Intake of low-dose leucine-rich essential amino acids stimulates muscle anabolism equivalently to bolus whey protein in older women at rest and after exercise
Sarcopenia, the reduction in skeletal muscle mass due to aging, leads to increased risk of frailty, falls, and metabolic diseases, a greater propensity toward a sedentary lifestyle and a decline in quality of life, and an overall higher risk of all-cause mortality. Both nutritional intake of dietary protein made up of essential amino acids (EAAs) and physical activity have been shown to increase muscle protein synthesis, and recent research suggests that the EAA leucine goes one step further by triggering muscle-building mechanisms in the body.
In this present study, researchers set out to investigate if a lower dose of essential amino acids combined with higher leucine content provides a lower-calorie anabolic (muscle-building) alternative to higher calorie whey protein. Participants included older women, an underrepresented group in previous studies on muscle protein metabolism in aging. A lower calorie EAA supplement may be more advised in older individuals unwilling or unable to consume a high-calorie, satiating supplement such as whey.
Acute metabolic study
Number of Subjects
To determine the effects of a 3-gram dose of essential amino acids made up of 40% leucine compared to the effects of 20 grams of whey protein bolus on muscle protein metabolism in older women during periods of rest and during an acute bout of resistance exercise, which has previously proven effective at stimulating muscle protein synthesis.
Researchers hypothesized that the leucine-enriched EAA supplement would provide equivalent muscle-building gains to whey protein, as well as increased albumin protein synthesis, all at a lower caloric cost. The addition of resistance exercise is believed to increase this effect.
Results showed that an EAA mixture of approximately 1.2 grams of leucine plus 1.8 grams of additional essential amino acids was enough to stimulate muscle protein synthesis in older women and that greater quantities of EAAs as meals or supplements may not be necessary. Further studies are warranted.
The leucine-dominant EAA supplement stimulated muscle protein synthesis to the same degree as a higher calorie whey protein supplement, which provides 3 times more EAAs but to no greater effect. While the whey protein raised leucine levels for longer, there was not an increased impact on muscle protein synthesis.
Based on the study’s findings, researchers conclude that a low-dose leucine-enriched essential amino acid supplement is just as effective as a higher protein and higher calorie whey protein supplement at increasing muscle protein synthesis in older women at rest and during exercise, but won’t adversely impact overall energy and protein intake.
The importance of albumin protein
Low levels of albumin signify inadequate protein intake, decreased muscle mass and strength, functional decline, and age-related diseases. It is well known that albumin levels decrease with age and that women have slower albumin rates than men. This study shows that the leucine-enriched EAA dramatically increased albumin protein levels to the same extent as whey protein, which indicates that supplementing with EAAs may help boost albumin production in women, thereby benefiting muscle health and overall health.
The effect of physical activity on muscle maintenance
Resistance exercise helps improve the decline of muscle mass that accompanies aging, however, the anabolic response to exercise is blunted in older individuals, which propels researchers to investigate how to maximize the impact of physical activity with the addition of optimized nutrition.
This study suggests that older women experienced a longer duration of muscle protein synthesis after exercise when supplemented with leucine-enriched EAAs or whey protein.
While supplementing with protein-based supplements such as whey protein and essential amino acids have shown anabolic benefit to older men, the same effects have been studied to a far less degree in women. Maintaining muscle mass as we age is important for sustaining quality of life, reducing the risk of frailty, and protecting against morbidity and all-cause mortality. This study shows that a low-dose, low-calorie essential amino acid supplement enriched with leucine can help increase muscle protein synthesis in older women, particularly when combined with resistance exercise.
Bukhari SS, Phillips BE, Wilkinson DJ, Limb MC, Rankin D, Mitchell WK, Kobayashi H, Greenhaff PL, Smith K, Atherton PJ. Intake of low-dose leucine-rich essential amino acids stimulates muscle anabolism equivalently to bolus whey protein in older women at rest and after exercise. Am J Physiol Endocrinol Metab. 2015 Jun 15;308(12):E1056-65. doi: 10.1152/ajpendo.00481.2014. Epub 2015 Mar 31. PMID:25827594