Protein and amino acid supplementation enhance muscle size and strength

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In my life and work I commonly come across men who are keen on being stronger and more muscular, and will ask about the sort of diet that might help them achieve their ends. Perhaps not surprisingly, I recommend a diet relatively rich in protein, seeing as protein is a major component in muscle. For those keen to go the extra yard, I do think that some protein supplementation may be in order, usually in the form of whey protein concentrate consumed around the time of exercise.

I was interested to read a recent study in which the effects of whey protein in combination with the amino acid leucine on physical performance and body composition in ‘moderately fit’ individuals [1]. Leucine is an amino acid (building block of protein) that is believed to have particular value in stimulating the formation of muscle.

In this study, individuals were randomly assigned to consume about 20 g of whey protein and 6.2 grams of leucine each day, or a ‘placebo’ (which did not contain whey and leucine but contained the same number of calories). The study lasted eight weeks.

In the whey/leucine group, significant improvements were seen in performance in the bench-press (pushing weights up with the arms while lying down). Press-up (push-up) performance was also improved. These improvements were not seen in the group consuming the placebo.

On the other hand, no improvements were seen in other measures including crunches (a form of sit-up), chin-ups or the time taken to run 3 miles.

Each of the study participants was assessed for body composition at the start at the end of the study. The group consuming the whey/leucine supplement saw gains in body weight and lean body mass (a measure of muscle mass). No such changes were seen in the group supplementing with the placebo.

The authors conclude that “supplementing with whey protein and leucine may provide an advantage to people whose performance benefits from increased upper body strength and/or lean body mass.”


1. Walker TB, et al. The influence of 8 weeks of whey-protein and leucine supplementation on physical and cognitive performance. Int J Sport Nutri Exerc Metab. 2010;20(5):409-17

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