Everyone, including people with diabetes, should eat a wide variety of foods that contain fiber—with a goal to consume at least 20–35 g of dietary fiber each day. Fiber is a type of carbohydrate that is not broken down during the digestion process.
Some studies show that a diet high in soluble fiber—found in oats, oat bran, legumes, barley, citrus fruits, and apples—can lower blood glucose and blood cholesterol levels. Insoluble fiber—found in whole wheat, wheat bran, vegetables, and fruit—can help prevent constipation. Both types of fiber are needed in a healthy diet.
Experts aren't sure exactly how fiber lowers blood glucose levels. It's possible that fiber slows the digestion of food and delays the breakdown of carbohydrates, which means that glucose enters the bloodstream more gradually. The resulting slower rise in blood glucose after a meal gives insulin a greater opportunity to convert the glucose into energy.