As we age there is a decline in muscle mass, muscle strength and endurance. Associated with this is decline in aerobic capacity, and this causes people to become easily fatigued. This happens beginning in the 30s, with rapid deterioration in the mid-60s.
So as we get older, it’s natural for all of us to lose muscle fiber. This is called ’sarcopenia’ which translates into ’muscle-wasting disease’.
I advocate increasing our levels of physical activity as we get older so we maintain muscle fibers. Don’t ever become sedentary or allow a sedentary lifestyle. If this slow-down in activity and hence, muscle metabolism isn’t reversed through changes in diet and exercise, the slide toward sarcopenia begins.
A recent study published in the journal Clinical Nutrition shows that the amino acid leucine may be able to play a role in improving “muscle protein synthesis” and combating the onset of sarcopenia.
The amino acid leucine may help older people synthesize muscle in response to lower protein meals. While increasing protein intake can counter this, barriers including palatability, cost, satiety and habitual practices can inhibit regular protein intake.
Supplementing regular daily meals with a relatively small amount of leucine improves both mixed muscle protein synthesis and anabolic signaling in older adults.
The researchers supplemented meals with leucine at a dose of 12 grams per day for 14 days. Results showed that leucine supplementation increased the rate of protein synthesis, as well as markers of nutrient signaling.
The rationale for the use of a dietary supplement like PhytoMulti by Metagenics makes even more sense.
Consumption of leucine-enriched essential amino acid supplements during endurance exercise may enhance the synthesis of muscle protein by 33%, says a new study from the U.S. Army.
In addition to the implications for sports nutrition, results of the randomized crossover study, published in The American Journal of Clinical Nutrition, may have implications for populations susceptible to muscle loss due to conditions such as sarcopenia.
“… increasing leucine provision during endurance-type exercise by dietary supplementation enhances muscle protein anabolism in recovery,” wrote researchers from the U.S. Army Research Institute of Environmental Medicine, Tufts University, and Louisiana State University System.
The effects of resistance exercise on the metabolism of protein in muscles and the effects of endurance exercise on protein metabolism is not well established. “Increasing the concentration of leucine within an optimal dose of EAA [essential amino acid] does not have an added stimulatory effect on resting and post-resistance exercise muscle protein synthesis,” explained the researchers, led by the U.S. Army’s Stefan Pasiakos.
“In contrast with resistance exercise, sustained endurance exercise is mainly catabolic, yielding simultaneous reductions in muscle protein synthesis and plasma leucine concentrations during exercise, which may be attributed to the metabolic demand for branched chain amino acids in exercising skeletal muscle.”
Eight volunteers consumed 10 grams of protein drinks with either 1.87 or 3.5 grams of leucine during a cycling test.
Results showed that the leucine-enriched beverage was associated with a 33% increase in muscle protein synthesis, compared with the control beverage. “[In addition] whole-body protein breakdown and synthesis were lower and oxidation was greater after consumption of [leucine-enriched essential amino acid supplement] than after consumption of [essential amino acid supplement],” added the researchers.
“These data indicate that increasing leucine availability during steady state exercise promotes skeletal muscle protein anabolism and spares endogenous protein,” wrote Pasiakos and his co-workers.
“Our findings indicate that increasing the leucine content of protein supplements provided for those populations susceptible to muscle loss, including proteolytic conditions—such as cachexia, sarcopenia and calorie deprivation—may warrant further exploration,” they added.
American Journal of Clinical Nutrition 94(3):809-181, 2011