How Long Does Whey Protein Take To Digest + Why It Matters

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When you start taking whey protein powder after your workout, you might hear about the “window of gains” and worry about whether you’re digesting the whey protein fast enough to optimize your results.

So, how long does it take for whey protein powder to digest?  The time it takes for whey protein powder to digest depends on the type of whey protein powder, the other foods the whey protein powder is eaten with, and whether you’re consuming whey protein powder on an empty stomach.

It’s important to understand when to consume faster-digesting proteins and when to consume slower-digesting proteins so that you’re maximizing your ability to repair muscle damage and build additional muscle mass. 

In this article, I’ll cover:

  • How quickly whey protein absorbs
  • When to consume slow and fast digesting proteins
  • If absorption rates are more important than daily protein intake
  • How much protein the body can absorb at once
  • The best protein powder for maximum absorption

Whey Protein Absorption

whey protein absorption
Absorption rate of Whey Protein Isolate, Concentrate, & Hydrolysate

Whey protein is considered a “fast-acting” protein, with an estimated average absorption rate of ~10g per hour.  There are slight differences in absorption rates depending on the exact type of whey protein (whey protein hydrolysate, whey protein isolate, and whey protein concentrate) and what you’re consuming with it.

Here are the different kinds of whey protein and their specific absorption rates:  

  • Whey protein isolate gets its name because it isolates the protein, stripping away fat and lactose. Whey protein isolate is absorbed at a rate of about 10g/hour.
  • Whey protein concentrate contains both whey protein and lactose, the naturally-occuring form of sugar in milk, along with a small amount of fat from the milk. The fat content of this type of whey protein makes it the slowest to digest at 8g/hour.

Along with the type of whey protein you’re choosing, absorption is also affected by what you eat or drink it with, and whether you take it on an empty stomach.  

For example, fat and fiber digest more slowly, so if you combine whey protein powder with liquids or foods that contain fat and/or fiber (e.g. peanut butter, which has fat, and an apple, which has fiber), then the absorption rate of the overall meal or snack will be slower than if you had whey protein powder mixed with water.

Similarly, if you are not taking whey protein powder on an empty stomach, then its absorption will be impacted by what is already in your stomach and how long that food takes to absorb.  

For example, if you just had a cheeseburger and fries, your body will take some time to digest that meal, and will slow down the absorption of the whey protein powder that you consumed afterward.

How Does Whey Protein Absorption Compare With Other Types of Protein?

All forms of whey protein powder (concentrate, isolate, and hydrolysate) digest more quickly than other types of protein, like whole foods or other protein supplements, because of the structure of whey protein, and because whey protein powder has very limited amounts of fat and fiber.

Whole food sources of protein generally also contain small amounts of other macronutrients: meat usually contains fat, which is slower-digesting, and legumes contain fiber, which is slow-digesting. This means that whole food sources of protein are generally slower to digest than whey protein.

Other protein supplements (such as plant-based protein powders) often have more carbohydrates and fat than whey protein powder, which makes these protein powders slower to digest. 

For example, hemp protein powder also has carbohydrates (~12g per 30g serving, including 10g of fiber) and fat (2g per 30g serving).

Finally, the structure of whey protein itself is faster for the body to digest than other types of protein, even if those types of protein are also low in fat and fiber. 

For example, egg white protein powder is fat-free and has zero carbs, but the protein itself takes longer for the body to break down and absorb than whey protein.

Proteins can be categorized by the following absorption rates:

  • Medium-digesting proteins (~6-7g/hour): whole eggs and egg white, pea, rice, and soy protein powders
  • Slow-digesting proteins (~4-5g/hour): Casein protein

Related Article: Whey Protein Foods: 10 Foods Rich In Whey Protein

Why Does Whey Protein Absorption Matter?

The absorption rate of whey protein matters because there are times when fast-digesting proteins are beneficial, and other times when slower-digesting proteins are more beneficial.

Protein is important for many reasons but the two most important ones for aesthetics and performance are (1) to preserve the muscle mass that you already have, and (2) to build additional muscle mass.

A slow-digesting protein is best for helping to preserve the muscle that you already have by preventing your muscles from breaking down.

Muscle breakdown is more likely to occur while you’re sleeping and when you’re going longer periods without eating; therefore, consuming slow-digesting proteins, like casein, is better than whey before bed and when you’re going more than 3 hours before eating again.

A fast-digesting protein is best for helping to build additional muscle mass by encouraging muscle protein synthesis, which is necessary for muscle growth.

The best time to consume fast-digesting proteins is after a workout because the workout provides the stimulus to your muscles to repair themselves and grow even bigger and stronger than they were before, especially in the case of resistance training.  

Although a fast-digesting protein is encouraged post-workout, you don’t have to panic about consuming it as soon as possible after your workout. It was previously thought that there was a 30-minute anabolic window where you needed to consume a protein shake or else you would lose your gains entirely. 

