Several studies have shown that drinking a shake containing protein and simple carbohydrates aids the exercise-recovery process. Indeed, the effect is so powerful that a mere six grams of essential amino acids, or the amount found in just one medium egg, potently accelerates anabolic cellular mechanisms. The drink’s effects relate to increased blood flow following exercise, heightened activity of specific enzymes and increased insulin release.
A new study focused on the use of a postexercise protein drink during conditions of extreme stress.1 The stress consisted of 54 days of basic training for U.S. Marine Corps recruits on Parris Island, South Carolina. Boot camp imposes a level of stress that can lead to catabolic reactions in the body and loss of lean mass, or muscle. It’s also linked to immune suppression, poor wound healing and decreased strength.
Intense exercise itself is associated with muscular soreness, fatigue, dehydration and other physical maladies. While few would argue that the training is required for marines facing combat, it also makes sense not to send depleted leathernecks into hellholes such as Iraq.
A study compared the effects of using a postworkout protein supplement by recruits during the 54 days of basic training. Marines who drank the postworkout protein drink got much less dehydrated, had an average of 33 percent fewer medical visits, fewer problems related to bacterial or viral infections, fewer muscle or joint problems and 83 percent fewer events of heat exhaustion than those in the placebo and control groups. Those in the protein group also reported less muscle soreness on days 34 and 54.
Why drinking a postworkout protein beverage produced such improved health isn’t clear, but the authors offer a few theories. Previous research shows that intense exercise accelerates the breakdown of gastrointestinal-tract proteins that maintain the competency of the gut wall. When that’s compromised, bacteria have a greater chance of gaining entrance into the body. The increased protein intake, particularly the amino acid glutamine, may have helped replenish and protect gut-wall proteins.
Increased amino acid availability also has antistress effects. Certain amino acids, such as tryptophan and tyrosine, act as direct precursors of brain chemicals called neurotransmitters, which play a role in lessening the effects of stress in the body.
The lower incidence of dehydration defies the common belief that increased protein intake promotes dehydration. (The idea is that more water is required to metabolize protein waste products, such as urea, for excretion through the kidneys.) The authors suggest that the increased cellular-hydration effect of protein intake, along with increased synthesis of blood proteins involved in water regulation in the body and blood, such as albumin, may have stabilized hydration in the protein-drinking marines.
This study points to another advantage of post-training protein supplements. They may also act as a buffer against stress induced by intense exercise that would otherwise threaten systems of the body related to immunity and maintenance of overall health.
1 Flakoll, P.J., et al. (2004). Postexercise protein supplementation improves health and muscle soreness during basic military training in marine recruits. J Appl Physiol. 96(3):951-6.