The Effect of Dietary Fiber on Glucose and Hormone Responses to a Mixed Meal in Normal Subjects and in Diabetic Subjects With and Without Autonomie Neuropathy

We investigated the effects of fiber on responses of blood glucose, serum insulin, gastric inhibitory polypeptide (GIP), and immunoreactive pancreatic glucagon (IRG) to ingestion of a mixed meal with and without added fiber (5 g guar and 5 g pectin) in 12 normal, healthy subjects and in 12 age-, sex-, and weight-matched non-insulin-dependent, maturity-onset diabetic subjects (NIDDM). Fiber markedly enhanced glucose tolerance in the normal subjects without a change in insulin or GIP but with a significant reduction in glucagon responses. Fiber also markedly improved glucose tolerance in the NIDDMs without changing insulin or GIP but with a significant reduction in the glucagon responses. The NIDDMs were divided into two groups of six subjects, with and without autonomic neuropathy (AN). In NIDDMs without AN, glucose tolerance was improved by fiber without a change in insulin, IRG, or GIP. In diabetic subjects with AN, glucose tolerance was not improved, although glucagon levels were lowered and insulin and GIP responses were unchanged. It appears, therefore, that fiber improves glucose tolerance by altering factors other than insulin. It seems also that autonomie nervous supply to the gastrointestinal tract is important in mediating the effect.