Munro H N
Kidney Int. 1978 Oct;14(4):313-6. doi: 10.1038/ki.1978.129.
Changes in caloric intake below or above energy needs affect nitrogen balance, so that any change in caloric intake results in a corresponding alteration in nitrogen balance. The improvement in nitrogen balance caused by an increase in energy intake, however, can be frustrated if intake of protein is inadequate; conversely, the beneficial effects of an increase in protein intake can be inhibited by an inadequate energy intake. These observations mean that, in experimental studies, nitrogen balance is the result of levels of both energy and protein; in consequence, protein requirements can be interpreted only from such studies, where energy intake is also defined under the experimental conditions. In addition to the effect of dietary energy supply, dietary carbohydrate has a short-term specific effect on protein metabolism not shared by fat, in which plasma amino acids are diverted into muscle protein through the action of insulin released by the dietary carbohydrate. This metabolic interaction also occurs between carbohydrate and amino acids absorbed from the same meal.
热量摄入低于或高于能量需求时会影响氮平衡，因此热量摄入的任何变化都会导致氮平衡相应改变。然而，如果蛋白质摄入量不足，能量摄入增加所引起的氮平衡改善可能会受到阻碍；相反，能量摄入不足会抑制蛋白质摄入增加所产生的有益效果。这些观察结果表明，在实验研究中，氮平衡是能量和蛋白质水平共同作用的结果；因此，只有在这类研究中，且实验条件下能量摄入也已确定时，才能解读蛋白质需求。除了膳食能量供应的影响外，膳食碳水化合物对蛋白质代谢有短期特定作用，而脂肪则没有这种作用，膳食碳水化合物释放的胰岛素会促使血浆氨基酸转化为肌肉蛋白。这种代谢相互作用也会发生在同一餐中吸收的碳水化合物和氨基酸之间。
