Protein nutrition: is whey alone enough for recovery?

Muscle tissue synthesis was much lower when the cyclists in this study drank the no-protein/carbohydrate-only drink for recovery. The low-protein, high-leucine drink meanwhile produced almost as much muscle synthesis as the high-protein, drink containing triple the protein! NB: Myofibrillar FSR = amount of muscle tissue synthesis measured in % per hour.

The muscle connection

As we stated above, studies show that whey is an excellent protein for promoting muscle tissue growth and repair, with intakes of 20-25 grams delivering strong gains^(7,8). However, while the growth and repair of muscle fibers is very desirable for promoting post-exercise recovery and strength development, there’s more to muscles than just muscle fibres.

Muscle connective tissue protein (the tough, non-contractile tissue forming muscle sheaths, tendons and myofascial tissue) is also an essential part of the muscle system. This network of connective tissue is made mostly from a protein called collagen, and is essential for transmitting the force generated in muscle fibers to the skeletal system. This coupling of muscle tissue to the skeletal system is needed to produce movement. Muscles without connective tissue would be rather like a car fitted with an engine but no gearbox or transmission – the car would rev but not move!

Whey is not enough

It turns out that although post-exercise whey ingestion stimulates muscle fiber growth and repair, it does NOT seem to enhance the synthesis of muscle connective tissue protein^(9,10). But if whey protein stimulates muscle fiber protein synthesis, why does it not do the same for connective tissue protein post exercise?

A clue comes from research showing that when whey (and other dairy) protein is ingested during recovery from exercise, there is a decline in the circulating levels of an amino acid glycine concentrations - despite the substantial rise in circulating essential amino acids needed for muscle fiber tissue growth⁽¹¹⁾. This suggests that the body is ‘raiding’ glycine from the bloodstream for muscle connective tissue synthesis, despite the ingestion of whey. That would make sense because connective protein and its main constituent, collagen, are rich in glycine while whey (and dairy in general) protein is relatively deficient in glycine^(12,13) – ie whey protein consumption is unable to supply enough glycine to promote optimal muscle connective tissue synthesis following exercise.

For athletes seeking optimum recovery, this could be less than ideal. One can imagine a scenario where athletes in hard training reply heavily on whey and other dairy protein consumption following exercise; the muscle fibers are getting optimum recovery and growth whereas the muscle connective tissue isn’t. Over long time periods, this could lead to a situation where the muscle connective tissue strength lags behind muscle fiber strength. This imbalance in turn could lead to an increased risk of injury as muscle connective tissue may not be properly adapted to handle the increased forces generated by the (stronger) muscle fibers.

A good option to overcome this scenario would be to consume extra glycine (and proline, which is easily converted to glycine) along with post-exercise whey ingestion. One way of doing this is to consume a post-exercise protein blend containing both whey and some collagen protein. Collagen protein is rich in both glycine and proline, and when blended with whey, could in theory provide the perfect spectrum of amino acids for optimal synthesis of BOTH muscle fiber and connective tissue, being rich in leucine and in glycine/proline. But can this approach work in practice?

New research

The good news is that a recently published study has managed to answer this very question. Published in the journal ‘Human Kinetics’, this study compared the effects of feeding pure whey protein or a whey/collagen blend in recreationally trained men following a bout of resistance exercise⁽¹⁴⁾. In particular, the goal was to see what effect the addition of three different levels of collagen to standard whey protein had on the blood amino acid levels of the men, and whether the addition of collagen enabled them to avoid a ‘glycine dip’ (indicating a relative lack of glycine availability for muscle connective tissue synthesis).

What they did

Fifteen fit, healthy and recreationally active men aged 18-35 and training between once and three times per week were recruited for the study (of which 14 went on to complete the study). Prior to the experimental training sessions and protein consumption, all the men underwent pretesting, which included baseline measures of leg strength, whole-body lean mass, fat mass, and bone mineral content, body mass index (BMI).

Five days after baseline testing, the participants completed four identical resistance workouts on four separate occasions. These were performed in a randomized order, with each workout spaced at least five days apart and always the first thing in the morning before breakfast (ie in a fasted state). This was important as the researchers wanted to find out how the levels of blood amino acids changed in response to the post-exercise drink consumed, without the interfering effects of a pre-workout meal!

The resistance workouts

Each of the four workouts consisted of the following:

·        A 5-minute warm-up on a cycle ergometer.

·        A warm-up set of 10 repetitions at 40% 1RM for the leg press followed by two sets of eight repetitions at 80% 1RM followed by a final set performed at 80% 1RM until failure.

·        A warm-up set of 10 repetitions at 40% 1RM for the leg extension followed by two sets of eight repetitions at 80% 1RM followed by a final set performed at 80% 1RM until failure.

