Sodium: Basic Nutritional Aspects

Sodium is a micronutrient required to maintain the most basic aspects of cellular and organismal functions. Thus systemic sodium homeostasis is tightly regulated by a complex system of membrane transporters and neurohormonal factors. Insufficient or excessive sodium intake (predominantly in the form of sodium chloride) have been associated with numerous pathologies, including hypertension, stroke, cardiovascular disease, gastric cancers, and metabolic syndrome. It is well recognized that the current intake of sodium for most individuals in the United States and other countries greatly exceeds the adequate intake and the tolerable upper intake level. Significant efforts are made to reduce sodium intake, which require changes in individual behavior toward salt consumption, increased consumption of low-salt foods, and increased collaboration of clinicians and scientists with the food industry and with public health officials. However, the preponderance of evidence does not support the current recommendations of a generalized and indiscriminate reduction of salt intake in the general population, although the blood-pressure-lowering effect of dietary sodium restriction might be of value in hypertensive patients and other at risk populations. The current state of knowledge strongly indicates further need for additional well-controlled population-based studies to understand and resolve the existing controversies. In this chapter we briefly review physiological roles of sodium, mechanisms of intestinal and renal (re)absorption, dietary intake recommendations, and health outcomes associated with inappropriate sodium intake.