All You Need to Know About Protein Intake!

Is protein really that important? What is it? How much protein should I take? When? How?

What is protein? Why is it important?

Proteins are large molecules and are made from many chains of ‘building blocks’ called amino acids. Proteins can be found in many parts of the body – for example, in the muscle, bone and skin. They play an important role in making sure that all processes in the cells of our body are regulated. One of these processes include the optimisation of the function of our muscles.

When we do an intense exercise or resistance training, muscle proteins start to breakdown which therefore, leads to the wearing and tearing of the muscles. The only way that muscles can regenerate again is by the synthesis of muscle protein. When muscle protein synthesis (MPS) and muscle protein breakdown are occurring at the same rate, we describe this as having protein balance (i.e. no loss of protein) – where no muscle wasting or growth is occurring [1].

Protein balance = muscle protein synthesis ⇌ muscle protein breakdown

To actually stimulate muscle growth from training, our muscle needs to have a positive protein balance. This means that the (MPS) needs to exceed muscle protein breakdown [1-2]. The extent to which our muscles adapt to training depends on two factors: 1) how long our muscles have been in positive protein balance and; 2) how large this positive balance is [2]. Both training AND nutrition play a big role in determining the rate of MPS and muscle protein breakdown [1-2]. Training alone can stimulate MPS but nutrition is needed to enhance net protein balance [2].

Positive protein balance = muscle protein synthesis ˃ muscle protein breakdown = muscle growth

How much do you need?

The recommended dietary protein for trained individuals ranges from 1.2-2.0 g/kg body weight (BW)/day [3-4]. When doing endurance training (i.e. long distance running), 1.2-1.5 g/kg BW/day is recommend; for those looking to build muscle mass and to maintain muscle mass, your protein intake should be between 1.8-2.0 g/kg BW/day [3-4]. The higher the intensity of an exercise, the higher the protein intake requirement.

According to multiple studies, it seems like the most ‘optimal’ amount of protein to be taken after an exercise session that would stimulate MPS would be around 20g (~0.25 g/kg).

** Do note: taking more than this amount has no beneficial effects on MPS. In fact, some studies have shown that taken more than 0.25 g/kg/day of protein favours the build-up of fat [5].

When should I take it?

There is no definitive time in which one should consume protein; however, it has been postulated by multiple studies that protein ingestion immediately after exercise would maximise MPS [3, 6]. Although protein consumed even up to 24h after an exercise session has also shown to improve MPS [3]. To date, there is no solid evidence that supports the ingestion of protein before and during an exercise.

Where can I get high-quality protein from?

Proteins are made up of 20 amino acids, 11 of which are non-essential amino acids (non-EAA) and 9 are essential amino acids (EAA). EAA cannot be digested by our body therefore, we can only obtain them from dietary sources [3].

In order to maximise MPS, one should be consuming high-quality protein. This means that the protein source should have a high amount of EAA. Animal-source proteins such as beef, eggs and diary (and its constituent proteins such as, whey and casein), are considered to have high EAA content [3]. In contrast, plant-based proteins such as rice and legumes, are of lower quality and generally have a lower protein content.

Whey or Casein protein?

If you decide that you are going to get protein as a supplement to your diet, you may realise that web shops are promoting both whey and casein protein. To make things more complicated, the way they promote both types of protein gives the impression that they are equally good. Well, let me be the first to say that they are NOT.

Obtained from Pennings et al., 2011[7]

Casein is a slow release protein which means that it is digested really slowly; whereas whey is a fast release protein and is digested much rapidly. As you can see from the graph above, protein that is digested much rapidly leads to a higher MPS rate (FSR = fractional synthesis rate). Moreover, there is evidence that consuming casein protein right after exercise does not lead to any benefits.

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References

[1] Tipton K, Wolfe R. Exercise, Protein Metabolism, and Muscle Growth. International Journal of Sport Nutrition and Exercise Metabolism. 2001;11(1):109-132.

[2] Tipton K. Protein for adaptations to exercise training. European Journal of Sport Science. 2008;8(2):107-118.

[3] Burke L, Deakin V. Clinical sports nutrition. 5th ed. Sydney: McGraw-Hill; 2015.

[4] Wolfe R. Protein supplements and exercise. The American Journal of Clinical Nutrition. 2000;72(2):551S-557S.

[5] Westerterp-Plantenga M. Protein intake and energy balance. Regulatory Peptides. 2008;149(1-3):67-69.

[6] Phillips S, Van Loon L. Dietary protein for athletes: From requirements to optimum adaptation. Journal of Sports Sciences. 2011;29(sup1):S29-S38.

[7] Pennings B, Boirie Y, Senden J, Gijsen A, Kuipers H, van Loon L. Whey protein stimulates postprandial muscle protein accretion more effectively than do casein and casein hydrolysate in older men. The American Journal of Clinical Nutrition. 2011;93(5):997-1005.