To evaluate selected metabolic effects of plant fibers, we fed control and oat-bran diets in an alternating sequence to eight men with previously documented hypercholesterolemia. The two solid diets differed only in the inclusion of 100 g of oat bran in the test diet. We randomized diet sequences and the measured intakes of carbohydrate, protein, fat, and cholesterol were virtually identical on the two diets. Serum total cholesterol concentrations were stable on control diets whereas a progressive reduction was observed in seven men on oat-bran diets. On oat-bran diets, average reductions in serum total cholesterol concentrations were 13% (p less than 0.01, N = 8); plasma low-density lipoprotein cholesterol concentrations were 14% lower (p less than 0.05) while high-density lipoprotein cholesterol concentrations were not changed. Fasting and postprandial serum glucose, insulin, and triglyceride concentrations were similar on the two diets. Fecal excretion of total bile acids was 54% higher (p less than 0.001) on oat-bran diets than on control diets but neutral steroid excretion was slightly lower while on oat bran. Palatable and inexpensive high-fiber foods such as oat bran may have a role in the treatment of certain patients with hypercholesterolemia.

Citrus pectin (15 g/day) was added for 3 weeks to metabolically controlled diets in nine subjects. Pectin was consumed with fruit and sugar as a gel in divided doses with meals. Plasma cholesterol concentrations were reduced by a mean of 13% (P less than 0.001). Fecal fat excretion increased by 44% (P less than 0.001); neutral steroids by 17% (P less than 0.001) and fecal bile acids by 33% (P less than 0.02). Plasma triglyceride levels did not change.

To identify diets that are more effective than existing ones in reducing lipoprotein-mediated risk of atherosclerotic heart disease, the serum lipids and lipoprotein response to three modified diets was studied in twelve normal men living in an institution. The "Western" reference diet (40% energy from fat, P/S ratio 0.27) was compared in Latin square design with a fat-modified diet (diet B, 27% energy from fat, P/S 1.0, reduced cholesterol content); with a fat-modified diet supplemented with fruit, vegetable, and cereal fibre (diet C); and with a diet providing 40% energy from fat, having P/S ratio 1.0 and supplemented by fibre (diet D). The effects of fat modification and fibre-supplementation (diets C and D) were strongly additive-a fall serum cholesterol by 24-29%, in low-density-lipoprotein (LDL) cholesterol by 31-34%, and in serum triglyceride by 21-26%; and the reduction, by diet C, of the ratio of serum cholesterol to high-density-lipoprotein (HDL)-cholesterol by 21%, and that of LDL-cholesterol to HDL2-cholesterol by 26%. The additive effects of multiple changes in nutrient intake, each moderate in extent, permits the design of diets which are remarkably effective in reducing serum-cholesterol level.

Summary. The influence of low and high fibre diets upon carbohydrate tolerance was examined in five maturity-onset, non-insulin dependent diabetics. After 14 days on a diet rich in natural fibre (30 g/ day), the subjects consumed a high fibre (13 g) test meal. They, then ate a low fibre diet (10 g/day) followed by a low fibre (1 g) test meal. Mean basal plasma glucose concentrations were similar after both fibre diets; however, both mean basal plasma insulin and gastric inhibitory polypeptide (GIP) were sigriificantly lower after the high fibre diet. After the high fibre test meal, significantly lower mean plasma glucose, insulin and GIP concentrations were measured. This study is the first study to demonstrate the ability of an institutionally supervised diet of natural foodstuffs rich in fibre to improve carbohydrate tolerance in maturity-onset, non-insulin dependent diabetics. This finding is relevant to the dietary management of diabetics.