The Importance Of Protein For People Who Exercise


Protein Supplements Can Help You Perform Better  

There has been a long- term debate over the possible benefits of a high-protein diet for those who exercise.  Views are polarised, some believing there are no benefits, and even potential danger, whilst others claim marked benefits.  Both camps have staunch advocates and, probably as there have historically been mixed results from studies. This due to the fact that it has been difficult to measure effects of a high-protein diet in humans. 

However, conclusive evidence is emerging to support the theory that a high-protein diet has significant benefits for those who exercise.  It is becoming clear that increasing levels of protein and the use of protein-rich supplements helps exercisers build and maintain muscle, repair damaged muscle tissue and prevent muscle loss.  There is also evidence that consuming protein, particularly dairy-derived proteins, in combination with exercising has beneficial effects on blood pressure and artery elasticity – potentially lowering risks for development of heart disease, heart attack and stroke. 

Muscles are mostly made of protein, the building blocks of which are amino acids.  Our muscles are undergoing buildup and breakdown all the time – we are constantly renewing our muscle tissue.  Biolo (1995) showed that, when resting, we breakdown more muscle tissue than we build up (e.g. synthesise).  When we exercise, muscle synthesis is significantly increased.  However, breakdown is also increased.  If we exercise without consuming energy and protein, the synthesis that occurs uses only amino acids that have been released by muscle breakdown which simultaneously takes place. This is not a perfect system though, some of the amino acids released by breakdown are lost to oxidation.  In this scenario, we have a negative protein balance.  That is to say, overall we are losing protein from our muscle.  

It is therefore clear that we need to supply proteins and energy, both at rest and when we exercise. We all know this to be true.  We also know that the more exercise we do, the more energy we need to consume.  So the question is: ‘What energy source should we use to maximize the benefits of our exercise?’  Can we just eat more of our normal diets? 

Well, this does have benefits: an increase in calorie intake does help to maintain levels of protein found in muscles, as shown by Butterfield and Calloway (1984). But the effect is limited, and it is only through specifically increasing the levels of protein we ingest that we can achieve a positive protein balance – a situation where we are building up more muscle tissue than we are breaking down. 

Indeed, Meredith et al showed that long distance runners, who consume the recommended dietary allowance (RDA) of protein for their activity-level, would not actually meet their needs.  In fact, they needed to consume up to twice as much protein to achieve a positive protein balance, reaching a state where they were building muscle strength and mass.  

The idea that exercising necessitates more protein in your diet was confirmed in Pasiakos’ study (2013).  He discovered that doubling the protein RDA was required to prevent muscle loss in dieters who exercise.  He also found that doubling protein intake promoted fat loss.  

Based upon these studies, scientists are now focussing on diet and supplementation in order to put this knowledge to use  and create the ideal fuel for those who exercise. 

The protein supplement of choice is whey protein, derived from milk.  Several studies have shown that ingestion of whey protein after exercise increases levels of muscle protein synthesis significantly.  Reidy showed in 2013 that whey protein, taken one hour after resistance training, gave a marked increase (above resting rate) in muscle protein synthesis.  This peaked at 30% above resting rate, at 40 minutes after ingestion, with increased synthesis levels lasting up to 2 hours.  Although a supplement including whey, soy protein and casein may increase the ‘anabolic window’ (the time period where muscle synthesis occurs post-exercise), only whey protein gives these high levels of increase in synthesis rate.  Tang (2009) and Yang (2012) confirm that whey protein supplementation is more effective than casein or soy protein in stimulating muscle protein synthesis. 

Not only can a protein supplement be useful after exercise, it can help when taken before exercise to improve performance.  Fukuda et al (2010) showed that the ingestion of amino acids before exercise ‘may be an effective strategy for increasing anaerobic energy 

As well as increasing muscle synthesis and running performance, milk proteins have been shown to improve cardiovascular health in women who exercise.  Figueroa studied obese women and compared those who exercised and consuming a milk protein supplement with those who exercised and only consumed a control carbohydrate supplement.  The group on milk protein supplements showed significant reductions in brachial and aortic blood pressure and arterial stiffness.  The control group showed no change. It is well known that elevated blood pressure and increased arterial stiffness are risk factors for the development of poor cardiovascular health. 

In conclusion, daily intake of a whey protein supplement before and after exercise can help maintain current muscle levels, increase your muscle mass and strength, increase your anaerobic capacity, as well as reduce your blood pressure.



1.  Biolo G, Maggi SP, Williams BD, Tipton K, Wolfe RR. Increased rates of muscle protein turnover and amino acid transport following resistance exercise in humans. Am J Physiol 1995;268: E514–20.

2.  Butterfield G, Calloway DH. Physical activity improves protein utilisation in young men. Br J Nutr 1984;51:171–84.

3.  Fukoda DH, Smith AE, Kendall KL, Stout JR.  The possible combinatory effects of acute consumption of caffeine, creatine, and amino acids on the improvement of anaerobic running performance in humans. Nutrition Research 2010; 30:9, 607-614 

4. Meredith CN, Zachin MJ, Frontera WR, Evans WJ. Dietary protein requirements and body protein metabolism in endurance-trained men. J Appl Physiol 1989;66:2850–6.

5.  Pasiakos SM, Cao JJ, Margolis LM et al. Effects of high-protein diets on fat-free mass and muscle protein synthesis following weight loss: a randomised controlled trial.  The FASEB Journal 2013; Sep 27(9):3837-47.6. Reidy PT, Walker DK, Dickinson JM et al. Protein blend ingestion following resistance exercise promotes human muscle protein synthesis.  J Nutr.  2013; 143(4):410-6.

7.  Tang JE, Moore DR, Kujbida GW, Tarnopolsky MA, Phillips SM. Ingestion of whey hydrolysate, casein, or soy protein isolate: effects on mixed muscle protein synthesis at rest and following resistance exercise in young men. J Appl Physiol. 2009;107:987–92.

8.  Yang Y, Churchward-Venne TA, Burd NA, Breen L, Tarnopolsky MA, Phillips SM. Myofibrillar protein synthesis following ingestion of soy protein isolate at rest and after resistance exercise in elderly men. Nutr Metab (Lond). 2012;9:57.

9.  Wolfe RR. Protein supplements and exercise.  Am J Clin Nutr 2000; 72(2):551s-557s.

10. Cermack NM, Res PT, et al.  Protein supplementation augments the adaptive response of skeletal muscle to resistance-type exercise training: a meta analysis.  Am J Clin Nutr. 2012;96:1454–64

11. Arturo Figueroa et al.. Effects of Milk Proteins and Combined Exercise Training on Aortic Hemodynamics and Arterial Stiffness in Young Obese Women With High Blood Pressure . Am J Hypertens (2014) 27 (3):338-344.