A review of the studies of the safety of polydextrose in food.

Polydextrose (CAS no. 68424-04-4) is a water-soluble polymer of glucose that provides to foods the bulk and texture of sucrose. There are two main forms of polydextrose, an acidic form (PD-A) and a neutralized potassium salt (PD-N). Polydextrose is resistant to mammalian metabolic and microbial degeneration, rendering it both low in caloric value and non-cariogenic. Little polydextrose is absorbed intact although some is metabolized by caecal/colonic bacteria. At high enough levels of ingestion, this bacterial metabolism results in flatus, bloating, loose stools and ultimately a frank diarrhoea. Microbial metabolism also produces some volatile fatty acids that are absorbed by the animal and have calorigenic value. The species and dose threshold for persistent loose stools/watery diarrhoea determines the degree of electrolyte loss by the animal. In the dog, an obligate carnivore, sodium-sparing activity by the kidney and concomitant and obligatory calcium reuptake result in a well-defined aetiology of hypercalcaemia and subsequent nephrocalcinosis, particularly for PD-N. Of the species tested, the dog was the most sensitive to this carbohydrate with a no-effect level of 2000 mg/kg body weight/day. Omnivores, including the rat, mouse and monkey, have a no-effect level ranging from 2500 to 10,000 mg/kg body weight/day. No toxicity has been demonstrated in man, although the dose for laxation (to be distinguished from diarrhoea) is approximately 90 g/day (v. sorbitol at 70 g/day). Polydextrose did not show any reproductive toxicity, teratology, carcinogenesis, mutagenicity or genotoxicity. Polydextrose has been approved for food additive use (21 CFR 172.841) in the US, and an "ADI not specified" by the Joint WHO/FAO Expert Committee on Food Additives (JECFA, 1987). It has been approved in over 50 countries around the world and has been used extensively in the diet for over15 years. Specification monographs are published in the Food Chemicals Codex (FCC) (NAS, 1996) and the FAO Compendium (JECFA, 1995). This review provides an overview of the studies and salient data, not previously reported in the scientific literature, which had been submitted to regulatory agencies in support of these approvals.