Abstract
BackgroundThe peritoneal injection of monosodium glutamate (MSG) can induce kidney injury in adult rats but the effects of long-term oral intake have not been determined.MethodsWe investigated the kidney histology and function in adult male Wistar rats that were fed ad libitum with a standard rat chow pellet and water with or without the addition of 2 mg/g body weight MSG/day in drinking water (n=10 per group). Both MSG-treated and control animals were sacrificed after 9 months when renal function parameters, blood and urine electrolytes, and tissue histopathology were determined.ResultsMSG-treated rats were more prone to kidney stone formation, as represented by the alkaline urine and significantly higher activity product of calcium phosphate. Accordingly, 3/10 MSG-treated rats developed kidney stones over 9 months versus none of the control animals. Further, 2/10 MSG-treated rats but none (0/10) of the controls manifested hydronephrosis. MSG-treated rats had significantly higher levels of serum creatinine and potassium including urine output volume, urinary excretion sodium and citrate compared to controls. In contrast, MSG-treated rats had significantly lower ammonium and magnesium urinary excretion.ConclusionOral MSG consumption appears to cause alkaline urine and may increase the risks of kidney stones with hydronephrosis in rats. Similar effects in humans must be verified by dedicated studies.
Highlights
Monosodium glutamate (MSG) is used as a flavor enhancer in food preparation to increase its palatability [1,2] and the monosodium glutamate (MSG) consumption is growing worldwide with average daily intake estimated as 3-4 g/day [3,4,5]
Animals allocated to the MSG or control groups had similar daily food intake, body weight and kidney weight at the end of the study (Figure 1a, 1c and Table 1)
In MSG-treated rats the mean ± SD daily MSG intake was 2.10 ± 0.32 mg/g body weight throughout the study corresponding to 0.29 ± 0.04 mg/g bw/day (0.19 g/day) Na from MSG supplementation
Summary
Monosodium glutamate (MSG) is used as a flavor enhancer in food preparation to increase its palatability [1,2] and the MSG consumption is growing worldwide with average daily intake estimated as 3-4 g/day [3,4,5]. Dietary MSG increases the urinary pH in rats [12] and alkaline urine may influence the kidney capacity to secrete or reabsorb metabolites that contribute to stone formation, as in the case of calcium phosphate products [13]. Methods: We investigated the kidney histology and function in adult male Wistar rats that were fed ad libitum with a standard rat chow pellet and water with or without the addition of 2 mg/g body weight MSG/day in drinking water (n=10 per group) Both MSG-treated and control animals were sacrificed after 9 months when renal function parameters, blood and urine electrolytes, and tissue histopathology were determined. Similar effects in humans must be verified by dedicated studies
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