The amount of diet-derived citrate that may escape in vivo conversion to bicarbonate is reportedly minor. 7 Medical interventions to increase urinary citrate are a primary focus in the medical management of urolithiasis. 6 There is also evidence that citrate blocks the adhesion of calcium oxalate monohydrate crystals to renal epithelial cells. Citrate binds to the calcium oxalate crystal surface, inhibiting crystal growth and aggregation. Citrate retards stone formation by inhibiting the calcium oxalate nucleation process and the growth of both calcium oxalate and calcium phosphate stones, largely by its ability to bind with urinary calcium and reduce the free calcium concentration, thereby reducing the supersaturation of urine. The activity of citrate is thought to be related to its concentration in urine, where it exhibits a dual action, opposing crystal formation by both thermodynamic and kinetic mechanisms. Hypocitraturia, defined as <320 mg (1.67 mmol) urinary citrate/day, 5 is a major risk factor for calcium urolithiasis. Citrate is the most abundant organic ion found in urine. Approximately 10% to 35% of urinary citrate is excreted the remainder is absorbed in various ways, depending on urine pH and other intra-renal factors. Citrate is freely filtered in the proximal tubule of the kidney. Urinary citrate is a potent, naturally-occurring inhibitor of urinary crystallization.

Gastrointestinal absorption of citric acid from dietary sources has been associated with a modest increase in urinary citrate excretion. A major source of citric acid in vivo results from endogenous metabolism in the mitochondria via the production of ATP in the citric acid cycle. Among fruits, citric acid is most concentrated in lemons and limes, 1 comprising as much as 8% of the dry fruit weight. Citrate salts of various metals are used to deliver minerals in biologically-available forms examples include dietary supplements and medications. Citric acid is frequently used as a food additive to provide acidity and sour taste to foods and beverages. At physiologic blood pH, and to a lesser extent in urine, it exists mainly as the trivalent anion. Citric acid (2-hydroxy-1,2,3-propanetricar-boxylic acid) is a weak tricarboxylic acid that is naturally concentrated in citrus fruits.

How much juice in one lemon