fiber

Foods Richest in fiber

About fiber

Basic description

Scientific understanding of dietary fiber has expanded dramatically in the past decade. Debates continue about how “fiber” should be defined and which substances qualify. Before examining these complexities, the basic WHF Recommendations for fiber are as follows.

Recommendations for fiber

Food groups richest in fiber include Beans & Legumes, Vegetables, Fruits, Grains, and Nuts & Seeds. Because each group provides different proportions of insoluble/soluble fiber, viscous/non-viscous fiber, and fermentable fiber, optimal intake requires drawing from all five groups. This goal can be approached on a weekly basis or within shorter timeframes.

A second goal is meeting a minimum recommended intake level for fiber. The WHF recommendation matches the FDA’s Daily Value (DV) of 25 grams, though this should be considered a floor rather than an optimum. Public health organizations have not set upper limits on fiber recommendations. Health benefits have been associated with intake levels three to four times the DV in individuals routinely consuming these amounts from whole, natural foods, with no evidence of adverse effects. The Healthiest Way of Eating Plan averages 52 grams of daily fiber, double the Daily Value.

Key features of fiber

Before examining current debates, some foundational facts about fiber remain universally accepted.

First, fiber has always been recognized as a plant-based nutrient. To make a simple comparison, plants have fiber in the same way that animals have muscles and bones. Fiber allows plants to maintain their shape and structure. And even though fungi (including mushrooms) are classified by scientists as belonging to their own separate category of living things, we would want to include them alongside of plants in this fiber discussion since they often contain chitooligosaccharides (CHOS) which most researchers consider a type of fiber. Although not widely popular in the U.S., there are other non-plant foods that contain CHOS and would be considered by many researchers as non-plant sources of fiber. Insects would be the largest single group here, followed by crustaceans like shrimp, crab, and lobster. While these last three crustaceans can be popular foods in the U.S., their CHOS content is not usually consumed because it is found in their outer shells which typically aren’t consumed. At WHF, the bottom line here is simple: for most U.S. eaters, plant foods (and fungi like mushrooms) are going to be your exclusive whole, natural food sources of fiber.

Second, fiber does not digest in the same way that most other nutrients digest. Most nutrients undergo full digestion as they get chewed, chemically transformed in our stomachs, and then combined with enzymes and digestive fluids in our small intestine. This combination of chewing plus digestive fluids plus digestive enzymes is usually sufficient to allow our bodies to digest and absorb nutrients from food. In the case of fiber, however, the above processes do not substantially alter the fiber’s basic nature. Fiber passes all the way through our stomach and small intestine and then proceeds on to our large intestine, still largely recognizable as dietary fiber. Our chewing and digestive fluids and enzymes are not enough to dramatically change it. It is only in the last portion of our digestive tract—our large intestine—that fiber can undergo a major transformation; if this transformation occurs, it is not brought about by human enzymes or human digestive fluids but rather by trillions of bacteria living in our large intestine.

Current issues in fiber research

Given these two basic distinctions that are fully embraced by all researchers, how has fiber become such a complicated nutrient to define? First, most scientists like to define nutrients according to their chemical structure. Their confidence in the nourishment provided to us by a vitamin like vitamin C is closely related to their ability to define vitamin C in chemical terms (i.e., a 6-carbon molecule with the chemical formula C6H8O6). The fact that vitamin C functions as an antioxidant is not regarded as a defining characteristic of vitamin C, since many nutrients function as antioxidants. So scientists tend to rely on definitions involving chemical structure. But researchers also know that a simple chemical formula is not possible when it comes to fiber. From a chemistry standpoint, fiber is structurally diverse, and this diversity has made fiber more difficult than other nutrients for researchers to define and universally adopt.

Second, while some of the health benefits of fiber are unrelated to its bacterial breakdown in the large intestine, many important benefits from this nutrient depend on its transformation by bacteria. As you might imagine, with literally trillions of bacteria in our large intestine and as many as 1,000 different species, interactions between any substance and bacteria can be difficult to predict. So it can be difficult to conclusively determine if a substance should be classified as a fiber based on any function that it might serve following transformation by bacteria.

Most common classification systems for fiber

Soluble versus Insoluble Fiber.

