- A new study in mice suggests that consuming a moderate amount of protein may be most conducive to metabolic health.
- In the study, the sweet spot for moderate protein intake was between 25% and 35% of a mouse’s daily diet.
- Older people need more protein because the body is no longer able to process macronutrients efficiently.
It makes sense that a person’s nutritional needs change over their lifetime, from childhood to adulthood. As we grow, reach maturity and age, our bodies are occupied with different tasks.
As researchers seek to extend our healthy lifespans — periods free of serious illness — they hoped to identify the optimal balance of macronutrients that support good health at every stage of life.
A new mouse study investigates the role of proteins at different life stages.
The study reveals that consuming moderate amounts of protein in young and middle-aged people may be the key to good metabolic health.
The study authors fed diets of young (6 months) and middle-aged (16 months) mice with different protein levels for two months. Their diet consisted of 5%, 15%, 25%, 35% or 45% protein. The moderate amounts identified in the study were 25% and 35%.
All mice were fasted for three hours before being euthanized for tissue harvesting and analysis.
In mice, a low-protein diet led to the development of fatty liver disease, and middle-aged mice had higher levels of lipids or fats in their systems than younger mice.
Moderate-protein diets lowered lipid and blood sugar levels in mice.
The study is published in Geroscience.
Protein is essential at all stages of life. As Conner Middlemann of the modern Mediterranean noted: “The word ‘protein’ is derived from the Greek word protectionsmeaning “first” or “primary”, which reflects its prominent status in human nutrition. »
Dr. Stuart Phillips from McMaster University explained the importance of protein:
“As we grow, proteins provide the building blocks (amino acids) necessary for the formation of new bones, skin, teeth, muscles, etc. Basically, every tissue needs protein to grow. Once we are fully grown, proteins still provide building blocks – this is not for growth, but to replace proteins that are being processed (broken down). The turnover of body proteins occurs throughout our lives.
In the United States, the required daily amount (RDA) of 0.8 grams of protein per kilogram of body weight is well below the body’s actual needs, Middlemann said. She clarified that the figure only represents the amount of protein required to avoid malnutrition, not the amount to promote good health.
How much protein?
Middlemann noted that the RDA is a holdover from a time when nitrogen balance studies that are no longer considered valid formed the basis of these recommendations. She said that a more accurate understanding of nutritional requirements could be obtained by using the Amino Acid Oxidation Indicator (IAAO) technique.
The IAAO technique, Middlemann said, provides a more reasonable daily recommendation. He suggests that 1.2 grams of protein per kilogram of body weight is appropriate for healthy young men, older men, and older women.
The difference between the two recommendations is significant. The RDA for a 150 pound person is 54g of protein per day, whereas according to the IAAO measurement it would be 81g of protein.
But can we eat too much protein?
“We have a great ability to digest and absorb protein, so I’m not sure you can get so much of it that it’s ‘too much,'” Dr. Phillips said.
He noted that some have suggested that excess protein can lead to kidney and bone problems, “but those are largely debunked.”
“For the most part, protein is relatively equal, but one axiom that is true is that animal-based protein is of higher quality than plant-based protein,” Dr Phillips noted, but added “Most work shows that this difference is probably quite small.”
As to whether the study results will carry over to humans, Dr Phillips said, “Still hard to know, but as short-lived mammals, mice are a proxy for humans, but much of what is seen in mice may not be easily translatable to humans.”
Middlemann felt that the study was nonetheless of value:
“Even though this is a mouse study, it reinforces my view that most of us, especially people over 50, stand to gain from shooting around 25% of energy we consume protein, which is significantly more than the average American currently consumes.
“Some people need even more protein,” Middlemann said.
Of particular note are people who do resistance training. To maximize lean mass, the average amount needed, she said, is about 1.6 grams per kilogram of body weight, and “some people may need 2.2 g/kg or more.”
For people who want to burn fat while maintaining muscle, 1.6 to 2.4 grams per kilogram may be appropriate.
While the study finds that a moderate protein intake may be optimal for younger and middle-aged people, older people still need more protein, Middlemann explained.
“Sarcopenia is the leading cause of age-related frailty, which is associated with a higher risk of disability, having to go to a nursing home, falls, fractures, hospitalizations and premature death. “, Middleman said.
This occurs with age-related muscle loss, she said, ranging “from 0.5% to 2% of total muscle mass each year, beginning around age 50 (although in largely inactive people, it could start even earlier).”
Middlemann also said his clients have been able to increase “muscle mass, cardio-metabolic health, and overall quality of life” by consuming 25-35 grams of protein with each meal and engaging in resistance training.