We’ve all been told that protein intake after exercise is important, but just how much is enough?   As it turns out, a definitive study was published recently in the American Journal of Clinical Nutrition with the answer to that exact question.

What’s even better is that I managed to snag Dan Moore, the lead author of the study and also an old school mate, to chat with us about some of the findings.

For those who need to check out the study for themselves, here’s the reference:

Moore DR, Robinson MJ, Fry JL, Tang JE, Glover EI, Wilkinson SB, Prior T, Tarnopolsky MA, Phillips SM.  Ingested protein dose response of muscle and albumin protein synthesis after resistance exercise in young men.  Am J Clin Nutr. 2009 Jan;89(1):161-8. 

In the meantime, let’s get down to the interview.

Hey Dan!  Long time no chat.  Obviously this new paper has shed some light on the amount of protein we really require after exercise.  Can you tell us a little bit about the study?

Sure Mark.  Thanks for taking an interest in our recent study. The reason for conducting the study was that most people know that lifting weights builds muscle and that eating some protein after exercise helps this process along; however, no study had ever really looked at how much protein we need to maximize muscle protein synthesis (which is essentially a marker of how much new protein is made) during recovery from exercise.

Therefore, we designed the study so that normal resistance trained young men performed five separate sessions of intense of lower body resistance exercise followed immediately by the ingestion of a drink containing 0, 5, 10, 20, or 40g of high quality egg protein to help stimulate muscle protein synthesis. However, because there is a limit to how quickly our bodies can make new protein, we also measured how much of the protein in the drink was converted to fuel and used as a source of energy (which is the main fate of excess dietary protein).
 

What we found was that as little as 5 g of dietary protein increased the rate of muscle protein synthesis showing that even small amounts of protein can help your muscle rebuild after exercise. However, 10 g of protein was slightly better than 5 g at making new muscle proteins. After eating 20 g of protein the muscle was making new proteins at a rate that was twice as great as when no protein was eaten, clearly showing that eating protein after exercise helps make new muscle proteins. However, we were intrigued to find out that even if the protein that was eaten after exercise was doubled from 20 to 40 g (which is the amount of protein commonly found in a single serving of most weight gain protein shakes) there was no additional increase in muscle protein synthesis showing that there is a limit as to how much protein your body can use to build new muscle.

In fact, we also saw that leucine oxidation (which is a marker of how much protein your body is using as energy) was markedly increased after ingestion of 20 and especially 40 g of protein. This suggests that the amount of protein in the recovery drink had saturated the body’s ability to make new protein and that it was now being converted to a source of fuel for the muscle and other organs of the body, which then makes the amino acids from the protein drinks unavailable for muscle rebuilding. Therefore, based on the findings from this study we suggested that the amount of dietary protein that maximizes muscle rebuilding yet minimizes the use of amino acids for fuel (what we defined as the “optimal” amount) is about 15-20g of high quality protein.

So basically what you’re saying is that we don’t need to consume any more than 15-20 grams of high quality protein to maximize protein synthesis after exercise?  That’s great info!  You could basically get that in a 500ml serving of milk!
 

What do you think about the addition of other macronutrients like carbohydrates to the 20 grams of protein?  Obviously you’re aware of the studies that suggest that carbs and protein together are better than protein alone post-exercise.  Would you be able to speculate whether this might work better or do you think that synthetic response might be totally maxed out with the 20 grams of protein?
 

Most studies that have included carbohydrates in the post-exercise nutrition have actually failed to detect an additional stimulation of protein synthesis relative to protein ingestion alone. These findings are consistent with the fact that the stimulation of protein synthesis is related almost entirely to the presence of amino acids, especially the essential amino acids (which are found in fairly large amounts in most high quality proteins).

However, there are some studies that suggest that carbohydrates may be slightly better than protein or amino acids at inhibiting muscle protein breakdown, which would function to increase the net protein balance of the muscle (protein synthesis minus protein breakdown) and could therefore translate into a slightly greater amount of total muscle proteins made after exercise.
 

What is clear about the role of carbohydrates in post-exercise nutrition is that they help replenish muscle glycogen stores, which is important for those individuals who have relatively long or intense training sessions or who train more than once per day. Therefore, from a practical standpoint it would be important for individuals to consume adequate carbohydrates to at least replenish the energy used during the training session.
 

