Protein Improves Reaction Time

This study has evaluated the effect of consumption of excess protein on muscle power and reaction time in a set group of male patients. The researchers compared the quality of life between participants who consumed high protein diet and those who consumed World Health Organization (WHO) recommended quantities of protein. The researchers looked for any adverse effects caused due to an increased consumption of protein and the potential benefits that can be seen with the increased protein intake. “Healthy young males fed on a high protein diet improved reaction time. No adverse effects of high protein diet were observed.” There was no significant difference in the quality of life of both the groups.

The present WHO recommendations for protein consumption are based on nitrogen balance. According to this, only the amount of nitrogen lost from the body must be replaced in the form of proteins. The authors of the study felt that these recommendations must take into consideration the overall wellbeing of an individual, rather than just the nitrogen balance. Studies carried out in the past have shown that consuming high amount of protein can have beneficial effects like  properly maintained body weight, lowered glucose levels, increased  bone strength etc. In the present study, the researchers wanted to evaluate the effect of consuming excess amounts of protein on muscle strength, reaction time and quality of life.


  • The study included 23 healthy men, aged between 19 and 31 years. Before the start of the experiment, all of them were asked to consume a normal protein diet containing 1.5 gm of protein per kilogram body weight of the individual.
  • The participants were then divided into two separate groups. For three weeks, the first group continued with the usual protein diet, while the second group received high protein diets. The high protein diet contained 3 gm of protein per kg of body weight.
  • After three weeks, muscle power was measured by assessing hand grip strength. Reaction time was measured using a computer, where participants were asked to press a button, when a particular signal was given to them. Quality of life was evaluated using a questionnaire called “Short-Form Health Survey.”
  • Blood sample was collected to measure various substances such as sodium, potassium, glucose, insulin, thyroxin and various amino acids. Urine was collected to measure urea, creatinine and albumin.


  • Participants on a high protein diet had better reaction time. They also had a significantly higher amount of phenylalanine and tyrosine in their plasma. These higher levels of phenylalanine can increase the amounts of neurotransmitters dopamine and norepinephrine that are produced. Increased tyrosine levels can also increase reaction times.
  • There were increased levels of Branched Chain Amino Acids (BCAA) and a few amino acids, in the high protein diet group. Previous studies have shown that BCAA can reduce fatigue and improve mental functioning after physical exertions.
  • There was no significant difference between the two groups, as far as muscle power and quality of life was concerned. Urine examination showed no difference in excretion of creatinine and albumin. No adverse reactions were found in people who consumed a high protein diet.

Shortcomings/Next steps
The main limitation of this study is the very low sample size (23). As a result, the observations of this study cannot be generalized to the community at large. Moreover, all the participants were young, healthy men. This age group is known to be less responsive to alterations in diet. Hence this study may give significant results if repeated on malnourished or older individuals.

Improvement in reaction time in participants consuming a high protein diet has been convincingly proved in this study. This improvement is probably because of the high levels of branched chain amino acids such as phenylalanine tyrosine and Branched Chain Amino Acids in the blood. This improvement may also be because of increased intake of vitamin B and D in those who consumed meat. Another important finding of this study is the nil adverse effects in those who had a high protein diet. As a result, there is a need to bring in amendments in the WHO Recommendations for daily protein intake. Such a measure would help in improving the health of the community at large.

For More Information:
Effect of a High Protein Meat Diet on Muscle Power and Reaction Time: A Randomized Controlled Dietary Intervention Trial in Healthy Men
Clinical Nutrition, 2011
By Lene M Jakobsen; Jens Kondrup
From the University of Copenhagen, Copenhagen, Denmark and Rigshospitalet, Denmark

*FYI Living Lab Reports Are Summaries of the Original Research.