Objective: The aim of our work was to carry out a randomized clinical trial with two diets, one enriched in fiber (total fiber 30 g and soluble fiber 4 g) to investigate the effect on lipid and glucose levels in healthy subjects.
Research design and methods: Fifty-three subjects were prospectively randomized to two groups (see Table 1). Group I received a diet with 10.4 g of fiber given as 1.97 g soluble fiber (pectins, gums and mucilages) and 8.13 g of insoluble fiber (hemicelullose, cellulose and lignins) and Group II received a diet with 30.5 g of fiber of which 4.11 g were soluble fiber and 25.08 g insoluble fiber. Prospective serial assessment of weight and nutritional intake (3 days written food records) were made. These determinations were performed at baseline and at 3 months. All enrolled subjects underwent the following examinations; fasting blood samples were drawn for measurement of total cholesterol, triglyceride concentrations and other lipid fractions, low density lipoprotein (LDL-cholesterol), high density lipoprotein (HDL-cholesterol), glucose, and insulin.
Results: Total calorie and fat consumption were lower than recommended in both groups (calories; group I 1633+/-417 kcal per day versus group II 1707.5 +/- 579 kcal per day:ns) and (fats; group I 73.4 +/- 22.7 g per day versus group II [72.6 +/- 28 g per day:ns), without differences in fatty acid intake profile. Total fiber intake did not reach that recommended in both diets but it was higher in group II ( 9.06 +/- 2.7 g per day versus 25.95 +/- 7.12 g per day: P < 0.05). Soluble fiber intake did not reach that recommended in both diets but it was higher in group II (1.7 +/- 0.58 g per day versus 3.5 +/- 0.96 g per day: P < 0.05). Body weight did not change in both groups during treatment. During treatment, in group II a significant change was detected from baseline in LDL-cholesterol and fasting glucose levels. LDL-cholesterol decreased by 12.8% (P < 0.05) and glucose decreased by 12.3% (P < 0.05). No statistical differences were detected among triglycerides, HDL-cholesterol, and insulin levels.
Conclusions: Modest increases in soluble fiber intake in healthy subjects improved LDL cholesterol and glucose levels.