After a heavy bout of exercise your muscles are left with micro tears that need to be healed. The body responds to the stress by building more muscle to avoid the micro tears from occurring again. This is how muscle is built. But without the proper fuel from your diet, your body will struggle to pack on the muscle. This article will run you through exactly what is needed from your diet to build lean muscle tissue and what the best sources are.
Amino acids are the building blocks for lean muscle. Leucine is an essential amino acid which the body cannot produce naturally, so this means that it needs to be obtained from the diet. Much research has gone into this amino acid and it is well established that leucine is directly involved in muscle protein synthesis (1,2), the body's natural muscle building process. It does this through the activation of mTOR - a key signalling protein found in the myocytes that is linked to the synthesis of muscle proteins (7).
Muscle protein synthesis has been found to be higher after ingestion of leucine alone compared to after a heavy bout of resistance exercise (3). This chart below shows the potency of leucine.
The chart compares the independent and combined effects of resistance exercise and leucine-enriched essential amino acid and carbohydrate (EAA+CHO) ingestion on muscle protein synthesis (MPS). You can see that exercise alone has the smallest increase in MPS at around 40%. The ingestion of leucine with carbohydrates alone led to an increase in MPS of 100%. Exercise coupled with the ingestion of leucine and carbs resulted in an increase in MPS of about 145%. This demonstrates the powerful effects leucine has on building muscle, even when consumed without the presence of exercise.
So what foods contain leucine and how much do you need to consume a day? The research so far is limited on the exact amount of leucine to consume, but one study looked at optimal intakes and they concluded that 0.14g per kg of bodyweight is a good starting point (5). So for a 70kg man, he would look to consume around 10g of leucine a day to optimise muscle protein synthesis.
In terms of the best sources of leucine, I have compiled this chart below taken from the nutrition data website (6). Unsurprisingly, foods that are high in protein are generally high in leucine. With animal proteins dominating the list. Leucine content is based on 200kcal servings.
Optimise your muscle building potential outside of the gym and make sure to consume foods that are high in leucine.
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