Postprandial serum glucose, insulin, and lipoprotein responses to high- and low-fiber diets.

The effects of high-fiber (HF) and low-fiber (LF) meals on postprandial serum glucose, insulin, lipid, lipoprotein, and apolipoprotein concentrations of 10 hypercholesterolemic men were examined using a random-order, cross over design. HF and LF meals provided 15% of energy as protein, 40% as carbohydrate, and 45% as fat, 200 mg cholesterol/1,000 kcal, and 25 g fiber/1,000 kcal for HF or 3 g fiber/1,000 kcal for LF. Responses over a 15-hour period after multiple meals (MM) and over a 10-hour period after a single meal (SM) were compared. HF meals were associated with a significant reduction in postprandial serum glucose (P < .0005 after SM) and insulin (P < .0005 after SM). Serum free fatty acid (FFA) levels decreased significantly after MM and SM, but differences between HF and LF meals were insignificant. Although serum triglyceride responses did not differ significantly (ANOVA) between HF and LF meals, values were higher at 2 and 3 hours after a HF SM than after a LF SM and at 16 hours after HF MM than after LF MM. Although serum cholesterol values did not differ significantly (ANOVA) between HF and LF meals, values were higher after a HF SM than after a LF SM. Other subtle differences in responses of high-density lipoprotein (HDL) cholesterol, HDL2, and HDL3 concentrations were noted. These studies indicate that large increases in dietary fiber intake are accompanied by small changes in postprandial serum lipoprotein concentrations.

Lipid responses of hypercholesterolemic men to oat-bran and wheat-bran intake.

The hypocholesterolemic effects of oat bran (OB) have been recently challenged. To carefully document the hypocholesterolemic effects of OB, 20 hypercholesterolemic men admitted to a metabolic ward were randomly allocated to either OB or wheat bran (WB) for 21 d after a 7-d control-diet period. Control and treatment diets were designed to be identical in energy content and nutrients, differing only in the amount of soluble fiber. After 21 d, OB significantly decreased total cholesterol by 12.8% (P less than 0.001), low-density-lipoprotein cholesterol by 12.1% (P less than 0.004), and apolipoprotein B-100 by 13.7% (P less than 0.001) whereas WB had no significant effect. High-density-lipoprotein cholesterol and apolipoprotein A-I did not change significantly in either group. Serum triglycerides decreased by 10% in both groups but the decrease was only significant (P less than 0.04) in WB subjects. OB but not WB significantly reduced total cholesterol and other atherogenic lipoprotein fractions independent of other dietary changes.

Hypocholesterolemic effects of different bulk-forming hydrophilic fibers as adjuncts to dietary therapy in mild to moderate hypercholesterolemia.

Hypercholesterolemia is a significant risk factor for coronary heart disease, and the hypocholesterolemic effects of psyllium are well established. This placebo-controlled, parallel study compared psyllium with methylcellulose, calcium polycarbophil, and placebo as dietary adjuncts in treating mild to moderate hypercholesterolemia. Of 163 men and women recruited with serum cholesterol levels above 5.17 mmol/L (200 mg/dL), 105 completed 8 weeks of an American Heart Association step I diet and then augmented the diet with one of the fiber supplements for 8 additional weeks. Incremental differences from placebo for low-density lipoprotein cholesterol were -8.8% for psyllium, -3.2% for methylcellulose (not significant), and +8.7% for calcium polycarbophil; and for total cholesterol the differences were -4.3% for psyllium (not significant), -1.4% for methylcellulose (not significant), and +5.9% for calcium polycarbophil. Compliance was 94% to 96%, and only mild gastrointestinal side effects were observed. In managing mild to moderate hypercholesterolemia, methylcellulose and calcium polycarbophil provide little or no additional benefit, while psyllium significantly enhances the American Heart Association diet effects.