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Fact: Protein Blends are Better Than Whey Alone

Fact: Protein Blends are Better Than Whey Alone

To get the best possible size and strength gains from whey protein, make sure it’s combined with slower-digesting protein sources.

Written By Jim Stoppani, PhD

Updated May 13, 2024

If you're still using a whey protein shake around workouts, then you haven't been listening to my advice over the last few years—and you're actually undermining your results. Just a few years ago we thought that whey was the absolute best protein source—and only source to take before and after workouts. And it still is the best source of protein to take. It's just not best to take it alone without other sources.

There is a growing body of research that now confirms that combining the fast-digesting whey protein with at least the slow-digesting casein protein is better for muscle growth than just going with whey protein alone. Let's break down the science...

Original Research – Blends are Better for Mass Gains and Fat Loss

One of the first studies to suggest that adding casein to whey is best for muscle growth comes from Baylor University (Waco, TX). They discovered that trained men following a 10-week weight-training program and taking a whey/casein blend after workouts gained 4 pounds of lean muscle mass while experiencing a slight decrease in body fat.¹ Another group following the same training program but taking whey without casein added to it did not gain any muscle mass over the ten weeks, and had a slight increase in body fat.

Research from the Mayo Clinic (Rochester, MN) later found that the reason adding casein to whey leads to better muscle growth may be due to the different digestion and absorption rates of these two different proteins.² Whey is digested and absorbed rapidly. This means that it delivers its amino acids to the muscles ASAP, which spikes muscle protein synthesis sky high.

This is one property of whey protein that makes it superior to other protein sources, yet not perfect. Its speed of digestion and absorption is its benefit, but also its downfall. The problem with whey being absorbed so quickly is that it gets to the muscles and spikes muscle protein synthesis, but then it is used up and protein synthesis drops sharply.

Casein protein—particularly micellar casein—is digested and absorbed at a slow and steady rate. The research from the Mayo Clinic found that adding it to whey protein allowed the amino acids from casein to continue supplying the muscles long after the amino acids from whey were gone. Amino acid retention in the muscles studied was significantly higher 4 hours later when amino acid retention from whey was barely noticeable. This essentially prolongs the anabolic response initiated by the whey protein, which leads to greater muscle growth

New Research – Blends Extend Protein Synthesis

The two latest research studies on protein blends versus whey alone come from the University of Texas Medical Branch (Galveston, TX). This lab, by the way, has been a leader in helping us better understand protein intake around workouts, muscle protein synthesis, and muscle growth.

The first study—published in 2013—had men consume 20 grams of whey or 20 grams of a whey/soy/casein combo one hour after a leg workout. The combo was 25% whey (5 grams), 25% soy (5 grams) and 50% casein (10 grams). They reported in the Journal of Nutrition that both the whey protein and the mixed protein increased muscle protein synthesis to a similar degree. However, the mixed protein maintained that higher rate of protein synthesis for hours longer than whey alone.³

A 2014 follow-up study by the UTMB researchers also provided the same amount and kind of whey, casein, and soy blend protein shake or a solely whey protein shake one hour after a leg workout. They reported in the Journal of Applied Physiology that the whey, soy, and casein blend led to a prolonged and greater net amino acid balance.

Taken with their previous study, these results basically mean that when you use a protein that contains a very fast-digesting protein (whey), a medium-digesting protein (soy or egg), and a very slow-digesting protein (casein) post-workout, more amino acids from the protein are taken up by the muscles for a longer period of time, they increase muscle protein synthesis for a longer period, and they result in more muscle protein being built which can result in greater muscle size and strength compared to if you took just whey protein alone post-workout.⁴

Jim's Take-Home Points:

Although both the UTMB studies—as well as the Baylor University study—provided the protein blends post-workout, I believe that you not only want a protein blend after workouts but also pre-workout and/or during if you do a pre/during/post shake like I do, as well as any other time of day that you may have a protein shake—such as in the morning when you wake, before bed, and between meals.

The Mayo Clinic study supports this line of thinking as they supplied a whey/casein protein blend during rest and if further enhanced amino acid uptake in the muscle fibers. Plus, this recommendation has worked very well for thousands of people who have followed my advice over the years.

What may be surprising about the UTMB studies to many people is that the blend used in the studies that proved to be superior to whey alone was only 25% whey and 50% casein. It appears that just a small amount of whey is needed to quickly get some amino acids to the muscle and spike muscle protein synthesis up to maximal levels. But then you need a bit more casein to keep amino acids going to the muscles for several hours later to keep muscle protein synthesis elevated for longer and promote greater muscle growth.

The UTMB researchers did not investigate different ratios of whey and casein. They used the same 25% whey, 50% casein, and 25% soy in both studies. This does not mean that this is the ideal blend, but it does show that whey should be adequate at well under 50%.

Although I don't have data on protein synthesis or amino acid net balance in muscle fibers, I do have a lot of data showing superior gains in muscle size and strength from the precise blend in Pro JYM — with roughly one-third each of whey protein isolate, micellar casein, and milk protein isolate (which contains both whey and casein). After all, I formulated it so that I can get the best results from my training and so that you can get the best results from yours.