By Adam Freeman
This subject has gained a lot of attention and research over the past decade. Therefore you would think this would have a straightforward simple answer, however like most things in the world of sports nutrition there is no definitive answer. I will attempt to break my answer down into three key components. Looking firstly at the quality of protein intake, then the timing of protein intake and lastly the optimal protein intake throughout the day based on individual requirements.
Protein quality
There are various animal and plant based proteins that make up our dietary requirements. Animal based proteins include; chicken, beef, fish, whey and other dairy products. Plant based proteins include beans, peas, lentils, nuts and seeds.
Protein quality can be estimated by its make up of amino acids, in particular indispensable amino acids (IAA), and its digestibility in order to be synthesised by the body. IAA are amino acids that cannot be produced the human body and so must be obtained through dietary protein.
Therefore a high quality protein will have a high availability of IAA and be easily digestible in the body.
Animal based proteins tend to have a higher protein quality than plant based proteins as animal based proteins contain all these IAA and are more easily digestible. Pinckaers et al 2021 (1) performed a meta-analysis of numerous studies and concluded that plant based protein consumption post-exercise results in a significantly lower muscle protein synthesis (MPS) response compared to animal based protein consumption. The study reasons it is due to this lack of amino acids diversity and overall lack of optimal digestive properties.
Protein timing
The timing of protein intake has been widely researched in recent years in the context of health and fitness. Some questions studies have tried to answer include:
Should protein be spaced out throughout the day?
Is it just a matter of total protein intake over the course of the day and you shouldn’t worry about timing?
Do I need to consume protein right after exercise?
Arent et al 2013 (2) conducted research on whether spacing out protein intake throughout the day post-exercise affects muscle protein synthesis (MPS). Twenty-four healthy trained males were assigned to three groups and undertook a bout of resistance exercise followed by ingestion of 80 g of whey protein throughout a 12 hour period post exercise in one of the following protocols: 8 × 10 g every 1.5 hours; 4 × 20 g every 3 hours or 2 × 40 g every 6 hours.
They concluded that repeated 20g doses of protein were significantly superior for stimulating MPS post-exercise over a 12 hour period. So ultimately just make sure to get a decent portion of protein at each meal throughout the day and have it spaced out. This keeps a positive protein balance throughout the day and allows for a steady absorption of protein leading to higher levels of MPS.
What is interesting in this study from Arent et al 2013 was that all the groups consumed the same amount of protein (80g). So this seems to indicate that timing and in particular spacing protein intake out is critical. But ultimately if you don’t meet your overall protein and calorie targets for the day then your MPS would be hugely hindered regardless of if you try to time your intake appropriately.A limitation of this study is it only shows MPS throughout a 12 hour window which is a relatively short time frame, we do not get to see if all the groups will end up with the same long-term muscle adaptations. This is why many experts simply recommend to set an overall daily target for your calories and protein and aim to hit that every day through eating regular healthy meals spaced appropriately throughout the day. I will talk more about these specific targets in the next section.
Schoenfeld et al 2013 (3) performed a meta analysis compiling research across the area of whether protein consumption immediately post-exercise affects muscular strength and hypertrophy . Contrary to popular belief they concluded that protein consumption immediately post-exercise does not have a significant effect on muscle strength or hypertrophy compared to eating >2hrs post-exercise. Having worked and grown up with sports nutrition/health and fitness as my main passion this definitely goes against the popular belief that you should consume your protein as soon as you finish training. It does give some peace of mind that at least you don’t have to rush right away to consume your protein, as long as you get it consumed at some point within the following hours post exercise. For me personally I will likely continue to have my protein immediately after training, more for convenience and the fact that I may forget it later in the day.
Optimal protein intake
Optimal protein intake will vary from person to person depending on a number of factors. For instance a 20 year old active male will have far higher protein requirements than a 50 year old sedentary male. A lot of the research I will talk about here generally will be referring to already active individuals.
In one meal it is recommended that we get between 20-40g of protein. This can be from these high quality protein sources that I have previously talked about. Previously Moore et al 2009 (4) showed that there was no difference in MPS between 20g and 40g protein intake post-exercise but more recent research has cast a doubt over this. More recently, Macnaughton et al 2016 (5) conducted a study whereby resistance-trained men participated in two trials separated by ~ 2 weeks. During one trial subjects received 20 g of whey protein immediately after performing a total body resistance training bout; during the other trial the same protocol was instituted but subjects received a 40-g whey bolus following training. Results showed that the myofibrillar fractional synthetic rate was ~ 20% higher from consumption of the 40 g compared to the 20 g condition. A key reason why these two studies showed a difference in results is due to the type of exercise participants performed. Moore had their participants perform unilateral exercises while MacNaughton had their participants perform whole body exercises. This leads me to believe that higher protein doses may be more beneficial when performing whole body resistance exercise. More research needs to be conducted in this area, but for now I will recommend a minimum of 20g protein per meal to meet your requirements for the majority of people. Doses up to 40g won’t do any harm and might provide some more benefit for those performing whole body resistance exercise.
Overall protein dose throughout the day is more widely agreed upon and seen as more important to achieve than over a single meal. Here are some guidelines:
General Population: The Recommended Dietary Allowance (RDA) for protein for the average adult is 0.8 grams per kilogram of body weight per day. For example, a person weighing 70 kg should consume about 56 grams of protein daily.
Active Individuals and Athletes: Those who are physically active or involved in regular strength training may require more protein to support muscle repair and growth. Recommendations typically range from 1.2 to 2.2 grams per kilogram of body weight per day.
Older Adults: Older adults might need higher protein intake to help prevent muscle loss associated with ageing. The recommended range is about 1.0 to 1.2 grams per kilogram of body weight per day.
Weight Loss: For individuals aiming to lose weight, higher protein intake can help preserve lean muscle mass and promote satiety. A common recommendation is about 1.2 to 1.6 grams per kilogram of body weight per day.
Muscle Gain: To support muscle hypertrophy, intake can range from 1.6 to 2.2 grams per kilogram of body weight per day.
Quick summary
The majority of research points at spacing protein intake out throughout the day while aiming to consume an overall daily protein target. Aim to eat high quality proteins and have a minimum of 20g protein per serving to optimise muscle recovery, especially post-exercise.
References
Pinckaers, P.J.M., Trommelen, J., Snijders, T. and van Loon, L.J.C. (2021). The Anabolic Response to Plant-Based Protein Ingestion
Arent, M.A., Antonio, J. and Arent, S.M. (2013). Effects of Protein Supplementation on Performance and Recovery in Resistance and Endurance Training. Frontiers in Nutrition
Schoenfeld, B.J., Aragon, A.A. and Krieger, J.W. (2013). The effect of protein timing on muscle strength and hypertrophy: a meta-analysis. Journal of the International Society of Sports Nutrition
Moore D.R., Robinson M.J., Fry J.L., Tang J.E., Glover E.I., Wilkinson S.B., Prior T., Tarnopolsky M.A., Phillips S.M. Ingested protein dose response of muscle and albumin protein synthesis after resistance exercise in young men. Am. J. Clin. Nutr
Macnaughton L.S., Wardle S.L., Witard O.C., McGlory C., Hamilton D.L., Jeromson S., Lawrence C.E., Wallis G.A., Tipton K.D. The response of muscle protein synthesis following whole-body resistance exercise is greater following 40 g than 20 g of ingested whey protein
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