BIOCHEMISTRY - Key Regulators and Biological Fluids of the Human Body - 2016

4. CHEMICAL COMPOSITION OF URINE

4.4. Physical and Chemical Properties of Urine

Urine volume (diuresis) depends on fluid intake and accounts for 50 - 80 % of the consumed volume. The daily output is 1000 - 2 000 mL.

Polyuria (increased urine output) is observed after high fluid intake, especially tea, coffee, and alcohol. The caffeine and ethanol contained in these beverages suppress the Synthesis of the antidiuretic hormone, vasopressin.

Oliguria (decreased urine output) occurs when fluid intake is restricted, as well as in Kidney and other diseases. In athletes, it may occur during heavy physical

exertion due to significant Water loss through sweat and exhaled air.

Anuria (cessation of urine excretion) can be triggered by stress caused by severe pain or intense negative emotions.

Specific gravity of urine. In healthy individuals on a normal diet, urine density typically ranges from 1.010 to 1.025 g/mL. During physical exertion accompanied by heavy sweating, urine density may increase up to 1.035 - 1.040 g/mL.

Urine acidity. In healthy individuals, it depends on dietary habits. Urine normally has a mildly acidic reaction (pH = 5 - 7). A predominantly meat-based diet lowers the pH to below 5, whereas a plant-based diet raises it above 5 (alkalinization).

Increased acidity (pH = 4 - 5) is observed in athletes following intense Physical Exercise, as large amounts of lactic acid are excreted in the urine.

Urine color. Typically pale yellow, imparted primarily by pigments generated during Hemoglobin breakdown.

Urine transparency. Freshly voided urine in healthy individuals is clear, though it may become turbid upon standing.