What is the daily requirement for fiber?
The Institute of Medicine, an agency that advises the federal government on health and science, recommends for adult women under the age of 50, 25 grams of fiber a day, and for men 38 grams of fiber a day. Over the age of 50, the requirements are 21 grams of fiber a day for women and 25 grams of fiber for men. The reason the requirement goes down with age is a function of calorie needs being less as we get older.
For children up to the age of 18, there is a formula: it is the child's age plus 5 (in grams).
Why aren't most Americans meeting these requirements?
People often assume that they can only get fiber from fruits and vegetables, and they find that to be incredibly inconvenient. People don't necessarily have fruits and vegetables in their desk drawer, so they're not getting the fiber that they need.
The other reason is that, in terms of other fiber-containing foods, people aren't always opting for a whole-grain bread or cereal, although they are available. And they aren't eating things like beans and nuts, which are sources of fiber as well.
What is the difference between soluble and insoluble fiber?
Insoluble fiber foods pull water into the body in the intestines, so they tend to make the stool a little more bulky and therefore things move through the gastrointestinal tract more quickly. So the primary role insoluble fiber plays is in promoting bowel regularity, by moving things through the gut.
