Research Review:
How Type and Timing of Protein Intake Effects Strength-Training Individuals
By: Morgan Davis, RD, LDN
Various scientific studies have undertaken the task of pinpointing the exact amount, type and timing of protein supplementation needed to maximize physical strength and muscle hypertrophy (increase in muscle cells leading to muscle growth). In a recent meta-analysis, Stark et al reviewed multiple areas of research in order to determine the best advice for individuals engaged in a strength-training regimen.
How much protein do I need?
One of the first questions regarding protein intake with the purpose of gaining muscle mass- exactly how much protein is needed? Different studies have produced different results with a general range of 1.3-1.8g protein/kg body weight. The recommended dietary allowance for someone wishing to maintain weight/not gain muscle mass is 0.8-1.0g/kg; therefore, if the goal is increased mass and strength, an increase in protein intake is required. Stark et al have also determined that increase in muscle and total mass cannot occur without also having an increase in caloric intake.
Stuart Phillips, PhD went on to determine the amount of protein needed in single doses (or the amount of protein required at each meal). His recommendations for optimal protein intake are 0.25-0.3g protein/kg body weight per meal consuming 4 equally spaced meals daily, as well as 0.6 g protein/kg body weight at a 5th pre-sleep meal. For a 180lb (81.2kg) man, this equates to 24g protein at four equally spaced meals during the day with a fifth pre-sleep meal providing 48g protein. For a 140lb (63.6kg) woman, this equates to 19g protein at four equally spaced meals and a fifth pre-sleep meal providing 38g protein. Per the research of Dr. Phillips, this type of protein dosing provides the maximal amount of protein synthesis leading to desired muscle hypertrophy.
What else do I need besides protein?
With all the protein supplements currently on the market, one has a wealth of options between those providing creatine, essential amino acids (EAA’s), branched chain amino acids (BCAAs) and a number of other complexes and proprietary blends. When it comes to amino acids, Leucine plays a significant role in protein synthesis by acting as a regulator in multiple parts of the metabolic pathway. Multiple studies have concurred that when leucine is consumed with protein and carbohydrate post-workout, there are greater levels of protein synthesis. When choosing a supplement containing leucine, the recommendation is approximately 3-4g leucine per serving to promote max protein synthesis. More research is needed before making concrete recommendations regarding intake of creatine-containing supplements.
Which type of protein is best?
Most studies are in agreement when it comes to advice for the best source of protein for muscle development. For post-workout regimens, the focus is on dairy vs. soy. Stark et al have described the system for which protein is evaluated.
Biological value (BV) is the degree to which our body can use protein, or how efficiently the protein we eat leads to protein synthesis in body tissues. The ideal score is 100. For example, an egg is the golden standard of whole food proteins, with a BV of 100. Although an ounce of beef provides roughly the same amount of protein as 1 egg, the BV is 80, meaning our body will use the protein from beef less efficiently.
Protein digestibility corrected amino acid score (PDCAAS) is another way of scoring protein. PDCAAS ranks proteins by their essential amino acid (EAA) content. Proteins that have a complete profile of EAAs will receive a PDCAAS score of 1.0. Most animal sources of protein have a PDCAAS score of 1.0. Soy is the one plant source of protein with a complete EAA profile; other plant sources of protein are not complete in EAAs. For example, most beans have a PCDAAS score around 0.6.
Stark et al compared the BV and PDCAAS in the protein sources typically used in muscle hypertrophy studies. As the results in the table below indicate, all the protein sources studies provide a complete profile of essential amino acids. However, protein in milk is more efficiently used by the body than protein in soy; isolated whey protein is superior to other sources of protein- the high BV leads to faster protein synthesis.
|
Protein Source |
BV |
PDCAAS |
| Cow’s Milk | 91 | 1.0 |
| Casein (a milk protein) | 77 | 1.0 |
| Whey (a milk protein) | 104 | 1.0 |
| Soy | 74 | 1.0 |
When should protein be consumed?
Two different studies by Cribb et al and Hoffman et al compared the results of taking protein supplements pre- and post-workout vs. taking a protein supplement in the morning and at night. Although study designs differed slightly, both found that increases in strength, increases in lean body mass and decreases in body fat percentage were greater in those who consumed supplements pre- and post-workouts as opposed to in the morning and evening. Stark et all have determined that when protein has been consumed, the body experiences increased anabolism (state of growth) for about 3 hours after the meal. There is peak anabolism at about 45-90 minutes after a meal- this provides guidance for how long before working out a protein-containing supplement should be consumed.
What if my goal is to maintain muscle mass while decreasing weight and fat mass?
The I.D.E.A.L (improving diet, exercise and lifestyle) for women study looked at the effects of protein consumption during periods of weight loss. Daily intakes of 1.3-1.8g protein per kg body weight are needed to optimally maintain lean body mass during weight and fat mass loss. Women who consume increased protein as part of a reduced-calorie diet are better able to maintain their lower weight over time and have greater decreases in fat mass.
What is the bottom line?
A supplement containing the amino acid, leucine (optimal dose 3-4g per serving), can help maximize protein synthesis. Milk proteins have been indicated as superior to soy proteins for muscle development. Interestingly though, milk does not have a very high content of leucine; one belief is that there are other components in milk that lead to optimal muscle hypertrophy. Equally spaced doses of protein throughout the day, including pre- and post-workout can lead to optimal increases in strength, physical performance, recovery from a training session, and muscle hypertrophy. However, all these effects of protein supplementation are completely negated if there is inadequate training- for increases in strength and muscle mass, one should engage in at least three to five strength training sessions weekly, with both upper and lower body exercises, for a period of at least ten to twelve weeks.
Sources
Stark M, Lukaszu, J, Prawitz A, Salacinski A. Protein timing and its effects on muscular hypertrophy and strength training in individuals engaged in weight training. jISSN 2012, 9:54.
Josse A, Atkinson S, Tarnopolsky M, Phillips A. Increased Consumption of Dairy Foods and Protein During Diet- and Exercise-Induced Weight Loss Promotes Fat Mass Loss and Lean Mass Gain in Overweight and Obese Premenopausal Women. J. Nutr. Doi: 10.3945/jn.111.121028
Phillips S. The Importance of Dietary Protein in Resistance Exercise-Induced Adaption: All Proteins are not Created Equal. Exercise Metabolism Research Group, McMaster Univ. Webinar Oct. 18 2012.