However, there are also some important disadvantages to this simple classification system. First, it is possible for fibers to have soluble and insoluble components. In this case, the distinction tends to be less helpful. Second, the vast majority of foods providing fiber not only contain both soluble and insoluble types, but they often contain both in nutritionally significant amounts. So this distinction isn’t always helpful in making food choices. Third, these two categories are often insufficient to account for important health benefits. For example, within the soluble fiber group can be found both viscous and non-viscous soluble fiber. Viscous soluble fibers are gel-forming and much more closely associated with cardiovascular and blood-sugar regulating benefits than non-viscous soluble fibers. So as you can see, even though this distinction between soluble and insoluble makes sense and has value, it has seemed less helpful over time as researchers learn more and more above fiber and try to determine the best way to obtain optimal benefits from fiber-containing foods.

Dietary reference intake (DRI) classification system

In 2005, the National Academy of Sciences (NAS) updated its classification system for fiber to include three basic categories: Dietary Fiber, Functional Fiber, and Total Fiber. Since the Total Fiber category was simply a combination of the first two categories, we will focus on those first two. The NAS described Dietary Fiber as fiber naturally found in plants in an intact form. By contrast, they described Functional Fiber as fiber that could naturally be found in plants, but could also be synthesized. In addition, they noted that while Functional Fiber could naturally be found in plants, it should not be placed in this category unless it has been isolated from its natural plant context through food processing. This contrast between Dietary Fiber and Functional Fiber makes sense to us if the goal is to look comprehensively at fiber with an approach that includes processed foods and dietary supplements. There are a large number of foods to which fiber has been added during processing, as well as numerous dietary supplements containing fiber.

However, a complication with this fiber classification system involves the inclusion of most fiber types in both categories. For example, some resistant starch falls into the Dietary Fiber category, and other resistant starch falls into the Functional Fiber category. The same is true for other fiber types, including oligosaccharides, pectins, gums, and lignin. So this classification can be confusing in this regard. In addition, since we only focus on whole natural foods at WHF, Functional Fiber (as defined by the NAS) would not be present in any of our foods, since it requires isolated fiber rather than intact, whole food fiber.

Fermentable Carbohydrate: You can find this term being used more and more often to refer to fiber. It is a term that simply refers to the ability of fiber to pass through our stomach and small intestine without being broken apart by digestive fluids and digestive enzymes, and to make it all the way to our large intestine where bacteria can “ferment” it into other substances. “Ferment” in this context simply means metabolize it into other forms. The category of fermentable carbohydrate is a great way to focus on the role of fiber in supporting balanced bacterial populations in our large intestine, but it does leave aside the other many valuable health-support roles of this nutrient.

European food safety authority (EFSA) system

The EFSA system contains four basic categories of fiber based on its chemistry. From our perspective, this approach does a good job of explaining the full range of substances that can be considered as types of fiber. We would also note that all of the fiber types in the EFSA system can be found in whole, natural foods. We use this classification system for thinking about the fiber content of our foods, and have found it helpful in putting fiber research studies into context. The chart below summarizes the EFSA categories and specific types of fiber belonging to each category.

Types of fiber

Non-Starch Polysaccharides (NSP)

Resistant Oligosaccharides

Resistant Starches

Lignin*

celluloses

fructo-oligosaccharides (FOS)

numerous dextrins

hemicelluloses

galacto-oligosaccharides

numerous maltodextrins

pectins

chito-oligosaccharides (CHOS)

some high-amylose starches

hydrocolloids (gums, mucilages, beta-glucans)

*There is only one basic molecule with a single uniform structure called “lignin,” even though its three basic components (three different cinnamyl alcohols) vary in their proportion.)

Our recommendation for obtaining fiber from all five major fiber-containing food groups (Beans & Legumes, Vegetables, Fruits, Grains, and Nut & Seeds) is largely based on distribution of the ESFA fiber types throughout these five groups.

Role in health support

Optimal food passage through the digestive tract

Food consumed in the past day moves slowly through the digestive tract. Between the small and large intestine, digesta must travel more than 25 feet, a process that takes 24-72 hours depending on fiber content, hydration, and individual physiology.

This transit is controlled by coordinated peristaltic contractions, which are partly triggered by mechanical distension of the intestinal wall. The volume of food in the intestinal lumen directly influences the rate and force of peristaltic movement.

Insoluble fiber plays a unique role in this process. Because it cannot be broken down in the small intestine, and because it has the ability to attract water to it, insoluble fiber can help control the consistency of food in our digestive tract as well as the pace at which it passes through. (To put the result in everyday terms, it can help with “regularity.”) However, viscous soluble fiber also has a role to play in this process, alongside of the role played by insoluble fiber. This second type of fiber helps control the “thickness” of your food as it gets digested. It’s especially important when food is in our stomach because it can help pace and regulate the passage of food out of our stomach and along to our small intestine. This moment in the digestive process is called “gastric emptying,” and soluble, viscous fiber is known to help slow gastric emptying, as well as helping keep it on a steady pace. Since rate of gastric emptying is related to our blood sugar and blood insulin balance, you can see how helpful soluble viscous fiber can be in steadying the amount of food that begins its passage through the intestinal tract at any one moment in time.

