Plasma and Urine Kinetics of Erythritol after Oral Ingestion by Healthy Humans

MATERIALS AND METHOD

Subjects
Six volunteers, consisting of three males and three females aged 24 to 43 years (mean 32.67 ± 6.8 years) with a body mass index (BMI, 22 ± 1.65; range = 19­24), were studied. No subjects were included in the study who had fasting blood sugar levels above 5.5 mmol/liter, were pregnant, had diabetes mellitus, or were HN positive. All subjects participated in the study after their informed consent was obtained. The study protocol was approved by the ethics committee of Hopital Hotel-Dieu.

Materials
Erythritol (99.9% purity) was provided by Cerestar, Belgium

Study Design
Following an overnight fast, all subjects ingested a single oral dose of
1 g erythritol/kg body wt dissolved in 250 ml of water. The total dose administered to each subject ranged from 56 to 78 g, depending on the body weight ofthe individual. Fifteen minutes prior to eryth­ritol administration and every 30 min during the period from 0 to 3 hr postingestion, blood samples were col­lected for analysis of plasma glucose and insulin levels. Blood samples also were collected for analysis of plasma erythritol levels every 5 min during the period from 0 to 15 min postingestion, every 15 min during the period from 15 min to 1 hr postingestion, and every 30 min during the period from 1 to 3 hr postingestion. A blood sample also was taken prior to erythritol inges­tion for the determination of plasma creatinine levels.
At 30 min and 1, 2, and 3 hr postingestion, urine was collected, its volume was measured, and erythritol and creatinine concentrations were determined. Over the next 21 hr, total urine output was measured. Follow­up medical examinations were performed 24 hr after erythritol administration.
Urine samples were stored at -20°C for 5 weeks prior to erythritol determinations. Similarly, plasma samples were stored at -20°C for 4 to 5 weeks prior to erythritol and insulin determinations. Plasma glucose determinations were conducted immediately after collection.

PLASMA AND URINE KINETICS OF ERYTHRITOL AFTER ORAL INGESTION

Determinations
Plasma erythritol concentration. The plasma eryth­ritol concentration was determined using a high-pres­sure liquid chromatograph (HPLC) method with 1,3­butanediol as an internal standard (IS). 1,3-Butanediol has similar chromatographic properties to erythritol and was added to plasma samples before deproteinization. A 1/100 dilute solution of IS was originally pre­pared and the area under the HPLC curve measured under the conditions of the assay.
Plasma samples were centrifuged and analyzed in triplicate. One milliliter of the 1/100 dilution ofIS was mixed with 3 ml of centrifuged plasma sample before deproteinization. Deproteinization was performed by mixing 3 ml of ice-cold perchloric acid (0.6 mol/liter) with the IS/plasma sample mixture in a centrifuge tube. Mter centrifugation, 1 ml of potassium carbonate solution (0.75 mol/liter) was mixed with 3 ml of supernatant, put in an ice bath for 3 min, then centrifuged. The supernatant was immediately frozen at -20°C for HPLC analysis at a later time. Mter thawing, the sam­ples were centrifuged and the supernatant was de­canted and put into HPLC vials. Erythritol was mea­sured by means of HPLC using a Waters HPLC Solvent Delivery System M45 with a Waters HPLC Differential Refractive Index Detector R401 (Millipore Corp., Mil­ford, MA). A Shodex Ionpack Column KC811 with an internal diameter of 8 mm and a length of 300 mm was used. The injected sample volume was 5 p,l. The column operating temperature was 75°C and the flow rate was 1 ml/min. HPLC-grade water containing 0.0018 H2S04 was used as the eluent.
A dilution factor of 2.60 was used to account for the dilution of samples which occurred during plasma sep­aration and protein precipitation. Results were ex­pressed as erythritol concentration (g/liter)
Sample preparation and HPLC processing proce­dures, such as adding the IS before the deproteinization step, were designed to avoid manipulation errors. The recovery of the IS in the final sample was calcu­lated based on the original amount of IS added to the sample. The percentage recovery was applied to the analytically determined erythritol levels to compensate for manipulation errors.

Urine erythritol concentration
Urine samples were frozen and stored at - 20°C for HPLC determination of erythritol content at a later time. After thawing, urine samples were rehomogenized and filtered through a 0.45-p,m filter. Samples of 0.5 ml were mixed with 0.25 ml of the IS before being placed in HPLC vials. The HPLC method was the same as described for the plasma erythritol determinations. Urine erythritol con­centration was expressed as g/liter and erythritol out­put as g/min.
Erythritol clearance (expressed as ml/min) was cal­culated as the ratio of erythritol excreted in urine dur­ing the 120- to 180- min period following ingestion to the mean plasma erythritol concentration during the same period. Plasma glucose levels (expressed in mmoll liter) were measured by a glucose oxidase method using the Beckman Analyzer II. Plasma insulin levels (expressed as mU/liter) were determined by a radioimmu­nological assay using dextrancharcoal separation (in­traassay variability = 6%). Plasma and urine creati­nine levels (expressed as Tmol/liter and mmol/liter, respectively) were measured using a kinetic colorimet­ric assay (Synchron CX3, Beckman). Creatinine clear­ance (expressed as mllmin) was calculated as the ratio of urine creatinine excreted for the 120- to 180- min period to the fasting plasma creatinine level.

