Whole Foods:

Doses of 8-26 grams dietary fiber at a single meal or 30-50 grams of dietary fiber per day produced short and long term benefits on glycemic control. Sources of soluble fiber may be more effective in decreasing serum glucose than insoluble fiber.

These diets may also have beneficial effects on serum lipids, insulin sensitivity, and markers of inflammation in this population, however further study is required to identify specific recommendations for optimal dosage and types of fiber.

Fiber Supplements:

Doses of 6-19 grams of fiber supplements per meal or 10-29 grams of fiber supplements per day produced inconsistent short and long-term benefits on glycemic control. Soluble fiber supplements may be more effective in decreasing serum glucose than insoluble fiber. These studies are limited by the utilization of both soluble and insoluble fibers from several sources, some with combinations of sources within studies. Further study is required to identify specific recommendations for optimal dosage and types of fiber.

It is unclear at this time if fiber supplements have a beneficial effect on serum lipids in diabetes.

Conclusion:

Based on the current data, it would appear that diets providing 30-50g fiber per day from whole food sources consistently produce lower serum glucose levels compared to a low fiber diet. Fiber supplements provided in doses of 10-29 grams per day may have some benefit in terms of glycemic control.