However, research shows that as long as you consume a source of protein within 1.5 to 2 hours of your workout, you can still increase muscle protein synthesis and encourage muscle growth.

Absorption Rate or Overall Protein Intake: Which Is Most Important?

What remains most important in terms of muscle growth and retention is the total overall protein intake for the day.  Therefore, it won’t matter if you’re taking a fast-digesting protein after your workout and a slow-digesting protein before bed if your total daily intake isn’t high enough overall.

In this study, a protein intake of at least 1.5g of protein per kilogram of body weight (or at least 0.7g of protein per pound of body weight) can lead to protein synthesis (and muscle growth).

For example, if you weigh 70kg then you may only need 105g of protein per day to meet your daily protein requirement.

Key Takeaway: The most important factor for retaining and building muscle is your total daily protein intake. If you’re not meeting your protein goals then the absorption rate of the proteins you’re eating doesn’t matter. It’s more important to be consistent with hitting your protein target before you worry about types and timing of protein intake.

How Much Protein Can The Body Absorb At Once?

You may have heard that the body can only absorb a maximum of 20-30g of protein in one meal, and that any amount beyond that is wasted; however, this isn’t accurate for everyone. 

Research suggests that protein intakes of 0.4 grams of protein per kilogram of bodyweight per meal are sufficient to maximize muscle protein synthesis (aka muscle growth). 

Therefore those who weigh between 50-75kg should have 20-30 grams per meal but those who weigh more than this may need more protein per meal.

Additionally, the amount of protein that can be absorbed is virtually unlimited, especially since mixed-food meals introduce additional macronutrients (carbs and fat) that delay absorption and allow the protein to be absorbed gradually rather than all at once.  

Eventually, all of the protein ingested will be absorbed by the body; however, consuming more protein than 0.4/kg/meal may be unnecessary since there doesn’t appear to be any additional benefits beyond this intake for muscle repair and growth.

The Best Protein Powder For Maximum Absorption

The best protein powder for maximum absorption is Optimum Nutrition’s Platinum Hydrowhey because it’s made with the fastest digesting form of whey protein (whey hydrolysate). This fast-absorbing whey is perfect post-workout to deliver protein to your muscles for muscle repair and growth.

Frequently Asked Questions

Is Whey Protein The Fastest Absorbing Protein?

Yes, whey protein is the fastest absorbing protein; specifically hydrolyzed whey that digests at a rate of 15g/hour. Whey isolate and concentrate are also fast absorbing at rates of 10g/hour and 5g/hour respectively.

How Long Does It Take To Digest A Scoop of Protein Powder?

Whey protein is absorbed at a rate of approximately 10g per hour, so a 25g scoop of protein power would take about two and a half hours to absorb.

Is Whey Protein Easy To Digest?

Yes, whey protein is easy to digest because it absorbs the fastest of all other proteins. The exception to this is for those who are lactose intolerant, because these individuals will have a hard time digesting whey protein.

What To Read Next:


Schoenfeld, B. J., & Aragon, A. A. (2018). How much protein can the body use in a single meal for muscle-building? Implications for daily protein distribution. Journal of the International Society of Sports Nutrition, 15, 10.

Manninen A. H. (2004). Protein hydrolysates in sports and exercise: a brief review. Journal of sports science & medicine, 3(2), 60–63.

Alan Albert Aragon & Brad Jon Schoenfeld (2013) Nutrient timing revisited: is there a post-exercise anabolic window?, Journal of the International Society of Sports Nutrition, 10:1, DOI: 10.1186/1550-2783-10-5

Dangin, M., Boirie, Y., Garcia-Rodenas, C., Gachon, P., Fauquant, J., Callier, P., Ballèvre, O., & Beaufrère, B. (2001). The digestion rate of protein is an independent regulating factor of postprandial protein retention. American Journal of Physiology-Endocrinology and Metabolism, 280(2), E340-E348.

Arnal MA, Mosoni L, Boirie Y, Houlier ML, Morin L, Verdier E, Ritz P, Antoine JM, Prugnaud J, Beaufrère B, Mirand PP. Protein pulse feeding improves protein retention in elderly women. Am J Clin Nutr. 1999 Jun;69(6):1202-8. doi: 10.1093/ajcn/69.6.1202. PMID: 10357740.

Brad Jon Schoenfeld & Alan Albert Aragon (2018) How much protein can the body use in a single meal for muscle-building? Implications for daily protein distribution, Journal of the International Society of Sports Nutrition, 15:1, DOI: 10.1186/s12970-018-0215-1

About The Author

Lauren Graham

Lauren Graham is a Precision Nutrition Level 1 certified nutrition coach. She focuses on helping busy professionals balance healthy eating and purposeful movement.  Lauren has a background in competitive swimming and is currently competing as a CrossFit athlete.  She has a passion for training, teaching, and writing. 

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