Dietary fiber refers to plant cell wall components that are not digestible by human or other mammalian digestive enzymes. However, they can be fermented, partly or fully, in the colon by bacterial enzymes.

Dietary fiber requirement can be meet by adopting a diet rich in plant origin foods including fruits, vegetables, legumes and grains.

It is a common knowledge that daily intake of fiber is a requirement for a healthy lifestyle. Based on experiments and observations on fiber and its associated health benefits, the US Food and Nutrition board has only Adequate Intake (AI) recommendations for total fiber.

However, the board finds no sufficient evidence to set the Estimated Average Requirement (EAR) or Dietary Recommended Allowance (RDA ) for fiber for all life stage groups. The Dietary Reference Intake (DRI) recommendation for total fiber is Adequate Intake (AI) only.

Adequate Intake is the daily average amount assumed to be adequate for healthy persons. Total fiber, in this context, refers to dietary fiber and functional fiber, fiber in the form of supplements proven to be as functional as fiber.

Table: Dietary Reference Intakes (DRIs), daily recommended average Adequate Intakes of total fiber for children and adults.

Age, gender, life stage group AI total fiber (grams/day)
0–6 mo Not determined
7–12 mo Not determined
1–3 years 19
4–8 years 25
9–13 years 31
14–18 years 38
Adult Men
19–30 years 38
31–50 years 38
51–70years 30
> 70 years 30
9–13 years 26
14–18 years 26
Adult Women
19–30 years 25
31–50 years 25
51–70years 21
> 70 years 21
Pregnant Women
14–18 years 28
19–30 years 28
31–50 years 28
Lactating Women
14–18 years 29
19–30 years 29
31–50 years 29

Note: Daily Reference Intakes (DRI) has been developed, since 1996 by the Food and Nutrition Board, Commission on Life Sciences, National Research Council, to replace the Recommended Dietary Allowance (RDA).


What is one dietary fiber serving? Examples one fiber servings of vegetables, fruits and whole grains?

Dietary fiber related links:
Total dietary fiber, soluble fiber, insoluble fiber content of foods
Definitions of dietary fiber food.
List of high fiber food: vegetables and fruits
List of low fiber foods

Dietary Reference Intakes source:

Institute of Medicine. 2005. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. National Academy Press. (Food and Nutrition Board, Institute of Medicine, National Academies).