Soluble Fiber: Effect on Lipid and Glycemic Control

1. Cholesterol: 

• The updated NCEP guidelines recommend increasing daily intake of soluble fiber to 10-25 g/day as an option to enhance the LDL cholesterol-lowering efficacy of diet.      
• Increased intake of soluble fibers, such as those found in legumes, oats, guar gum, and those found in gel-forming dietary supplements can modestly lower serum LDL cholesterol without affecting serum triglycerides or HDL cholesterol levels. 
• For each 1g increase in soluble fiber intake a decrease in serum LDL cholesterol level of about 1-2 mg/dL can be obtained.
• Soluble fiber apparently lowers cholesterol levels by increasing bile acid excretion.

2.  Glycemic Control 

In patients with type 2 diabetes mellitus, a diet high in soluble fiber significantly improves glycemic and lipid control.  A diet high in soluble fiber (up to 25 g/day) produces significant improvements in preprandial plasma glucose concentrations, in mean daily urinary glucose excretion, and in the area under the curve for 24-hour plasma glucose and insulin concentrations.  The mechanism for the effect on glucose metabolism is not known.

3. Source of Soluble Fiber

Soluble fiber can readily be obtained from legumes, oats, fruits, vegetables and nuts. Good sources of soluble fiber are listed in the table below.

Source:  Schakel SF, Sievert YA, Buzzzard IM. In: Appendix I, Table 1, Dietary Fiber Values for Common Foods.  Spiller GA, Ed,  CRC Handbook of Dietary Fiber in Human Nutrition, 2nd Edition (CRC Press, Inc.: Boca Raton, 1993)

References

1. Brown L, Rosner B, Willett WW, Sacks FM.  Cholesterol-lowering effects of dietary fiber:  a meta-analysis.  Am J Clin Nutr 1999; 69: 30-42.
   
   Meta-analysis that concludes that for each 1g increase in soluble fiber intake, LDL cholesterol is lowered by ~2 mg/dL.
   
   
2. Chandalia M, Garg A, Lutjohann D, von Bergmann K, Grundy SM, Brinkley LJ. Beneficial effects of high dietary fiber intake in patients with type 2 diabetes mellitus. N Engl J Med 2000; 342: 1392-1398.
   
   A randomized, crossover, well-controlled study in 11 subjects with type 2 diabetes mellitus that compared moderate soluble fiber intake of 8 g/day versus high soluble fiber intake of 25 g/day from unfortified foods.  The study found significant improvements in lipid and glycemic control on the high soluble fiber diet.