Recommended Dietary Protein Intake for Adults

Current Guidelines

The standard dietary protein intake is currently consistent for both young and older adults. Present recommendations suggest that all adults should consume 0.8 grams of protein per kilogram of body weight, equating to approximately 0.36 grams per pound.

Research into Protein Intake and Muscle Mass

A recent study aimed to explore whether increasing protein intake could enhance muscle mass in older men, particularly in conjunction with testosterone injections. As individuals age, maintaining or building muscle becomes increasingly challenging, resulting in diminished strength and a heightened risk of injury. Some studies indicate that testosterone supplementation may assist older adults in regaining muscle mass lost with age.

The OPTIMen Trial: A Study on Older Men

Study Overview

Researchers conducted a clinical trial involving 92 men aged 65 and older, all of whom displayed moderate impairments in physical function but did not suffer from severe medical conditions such as heart disease or cancer. The participants had an average age of 73 years and were primarily overweight at the study’s outset. Notably, none had been consuming more than the recommended daily protein intake prior to the trial.

Methodology

During the study, participants were provided with nutritionally balanced, pre-packaged meals to ensure precise monitoring of their dietary intake. Participants were divided into two groups: one group consumed the recommended protein amount of 0.8 g/kg of body weight, while the other group received an increased intake of 1.3 g/kg. Both groups received equal total caloric intake from their meals. Additionally, participants were further divided into two subgroups where half received weekly intramuscular injections of 100 mg of testosterone enanthate, and the other half received placebo injections. This created four distinct groups for analysis:

1. Normal protein amount
2. Normal protein amount plus testosterone
3. Extra protein
4. Extra protein plus testosterone

Study Duration and Results

The trial lasted six months, during which researchers utilized specialized X-ray techniques to measure changes in fat and lean tissue mass at both the beginning and end of the study. Lean tissue, which includes muscle and organs, was the primary focus for assessing muscle mass.

Key Findings

Impact of Testosterone and Protein Intake

Results indicated that testosterone injections significantly enhanced muscle mass, with an average increase of 4 kg (8.8 lbs) and a reduction in fat mass by nearly 2 kg (4.4 lbs). In contrast, increasing protein intake alone did not yield any improvement in muscle mass. The testosterone group also exhibited increased muscle strength in both the legs and chest, whereas additional protein had no effect on strength.

Interestingly, the group that adhered to the recommended protein intake without testosterone gained a small amount of fat, a change not observed in those who received higher protein levels. Most changes in weight occurred within the first three months of the study, with muscle and fat mass stabilizing in the latter half.

No Improvement in Quality of Life

The study found no enhancements in walking speed attributable to testosterone, additional protein, or their combination. Participants’ perceived quality of life, assessed through various surveys, showed no significant differences pre- and post-study. Furthermore, the incidence of new health issues reported among the groups was comparable.

Study Limitations and Recommendations

Considerations

The researchers acknowledged certain limitations in their findings. Notably, the study did not include female participants or older men with more severe physical dysfunction or health conditions, which might influence protein needs. The use of pre-packaged meals allowed for precise control over protein intake, a practice that may not be realistic for the general population.

Conclusion

Overall, the findings suggest that the current recommended protein intake is adequate for older men with some physical limitations, even when receiving testosterone treatment to promote muscle growth. Increasing protein intake did not confer any additional benefits in this study.

Reference

Bhasin, S., Apovian, C. M., Travison, T. G., Pencina, K., Moore, L. L., Huang, G., Campbell, W. W., Li, Z., Howland, A. S., Chen, R., Knapp, P. E., Singer, M. R., Shah, M., Secinaro, K., Eder, R. V., Hally, K., Schram, H., Bearup, R., Beleva, Y. M., McCarthy, A. C., Woodbury, E., McKinnon, J., Fleck, G., Storer, T. W. & Basaria, S. Effect of Protein Intake on Lean Body Mass in Functionally Limited Older Men: A Randomized Clinical Trial. JAMA Internal Medicine (2018).