It’s no secret that dietary protein is essential to promote muscle growth following hard exercise. However, there is still a great deal of confusion stemming from questions such as ‘what is whey protein?’ and ‘when to eat protein’ as well as debate on protein type, amount and timings that should be used in order to optimise training adaptation and maximise gains. This short article disambiguates our current understanding of dietary protein and offers some recommendations on how to use this valuable macronutrient to achieve your training goals.
Why Protein, Why Whey?
According to The Institute of Medicine , the protein intake for a sedentary person should be ~0.8 g of protein per kilogram of bodyweight per day (g/kg/d). This is thought to be sufficient for this population to maintain a positive nitrogen balance and healthy metabolic function. High-intensity and long-duration exercise, however, result in the structural breakdown of muscle proteins (Tarnopolsky, 2004). As a result, dietary protein requirements are generally much higher in people participating in strength training (Tarnopolsky et al., 1988) and endurance training (Friedman et al., 1989). Increasing protein intake to meet these demands will promote a net protein synthesis in the muscle (i.e, muscle protein synthesis that exceeds the rate of protein breakdown) to rebuild from training-induced muscle damage. Of the various forms of supplemental protein (whey, casein, soy, egg, hemp), whey contains the highest concentration of amino acids (Smithers, 2008), is easily digestible and is effectively incorporated into body cells (Smithers, 2008).
Types of whey protein: what’s the difference?
So what is whey protein? Whey is the watery by-product of the milk manufacturing process. Depending on the filtration process used after the milk has coagulated (microfiltration, ultra/diafiltration), whey it is usually developed in two forms; whey protein concentrate which typically comprises ~80% protein, and whey protein isolate which comprises ~85 - 90% protein (Smithers, 2008). Whey concentrate contains the naturally occurring macro- and micro-nutrients derived from the manufacturing process and is the most calorie dense form of the supplement. By contrast, isolated whey has undergone additional purification to minimise extraneous carbohydrates and fats and enhance the protein content. The disadvantage of a whey isolate is that the additional processing also eliminates important micronutrients and sub-fractions (e.g. lactoferrins, beta-lactoglobulins and immuno-globulins). Whey protein hydrolysate is a concentrate or isolate in which some of the amino bonds have been broken by exposure of the proteins to heat, acids or enzymes. This pre-digestion makes hydrolysed proteins more rapidly absorbed in the gut than either whey concentrates or isolates. Whey hydrolysates accompany whey isolates at the more costly end of the spectrum, despite anecdotal reports that it is generally less palatable.
How much protein do I need? - Dosage and timing
The dietary protein requirements for exercising individuals have been widely studied. In a milestone study, Tarnopolsky et al. (1992) investigated the effect of low (0.86 g/kg/day), moderate (1.4 g/kg/d) and high (2.4 g/kg/d) protein diets on muscle development in a group of strength-trained individuals. While the low protein diet was unable to offset the muscle damage that occurred following resistance exercise (i.e. whole-body protein synthesis was reduced), the medium protein diet appeared to fulfil the group’s requirements for muscle protein synthesis. Importantly, the high protein diet used in the study did not result in any further benefits. As such, a protein intake of between 1.5 – 2 g/kg/d appears appropriate to optimally stimulate muscle protein synthesis in exercising individuals.
The appropriate amount of protein to consume per serving also deserves consideration to ensure maximal absorption. This depends on several factors such as body mass, training status and activity levels. The extent of protein synthesis in the muscle following heavy resistance exercise appears to be proportional to the size of the ingested dose up to approximately 30 g. For example, an average-sized adult (70 – 85 kg) will optimally-stimulate muscle protein synthesis following exercise with a protein dose of 20 – 30 g, but doubling the dose to 40 g is unlikely to result in significant increases in muscle protein synthesis in these people (Moore et al., 2009). Consuming protein in doses of 30 – 40 g may have additive effects for larger adults (> 85 kg). Your daily protein intake should be ‘drip fed’ throughout the day by consuming relatively small but frequent portions of around 20 g per meal or snack.
|Activity||Protein Recommendations (g/kgBM)|
|Sedentary / low activity||0.8|
|Regular activity||1.0 - 1.2|
|Endurance exercisers||1.2 - 1.4|
|Strength & speed exercisers||1.2 - 2.0|
|Phillips & Van Loon, 2011|
What does this mean for my diet?
Your protein requirements are largely dependent on your body mass, activity levels and the nature of your exercise routine. If you’re participating in regular training, particularly heavy resistance or endurance exercise, you should aim to approximately double the Recommended Dietary Intake (RDI) for protein and consume ~1.5 g/kg/day with an upper-limit of 2 g/kg/day. Daily ingestion rates which dramatically exceed this upper limit are unlikely to provide additional benefits and may have a negative impact on health. Ideally you should look to meet your protein requirements by consuming a balanced diet containing low-fat, protein-rich food sources such as red meats, poultry, fish, combined with fruits, vegetables beans and pulses. When this isn’t possible, you can look to complement your diet with an appropriate supplement. Whey protein has a strong amino acid profile and a high biological value. The concentrated form offers a wider variety of nutrients and is more cost-effective.
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