Subchronic oral toxicity study with regular and enzymatically depolymerized sodium carboxymethylcellulose in rats

Enzymatically depolymerized sodium carboxymethylcellulose (CMC-ENZ) is a new functional food ingredient which has a lower molecular weight and viscosity than regular sodium carboxymethylcellulose (CMC). Both compounds are known not to be absorbed to a significant extent, and the human safety of CMC as a thickening agent and stabilizer in food is well established. In the present study, the subchronic oral toxicity of CMC-ENZ was examined and compared with that of CMC in Wistar rats. Seven groups of 20 rats/sex were fed diets with 0 (controls), 2.5, 5 and 10% CMC and 2.5, 5 and 10% CMC-ENZ for a 3-month period. There was only one death that was unrelated to the treatment. Water intake, urine production and urinary sodium excretion increased with increasing doses of CMC and CMC-ENZ due to their sodium content of about 7-8%. The treatment-related occurrence of diarrhoea and caecal enlargement in the mid- and high-dose groups, a slight increase of plasma alkaline phosphatase, and increased urinary calcium and citrate excretions were considered to be generic effects that typically are observed in rodent studies with low digestible carbohydrates. The increased occurrence of nephrocalcinosis and hyperplasia of the urothelial epithelium in some of the treated groups was interpreted as an indirect consequence of a more alkaline urine coupled with an increased calcium excretion. As the frequency and severity of all these changes did not differ between corresponding CMC and CMC-ENZ dose groups, it is concluded that the two products have a similar toxicological profile.