How much protein can you absorb in one meal?

Getting the right nutrition to help you meet (and smash) your sports performance goals is important. One major part of that is giving your body the optimal amount of protein.

Many people have speculated how much protein your body can handle at once. Some quote 20 to 30g, but it’s not simple. The optimal amount of protein for you will vary depending on the type of protein you’re consuming and the type of training. 

Before getting to the maths, let’s first understand why protein is your best friend when exercising.

• Why do we need protein for training?
• How much protein do I need to build muscle?
• Does more protein = more muscle growth?
• Fast vs slow-digesting proteins
• Plant-based protein vs animal-based protein
• How much protein do I need after a workout?

Why do we need protein for training?

Whether you’re a long-distance runner or regularly lift weights, it’s clear that protein before or after a workout is beneficial.

The benefits of protein: 

• Optimises physical performance
• Enhances recovery
• Encourages muscle protein synthesis (muscle building) [1]

Any kind of moderate exercise, especially resistance training, causes small tears (microtears) in the muscle which the body must repair — this process is how we build muscle. When you have a protein shake or any other meal containing protein, it’s absorbed and broken down into amino acids that can be used to rebuild the muscle stronger than before. 

Even when you’re not exercising, a high-protein diet will help to preserve muscle mass and reduce the extent of age-related muscle loss [1]. And it’s not just useful for muscle building either. Protein plays a critical role in immunity, carrying important molecules, hormone regulation, and just about every other physiological process [2]!

So, protein is important — but how much do you need and is it possible to overdo it?

How much protein do I need to build muscle?

When it comes to resistance training and maximising muscle growth, how much protein you need will depend on many factors. 

Factors that affect your protein requirement include:

• Age
• Sex
• Body composition
• Intensity and duration of your workout.

However, understanding how the amount and type of protein affect muscle growth can be helpful to optimise your post-workout nutrition.

Does more protein = more muscle growth?

In very simple terms, more protein equals more muscle growth after a workout — but this only applies up to a certain point. 

When it comes to quick-digesting proteins like whey, 20g is enough to reach near-maximal muscle-building capacity following a resistance workout. And this dose can be repeated every few hours [3]. 

Anything over 20g gives only a marginal benefit. For example, even when doubling the protein content to 40g, it will only boost muscle growth by up to an additional 10% [4, 5]. The rest will be excreted from the body as waste products (urea) because the rate of absorption exceeds the body’s ability to digest and process it. Beware that a large surplus of protein may be harmful in the long term and can affect the bones, kidneys, and liver [4].

Adapted from Trommelen et al. (2019)

It’s important to note that these findings were based on young, fit males after resistance-type exercise. The protein consumed was isolated, fast-digesting protein — this means that the formulations had very high concentrations of protein that were fully digestible within a couple of hours. So, what’s the difference between fast and slow-digesting proteins?

Fast vs slow-digesting proteins

Protein comes in different forms based on how quickly it’s digested — fast and slow. 

• Fast-digesting proteins, such as whey and hydrolysed whey, cause a rapid spike in amino acid blood levels within an hour or two.
• Slow-digesting proteins such as casein or chicken breast, can take four or more hours for your body to digest and reap the benefits. 

When proteins are digested more slowly, the body can tolerate higher doses. Even if you were to have two chicken breasts for dinner (about 50g of protein), your body is likely to absorb most of the protein (unlike a 50g whey protein shake, where some of it will be wasted).

Does this mean you should always opt for slow-digesting proteins? 

Not always. Fast-digesting proteins are more effective at stimulating muscle growth in the post-workout phase. If it will be a long time before your next meal, a high-dose, slow-digesting protein may be better as it’s likely to continue to provide benefits for many hours afterwards [7].

Adapted from Trommelen et al. (2019)

If you’re unsure whether you’re better off having protein before or after your workout, check out our article on the anabolic window. 

Plant-based protein vs animal-based protein

Generally, animal-based proteins (such as whey and casein) are more effective at stimulating muscle protein synthesis than plant-based proteins [7].