Now this study was conducted when people were in a weight maintenance phase.  Some studies suggest that if people are in negative calorie balance they might require a slightly greater amount of protein to maintain muscle mass.  Do you think this would have any significant influence on the amount of protein required after exercise as well?
 

This is a good question. There is some evidence to suggest that increasing the amount of protein in the diet helps maintain muscle mass during a situation of negative energy balance when individuals are restricting calorie intake without exercise. However, we know that resistance exercise is inherently anabolic and improves the muscle’s ability to reutilize the amino acids that come from the breakdown of muscle proteins. Also, compared to individuals who don’t exercise, resistance exercise increases the muscle’s ability to use small amounts of amino acids from the diet to build muscle tissue. Collectively, this ultimately translates into a more efficient use of dietary protein with resistance exercise and would function to help maintain lean body mass during periods of reduced energy.
 

This situation may be altered slightly though if people are performing aerobic exercise during the period of negative energy as this form of exercise is not as anabolic as resistance exercise. There is some evidence showing that when individuals are in calorie deficit and performing endurance exercise that increasing the amount of protein in the diet helps reduce the loss of lean body mass.
 

Further work needs clearly needs to be done in this area, but from a practical standpoint people who are in negative energy balance and performing primarily aerobic exercise may need to eat an additional 5-10g of protein after exercise. However, if resistance exercise is included in the period of negative calorie balance then there is probably no need to consume large amounts of protein after exercise.
 

One quote from the study is going to piss off a lot of people and drive a lot of keyboard nutrition gurus absolutely nuts.  Frankly, I think it’s great.

“Our findings have implications for protein recommendations for resistance trained athletes in terms of the quantity of dietary protein that might maximize muscle growth. If we assume that a 20g protein dose maximally stimulates muscle protein synthesis after exercise and we know that resistance exercise enhances the synthesis of muscle protein for at least 24h, one could ask how many times in a day could someone consume such a dose to stimulate muscle anabolism that would ultimately translate into muscle growth?

Because muscle protein synthesis becomes refractory to persistent aminoacidemia [i.e., even if you infuse  protein into the muscle the synthetic response will drop off] and excess amino acids are lost to oxidation, we speculate that no more than 5–6 times daily could one ingest this amount (’20 g) of protein and expect muscle protein synthesis to be maximally stimulated. Protein consumption in excess of this rate or dose would ultimately lead to oxidative loss. In addition, given that the capacity to oxidize amino acids adapts to the diet and can actas a key regulator of protein stores, chronic protein consumption in excess of this rate or dose could actually lead to dampening of the protein synthetic response to suboptimal (ie,20 g) protein doses [i.e., getting less of a response from the same amount of protein].”

So you’re basically saying that somewhere from 100 - 120 grams of quality protein per day would be enough to maximize the protein synthetic response in a resistance trained male?
 

Yes. In the case of our ~85kg resistance trained males consuming 20g of protein 5-6 times per day (i.e. every 2-3h), this would translate into 100-120 g of protein over the course of a day or the equivalent of 1.2-1.4 g of protein per kg body mass per day. This level of dietary protein intake has been shown be sufficient to increase muscle strength and mass (which likely resulted from a maximized protein synthetic response) in young men. In addition, this level of protein intake and pattern of feeding would maximize the amount of dietary amino acids that would be used as substrates to build muscle protein rather than as a source of fuel (i.e. oxidized), which would increase the dietary efficiency of this relatively expensive macronutrient.

There is also considerable evidence showing that overall energy intake is more important than total protein intake for changes in lean body mass and strength. Therefore if the goal of training is to increase muscle mass, it is more important to ensure calorie intake is positive rather than to increase dietary protein intake.
 

And finally, based on your research experience do you have any parting recommendations with regards to post-workout supplementation to maximize muscle growth for the average lifter?
 

Consume 20g of protein and adequate energy immediately after exercise and roughly every 3h after that to maximize muscle protein synthesis and keep it elevated throughout the day. As a guideline, follow recommendations from the Canada Food Guide and eat a balanced diet containing a variety of different foods to ensure adequate vitamin and nutrient intake throughout the day. And above all, make sure you’re having fun!

Thanks Dan!  It’s been great talking with you.

No problem.

For those reading, thoughts, questions, and comments are welcomed below.