Answer to Question 1
Answers may vary. The Institute of Medicine recommends that adults consume at least 14 g of dietary fiber per 1,000 kcal. The average daily intake of fiber in the United States is about half this amount. Most experts agree that a diet high in fiber is beneficial to one's health and carries minimal adverse effects. While some fibers may have a tendency to bind minerals such as calcium, zinc, iron, and magnesium, it is doubtful that the consumption of dietary fiber in recommended amounts affects mineral status in healthy adults. A sudden and/or large increase in fiber intake may cause a gastrointestinal problem such as diarrhea or constipation. As such, a person should increase his or her fiber intake gradually and give the body time to adjust. It is also wise to increase fluid intake as one increases fiber-this can help alleviate common problems such as constipation.
Answer to Question 2
Answers may vary. Insulin is capable of communicating only with cells (e.g., those in adipose tissue and skeletal muscle) that have built-in receivers located on the surface of their outer membranes. These receivers, referred to as insulin receptors, bind insulin, in turn signaling the cell to take up glucose from the blood. Once it is inside the cell, glucose can be used as a source of energy (adenosine triphosphate).Insulin has other far-reaching effects in the body. For example, insulin promotes the storage of excess glucose as glycogen in liver and skeletal muscle cells. This is often important after a meal when there may be more glucose available than what is needed by the body. However, only small amounts of glucose can be stored this way. Once this limit is reached, glucose is redirected to metabolic pathways that convert it to fat. Unlike glycogen storage, the body has a seemingly endless capacity to store body fat. In addition to stimulating the storage of excess glucose as glycogen and fat, insulin also plays an important role in the preservation of muscle protein. All of these actions work together to help bring blood glucose levels back down to normal-an excellent example of how the body maintains glucose homeostasis.