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.

Ten different dietary fibers have significantly different effects on serum and liver lipids of cholesterol-fed rats.

The comparative effects of 10 different dietary fibers on serum and liver lipids were investigated by feeding male Sprague-Dawley rats diets containing 10 g cholesterol + 2 g cholic acid/kg diet, with 60 g fiber/kg diet. Diets were fed for 3 wk; cellulose was the control fiber. Rats fed psyllium (rich in soluble fiber) had the lowest serum and liver cholesterol concentrations. Rats fed other soluble fiber-rich fibers (oat gum, guar gum and pectin) also had significantly lower serum and liver cholesterol concentrations than rats fed cellulose. Although feeding diets containing both soluble and insoluble fibers (soybean fiber and oat bran) did not significantly alter serum cholesterol, liver cholesterol values were significantly lower than those of cellulose-fed rats. Rats fed rice bran, predominantly an insoluble fiber source, had significantly higher liver cholesterol and significantly lower body weight gains and serum triglyceride concentrations than cellulose-fed rats. Values for serum and liver cholesterol were similar for rats were fed insoluble-rich fibers (corn bran, cellulose and wheat bran). These observations indicate that feeding dietary fibers rich in soluble fiber produces lower serum and liver cholesterol concentrations than does feeding commonly available sources of water-insoluble fiber.

Cholesterol-lowering effects of psyllium-enriched cereal as an adjunct to a prudent diet in the treatment of mild to moderate hypercholesterolemia.

Psyllium hydrophilic mucilloid, rich in soluble fiber, significantly lowers serum cholesterol concentrations. To investigate the lipid-lowering effects of a ready-to-eat cereal enriched with psyllium, we studied 44 hypercholesterolemic ambulatory individuals for 7 wk, using a randomized, double-blind, parallel design. After a 1-wk baseline period, subjects were randomly assigned to consume 114 g/d of a psyllium-flake or wheat-bran-flake cerearl for 6 wk adjunctive to an American Heart Association Step I diet. Serum high-density-lipoprotein cholesterol and triglycerides remained unchanged throughout the study; however, serum cholesterol and low-density lipoprotein (LDL) concentrations were significantly lower on psyllium than on wheat-bran cereal. Additionally, serum total and LDL cholesterol values were significantly lower than baseline values in the psyllium group. The dietary nutrient intake of the two groups did not differ except for soluble fiber. Adding psyllium-enriched cereal to a prudent low-fat diet may enhance dietary management of hypercholesterolemia.