Even though fiber is considered a carbohydrate it doesn't raise blood glucose levels, and increased fiber intake has been shown to actually decrease glucose levels in people with diabetes. The recommended amount of fiber varies but all sources agree that 25 grams should be the minimum grams of fiber in a day. A large-scale analysis of medical research, published in the Journal of the American College of Nutrition recommends a range of 25 to 50 grams per day. Many people don't eat enough fiber.