protein intake

The recommended dietary intake of protein is currently the same for young and old adults. A recent study investigated if older men would benefit with increased muscle mass by increasing their protein intake, with or without testosterone injections.

Proteins are one of the essential building blocks of our body, making up the majority of the structure of our organs and muscles. As we age, it gets harder to gain or retain muscle and this can leave us weaker and more susceptible to injury. Some research suggests that testosterone supplementation may help older adults regain muscle mass that they have lost due to aging. Doctors currently recommend that all adults consume 0.8 grams of protein per kilogram of body weight or 0.36 grams per pound. However, some researchers speculate that increasing protein intake may benefit older adults who are taking testosterone to build muscle.

Researchers in the United States recently carried out a clinical trial investigating if an increased dietary protein is helpful for older adults seeking to gain muscle mass. The study was recently published in the scientific journal JAMA Internal Medicine.

The OPTIMen Trial: Optimizing protein intake in older men

The researchers recruited 92 men who were at least 65 years old, had a moderate impairment of physical function, and did not have a serious medical condition such as heart disease or cancer. The average age of men participating in the study was 73 years. The majority were overweight at the beginning of the study, which is typical for American men of this age. Prior to the study, none of the participants were consuming more than the recommended daily amount of protein.

During the study, all of the participants were given nutritionally balanced pre-packaged meals. This ensured that the researchers knew exactly what the participants were consuming. Half of the participants consumed the recommended daily amount of protein, 0.8 g/kg of body weight, and the other half received additional protein of 1.3 g/kg. The packaged meals were balanced so that both groups received the same total number of total calories.

Half of each group received weekly intramuscular injections of 100mg of testosterone enanthate, and the other half received injections of an inactive placebo. There were, therefore, four groups:

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

The study lasted six months. At the beginning and end of the study, the researchers used a special type of X-ray procedure to determine fat and lean tissue mass in the participants. Lean tissue consists of muscles and organs and was used by the researchers as a measure of muscle mass.

Testosterone injections increased muscle mass, but extra protein was unnecessary

By the end of the study, the testosterone injections significantly increased muscle mass, with an average increase of 4 kg (8.8 lbs). The testosterone injections also resulted in significantly decreased fat, by almost 2 kg (4.4 lbs) on average. In contrast, increasing protein intake had no effect on muscle mass. A similar effect was seen for muscle strength: testosterone injections increased leg and chest muscle strength, but extra protein had no effect. However, the group that received only the normal amount of protein and no testosterone gained a small amount of fat, and this fat gain was not observed in the group receiving extra protein. Most of the weight changes had already occurred after three months, with muscle and fat mass remaining mostly stable for the remaining three months of the study.

Walking speed was not improved by testosterone, extra protein, or the combination of the two. None of the treatments had any effect on the participants’ perception of their quality of life, which was assessed by a number of surveys carried out before and after the study. There was no difference in the number of new health problems reported by members of the four groups during the study.

The researchers acknowledged some limitations in their study. Notably, this study did not include women or older men with more serious physical dysfunction or illness, and it is possible that the protein needs of these groups are different.  Furthermore, they used pre-packaged meals and close supervision to ensure that participants consumed exactly the amount of protein desired. In practice, such tight control of protein intake may not be feasible for most patients.

The current recommended intake may be sufficient

Overall, the results of this study suggest that the current recommended dietary intake for protein is sufficient for older men who have some limitations to their physical functioning. This was true even when they were receiving testosterone to boost muscle formation. Increasing protein intake did not have any additional beneficial effect.

Written by Bryan Hughes, PhD

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)

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