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The metabolic effects of high-carbohydrate (70%), high-fiber (70 g) (HCHF) and low-carbohydrate (39%), low-fiber (10 g) (LCLF) diets were examined for 10 subjects with insulin-dependent diabetes mellitus (IDDM). After a 1-wk control period subjects on a metabolic ward were randomly allocated to HCHF or LCLF diets for 4 wk. After a 6-wk washout period subjects re-entered the metabolic ward for 4 wk on the alternate diet. Artificial-pancreas studies were performed on each diet for measurement of insulin requirements. Compared with the LCLF diet, the HCHF diet reduced basal insulin requirements (P less than 0.025), increased carbohydrate disposed of per unit insulin (P less than 0.0008), and lowered total (P less than 0.0004) and high-density-lipoprotein cholesterol (P less than 0.0013). Glycemic control and other lipid fractions did not differ significantly. These results suggest that in IDDM patients, HCHF diets enhance peripheral glucose disposal, decrease basal insulin requirements, and lower total cholesterol without altering glycemic control or triglycerides.

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.

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. ( Arch Intern Med . 1991;151:1597-1602)