Acidosis and nutrition

Abstract

In recent years there has been increasing evidence for the deleterious effect of acidosis on a number of fundamental systems of the body including nutrition [1, 2]. Approximately 70 mmol of hydrogen ions are produced daily by the body, and to maintain acid-base balance there must be an equivalent net acid secretion by the kidney. It is remarkable that extracellular fluid (ECF) pH is maintained within a very narrow range of 7.35-7.45 (35-45 nM), reflecting the fundamental importance of pH on many aspects of basic cellular function particularly proteins. It is important to differentiate between the terms acidosis and acidemia. The former is a pathophysiologic process tending to acidify body fluids, whereas the latter occurs when the ECF hydrogen ion concentration is above the normal range. It is possible to be acidotic (with a reduced serum bicarbonate) but not acidemic because of appropriate buffering of hydrogen ions. The major extracellular buffer is the carbonic acid/hydrogen carbonate system with plasma proteins and hemoglobin contributing significantly less. The major intracellular buffer is protein followed by bone [3]. The type of acidosis seen in patients with chronic renal failure changes with decreasing GFR; initially a non-anion gap acidosis is observed secondary to the loss of bicarbonate from the proximal tubule and impaired excretion in the distal tubule. With increasing severity of renal impairment, failure to excrete organic and inorganic acids results in an increased anion gap [4, 5].