Better Protein Intake for Healthy Aging

3 min readJul 24, 2023

While dietary restriction has shown potential for increasing lifespan, it is important to note that humans have a lower metabolic rate than mice, which makes them less responsive to interventions such as protein restriction [1]. Comparing body area sizes among different animals provides an intuition into the differences in metabolic rates. Generally, larger animals exhibit lower metabolic rates due to their smaller surface-area-to-volume ratios.

For older adults, maintaining a higher protein intake is necessary to counteract muscle loss and frailty associated with conditions like sarcopenia and osteoporosis, which can lead to disabilities and premature death. The significance of protein in promoting healthy aging becomes evident through these connections.

Studies on rhesus monkeys have yielded mixed results regarding extending lifespan through dietary restriction. Considering the potential risks of impaired function and reduced quality of life, protein restriction for the sake of longevity is questionable.

Ensuring an adequate protein intake is essential for promoting healthy aging. However, when protein-rich foods are scarce, individuals may gravitate towards alternatives that mimic protein in taste and texture, even if they primarily consist of fat and sugar — the ‘Protein Leverage Hypothesis’ posits that organisms will overeat if their diet is low in protein [2].

In their book “Eat Like Animals” [3], nutritionist David Raubenheimer and nutritional physiologist Stephen Simpson emphasize the importance of satisfying one’s appetite for protein-rich foods to prevent overeating. They propose a straightforward algorithm to achieve this.

1. Calculate your daily caloric intake based on age, gender, and activity level. The Harris-Benedict calculator (circa 1918) can be used for this purpose.

2. Determine the proportion of calories that should come from protein-rich foods by multiplying the total number of calories by a coefficient corresponding to the percentage of protein content. The coefficient varies based on age: multiply by 0.18 (18%) if you are 18 to 30 years old, by 0.17 (17%) if you are between 30 and 65 years old, and by 0.2 (20%) if you are over 65.

3. Convert calories into the required protein amount. Since 1 gram of protein contains 4 kilocalories, divide the resulting number of calories by 4 to determine the required grams of protein for the day.

Alternatively, you can use the Protein Intake Calculator [4] I have developed, which is based on the Revised Harris-Benedict Equation (circa 2023, which accounts for modern lifestyle factors, making it more applicable to today’s population) for estimating Resting Metabolic Rate [5]. This calculator is meant for illustrative and educational purposes only and is not warranted for any medical use.

In addition to the aforementioned guidelines, following a rule of thumb for protein consumption is generally recommended. It is advised to limit each meal to at most 30 grams of protein while considering that the body can effectively absorb around 10 grams of protein per hour. This optimal protein dose per meal appears to effectively stimulate muscle protein synthesis (MPS). Research suggests that exceeding protein intake of 0.4 g/kg/meal doesn’t further stimulate MPS in young men. [6, 7]

Even when considering whole food sources like lean ground beef, a moderate protein amount of approximately 30 grams is just as effective as a higher amount of around 90 grams in triggering MPS. Going beyond the 30 gram range results in increased protein oxidation and urea production, indicating a limit to the amino acids that can be utilized for MPS. Furthermore, when protein intake exceeds 1.6 g/kg/day, the benefits of such intake diminish significantly. [8]

Update: Recent research using a quadruple isotope tracer approach reveals that consuming 100 grams of protein significantly enhances and prolongs the anabolic response for over 12 hours, compared to 25 grams. This challenges the belief that the body’s ability to utilize protein for muscle building is limited and short-lived. Moreover, higher protein consumption does not significantly increase amino acid oxidation. [9]

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Better Protein Intake for Healthy Aging

Written by Denis Odinokov, MBBS, MSc, PMP