Fruits and vegetables contain soluble and insoluble fiber in varying proportions. When you eat soluble fiber, it absorbs water to form a gel-like mass, which helps you feel full and provides other health benefits. It prevents a surge in blood sugar after you eat by slowing down the absorption of carbohydrates.
If the blood glucose level falls to dangerous levels (as in very heavy exercise or lack of food for extended periods), the Alpha cells of the pancreas release glucagon, a hormone whose effects on liver cells act to increase blood glucose levels.
Second Phase Insulin Release. It is this combination of a robust first phase insulin response followed by a functional second phase insulin response that keeps the blood sugar of a normal person from ever rising over 140 mg/dl(7.8 mmol/L) even after a high carbohydrate meal.