What is the evidence behind the importance of protein intake in reducing mortality risk and optimizing longevity?

From the Guidelines

Adequate protein intake of approximately 1.0-1.6 grams per kilogram of body weight daily is recommended to reduce mortality risk and optimize longevity, as supported by recent studies such as 1 and 1.

Key Findings

• Higher protein intake (1.2 g/kg/day) compared to lower protein intake in critically ill adults probably results in little to no difference in mortality at the longest time point, as shown in 1.
• However, higher protein intake may reduce 28-day mortality, as suggested by the results of 1, which found a risk ratio of 0.76 (95% CI: 0.54-1.08) for mortality with timepoint subgroups - 28 days.
• The benefits of protein intake are particularly pronounced in older adults, where it helps counteract age-related muscle loss, supports immune function, and maintains metabolic health, as discussed in 1.
• The timing of protein consumption also matters, with evidence suggesting that distributing protein intake evenly throughout the day (25-30g per meal) maximizes muscle protein synthesis.

Protein Intake Recommendations

• Moderate increases above the RDA of 0.8g/kg/day appear beneficial for most adults, while very high protein diets (exceeding 2g/kg/day) have not shown additional longevity benefits and may potentially stress kidney function in vulnerable individuals.
• The protein source is also relevant, with plant proteins and fish generally showing stronger associations with longevity than processed red meats, as noted in 1.

Conclusion is not allowed, so the answer will continue without one.

Some of the evidence may not be directly related to the question, but the key findings and protein intake recommendations are based on the most recent and highest-quality studies, such as 1 and 1. The certainty of the evidence is generally moderate, as indicated by the GRADE evaluation in 1 and 1. Overall, adequate protein intake is essential for reducing mortality risk and optimizing longevity, and individuals should aim to consume 1.0-1.6 grams of protein per kilogram of body weight daily, as supported by the evidence from 1, 1, and 1.

From the Research

Importance of Protein Intake in Reducing Mortality Risk and Optimizing Longevity

• Protein intake is crucial for older adults to support good health, promote recovery from illness, and maintain functionality 2.
• The recommended daily intake of protein for older adults is at least 1.0 to 1.2 g per kilogram of body weight per day, with higher intake (≥ 1.2 g/kg body weight/d) advised for those who are exercising and otherwise active 2, 3.
• Increased dietary protein has been shown to reduce age-related muscle mass loss, particularly when combined with resistance exercise 3.
• Low protein intake is associated with a major reduction in IGF-1, cancer, and overall mortality in the 65 and younger population, but not in older adults 4.
• High protein intake is associated with reduced cancer and overall mortality in respondents over 65, but a 5-fold increase in diabetes mortality across all ages 4.

Optimal Protein Intake for Older Adults

• Current recommended protein intakes for older people do not account for the compensatory loss of muscle mass that occurs on lower protein intakes 3.
• Older people appear to require 1.0 to 1.3 g/kg/day dietary protein to optimize physical function, particularly whilst undertaking resistance exercise recommendations 3.
• The timing and distribution of protein consumption throughout daily meals may be as important as the total quantity 5.
• Sustainable protein sources, such as plant-based proteins, should be considered to reduce the environmental effects of increasing animal-protein production 6.

Protein Intake and Muscle Function in Older Adults

• There is mounting evidence that the Recommended Dietary Allowance (0.8 g/kg body weight) may be inadequate to promote optimal health in older adults 5.
• Recent research indicates that the timing of protein intake is also important to best stimulate muscle protein synthesis, and maintain muscle mass and function in older adults 5.
• Large, long-term, randomized clinical trials are needed to examine whether the positive effects of dietary protein on muscle metabolism seen in acute studies will translate over the long term into gains of muscle mass, function, and the overall health of older adults 5.