Plasma and urine
electrolytes were measured in five healthy non-obese young adults before, during and after a four-day period of total
starvation (distilled water only). Plasma
sodium, chloride and
bicarbonate concentrations decreased in all subjects by a mean value of 4 mmol/l, whereas the sum of
acetoacetate and hydroxybutyrate concentrations increased by 4-6 mmol/l. These changes occurred without alterations in the state of hydration or vascular volume. Hydroxybutyrate and
ammonium ions became the main urinary
ions during
starvation, whereas
sodium and
chloride, which were quantitatively the most important urinary
electrolytes before
starvation, decreased four-fold, and
potassium two-fold. Plasma
zinc concentrations rapidly increased in all subjects by a mean of 4 mumol/1 (25%) and returned to normal on refeeding. The excretion of
zinc in urine trebled and continued to rise on refeeding. There were no major changes in the excretion of
calcium, magnesium, phosphate or sulphate during the
starvation period. From knowledge of the intracellular concentrations of various minerals and extent of breakdown of lean tissues (N excretion), it is suggested that most of the urinary
calcium,
magnesium and
phosphate probably originates from bone, and that the amount of
zinc in urine is only a small fraction of that which is likely to be released from the breakdown of lean tissues. It is also suggested that the continued excretion of
zinc on refeeding is due to release of
zinc from tissues which 'buffered' it during the
starvation period. This study provides useful data in non-obese individuals with which to compare changes which occur in post-traumatic and post-infective
starvation.