RESULTS

Total erythritol intakes by the individual subjects are shown in Table 1. Intake ranged from 56 to 78 g per person, with a mean value of 64 g. Four of six subjects (three females and one male) described gastro­intestinal symptoms at the 24-hr follow-up examination. Two subjects reported diarrhea while the others reported abdominal cramping, discomfort, and flatu­lence.
Plasma glucose levels are shown in Fig. 1. Levels for insulin are shown in Fig. 2. The data indicate that nei­ther plasma glucose nor plasma insulin was affected by the ingestion of erythritol. Mean plasma erythritol lev­els are depicted in Fig. 3. An increase in plasma erythri­tollevels was observed over the first 30 to 40 min follow­ing ingestion, reaching a mean maximal value of approx­imately 2.2 mg/ml after 90 min. Two individuals (subjects 1 and 5) showed a plasma erythritol concentra­tion plateau of approximately 1.8 mg/ml after 90 min. The other four individuals showed a more pronounced elevation of plasma erythritol (approximately 2.3 mg/ ml) followed by a gradual decline. All subjects showed a tendency toward declining plasma erythritol levels 120 min following ingestion. By 180 min, comparable plasma concentrations (1.5 to 1.7 mg/ml) were reached in all subjects. Urinary volume following erythritol ingestion is shown in Table 2. Mean urinary erythritol concentrations are shown in Fig. 4. These data indicate that urine volume and erythritol levels reached a maximum during the period from 60 to 120 min after ingestion. Cumula­tive amounts of erythritol excreted in the urine for each period are shown in Fig. 5. The cumulative erythritol urinary excretion as a percentage oftotal ingested eryth­ritol is shown in Table 3. On average, 30% of ingested erythritol was excreted during the first 180 min. Mter 24 hr, approximately 78% of the total amount ingested was recovered in the urine. Individual values for erythri­tol and creatinine clearance for the period from ingestion to 180 min after ingestion are shown in Table 4. The mean erythritol clearance for the six subjects was 62.0 ± 2.8 ml/min. During the same period, creatinine clear­ance was 120.2 ± 12.3 ml/min.

PLASMA AND URINE KINETICS OF ERYTHRITOL AFTER ORAL INGESTION

Discussion
The results of the current study demonstrate that erythritol undergoes rapid absorption by the small intestine following single oral administration of 1g erythritol/kg body wt/day. Erythritol appeared in both plasma and urine within a few minutes of dos­ing. Plasma levels increased for up to 90 min after ingestion to reach a plateau after approximately 120 min, indicating a temporary balance between absorption and excretion. After 24 hr, close to 80% of the total amount of ingested erythritol was recovered in the urine. These findings compare well with the re­sults of previous metabolic studies in humans in which erythritol absorption was reported to range from 80 to 90% (Hiele et al., 1993; Noda et al., 1994). Renal clearance of erythritol was 62.03 mg/min, ap­proximately half the rate for creatinine, indicating tubular reabsorption of erythritol by the kidney. The relative renal excretion of erythritol may be com­pared to that of mannitol for which the ratio of excre­tion to that of creatinine is about 1 (Smith et al., 1940). Plasma and urine measurements of erythritol indicate a lack of metabolic change and no effect on glucose or insulin parameters. This indicates an over­all inertness.
Based on the high degree of intestinal absorption of erythritol, only small amounts appear to reach the colon. In this study, less than 20% of orally ingested erythritol would potentially have been available for fermentation by colonic microorganisms. In in vitro (INRA, unpublished report) or in vivo studies with humans (Hiele et al., 1993), erythritol is not fer­mented by gut microflora. Nevertheless, considering the potential energy value of short-chain fatty acids, the caloric value of erythritol was estimated to be ~0.4 kcal/g. The moderate gastrointestinal side ef­fects, which occurred in a few subjects, were consid­ered to be due to the extremely high liquid erythritol load (~60 g) used. These gastrointestinal effects were not observed when similar doses of erythritol were incorporated into food (Bornet et al., 1996).
The present study demonstrates that substantial amounts of erythritol are rapidly absorbed from the gastrointestinal tract following oral administration. Excretion also appears to occur rapidly, with only unchanged erythritol appearing in the urine. Eryth­ritol did not induce clinically significant changes in either plasma glucose or insulin concentrations de­spite being absorbed in large amounts. Based on these results, it can be concluded that erythritol has considerable potential as a low-calorie sugar substitute for use in food items for consumption by humans, including people with diabetes.

PLASMA AND URINE KINETICS OF ERYTHRITOL AFTER ORAL INGESTION

VIEW PDF ARTICLE