The production of growth hormone is regulated by many factors:
Stress, exercise, nutrition, fasting, sleep and growth hormone itself. However, its primary controllers are two hypothalamic hormones (Growth hormone-releasing hormone Somatostatin) and one hormone from the stomach (Ghrelin). L- Arginine is required before bed.
Somatomedin C, high blood sugar or fats, obesity, and depression reduce GH secretion.
Protein synthesis is stimulated by:
Very high concentrations of leucine have the capacity to stimulate protein synthesis and inhibit protein degradation in skeletal muscle. That means taking Branch Chain Amino Acid’s (BCAA’s) with your whey protein (isolate) powder.
Textbook Treason?
I just received two nutrition textbooks from Wadsworth/Thomson Leaning for review: Advanced Nutrition and Human Metabolism by Groff & Gropper and Understanding Nutrition by Whitney & Rolfes. As I read Whiney & Rolfes, I was struck by the following statements: “Protein supplements are expensive, less completely digested than protein-rich foods and, when used as replacements for such foods, often downright dangerous.”
This is not the case. Modern protein powders have a high biological value (quality) and are certainly not “downright dangerous”; see the review by Dr. Luke Bucci in Energy-Yielding Macronutrients and Energy Metabolism in Sports Nutrition (CRC Press, 2000).
“Whey protein appears to be particularly popular among athletes hoping to achieve greater muscle mass. A waste product of cheese manufacturing, whey protein is a common ingredient in many low-cost protein powders. Athletes and active people who want bigger muscles should know that whey protein does not increase muscle mass.”
There is some evidence suggesting that whey protein may enhance lean body mass in conjunction with appropriate training (J Nutr Biochem, 14:251-258, 2003). Whey proteins have a high biological value and contain a relatively high proportion of branched-chain amino acids (BCAA). The abundance of leucine in whey is of particular interest in this regard. Leucine plays a distinct role in protein metabolism and has been identified as a key signal in the translational initiation pathway of muscle protein synthesis.
Another point, beyond the composition of amino acids present in whey, is the manner in which whey and other intact proteins are absorbed and utilized
relative to each other, as well as to free amino acid solutions. Whey proteins have been compared to casein and a distinct difference is that whey is rapidly
absorbed compared to casein. Dr. Bohe and coworkers reported that continuous stimulation of protein synthesis (via a constant infusion of amino
acids) resulted in saturation of the response within two hours (J Physiol 532:575-579, 2001).
Thus, an effective protein source would be one that could stimulate a response in the periods between feeding which would be additive to the net accumulation of muscle protein in the course of a day. Further, certain amino acids and whey-derived bioactive compounds offer the potential to extend health benefits to active people beyond body composition. Many of the functions associated with these amino acids and whey components involve the immune system and may therefore be of particular importance to athletes in intensive training. The claim that certain whey peptides suppress appetite is being used to market some products, but well designed studies to validate this effect are lacking.
****** (MUST READ) Another excellent study by Dr. Tipton and coworkers was designed to determine whether consumption of an oral essential amino acid/carbohydrate supplement before exercise results in a greater anabolic response than supplementation after resistance exercise. The results indicated that the response of net muscle protein synthesis to consumption of an essential amino acid/carbohydrate solution immediately before resistance exercise is greater than when the solution is consumed after exercise.
