protein for muscle growth?
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