Rate Of Carbohydrate Absorption Research Articles

Diet wars: from Atkins to the Zone. Who is right?

Diet wars: from Atkins to the Zone. Who is right?

Effect of carbohydrates on calcium absorption in premature infants.

Premature infants are susceptible to disease related to deficient dietary calcium intake. Studies in adults suggest carbohydrates can enhance calcium absorption. However, little is known about how carbohydrates affect calcium absorption in premature infants due to a lack of direct in vivo studies. We adapted the triple lumen perfusion method for use in premature infants to compare calcium absorption 36 mmol/L (1.44 g/L) in the absence and presence of either 70 g/L lactose or glucose polymers. 44Ca was added to determine endogenous calcium losses. Fourteen infants were studied (gestational age: 31 +/- 0.4 wk; study weight: 1590 +/- 105 g; mean +/- SEM). Calcium absorption from the glucose polymer solution was greater than that from the control and lactose solutions (0.17 +/- 0.05 mumol.min-1.cm-1 versus 0.04 +/- 0.04 and 0.008 +/- 0.045 mumol.min-1.cm-1, respectively). Calcium absorption correlated positively with water and carbohydrate absorption. The rate of carbohydrate absorption was greater from the glucose polymers than from the lactose solution (0.40 +/- 0.10 mg.min-1.cm-1 versus 0.22 +/- 0.06, respectively). Based upon 44Ca absorption, endogenous calcium loss appeared to account for less than 1% of total calcium flux. We conclude that glucose polymers, but not lactose, enhance calcium absorption in the premature infant, a fact that may be useful in formula design.

Development of Insulin Resistance in the Rat is Dependent on the Rate of Glucose Absorption from the Diet

The effect of long-term consumption of diets of different carbohydrate composition was investigated by feeding rats for up to 52 wk on diets in which the carbohydrate was either glucose, amylose or amylopectin. A glucose-based diet was included to examine the relationship between the rate of carbohydrate absorption from the diet and the development of insulin resistance. Insulin sensitivity was assessed by subjecting animals to an intravenous glucose tolerance test (IVGTT). Amylopectin-fed animals became progressively insulin resistant from 12 to 26 wk of feeding. The area under the plasma insulin curves in response to a glucose load (IVGTT) for these animals rose progressively from 15.1 ± 2.5 nmol/L·30 min at 8 wk to 45.8 ± 3.5 nmol/L·30 min (P < 0.001) at 26 wk of feeding. Amylose-fed animals did not exhibit insulin resistance until 26 wk of feeding when insulin secretion in response to a glucose load was 28.3 ± 0.9 vs. 14.6 ± 3.2 nmol/L·30 min at 16 wk of feeding (P < 0.005). Glucose-fed animals displayed insulin resistance after only 8 wk of feeding. At this time, the area under their plasma insulin curves was almost double that for amylose- or amylopectin-fed animals (P < 0.001). We conclude that long-term consumption of a diet in which available carbohydrate is rapidly absorbed causes insulin resistance in rats. The more rapidly glucose is absorbed from the diet, the faster the insulin resistance develops.

Metabolic response to beet fibre test meals

Test meals with 10.9 g dietary fibre from sugar beet and corresponding control meals were given to eight healthy subjects, aged 67 ± 9 years. The postprandial glucose, triglyceride, hormone and glycerol responses were monitored during 3 hours. After the beet fibre meal the insulin and C‐peptide areas were reduced by 28 (P &lt; 0.01) and 22% (P &gt; 0.025), respectively, and the somatostatin levels increased by approximately 30% (P &gt; 0.05). Further, the maximum relative postprandial reduction of plasma glycerol levels was less evident after the fibre‐rich meal than after the control meal (36 ± 4% v. 46 ± 4%, P &lt; 0.05). There was no apparent difference in the overall glycaemic response between the meals. The triglyceride levels were similar after both test meals.Suspension of beet fibre bread given to rats by oro‐gastric intubation induced lower blood glucose response than a control bread at 15 and 30 min (P &lt; 0.001), respectively, but a similar insulin response.The results suggest an effect of beet fibre on the rate of carbohydrate absorption, expressed as a lower insulin response in the healthy volunteers and a reduced glucose response in the rat.The mechanism behind this effect in healthy subjects could possibly be mediated by an increased somatostatin response.

Effect of diet on intestinal xylose absorption in dogs.

The absorption of xylose at different levels of the intestine was compared in five dogs receiving diets containing either wheat bran, polyethylene particles (PE), or horse-bean hulls. The absorption was determined by serial collection of the interstitial fluid (ISF) in different parts of the small intestine and colon, and blood concentration after the administration of D-xylose as a solution (0.5 g/kg body weight) into the duodenal bulb. Xylose was mostly absorbed from the duodenum, and its concentration in the duodenal ISF and in plasma was reduced on a diet containing fiber, irrespective of the nature of fiber. In contrast, a negative linear relation between the mean retention time of digesta in the small intestine and the amount of xylose absorbed by duodenum was evidenced (r = -0.843). The results indicate that changes in transit linked to the presence of fiber in a diet are a major operative factor in the rate of carbohydrate absorption. They suggest that the absorption can be affected by a relatively minor change in the intestinal transit of digesta.

Effect of a modified guar gum preparation on glucose and lipid levels in diabetics and healthy volunteers

Six healthy volunteers and 17 diabetics (6 insulin-dependent and 11 diet- and tablet-treated) were treated with a special processed, palatable guar gum (10 g b.i.d. immediately before meals) for periods of one or three weeks or, in some cases, up to 13 weeks. A standardized test meal was given to study the effect of the fiber on postprandial glucose levels. Ten g guar was stirred in water and taken immediately before the test meal. The postprandial blood glucose levels were similar in the healthy volunteers but significantly lower in the diabetics following treatment with guar for one and three weeks, respectively. Furthermore, the fasting blood glucose levels were significantly lower in the diabetics after three, but not one, weeks of treatment. The lower postprandial glucose levels were coupled with attenuated and delayed insulin levels in accordance with an effect of guar gum on the rate of carbohydrate absorption. The cholesterol levels were on average reduced with 14% in the diabetics following three weeks' treatment with guar. The higher the initial cholesterol level, the greater the reduction in cholesterol; 26% reduction was achieved in four patients with initial levels above 7 mM. The α-lipoprotein cholesterol levels were not significantly changed, thus an increase in the α-lipoprotein cholesterol/total serum cholesterol ratio was obtained. Neither plasma triglycerides nor body weights altered during treatment. The reported side-effects were as expected and were usually mild and transient (e.g. increased flatulence). The data show that guar gum also reduces postprandial glucose levels on a long-term basis and may improve the diabetic control. Additionally, treatment with this fiber leads to a concentration-dependent decrease in cholesterol levels.