The effect of a vegetarian and different omnivorous diets on urinary risk factors for uric acid stone formation

Summary.

Background:

About 10–15% of all urinary stones are composed of uric acid. A high urinary uric acid excretion, a low urine volume and an acidic urinary pH value are suggested to be the most important risk factors for uric acid stone formation.

Aim of the study:

The effect of a vegetarian diet and different omnivorous diets on the risk of uric acid crystallization was investigated.

Methods:

Ten healthy male subjects ingested a self-selected meat-containing diet (SD) for two weeks, and three different standardized diets for a period of 5 days each. The Westerntype diet (WD) was representative of the usual dietary habits,whereas the balanced omnivorous diet (OD) and the ovo-lacto-vegetarian diet (VD) were calculated according to the requirements.

Results:

The risk of uric acid crystallization was highest on the ingestion of diets SD and WD, due to the high urinary uric acid excretion and the acidic urinary pH. The relative supersaturation with uric acid declined significantly by 85% on the intake of diet OD, consequent to the decrease in uric acid excretion and concentration and the increase in urinary pH value. The ingestion of the vegetarian diet VD led to a further significant reduction in the risk of uric acid crystallization by 93% compared to diet WD.

Conclusions:

The results indicate that the intake of a balanced vegetarian diet with a moderate animal protein and purine content, an adequate fluid intake and a high alkali-load with fruits and vegetables results in the lowest risk of uric acid crystallization compared to the omnivorous diets.