Extensive research on milk proteins (whey and casein) has been conducted as it relates to their roles in enhancing adaptations from exercise. This research has shown that milk proteins, ingested following exercise and throughout the day, can speed recovery, promote a positive nitrogen balance, increase glycogen replenishment, and improve hydration status— ultimately leading to increases in skeletal muscle hypertrophy and neuromuscular strength.
When compared to other protein sources, milk proteins have the highest PDCAAS (Protein Digestibility Corrected Amino Acid Score) and contain the greatest density of leucine (whey 11%; casein 9.3%), the primary branched chain amino acid responsible for stimulating muscle protein synthesis. While both whey and casein are high in quality, they do differ extensively in the rate they digest, which offers a unique benefit to individuals when they are combined together.
WHEY PROTEIN ISOLATES…The Fuel that Ignites Muscle Protein Synthesis
Whey protein isolates digest and absorb rapidly and are, gram for gram, the purest form of protein available (90–98% pure protein). This level of purity is achieved through a cold cross-flow micro- and ultra-filtration process that removes the larger, less-absorbable protein molecules while also filtering out the fat, lactose, and ash that can be present in whey concentrates and substandard protein powders. Furthermore, this process does not denature the valuable proteins and peptides in whey, so the protein itself is of a higher quality.
Studies suggest the ingestion of fast-acting protein sources, such as whey isolates, can increase amino acid levels in systemic circulation and stimulate robust increases in protein synthesis, arguably the most important physiological factor in existence when it comes to muscle growth, strength, and recovery. What’s more, since whey protein isolates generally are low in carbs, lactose free, fat free, cholesterol free, and gluten free, it makes them the perfect choice for low-carb dieters, lactose intolerant individuals, or athletes who want to get ripped while packing on muscle.
MICELLAR CASEIN…The Fuel that Sustains Muscle Protein Synthesis
While whey isolates digest and absorb quickly, micellar casein digests and absorbs more slowly. Because it is digested slowly and leads to a relatively sustained increase in amino acids, micellar casein seems to inhibit protein breakdown to a greater extent than whey protein isolates and prolongs muscle protein synthesis (MPS).
It should also be noted that not all casein is equivalent. Micellar casein, as opposed to caseinate, is isolated from milk by filtration rather than by use of acid or heat. This filtration method preserves the structural integrity of the protein. When heat or acid is used to separate casein out of milk, the micelle’s structures are altered, resulting in a loss of biological activity and digestibility. It’s not surprising then that undamaged milk proteins, such as micellar casein, provide more than just a source of amino acids. It also provides many biologically active proteins that have direct immune and physiological benefits.
WHEY ISOLATES + MICELLAR CASEIN = A powerful one-two punch for igniting and prolonging muscle protein synthesis
From the above information, it is not hard to see that when whey isolate and micellar casein are combined gym-goers, athletes, and fitness enthusiasts alike can reap the benefits of both proteins. On the one hand, whey isolate ingestion leads to a rapid spike in amino acids levels, which increases muscle protein synthesis more than micellar casein. On the other hand, micellar casein tends to have a more anticatabolic effect than whey isolates and prolongs muscle protein synthesis to a greater extent. The combination of the two means greater increases in lean muscle mass and shorter recovery times compared to when they are ingested separately.
In fact, a 2006 study conducted by Kerksick et al. examined the influence of a fast protein source (whey) compared to a blend of fast and slow proteins (whey and casein), ingested post-exercise over a 10-week period of resistance training. Subjects who ingested the blend of fast and slow protein showed significantly greater increases in muscle mass (+1.8 kg) than those who ingested only the fast protein.
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