What is fiber?
Fiber is plant matter that can't be digested by humans. It is basically the cell walls of plants. It makes up the structures that support the plant, gather water and sunlight, and protect its seeds. More or less, plants are made up of three things: water, carbohydrates that people can digest, and carbohydrates that people can't digest, namely fiber.
This fiber, or indigestible carbohydrate, is further classified as insoluble or soluble. Insoluble fiber is the stuff that wood is made out of: cellulose and lignin. Soluble fiber includes large sugar- and starch-like molecules, like polysaccharides and pectin.
Why eat fiber?
When modern civilizations process vegetable foods, they seek out the sugar and starch and protein: turning whole wheat and brown rice into white bread and white rice, peeling apples and potatoes, turning fruit into juice, turning beans into tofu. Along the way they remove and discard the fiber: the bran, the skins, the pulp, the gel, the big molecules that the human body never learned to break down into energy.
But these no-calorie, non-nutrient parts have health benefits of their own which are looking more important all the time. Not only does fiber regulate digestion, making people feel full and enabling the flow of digested matter through the body, but it absorbs toxins, feeds helpful microorganisms, reduces “bad” cholesterol, and fights diabetes, cancer, and heart disease.
Fiber content of different foods
The data below, from the USDA, includes many fruits, vegetables, and grain products that are high in fiber, plus a few that are less high in fiber but so low in carbohydrates or high in protein that they could be useful in a low carb/high protein diet.
Some fruits high in fiber
|Fruit||Fiber (grams)||Carbohydrates (grams)||Protein (grams)|
Some vegetables (and vegetable products) high in fiber
|Vegetable||Fiber (grams)||Carbohydrate (grams)||Protein (grams)|
Navy beans (cooked)
Kidney Beans (cooked)
Black Beans (cooked)
Green peas (cooked)
Winter squash (baked)
Refried beans (canned)
Brussels sprouts (cooked)
Tofu (firm, made with calcium sulfate)
Some fiber-rich cereals, seeds and grains
|Cereal, seed, or grain||Fiber (grams)||Carbohydrate (grams)||Protein (grams)|
General Mills Fiber One Bran Cereal
Kellogg's All-Bran Bran Buds
Wheat germ, raw
Post Shredded Wheat
Kellogg's Raisin Bran
Peanut butter, chunky
Pumpkin seed kernels
Whole wheat spaghetti (cooked)
Brown rice (cooked)
Health benefits of fiber
In the last few decades, nutritionists have realized that populations with traditional high-fiber diets are less subject to “diseases of affluence” like heart disease and diabetes than people on the refined-carbohydrate 20th-century Western diet.
Fiber seems to reduce cancer. Alice Bender, a nutritionist for the American Institute for Cancer Research, says it is likely that fiber-rich foods--either the fiber itself, or something else in these whole vegetable foods--reduce some kinds of cancer. “We know that a plant-based diet rich in fruits, nonstarchy vegetables, legumes, and whole grains is associated with a lower risk of a number of the most common cancers.”
"We don't dine alone, we dine with trillions of friends - we have to consider the microbes which live in our gut”
Prof. Jeffrey Gordon, Washington University School of Medicine
Relationship between fiber and microflora
Fiber may provide its more mysterious benefits to health by means of the microflora (bacteria and other microbes) in the human gut. Fiber feeds “trillions” of microorganisms living inside us, creatures that provide us with services we are just now beginning to appreciate. We can contain three to five pounds of these passengers. In fact, of the cells contained in the human body, only 10% are actually human: the other 90% are microbes of many kinds. The mix of microbe species changes with age and with diet. Babies are born with no bacteria in their gut, but quickly acquire them. People who eat a lot of carbohydrates have a different mix of species than those who eat a lot of meat. Obese people have a different mix than slender ones.
Many of these microorganisms can digest the soluble fiber components that people cannot. They live off this extra energy and in turn provide nutrition to human organs like the colon and liver. It’s beginning to appear that gut bacteria provide chemical signals that can affect mood and the immune system. These microbes have coevolved along with us and the plants we eat over millions of years; they belong with us, just like whole plants belong in our diet.
How much fiber do you need to eat?
Nutritionists recommend 25-30 grams a day; Americans eat about half that much. For children, nutritionists recommend five grams a day plus the child’s age.
