Nutrition
Wheyprotein in combination with weight training increases muscle growth. Australian scientists Alan Hayes and Paul Cribbs summarized the results of recent studies showing how whey protein and weight training work together to maximize gains in muscle mass and strength.
Amino acids contained in whey protein - especially leucine - serve as building blocks for muscle protein and stimulate genes that regulate protein synthesis and breakdown. Whey protein is rich in the branched-chain amino acids leucine, isoleucine and valine, which are crucial for maintaining a positive nitrogen balance, meaning that protein synthesis occurs at a higher rate than protein breakdown. Leucine is of particular importance as a signaling chemical for the regulation of protein synthesis, insulin sensitivity and energy expenditure. Leucine also increases the cycle rate of protein breakdown and protein synthesis. Branched-chain amino acids are crucial for the control of metabolism and energy expenditure. Training with weights generates muscle tension, which activates genes responsible for protein metabolism. Consumption of whey protein during and after exercise accelerates and optimizes protein synthesis.
(Current Opinion in Clinical Nutrition and Metabolic Care, 11: 40-44, 2008)
Conjugated Linoleic Acid (CLA) is a popular supplement among bodybuilders because it breaks down fat in the abdominal area and reduces inflammation associated with insulin resistance, diabetes and poor sexual performance. CLA is a fatty acid found in beef and the fat in dairy products and is also available in higher concentrations in supplement form.
Most studies conducted on animals but only 50 percent of human studies showed that CLA reduces body fat. We can conclude from this that there are people who respond to this supplement and others who do not. A study conducted at the University of Nebraska under the direction of Kimberly Hargrave-Barns showed that CLA-induced fat loss depends on an enzyme called alpha-6-desaturase (D6D). Genetic and environmental factors influence the activity of D6D and therefore the capacity of CLA to promote fat loss. These factors include aging, smoking, insulin resistance, inadequate intakes of vitamin B6, magnesium and zinc, poor metabolic health and high intakes of saturated and trans fats. People who have a genetic predisposition to obesity, such as Pima Indians, have low D6D levels.
This study sends an important message: a drug or supplement that works for one person may not necessarily work for another.
(Obesity, in press, published online July 24, 2008)
Creatine is one of the most popular sports supplements on the planet. It increases muscle mass, strength and performance in some high-intensity sports. Creatine has few known side effects. High doses (i.e. more than 20 grams per day) cause a sharp increase in formaldehyde levels in the blood, which can have toxic effects on the kidneys and the inner lining of blood vessels.
Carlos Ohanian and colleagues from the University of Uruguay found that soccer players who took creatine over a period of 56 days showed no changes in health markers in blood or urine. 14 soccer players were divided into either a creatine or a placebo group. The creatine group took 15 grams of creatine per day for seven days and 3 grams of creatine per day for the remaining 49 days. Only the creatine group gained weight during the study. Creatine kinase (a marker of muscle damage) and uric acid (a marker of amino acid metabolism) decreased in the creatine group, but these changes are probably more attributable to the training than the supplement.
Creatine appears to be safe for short-term use, but we need further detailed research into the long-term effectiveness and safety of this supplement.
(British Journal Sports Medicine, 42: 731-735, 2008)
Insulin is an important anabolic hormone that promotes the transport of amino acids (the building blocks of protein) into muscle cells and activates chemicals that promote protein synthesis. protein synthesis stimulate protein synthesis. The amino acid leucine is an important signaling chemical that promotes protein synthesis and stimulates insulin secretion.
A study conducted at the University of Minnesota showed that the consumption of glucose (sugar) and leucine increases insulin secretion and lowers blood sugar levels. The consumption of leucine alone had only a minor effect on insulin and blood sugar levels. We can conclude from this study that taking a leucine-carbohydrate supplement after exercise replenishes carbohydrate stores, increases the rate of protein synthesis and reduces protein breakdown.
(Metabolism Clinical and Experimental, 57:1747-1752, 2008)
Carbohydrates stimulate insulin secretion, which is crucial for the transport of amino acids into the cells and the promotion of protein synthesis. The availability of carbohydrates and amino acids is essential for maintaining an anabolic state. The body uses its protein stores as an energy source during periods of low calorie intake.
A Danish study showed that a pre-workout supplement containing carbohydrates and protein hydrolysate (predigested protein) before exercise promoted protein synthesis during and immediately after exercise, but had no further effect overnight. While this study is interesting, we don't know if this supplement strategy increases muscle mass and strength more than training alone.
(Journal of Nutrition, 138: 2198-2204, 2008)
