Positive Nitrogen Balance

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Joined: Thu Mar 08, 2012 11:02 pm

Positive Nitrogen Balance

Post by Kev » Sat Mar 10, 2012 9:06 pm

Proteins are nitrogenous compounds made of amino acids which serve as structural building blocks of the human body. Additionally, they are crucial for the synthesis of hormones, enzymes, red blood cells and can also be used secondary (carbohydrates and fats usually preferred) in energy production.

Generally, a nitrogen balance assessment is used to indicate the level of protein requirement for an individual. A net positive nitrogen balance indicates overall anabolism (protein synthesis more than breakdown), whereas a net negative nitrogen balance indicates overall catabolism (protein breakdown more than synthesis). However, this is only a rough estimate and may be inaccurate as it does not focus solely on exercise. A bout of resistance training would induce an anabolic state (more protein synthesis), but the body remains in a net negative nitrogen balance without protein supplementation, and may eventually lead to overall catabolism and delayed muscle recovery.
Given that dietary protein contributes mainly to anabolic processes of the body, strenuous, high- intensity workouts would require more protein to stimulate muscle protein synthesis (MPS) and subsequently aid recovery and adaptation to training. Studies have shown that dietary protein intake of 1.4-2.4 g/kg daily will help sustain a positive nitrogen balance in resistance-trained athletes. The current recommended intake is 2g protein per kg per day for strength training individuals. Additionally, it is important that to consider the quality of protein consumed, timing of consumption and intensity of training. For example, Whey protein isolate (WPI) is a high quality protein as it contains a high-proportion of branched chained amino acids (BCAAs) crucial for MPS. Studies have shown that a BCAA supplement post-workout can attenuate muscle damage and improve recovery. Consumption of a high-quality protein source with moderate to high carbohydrates is recommended immediately following high-intensity training.

Campbell, B et al, 'International Society of Sports Nutrition position stand: protein and exercise' (2007) 4 Journal of the International Society of Sports Nutrition 8

Hoffman, JR and MJ Falvo, 'PROTEIN–WHICH IS BEST?' (2004) 3(3) Journal of Sports Science and Medicine 118

Lambert, CP, LL Frank and WJ Evans, 'Macronutrient considerations for the sport of bodybuilding' (2004) 34(5) Sports Medicine 317

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