Even though fiber is good for you, people say not to make a drastic increase in your intake, but to add whole foods gradually, to avoid digestive disruption. No doubt our trillions of gut bacteria need a few lifetimes (a few weeks?) to adapt to change in their world, even beneficial change.
Fiber in a high-protein, low-carbohydrate diet
Some people control their weight by shifting their diet to include more protein and less carbohydrate. But such dieters risk not getting enough fiber, because animal proteins--meat, milk, eggs--do not contain fiber, and "meat substitutes" made from tofu and gluten may or may not contain much. Here are some fiber sources that may be useful in such a diet:
- Nuts, for example sunflower seeds and almonds (high protein, high fiber, relatively low carbohydrate).
- Non-starchy green (or greenish) vegetables like artichokes, broccoli, cauliflower, cabbage, brussels sprouts, and okra (low carbohydrate, high fiber).
- Juicy or leafy vegetables like celery, greens, and tomatoes (low carbohydrate, high in water and fiber)
- High-fat fruits: avocados, coconut (low carbohydrate, high fiber)
Unless a low-carbohydrate diet is very strict, it should include the following whole, high-fiber foods in moderation:
- Fruit (contains carbohydrate, but better than sweets or soda)
- Beans (high protein, though relatively high carbohydrate)
- Whole grains (relatively high carbohydrate, but some protein, and better than white bread or rice)
People can add additional fiber to their diet with supplements like bran cereals or psyllium, although this runs the risk of missing micro-nutrients present in whole plant foods themselves. Or they can sprinkle ground flaxseeds on their food as a fiber supplement (the seeds are easier to digest if they are ground up).
This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.
Jenny Balaji on June 20, 2011:
Hi, I am 63yrs old, female, and have just been diagnosed with thyroid, borderline diabetes and cholestrol. I am on medication and since i had pain in my legs and have put on weight, I am feeling so much better . I would like to know what veggies and fruits I can really eat without thinking twice about calories etc. Please help me lead a good and healthy life from today onwards....Thanks
mabmiles on May 26, 2011:
Thanks for the list.
Multiman on March 06, 2011:
Good information, I have voted up and linked
JPSO138 from Cebu, Philippines, International on July 07, 2009:
This is very informative and helpful...
advisor4qb from On New Footing on June 30, 2009:
bookmarking this page!
S K G Rao. from Bangalore City - INDIA. on June 30, 2009:
Dear Mr.Paul Edmondson,
Please give Veg Diet for 73+ Male ( Diabetic )
What should be for:
3) Evening Snacks.
6) Early Morinng.
Must be South Indian Veg.
S K G RAO
ocbill from hopefully somewhere peaceful and nice on June 24, 2009:
I wonder what is more favorable fruits that are higherin fiber thanothers or fruits that have more anti-oxidants..fibrousruits takes out pollutants in the body and anti-oxidants helps combat them.. correct me if I am wrong.
Ethel Smith from Kingston-Upon-Hull on June 23, 2009:
Love kidney beans, and chick peas
Staci-Barbo7 from North Carolina on June 22, 2009:
Paul, my favorite is kidney beans, served with basmati rice and homemade sweet yogurt. The juice of the kidney beans makes a wonderful soup base, too.
I found a webpage of video notes for the video "GUESS WHO’S COMING TO DINNER IN THE NEW MILLENIUM - FIBRE," produced by Video Education Australasia. The article can be found at:
According to the video notes, "Cooking foods does not reduce their fiber content, but cooking does make some foods more palatable and digestible. Much of the fiber is in the skins of fruit and vegetables."
It seems reasonable to me that you can't destroy fiber in food, so long as one can still CONSUME essentially the same amount of food (minus water loss) after all the soaking, boiling, poaching, baking, blanching, broiling, sauteeing, fricaseeing, stir frying, deep frying, skewering, and barbecuing!
Paul Edmondson (author) from Burlingame, CA on June 22, 2009:
I think cooking vegetables takes out some of the good stuff in them, but I don't know what the reduction value is, but isn't fiber non digestable. It seems to reason, although I don't know, that cooking them would increase the percentage of fiber.
gredmondson on June 22, 2009:
I am so surprised that raspberries are so high in fiber! I wonder if raw foods, such as carrots, have the same fiber content cooked.
RVDaniels from Athens, GA on June 22, 2009:
Heathy and tastes good too! Thanks.