Cardiovascular benefits including improved cholesterol metabolism

Numerous cardiovascular benefits are associated with fiber intake, but we will start with one of the best-documented benefits: improved control of blood cholesterol levels. Viscous soluble fiber is able to bind with cholesterol in the intestine and prevent its uptake into the body by allowing it to be eliminated in the stool. The most viscous fibers—including the beta-glucans found in barley, oats, sea vegetables, shiitake mushrooms, and other foods, as well as the pectins found in the skins of cherries, grapes, berries, citrus fruits, and other foods—have all been shown to have blood cholesterol-lowering effects. Soluble fibers, and especially viscous soluble fibers, appear to be the best type for blood cholesterol benefits. It’s important to note that in addition to the foods rich in pectins and beta-glucans listed above, there are other foods also provide substantial amounts of soluble fiber, including soluble fiber with varying degrees of viscosity. In this extended list would be included numerous other fruits and vegetables. Choosing fiber-rich fruits and vegetables is usually going to helpful in getting the cholesterol-lowering effects of soluble fiber.

Improved cholesterol levels, however, are not the only cardiovascular benefit provided by food fiber. Blood pressure reduction has also been associated with fiber intake, as has reduced overall risk of high blood pressure (hypertension). Overall cardiovascular disease risk, including risk of atherosclerosis and coronary heart disease specifically, has been shown to decrease in association with adequate fiber intake.

Stabilization of blood sugar

A number of research teams have been able to demonstrate that the addition of high-fiber foods to a regular meal not already rich in fiber can improve blood sugar control if done on a consistent basis over a period of weeks (and in some cases months). In addition, studies on blood sugar problems in whole populations have shown better blood sugar control when healthy levels of fiber are consumed. In other words, fiber-rich meals can help most of us regulate our blood sugars in a healthier way. Interestingly, some studies also show that the blood sugar benefits of a fiber-rich meal can often extend throughout the day, even after a second or third meal is eaten. As an example, a fiber-rich breakfast might be able to help us steady our blood sugar levels even after eating lunch or dinner. So you can see how the meal-by-meal benefits of fiber-rich founds can overlap and help establish a steady, ongoing healthy basis for blood sugar balancing.

As mentioned earlier, part of the blood sugar-balancing benefits of fiber come from the special ability of soluble, viscous fiber to impart a slow release of food from the stomach (called gastric emptying). But blood sugar benefits from soluble fiber go even further. High-fiber meals significantly increase production of a hormone called glucogon-like peptide 1 (GLP-1), a hormone known to reduce blood sugar levels. Interestingly, one research group has also suggested that this GLP-1 response gets triggered not directly by the presence of soluble fiber, but by the products of fiber fermentation by bacteria in the large intestine. So you can see how the blood sugar benefits of fiber may involve several different factors. It is also important to note that risk of adult onset, type 2 diabetes and insulin resistance have also been found to decrease with healthy fiber intake.

Maintenance of colon health

There are two key ways in which fiber helps to maintain colon health. “Colon” in this context simply means all of our large intestine. Both ways involve the bacteria that live in our large intestine.

A first way that we see fiber helping to maintain colon health is by directly acting as fuel for the growth of “friendly” bacteria. Some of the bacterial species in our gut are so specialized that they can digest specific subtypes of fiber. For example, some species of Bacteroides break down hemicellulose as their primary fuel source, while others in the same class (bacteria that share 96% of their DNA) break down pectins as their main fuel. The reason that bacteria can digest nutrients that humans cannot comes down to their production of very specialized enzymes. In other words, there is a very intimate and mutually supportive relationship between fiber in our diet and populations of bacteria in our large intestine. These bacteria do best when our fiber intake is best, and our colon stays healthiest when these bacterial populations are thriving and in balance.

The second way that fiber helps support colon health is also related to bacterial digestion of fiber. As food fibers are digested in the large intestine by bacteria, their metabolism can provide the short-chain fatty acids (SCFAs) that cells along the large intestinal wall use as a fuel source. SCFAs—and in particular, one SCFA called butyrate—are critical for colon health because they provide cells that form the lining of the colon with the fuel they need to carry out their metabolic activities. In addition to this key support of normal intestinal function, healthy intake of fiber has also been associated with reduced risk of colon cancer.