Resting periods of two minutes were allowed between all sets and all the participants followed the exact same protocol described above. The only difference between the protocols was the kind of recovery drink consumed afterwards.

What they consumed

Immediately after completing each identical workout as described above, the participants were given one of four identically tasting protein recovery drinks but with differing compositions:

·        A 500ml beverage containing 30 grams of pure whey protein.

·        A 500ml beverage containing 25 grams of pure whey protein plus 5 grams of collagen protein.

·        A 500ml beverage containing 20 grams of pure whey protein plus 10 grams of collagen protein.

·        A 500ml beverage containing 15 grams of pure whey protein plus 15 grams of collagen protein.

During the recovery period following the leg training workout, blood samples were collected at 15, 30, 45, 60, 90, 120, 150, 180, 210, 240, 300, and 360 minutes to see how the levels of amino acids varied according the to drink consumed.

What they found

The first finding was that (as expected) after consuming 30 grams of readily digestible protein, the total blood concentrations of amino acids rose strongly, regardless of the drink formulation. When it came to levels of glycine however, consuming pure whey resulted in a drop in blood concentrations of glycine from a baseline value of 200micromol/L to around 140micromol/L, which only slowly recovered over the 6-hour recovery period. This indicated a relative deficiency of glycine availability, and therefore a negative impact on muscle connective tissue synthesis

However, in the protein drinks containing five or more grams of collagen protein (ie 25g whey/5g collagen, 20g whey/10g collagen and 15g whey/15g collagen), this drop was completely eliminated, indicating enough glycine availability (see figure 2). Of the collagen-containing drinks, the 25g whey/5g collagen blend achieved the trick of maintaining blood glycine levels while ensuring a high spike in leucine concentrations (a good thing for muscle fiber growth for all the reasons set out earlier) thanks to the still high proportion (83%) of whey protein in the drink.

Figure 2: Drink formulation and changes in blood leucine and glycine concentrations

Black bars/squares = pure whey; dark grey bars/circles = 25g whey/5g collagen; light grey bars/circles = 20g whey/10g collagen; clear bars/circles = 15g whey/15g collagen. LHS = plot of leucine concentrations (top) and glycine concentrations (bottom) over the 6-hour recovery period. RHS = the total deficit or excess of blood amino acids compared to baseline over the 6-hour recovery period. Notice how the 25g whey/5g collagen blend prevented any glycine deficit (in fact produced a slight excess) of collagen while ensuring the peak in leucine remained high.

Practical recommendations for athletes

What this research shows is that athletes who rely mainly on whey drinks (or other dairy proteins) to aid post-exercise recovery may not be consuming the optimum amount of glycine (and related amino acids proline and hydroxyproline) for maximal synthesis and regeneration of muscle connective tissue. Although no research has been carried out to date, the implication is that connective tissue growth and development will fail to keep up with muscle fiber and strength development, which could, over a period time, increase the risk of injury.

Luckily, the solution is very simple; adding five grams or so of collagen to your post-exercise whey protein recovery drink corrects this glycine shortfall and provides the muscle connective tissue with what it needs for maximal growth and adaptation. A few points are worth making however:

·        Firstly, it’s important to remember that whey is still an excellent recovery protein, containing all the amino acids needed in the right ratios for muscle fiber growth, and is particularly high in Ieucine. Therefore, you shouldn’t be tempted to displace too much of your whey protein with collagen protein. Just add five grams or so of collagen to your existing whey drink.

·        While good for connective tissue, collagen as a post-exercise protein alone is not particularly effective at promoting muscle fiber strength and mass gain. Indeed, collagen alone has been classed as a ‘low-quality’ protein due to a lower essential amino acid and leucine content⁽¹²⁾. Therefore, don’t be tempted to switch to collagen-only drinks for recovery in the belief they are superior to whey because they are not!

·        Most of the collagen powders on the market are derived from bovine (beef sources). Typically, they are in the form of collagen ‘peptides’ – ie the collagen proteins are partly broken down by into smaller chains of amino acids by a process known as hydrolysis. This has the advantage of removing any taste artefacts, and ensuring the amino acids such as glycine in the collagen can be delivered rapidly to the muscles after consumption – so this is the form you should go for.

·        Vegetarians who do not want to consume products of animal origin can instead purchase pure glycine and mix that in with their whey drink instead. Two to three grams will do the trick and as a bonus, glycine has a sweet and quite pleasant taste. However, the downside is that unlike bovine collagen hydrosylate, this option is will be more costly.

·        Whilst marine collagen is regarded highly as a supplement in pill form, it has a rather ‘fishy’ taste and odour. Moreover, its extremely high cost makes it unsuitable as a whey drink additive. And while it may be superior to bovine collagen in a medical setting - for example in wound healing⁽¹⁵⁾ – it has no additional benefits for athletes simply seeking a bit of extra glycine!

References

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