Protein Metabolism

If there is one macro we would say is the most important for anyone looking to improve their strength, body composition, and health, it’s protein! Protein is different from carbs and fats in that it’s primary role is specific to long term adaptation and function resulting from a training program. It is the most important for building and maintaining muscle, and a whole host of other metabolic functions. The purpose of protein digestion is to liberate amino acids to be used for formation of muscle, enzymes, and hormones. Each day, we are constantly degrading and replacing some of the protein within our body. The term “protein turnover” is often used to describe this process. The process of protein turnover accounts for a significant portion of your basal metabolic rate which is why people with more muscle mass have higher metabolic rates.

Net Protein Balance and Muscle Protein Synthesis

Net protein balance is the difference between muscle protein synthesis and muscle protein breakdown. For muscle hypertrophy to occur, net muscle protein balance must be positive. In order to be in a positive net protein balance, protein synthesis rates must be greater than breakdown rates. How do we stimulate muscle protein synthesis? Through resistance training and ingesting protein! Some examples would include protein shakes, steak, chicken, beef and yogurt. Both resistance training and protein ingestion have shown to separately increase muscle protein synthesis, however a positive net protein balance is greatest when both of these important factors are combined.

How Much Protein Do You Need?

The RDA recommendation for protein is 0.8g/kg of body weight/day. So for a 130lb (59kg) female, this would equate to 47g of protein per day. However, this recommendation is to not become protein deficient and does not consider the need to repair exercise induced muscle tissue damage, or even remotely cover muscle building. For individuals who resistance train regularly, it is recommended that they ingest 1.5-2g/kg of body weight/day. The 130 lb female should then consume 89-120g of protein per day.

How much protein is too much?

Studies looking at ingestion of 3.3 and 4.4g/kg/day showed that there was no additional increase in lean body mass compared to 1.5-2.5g/kg/day. Therefore, very high amounts of protein may not be any more effective than moderate amounts of protein. Extra protein that does not go toward muscle protein synthesis will often get metabolized and excreted.

Protein Quality Matters

Protein quality affects protein bioavailability. Whey has been shown to be the best source of protein in terms of bioavailability, followed by egg protein, beef, casein, soy, and wheat protein respectively. Why? Because animal proteins have all of the essential amino acids whereas plant proteins do not. In order for wheat protein to match the effect on muscle protein synthesis that whey protein has, one would need to consume roughly twice as much wheat protein.

Protein Timing and Amount Per Meal

Research has shown that ingesting 20-40g of protein every 3-4 hours is optimal for stimulating muscle protein synthesis. However, the key player in time and serving comes down to leucine. Leucine is an amino acid that plays an important role in stimulating muscle protein synthesis. Research has shown that 20-45mg/kg body mass/meal of leucine is required for muscle protein synthesis to be maximized. Protein sources like beef, poultry, casein, egg, and fish are 8% leucine and whey is 12% leucine. Casein, egg, and fish are 8% leucine and whey is 12% leucine. Having higher amounts of protein per meal can help suppress muscle protein breakdown, which is also a key component when timing out protein.