Summary of food sources

An important point to remember about WHF and fiber is the fact that nearly three-quarters of our foods rank as good, very good, or excellent sources of this nutrient! Except for our animal foods, you will find ranked sources of fiber in all of our food groups, and in our Herbs & Spices as well. Fiber is a showcase nutrient for most any plant-based meal plan, and our WHF meal plans are no exception.

For the sheer total amount of fiber available from any single food group, it would be difficult not to place Beans & Legumes at the top of the list. If you measure our WHF strictly on the percent of the Dietary Reference Intake/Daily Value that they provide, all of our top 10 fiber-rich foods except one (barley) belong to the Beans & Legume food group. Of course, this approach does not factor in nutrient-richness and the number of calories provided by each bean serving. But even when calories and our full rating system approach is used for evaluation, Beans & Legumes still account for half of our top 10 foods.

A one-cup serving of most beans will contain approximately 10-20 grams of fiber and often provide at least half of our daily minimum recommended amount. In addition, beans contain both soluble and insoluble fiber, often at a ratio of about 1 gram of soluble to 3 grams of insoluble.

Our nutrient-richness rating system approach also places three vegetable greens—collard, turnip, and beet greens—in our top five fiber-rich foods. While you will not get 10-20 grams of fiber per serving, you will still get about 5 grams of fiber per serving and at a much lower cost in terms of calories. To give you one simple comparison, 15 grams of fiber from pinto beans will cost you about 240 calories out of your daily calorie total, and 15 grams of fiber from collard greens will cost you about 63 calories. Of course, both of these outstanding foods provide you with a wide variety of nutrients that extend far beyond fiber.

We also see whole grain foods contributing sizable amounts of dietary fiber. Grains tend to contain about five to ten grams of fiber per 1 cup serving. This food group tends to favor insoluble fiber, often with a ratio of insoluble to soluble fiber of 4:1 or sometimes greater. Oats are an exception here, with a somewhat evenly balanced ratio of the two fiber types.

Collard greens, turnip greens, and beet greens are by no means alone in providing rich amounts of fiber within the vegetables group. Other standout vegetables included in our top 25 fiber-rich foods are green peas, winter squash, broccoli, spinach, Brussels sprouts, green beans, and cabbage. Fruits also appear on our top 25 list. Within the fruit group, raspberries, pears, and cranberries are our top fiber-rich foods.

As mentioned earlier, it would be wrong to omit Nuts & Seeds as a fiber-rich group of foods. From this group we have flaxseeds in our top 25, but receiving rankings of a good source are sesame seeds and almonds.

Finally, it is important to remember that Herbs & Spices can also contain valuable amounts of fiber. Cinnamon would be a special standout here.

Let’s build a sample diet that draws on a variety of food groups for outstanding fiber results. For breakfast, we’ll start with granola with fresh fruit This choice will start the day with 9 grams of fiber. This combination will also provide us with valuable amounts of both soluble and insoluble fiber. For lunch, we’ll have black bean chili, a recipe that contains nearly 26 grams of fiber per serving. We’ll enjoy it with a pear to temper the heat from the spicy chili, and to provide another 5 grams of fiber.

For dinner, we’ll make baked miso salmon. For side dishes, let’s add 5-minute Brussels sprouts and warm quinoa salad. This meal will give us a variety of different fiber sources from the vegetables, grains, and herbs and spices. The 29 grams of fiber this meal will bring our fiber total to nearly 70 grams for the day!

Nutrient rating chart

Introduction to nutrient rating system chart

Read more background information and details of our rating system

WHF ranked as quality sources of
fiber

Food

Serving
Size

Cals

Amount
(g)

DRI/DV
(%)

