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How Much Dietary Fiber Should We Eat?

How much fiber is there in the different foods we eat? And how much should we eat? Recent posts (Where Do I Get That Beneficial Gut Bacteria? and A Special Gut Microbe) stressed the importance of eating dietary fiber for various health benefits and to feed the beneficial bacteria (such as Faecalibacterium prausnitzii) in our gut. But how much should we be eating daily? Are there different types of fiber and does it matter?

Currently the average American adult eats about 12 to 18 grams of dietary fiber daily. But the latest advice (from both National Academy of Sciences and Academy of Nutrition and Dietetics) is to eat over 20 grams of dietary fiber daily to about 35 grams daily, depending on weight. So a person eating a 2000 calorie daily diet should have about 25 grams of fiber daily.Their recommendation for children is that intake should equal age in years plus 5 g/day (e.g., a 4 year old should consume 9 g/day). Good fiber foods are: fruits, vegetables, whole grains, legumes (beans), nuts, and seeds. But people eating a typical westernized diet are instead eating a high fat, high meat, highly processed food diet which neglects plant-based foods. Go look at the ingredient labels of favorite American foods and see that many don't have fiber or are low in dietary fiber (e.g., hot dogs, salami, candy, cookies, potato chips).

Dietary fiber or roughage is the indigestible portion of food derived from plants. There are two types of fiber: soluble and insoluble, and both should be eaten for good health because they benefit health in a number of ways. Insoluble fiber doesn't dissolve in water and passes through the intestines (it provides bulking), while soluble fiber dissolves in water, and becomes a gel. Plant foods contain both types of fiber in varying degrees, depending on the plant's characteristics. For example, plums and prunes have a thick skin covering a juicy pulp. The skin is a source of insoluble fiber, whereas soluble fiber is in the pulp. One can also take fiber supplements, but actual real foods have many more benefits to them, and also provide a variety of fiber sources. Eating a variety of whole plant-based foods is beneficial in many ways, including feeding the variety of bacteria species in your gut. Remember that different bacteria need different foods, and so eating a variety of foods is best.

To increase your daily dietary fiber intake, first take a look at the amount of fiber in different foods. And then eat lots of fruits, vegetables, whole grains, legumes (beans), seeds, and nuts. The following tables give approximate fiber amounts in some high fiber foods (NOTE: different sources give slightly different numbers):

Fresh & Dried Fruit  Serving Size Fiber (g)
 Apples with skin  1 medium 5.0
 Apricot  3 medium 1.0
 Apricots, dried  4 pieces 2.9
 Banana  1 medium 3.9
 Blueberries  1 cup 4.2
 Cantaloupe, cubes  1 cup 1.3
 Figs, dried  2 medium 3.7
 Grapefruit  1/2 medium 3.1
 Orange, navel  1 medium 3.4
 Peach  1 medium 2.0
 Peaches, dried  3 pieces 3.2
 Pear  1 medium 5.1
 Plum  1 medium 1.1
 Raisins  1.5 oz box 1.6
 Raspberries  1 cup 8.0
 Strawberries  1 cup 4.4
Grains, Beans (Legumes), Nuts, Seeds  Serving Size Fiber (g)
 Almonds  1 oz 4.2
 Black beans, cooked  1 cup 13.9
 Bran cereal  1 cup 19.9
 Bread, whole wheat  1 slice 2.0
 Brown rice, dry  1 cup 7.9
 Cashews  1 oz 1.0
 Flax seeds  3 Tbsp. 6.9
 Garbanzo beans, cooked  1 cup 5.8
 Kidney beans, cooked  1 cup 11.6
 Lentils, red cooked  1 cup 13.6
 Lima beans, cooked  1 cup 8.6
 Oats, rolled dry  1 cup 12.0
 Quinoa (seeds) dry  1/4 cup 6.2
 Quinoa, cooked  1 cup 8.4
 Pasta, whole wheat  1 cup 6.3
 Peanuts  1 oz 2.3
 Pistachio nuts  1 oz 3.1
 Pumpkin seeds  1/4 cup 4.1
 Soybeans, cooked  1 cup 8.6
 Sunflower seeds  1/4 cup 3.0
 Walnuts  1 cup 5.0
 Vegetables  Serving Size Fiber (g)
 Avocado (fruit)  1 medium 11.8
 Beets, cooked  1 cup 2.8
 Beet greens  1 cup 4.2
 Bok choy, cooked  1 cup 2.8
 Broccoli, cooked  1 cup 4.5
 Brussels sprouts, cooked  1 cup 3.6
 Cabbage, cooked  1 cup 4.2
 Carrot  1 medium 2.6
 Carrot, cooked  1 cup 5.2
 Cauliflower, cooked  1 cup 3.4
 Cole slaw  1 cup 4.0
 Collard greens, cooked  1 cup 2.6
 Corn, sweet  1 cup 4.6
 Green beans  1 cup 4.0
 Celery  1 stalk 1.1
 Kale, cooked  1 cup 7.2
 Onions, raw  1 cup 2.9
 Peas, cooked  1 cup 8.8
 Peppers, sweet  1 cup 2.6
 Pop corn, air-popped  3 cups 3.6
 Potato, baked w/ skin  1 medium 4.8
 Spinach, cooked  1 cup 4.3
 Summer squash, cooked  1 cup 2.5
 Sweet potato, cooked  1 medium 4.9
 Swiss chard, cooked  1 cup 3.7
 Tomato  1 medium 1.5
 Winter squash, cooked  1 cup 6.2
 Zucchini, cooked  1 cup 2.6

The tables were from