If you do have plant-based proteins, one way of compensating for its reduced effect might be to consume a higher dose or to have a greater variety of protein sources. One study showed that consuming 60g of wheat protein rather than 35g showed a significant increase in muscle protein synthesis [8].

Other examples of plant-based protein include:

• Pea protein
• Soy protein
• Brown rice protein

One of the benefits of plant-based proteins is that they are associated with a longer lifespan when compared with animal-based proteins [9, 10]. 

How much protein should I eat after a workout?

• 20g of quick-digesting protein is the best to promote muscle protein synthesis. Anything over 20g will only provide a small benefit unless it’s a blend of fast and slow-digesting proteins.
• Over 40g of slow-digesting proteins may stimulate muscle protein synthesis for a longer period. A protein like casein is your best bet for overnight gains. 
• Animal-based proteins tend to be more effective at triggering muscle protein synthesis than plant-based proteins. If you do take plant-based proteins, consider increasing the dose and including multiple plant-based protein sources. 
• The effect of protein will also depend on your age, sex, and workout regime. 

If you’ve reached a plateau in your training, our Ultimate Performance Blood Test may be able to help you with markers that can detect signs of overtraining, hormone levels, and your nutritional status. 

Is it okay to eat 50g of protein at once?

You are probably better off having your 50g protein shake over two sittings if it contains a fast-digesting protein isolate. If you aim to build muscle, it will come down to an effective workout regime, a calorie surplus with an appropriate macro composition, and consistency. 

References

1. Carbone, J. and Pasiakos, S., 2019. Dietary Protein and Muscle Mass: Translating Science to Application and Health Benefit. Nutrients, 11(5), p.1136.
2. LaPelusa A, Kaushik R. Physiology, Proteins. [Updated 2021 Nov 21]. In: StatPearls [https://www.ncbi.nlm.nih.gov/books/NBK555990/]. Treasure Island (FL): StatPearls Publishing; 2022 Jan.
3. Deldicque, L., 2020. Protein Intake and Exercise-Induced Skeletal Muscle Hypertrophy: An Update. Nutrients, 12(7), p.2023.
4. Delimaris, I., 2013. Adverse Effects Associated with Protein Intake above the Recommended Dietary Allowance for Adults. ISRN Nutrition, 2013, pp.1-6.
5. Moore, D., Robinson, M., Fry, J., Tang, J., Glover, E., Wilkinson, S., Prior, T., Tarnopolsky, M. and Phillips, S., 2008. Ingested protein dose response of muscle and albumin protein synthesis after resistance exercise in young men. The American Journal of Clinical Nutrition, 89(1), pp.161-168.
6. Witard, O., Jackman, S., Breen, L., Smith, K., Selby, A. and Tipton, K., 2013. Myofibrillar muscle protein synthesis rates after a meal in response to increasing doses of whey protein at rest and after resistance exercise. The American Journal of Clinical Nutrition, 99(1), pp.86-95.
7. Trommelen, J., Betz, M. and van Loon, L., 2019. The Muscle Protein Synthetic Response to Meal Ingestion Following Resistance-Type Exercise. Sports Medicine, 49(2), pp.185-197.
8. Gorissen, S., Horstman, A., Franssen, R., Crombag, J., Langer, H., Bierau, J., Respondek, F. and van Loon, L., 2016. Ingestion of Wheat Protein Increases In Vivo Muscle Protein Synthesis Rates in Healthy Older Men in a Randomized Trial. The Journal of Nutrition, 146(9), pp.1651-1659.
9. Naghshi, S., Sadeghi, O., Willett, W. and Esmaillzadeh, A., 2020. Dietary intake of total, animal, and plant proteins and risk of all-cause, cardiovascular, and cancer mortality: systematic review and dose-response meta-analysis of prospective cohort studies. BMJ, p.m2412.
10. Song, M., Fung, T., Hu, F., Willett, W., Longo, V., Chan, A. and Giovannucci, E., 2016. Association of Animal and Plant Protein Intake With All-Cause and Cause-Specific Mortality. JAMA Internal Medicine, 176(10), p.1453.