Nutrient
Density

World’s
Healthiest
Foods Rating

Raspberries

1 cup

64.0

7.99

29

8.0

excellent

Collard Greens

1 cup

62.7

7.60

27

7.8

excellent

Turnip Greens

1 cup

28.8

5.04

18

11.2

excellent

Navy Beans

1 cup

254.8

19.11

68

4.8

very good

Dried Peas

1 cup

231.3

16.27

58

4.5

very good

Lentils

1 cup

229.7

15.64

56

4.4

very good

Pinto Beans

1 cup

244.5

15.39

55

4.0

very good

Black Beans

1 cup

227.0

14.96

53

4.2

very good

Lima Beans

1 cup

216.2

13.16

47

3.9

very good

Tempeh

4 oz

222.3

12.00

43

3.5

very good

Wheat

1 cup

151.1

8.19

29

3.5

very good

Green Peas

1 cup

115.7

7.58

27

4.2

very good

Winter Squash

1 cup

75.8

5.74

21

4.9

very good

Pear

1 medium

101.5

5.52

20

3.5

very good

Broccoli

1 cup

54.6

5.15

18

6.1

very good

Cranberries

1 cup

46.0

4.60

16

6.4

very good

Spinach

1 cup

41.4

4.32

15

6.7

very good

Beet Greens

1 cup

38.9

4.18

15

6.9

very good

Brussels Sprouts

1 cup

56.2

4.06

15

4.6

very good

Green Beans

1 cup

43.8

4.00

14

5.9

very good

Cabbage

1 cup

43.5

3.90

14

5.8

very good

Swiss Chard

1 cup

35.0

3.67

13

6.7

very good

Asparagus

1 cup

39.6

3.60

13

5.8

very good

Carrots

1 cup

50.0

3.42

12

4.4

very good

Strawberries

1 cup

46.1

2.88

10

4.0

very good

Mustard Greens

1 cup

36.4

2.80

10

4.9

very good

Cinnamon

2 tsp

12.8

2.76

10

13.8

very good

Fennel

1 cup

27.0

2.70

10

6.4

very good

Cauliflower

1 cup

28.5

2.68

10

6.0

very good

Kale

1 cup

36.4

2.60

9

4.6

very good

Summer Squash

1 cup

36.0

2.52

9

4.5

very good

Eggplant

1 cup

34.6

2.47

9

4.6

very good

Tomatoes

1 cup

32.4

2.16

8

4.3

very good

Romaine Lettuce

2 cups

16.0

1.97

7

7.9

very good

Chili Peppers

2 tsp

15.2

1.88

7

7.9

very good

Bell Peppers

1 cup

28.5

1.85

7

4.2

very good

Bok Choy

1 cup

20.4

1.65

6

5.2

very good

Black Pepper

2 tsp

14.6

1.47

5

6.5

very good

Cloves

2 tsp

11.5

1.42

5

7.9

very good

Celery

1 cup

16.2

1.40

5

5.6

very good

Garbanzo Beans

1 cup

269.0

12.46

45

3.0

good

Kidney Beans

1 cup

224.8

11.33

40

3.2

good

Barley

0.33 cup

217.1

10.61

38

3.1

good

Soybeans

1 cup

297.6

10.32

37

2.2

good

Avocado

1 cup

240.0

10.05

36

2.7

good

Rye

0.33 cup

188.5

8.42

30

2.9

good

Sweet Potato

1 cup

180.0

6.60

24

2.4

good

Quinoa

0.75 cup

222.0

5.18

19

1.5

good

Papaya

1 medium

118.7

4.69

17

2.5

good

Buckwheat

1 cup

154.6

4.54

16

1.9

good

Apple

1 medium

94.6

4.37

16

3.0

good

Olives

1 cup

154.6

4.30

15

1.8

good

Oats

0.25 cup

151.7

4.13

15

1.8

good

Flaxseeds

2 TBS

74.8

3.82

14

3.3

good

Potatoes

1 cup

160.9

3.81

14

1.5

good

Blueberries

1 cup

84.4

3.55

13

2.7

good

Beets

1 cup

74.8

3.40

12

2.9

good

Oranges

1 medium

61.6

3.14

11

3.3

good

Banana

1 medium

105.0

3.07

11

1.9

good

Onions

1 cup

92.4

2.94

11

2.0

good

Pineapple

1 cup

82.5

2.31

8

1.8

good

Kiwifruit

1 2 inches

42.1

2.07

7

3.2

good

Corn

1 each

73.9

1.85

7

1.6

good

Mushrooms, Shiitake

0.50 cup

40.6

1.52

5

2.4

good

Figs

1 medium

37.0

1.45

5

2.5

good

Grapefruit

0.50 medium

41.0

1.41

5

2.2

good

Cantaloupe

1 cup

54.4

1.34

5

1.6

good

Leeks

1 cup

32.2

1.04

4

2.1

good

Parsley

0.50 cup

10.9

1.00

4

5.9

good

Turmeric

2 tsp

15.6

0.93

3

3.8

good

Miso

1 TBS

34.2

0.93

3

1.7

good

Plum

1 2-1/8 inches

30.4

0.92

3

1.9

good

Oregano

2 tsp

5.3

0.85

3

10.3

good

World’s Healthiest
Foods Rating

Rule

excellent

DRI/DV>=75% OR
Density>=7.6 AND DRI/DV>=10%

very good

DRI/DV>=50% OR
Density>=3.4 AND DRI/DV>=5%

good

DRI/DV>=25% OR
Density>=1.5 AND DRI/DV>=2.5%

Impact of cooking, storage and processing

Fiber in foods does not get lost during storage. This is good news, since many important fiber-rich foods have a relatively long shelf life. Dried beans, for example, can often be safely stored for up to one year. As a reminder here, our individual food profiles provide exact storage times and steps not only for beans, but for each of our individual WHF.

