Bioavailability of glucose from Palatinit

Significance of Leydig Cell Neoplasia in Rats Fed Lactitol or Lactose

Lactitol is a disaccharide sugar alcohol (polyol) which is derived from lactose by catalytic hydrogenation and which may be used as a noncariogenic, reduced calorie sugar substitute in different foods. In the context of the safety evaluation of lactitol, a chronic carcinogenicity/toxicity study was conducted in a Wistar-derived strain of rats. In addition to effects that occur commonly in rats fed high doses of polyols, an increased incidence of Leydig cell tumors was observed in rats fed a diet with 10% lactitol for their lifetime. A comparison group receiving a diet with 20% lactose exhibited the same effect. At the 5% dose level of lactitol, no testicular changes were seen. Although lactitol is not genotoxic in standard in vitro tests and was also not associated with tumor formation in female rats and mice of either sex, it was necessary to assess the relevance of the testicular neoplastic growth for human safety. A comparative evaluation of the spontaneous and chemically induced formation of Leydig cell tumors in rats and humans demonstrates that the spontaneous occurrence is extremely low in humans but rather high in rats. Chemical agents or experimental conditions that in rats are associated with interstitial cell hyperplasia or neoplasia have not been associated with similar effects in humans. This is also true for lactose which, in Western countries, is consumed regularly and in substantial amounts with dairy products. Since lactitol is essentially not hydrolyzed in the small intestine, it gains access to the metabolism only after fermentation by the intestinal flora. It is therefore reasonable to assume that the testicular effects of lactitol and lactose were mediated by changes in the digestive tract such as by the known increase of calcium absorption which occurs in lactitol- and lactose-fed rats but not in humans or by effects of these compounds on the enterohepatic cycling of steroid hormones. Although these mechanisms are not yet elucidated, the available data on Leydig cell tumors indicate that the effects seen in male rats are not relevant to humans. The major lines of evidence supporting the human safety of lactitol and lactose are: (1) the lack of genotoxicity of lactitol, (2) the rat specificity of the testicular effects of lactose and lactitol, (3) the long history of safe consumption of lactose in humans, (4) the insensitivity of the human Leydig cells to agents and conditions that are known to cause neoplastic growth of Leydig cells in rats, (5) the generally very low spontaneous incidence of Leydig cell tumors in the human population, and (6) the absence of any epidemiological evidence establishing a link between nutritional factors and the occurrence of Leydig cell tumors in humans.

On the occurrence of free glucose in the caecal contents of rats

Free glucose was assayed in the caecal contents of rats. Whereas control animals had less than 60 nmol glucose per g of caecal contents, 230 nmol glucose/g caecal contents were determined 3 hours after the administration of 300 mg Palatinit by gastric intubation. In contrast to an earlier report (8), caecal fluid thus contained less than 3% of the glucose concentration of 11 mumol/ml claimed to occur after Palatinit administration by these authors (8). Since the anaerobic fermentation capacity for glucose by the caecal contents of rats amounted to at least 630 nmol glucose/min X g fresh weight at 37 degrees C, only the low glucose concentrations reported above are plausible.

Dose dependence of breath hydrogen and methane in healthy volunteers after ingestion of a commercial disaccharide mixture, Palatinit

Breath hydrogen and methane were determined by gas chromatography in eleven normal individuals given a low-fibre, mixed diet (control) and after ingestion of 20-50 g Palatinit/d, an equimolar mixture of D-glucosyl-alpha(1----1)-D-mannitol and D-glucosyl-alpha(1----6)-D-glucitol (Isomalt). A linear relation was found (r 0.85; P less than 0.001) between the amount of Palatinit ingested and breath H2 per 10 h in subjects who did not exhale methane. If methane was formed in addition to H2, the sum of both gases followed a linear dose-effect relation. The mouth-to-caecum time, indicated by the first increase in breath H2 after ingestion, was shortened by about half, yet no sign of diarrhoea was observed. Stool weight and stool frequency did not change significantly. The linear relation between a dose of 20-50 g Palatinit and exhalation of H2 (eventually plus methane) indicated that a relatively constant fraction of the dose given underwent cleavage and absorption in the small intestine, the remainder being transported into the large bowel. Microbial gas formation in the colon as well as the fractional transfer of these gases into the expiratory air occurred at fixed proportions, thus allowing an insight into colonic microbial contributions to carbohydrate utilization in the human large bowel.