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I have posted a summary of important information along with the abstract of a very good study on protein. In this review of literature the author covers the how much protein and calories we need; why and how much leucine is needed for growth; and the proper timing for taking protein supplements. It also discusses the why carbohydrates are needed with protein and what kind is best for optimal growth.

Matthew Stark, Judith Lukaszuk, Aimee Prawitz and Amanda Salacinski. Protein timing and its effects on muscular hypertrophy and strength in individuals engaged in weight-training. Journal of the International Society of Sports Nutrition 2012, 9:54.

• Abstract
• The purpose of this review was to determine whether past research provides conclusive evidence about the effects of type and timing of ingestion of specific sources of protein by those engaged in resistance weight training. Two essential, nutrition-related, tenets need to be followed by weightlifters to maximize muscle hypertrophy: the consumption of 1.2-2.0 g protein.kg -1 of body weight, and ≥44-50 kcal.kg-1 of body weight. Researchers have tested the effects of timing of protein supplement ingestion on various physical changes in weightlifters. In general, protein supplementation pre- and post-workout increases physical performance, training session recovery, lean body mass, muscle hypertrophy, and strength. Specific gains, differ however based on protein type and amounts. Studies on timing of consumption of milk have indicated that fat-free milk post-workout was effective in promoting increases in lean body mass, strength, muscle hypertrophy and decreases in body fat. The leucine content of a protein source has an impact on protein synthesis, and affects muscle hypertrophy. Consumption of 3–4 g of leucine is needed to promote maximum protein synthesis. An ideal supplement following resistance exercise should contain whey protein that provides at least 3 g of leucine per serving. A combination of a fast-acting carbohydrate source such as maltodextrin or glucose should be consumed with the protein source, as leucine cannot modulate protein synthesis as effectively without the presence of insulin. Such a supplement post-workout would be most effective in increasing muscle protein synthesis, resulting in greater muscle hypertrophy and strength. In contrast, the consumption of essential amino acids and dextrose appears to be most effective at evoking protein synthesis prior to rather than following resistance exercise. To further enhance muscle hypertrophy and strength, a resistance weight- training program of at least 10–12 weeks with compound movements for both upper and lower body exercises should be followed.

Protein and calorie intake

The first important fact this review of literature pointed out was the fact that caloric intake is a very important factor in muscle hypertrophy. For maximal muscle hypertrophy to occur, weightlifters need to consume 1.2-2.0 grams (g). protein kilogram. (kg)-1 and > 44–50 kilocalories (kcal).kg-1 body weight daily [1-9]. So as long as you work out hard, eat enough protein and calories to support growth, you will grow.

Leucine and muscle protein synthesis

Next of important fact was that out of all the amino acids we take in through the consumption of protein, leucine has been indicated as the sole stimulator of protein synthesis [10-15]. Leucine plays a role in muscle protein synthesis mostly through stimulation of the mammalian target of rapamaycin (mTOR) signaling pathway [15,17,18]. Leucine interacts with two mTOR regulatory proteins, mTOR raptor (or raptor) and rashomolog enriched in the brain (or Rheb) [19,20]. The importance of the regulation of mTOR is that when activated, it phosphorylates the proteins eIF4E binding protein 1 (4E-BP1) and ribosomal protein S6 kinase (S6K1) complex [21,22]. When 4E-BP1 is phosphorylated, it becomes inactive, which allows the continuation of the second step initiation phase of translation by inhibiting its binding to eIF4F complex [10]. This allows additional translation to occur. When S6K1 is phosphorylated, it produces additional eIFs which increases the translation of mRNAs that encode components of the protein synthesis pathway [10,12].

Leucine alone appears to be nearly as effective in stimulating protein synthesis as when all branched chain amino acids (BCAAs) are consumed [24-26]. Leucine also seems to have both insulin-dependent and insulin-independent mechanisms for promoting protein synthesis [27,28]. Approximately 3 to 4 g of leucine per serving is needed to promote maximal protein synthesis [29,30]. So you can take leucine, amino acids, branched chain aminos or just stick to your when protein shake.

Table 2. Leucine content of protein sources for studies that used a protein ingestion timing method.

http://www.jissn.com/content/9/1/54/table/T2

Timing of Protein 

The third important recommendation is when is it best to take protein; before or after training? The effects of timing of ingestion of essential amino acids (EAAs) on physical changes following exercise also have been studied [31,32]. Tipton et al. [31] found that the ingestion of EAAs prior to resistance exercise was more beneficial than post-ingestion in promoting protein synthesis [31], but these results did not hold true with respect to whey protein ingestion [32]. Once a protein has been consumed by an individual, anabolism is increased for about three hours postprandial with a peak at about 45–90 minutes [14]. After about three hours postprandial, MPS drops back to baseline even though serum amino acid levels remain elevated [14]. These data show that there is a limited time window within which to induce protein synthesis before a refractory period begins. With this in mind, an ideal protein supplement after resistance exercise should contain whey protein, as this will rapidly digest and initiate MPS, and provide 3–4 g of leucine per serving, which is instrumental in promoting maximal MPS [29,30]. A combination of a fast-acting carbohydrate source such as maltodextrin or glucose should be consumed with the protein source, as leucine cannot modulate protein synthesis as effectively without the presence of insulin [27,28] and studies using protein sources with a carbohydrate source tended to increase LBM more than did a protein source alone. Such a supplement would be ideal for increasing muscle protein synthesis, resulting in increased muscle hypertrophy and strength. In contrast, the consumption of essential amino acids and dextrose appears to be most effective at evoking protein synthesis prior to rather than following resistance exercise [31].

So if you are using whey protein it is best to take it post workout [32]. If you would rather use branch chained amino acids of Leucine, it would be best taken befoe you work out [31,32]. Remember it takes about 20 minutes to digest and assimilate protein shakes and it is important to have the amino acids in the blood stream before the anabolism peak which takes place in 45 to 90 minutes post exercise [14]. To get maximal protein synthesis you will also need to add fast-acting carbohydrate source such as maltodextrine or glucose with the whey shake. The addition of fast-acting carbohydrates will increase insulin production. This is critically important because leucine cannot modulate protein synthesis as effectively without the presence of insulin [27,28] . If you are using amino acid mixes pre-work out it is just as important to add a fast- acting carbohydrate. However, in this case dextrose appears to be most effective at evoking protein synthesis [31].

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