Protein has been a popular nutrient among athletes, recreational exercisers, bodybuilders and other fitness enthusiasts for some time now. High protein diets gained a reputation among sedentary public and fitness enthusiasts for aiding weight loss and gaining muscle mass. It is confirmed that athletes require more protein in their diet compared to sedentary populations however, despite the prevalence of high protein diets in both athletic and sedentary populations, evidence available regarding the type of protein – animal or vegetable – to consume is limited..
Before we get into any more detail, let’s remember the role of protein in our bodies. Proteins serve as the major structural component of muscle and other tissues in the body – primarily responsible for maintaining growth and repair of the tissues.
Before we can use protein in our bodies, they need to be metabolized into their simplest form, amino acids. There are 20 amino acids; of which 11 are identified as non-essential amino acids, meaning they can be synthesized by our body and therefore we don’t need to consume them in our diet. Remaining 9 are known as the essential amino acids (EAA), which we need to consume through our diet as they cannot be synthesized in our bodies. All 20 amino acids must be present in order to allow tissue to grow, be repaired or be maintained. Perhaps, this is the biggest difference between animal and plant proteins. Unlike animal proteins, plant proteins tend to lack one or more of the essential amino acids, giving them a lower protein quality compared to animal proteins.
In terms of gaining muscle mass, there have been a number of studies (Wilkinson et al., 2007; Hartman et al., 2007; Tang et al., 2009) showing that whey protein (animal protein) was superior to soy (plant protein). Couple of reasons behind this effect is said to be; 1) animal proteins tend to be more balanced in terms of amino acid composition; 2) they have a higher leucine (an essential amino acid) content – which has a direct stimulatory effect on protein synthesis; and 3) they are rapidly digested due to rapid amino acid concentration in plasma after ingestion.
Readers are directed to the references mentioned above for more detailed information on the topic. To support lean body mass gains, there are two very important tips to keep in mind;
1) Increase your habitual intake by around ~500 kcal (for males and ~350kcal for females);
2) ensure you’re consuming a well-balanced diet with approx. 1.8 – 2.0 g/ kg BM of protein, equally divided into each meal.
Contrary to general belief, carbohydrate and fat sources are very important in terms of lean body mass gains, as the body would need to satisfy its energy demands from these sources in order to use protein for only repair and growth. ‘More is better’ ideology is proven to be wrong in a number of academic journals, and although there’s no solid evidence that states that high protein diets (above 2.5 g/kg BM) are harmful within healthy populations, there is also no additional benefit in terms of muscle mass gains above 1.8 g/ kg BM of protein.
Hartman, J.W. & Tang, J.E. & Wilkinson, S.B. & Tarnopolsky, M.A. & Lawrence, R.L. & Fullerton, A.V. & Phillips, S.M. (2007) “Consumption of fat-free fluid milk after resistance exercise promotes greater lean mass accretion than does consumption of soy or carbohydrate in young, novice, male weightlifters”, American Journal of Clinical Nutrition, 86, 373-381. Hoffman, J.R. & Falvo, M.J. (2004) “PROTEIN – WHICH IS BEST”, Journal of Sports
Science and Medicine, 3, 118-130. Tang, J.E. & Moore, D.R. & Kujbida, G.W. & Tarnopolsky, M.A. & Phillips, S.M. (2009) “Ingestion of whey hydrolysate, casein, or soy protein isolate: effects on mixed muscle protein synthesis at rest and following resistance exercise in young men”, Journal of Applied Physiology, 107, 987-992.
Wilkinson, S.B. & Tarnopolsky, M.A. & MacDonald, M.J. & MacDonald, J.R. & Armstrong,
D. & Phillips, S.M. (2007) “Consumption of fluid skim milk promotes greater muscle protein accretion after resistance exercise than does consumption of an isonitrogenous and isoenergetic soy-protein beverage”, American Journal of Clinical Nutrition, 85, 1031-1040