A–Z of nutritional supplements: dietary supplements, sports nutrition foods and ergogenic aids for health and performance—Part 23

• Published in: British Journal of Sports Medicine 2011-08, Vol.45 (10), p.830-831
• Main Authors: Ranchordas, M K, Blomstrand, E, Calder, P C, Burke, L M, Stear, S J, Castell, L M
• Format: Article
• Language: English
• Subjects: Athletic Performance; Biosynthesis; Diet; Dietary Supplements; Fatty acids; Food; gamma-Linolenic Acid - adverse effects; gamma-Linolenic Acid - therapeutic use; Humans; Lecithins - therapeutic use; Leucine - physiology; Leucine - therapeutic use; Linoleic Acid - therapeutic use; Marathons; Medicin/Teknik; Medicine/Technology; Nutrition research; Phosphorylation; Plasma; Protein Biosynthesis - drug effects; Protein synthesis; Proteins; Rodents; Seeds; Studies; Vegetable oils
• ISSN: 0306-3674; 1473-0480; 1473-0480
• DOI: 10.1136/bjsports-2011-090294

Leucine E Blomstrand Leucine is one of the three BCAAs and is an essential amino acid (EAA) that has to be provided in the diet. Besides serving as building blocks for protein synthesis, leucine can also regulate the rate of protein synthesis via a stimulatory effect on enzymes involved in the translation of specific mRNAs. 1 Direct stimulation by leucine of the rate of protein synthesis in muscle tissue was first demonstrated in various preparations from experimental animals and, more recently, in the intact animal after oral administration. 2 Infusion of leucine in human subjects was shown to improve the net protein balance and to increase phosphorylation/activation of the regulatory enzyme 70-kD ribosomal protein S6 kinase (p70S6k), indicating a stimulatory effect of leucine on protein synthesis also on human muscle after oral ingestion, although this remains to be confirmed. 3 4 When leucine is ingested together with the other EAAs after resistance exercise, the rate of protein synthesis increases to a larger extent than without nutritional supply and a positive net protein balance is achieved during the period after exercise. 5 However, adding extra leucine to a protein hydrolysate or an EAA mixture has no effect, or only minor additional effect, on the rate of protein synthesis in young subjects. 6 On the other hand, recent data show that excluding leucine from the EAA mixture eliminates the stimulatory effect on protein synthesis and on phosphorylation of p70S6k. 7 In elderly subjects, in whom the required amount of leucine to reach optimal stimulation on protein synthesis may be enhanced, leucine-enriched diet improves muscle protein synthesis acutely, whereas no effect on muscle mass is observed during long-term supplementation. 8 There is some evidence from animal studies that leucine can also inhibit muscle protein breakdown, however, this has not yet been confirmed in human muscle. [...]plant tissues, seeds and nuts; their oils (eg, corn oil, sunflower oil, soybean oil); and foodstuffs produced from these oils (eg, margarines) have a high content of linoleic acid (often > 50% of the fatty acids are present).