Why Eating Protein Helps Build Muscle
Have you ever wondered why protein helps build muscle? Are all protein sources equal in building muscle?
Everyone knows that consuming protein is important. There’s a reason why amino acids are considered the building blocks of life. Taking protein supplements, whether it be in the form of a bar or in a shake, is commonly done to complement a weight training regimen.
Doing strenuous resistance training can cause damage to the working muscle, so protein ingestion post-workout is thought to enhance the ability to build muscle. And even though you can get enough protein through your diet alone, for many people protein supplements adds a convenient way for you to get enough protein.
Overview of Muscle Building:
The size of your muscle is dictated by your net protein balance, the difference in rates of muscle protein synthesis (MPS) and muscle protein breakdown (MPB). When you are at rest or fasting, rates of MPB will be greater than MPS, meaning there is a negative net protein balance. MPS is driven by two main factors: exercise and protein feeding. Protein feeding has been shown to increase MPS for around 2 hours, before it returns to base levels. So it’s important to understand that taking protein alone won’t really enhance your ability to build muscle. But resistance training has been shown to enhance MPS for up to 48 hours. So by exercising and then taking protein right after, you could optimize the increase of MPS, to help enhance muscle hypertrophy (muscle building).
Does the Source of Protein Matter?
When you’re looking for the type of protein supplement to consume, you’ll notice that there’s several different types that are often sold. Protein supplements can be from a countless number of sources, with milk-based and soy being the most common. Milk contains two types of protein: whey and casein. Vegan sources of protein such as from rice or peas is also gaining popularity, but not as many studies have been done on them.
Whey and soy proteins seem to be digested faster than casein, resulting in a larger but shorter lasting increase in MPS. Overall, it appears that whey protein can induce more MPS compared to casein or soy, but soy protein induces more MPS than casein. Casein on the other hand seems to sustain a more modest increase in MPS, over a longer period of time. This is why casein protein is often ingested prior to sleep, due to its ability to sustain MPS overnight. So yes, the source of protein you’re consuming post-exercise can affect the degree of MPS.
Why is Whey Protein Able to Stimulate a Greater Increase in MPS?
So based off many studies, it’s clear that whey protein stimulates MPS more than other sources of protein. Why is that? Well, lower quality protein sources which lack or are low in at least one essential amino acid (EAA, i.e. the amino acids our body cannot produce so we must get from our diet), cannot stimulate MPS as much as higher quality sources that have all the EAA’s (e.g meat, whey). It seems that MPS is driven solely by the essential amino acids found within protein sources, with the amino acid leucine being the most potent stimulator. It’s been shown that leucine alone or when incorporated into lower quality protein sources, can enhance MPS. Whey protein therefore seems to enhance MPS more since it has more leucine.
The idea of leucine being the driver of muscle protein synthesis is further shown in a study where 25g of whey compared to 6.25g whey + 5g leucine, resulted in a similar degree of MPS at rest and from exercise. Clearly, having sufficient levels of leucine is what’s needed to optimize MPS, even though the leucine group was consuming much less protein overall. Therefore, choosing a protein source that can be digested quickly, and has high levels of leucine is ideal to maximize post-exercise muscle protein synthesis.
Does the Amount of Protein Intake Affect MPS?
There have been many studies done to determine if the amount of protein you ingest would influence muscle protein synthesis. Overall, it seems that MPS reaches optimal levels post-exercise when you ingest around 20g of protein; so taking any less will result in sub-maximal stimulation and any more (at once) won’t increase MPS significantly. A study with males performing lower body resistance training prior to taking whey protein showed that taking 40g of whey doesn’t increase MPS more than 20g. By consuming more protein than the body needs for MPS, it results in the excess amino acids being used for purposes other than building muscle (i.e. broken down for energy or excreted in our urine).
Does the Timing of Protein Intake Affect MPS?
Resistance exercise has been shown to elevate MPS for up to 48 hours post-exercise, which helps make your muscle more responsive to protein ingestion. A study recruiting 24 males had them perform a resistance training routine before ingesting 80g of whey protein over a 12 hour span. It was shown that taking a moderate amount of protein (20g every 3 hrs) was more effective in elevating MPS than a bolus form (40g every 6 hrs) or pulse form (10g every 1.5 hrs). Of course, it’s not realistic to expect someone to consume protein exactly every 3 hours. The main takeaway from this study should be that moderate amounts of protein taken every several hours is optimal for muscle building.
Takeaway Points:
Taking protein after exercise is important to help build muscle. However, not all protein sources are equal; meaning sources that are high in leucine and are rapidly digested are more effective in stimulating MPS after exercise. It also appears that taking around 20g of protein post-exercise is sufficient to maximize MPS.
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