Ask the Experts - Fitness

Answers from Andrew Hamilton

Q. After eating a protein containing meal, how long does it take for that protein to become available for muscle intake? My understanding is that the muscles have maximum intake capacity while they are stressed with exercise.

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One of the most important factors that determines how quickly the protein you've eaten becomes available to the muscles (in the form of amino acids) is the type of protein you eat. Take for example the most commonly used proteins in sports drinks - whey, casein, egg and soy. Of these, whey is the most rapidly digesting, taking only about two hours to release its amino acids.

Soy and egg release their amino acids at a gentler rate – around 5 hours - while casein (found in milk) is a slow-releasing protein, taking up to seven hours to release its amino acids. However, all these figures are approximate, as there is a large degree of individual variability in digestion rates.

The research does indeed indicate that muscles are responsive to absorbing amino acids immediately after training, so the goal should be to consume a quick-digesting protein like whey after exercise. However, slower digesting proteins like milk and egg can be useful to sustain blood levels of amino acids for longer periods between meals, which explains why they are sometimes used in 'night-time recovery drinks'.

It’s also important to understand that post-exercise carbohydrates are also important to maximise the uptake of amino acids into muscles. This is because eating carbohydrates helps to stimulate the release of a hormone called insulin, which helps drive amino acids into muscles cells. It’s important therefore to eat both protein and carbohydrate rich foods after training.

Finally, it’s worth adding that new research seems to indicate that pure ‘free form’ amino acids taken immediately after (or even before training) can significantly increase the uptake of amino acids by the muscles. Because free form amino acids are the fundamental building blocks of protein in a free state, there’s no digestion needed to release them and they can therefore cross from the gut into the bloodstream within minutes rather than hours.

This means they’re almost instantly available to the muscles, even during exercise (if taken beforehand). The downside of this strategy is cost; pure free form amino acid capsules are dear. However, you may want to consider this option if you’re serious about building or maintaining muscle mass.