While changes in fiber content can occur along with cooking, we do not see these changes as being problematic with whole, natural foods; relatively short cooking times; and everyday cooking methods. Beans are an interesting category of fiber-rich foods in this regard because they are typically only consumed in cooked form. We’ve look at fiber changes involved with overnight soaking of beans as well as stovetop boiling/simmering of beans and as a general summary, we believe you are still highly likely to get fantastic fiber-richness from cooked beans. All of the fiber data for our WHF beans and legumes has been calculated using their cooked form, and the same is true for all of our fiber data on grains.

Other processing steps can sometimes take a greater toll on fiber. Luckily, the canning of beans is not one of them. You’ll be getting a similar level of total fiber in most commercially canned beans to the amount you will get if you cook simmer dry beans in your kitchen. However, because of the higher heats involved with canning and other processing factors, significant losses of other nutrients are definitely possible with commercial canning of beans. (Loss of molybdenum would be one example here.)

With the processing of grains, however, the impact on fiber can be much greater. The impact of grain processing on flour, for example, depends almost completely on the percent extraction used in production of the flour. While the terminology here can seem backwards from the meaning, you might expect “100% extraction” flour to mean that every single part of the original grain was included in the flour. Importantly, this 100% level includes all of the bran and all of the germ, which are the portions of the grain providing you with its fiber richness. Few breads or baked products are made with 100% extraction flour. The average extraction percentage for most U.S. breads and baked products is approximately 60%. This rate means that 60% of the original whole grain was incorporated into the flour, and 40% was discarded. Unfortunately, since most of the fiber-rich bran and fiber-rich germ from the grain was discarded, most of its fiber was discarded as well. To give you one practical example: it is not unusual to find “100% wheat bread” in the grocery store that has been made from 60% extraction flour and contains only 1 gram of fiber or less per slice.

While cooking vegetables (especially overcooking) can result in significant nutrient loss, fiber is not greatly impacted by standard cooking methods.

Risk of dietary deficiency

Based on the NHANES 2009-2010 survey of dietary intake, U.S. adults average only 16 grams of fiber intake per day. In fact, no age or gender group averages the Daily Value (DV) of 25 grams. For teenage girls, the average is about 12-13 grams, or the same as about 50% DV. A conclusion from this survey would be to point out that in the U.S. population as a whole, a person’s risk of fiber deficiency is basically 100%. We just don’t get anywhere close to enough fiber from our meal plans, even at the minimal DV level of 25 grams.

Many problematic practices contribute to this poor level of fiber intake. Included in the list would be routine consumption of heavily processed grain products, sparse consumption of fresh fruits and vegetables, and heavily reliance on animal foods. As explained in an earlier example, routine intake of whole, natural foods from the vegetables, fruits, beans and legumes, nuts and seeds, and grains food groups can easily boost fiber intake over the 25-gram level, and in the case of many of our meal plans, above the 50-gram level as well.

Other circumstances that might contribute to deficiency

Beyond the problematic, everyday food practices listed above that greatly compromised fiber intake, other diet-related practices can impact fiber intake as well. Weight loss diets that encourage very liberal intake of animal foods and severe restriction on carbohydrates can often create too little fiber intake, since animal foods do not provide fiber and since most whole, natural fiber-rich foods also provide at least moderate amounts of total carbohydrate.

While outside the scope of this nutrient profile, it is worth noting that in treatment of some health conditions requiring special feeding methods and/or special diets, fiber intake is deliberately restricted to facilitate the healing process.

Relationship with other nutrients

As researchers have learned more and more about the role of fiber in support of large intestine bacteria, they have also learned more about the relationship of fiber to other nutrients. As a general rule, researchers have traditionally dismissed the large intestine as a possible site for absorption of most nutrients, and they have focused instead on the small intestine when studying nutrient absorption. However, thanks to our present-day understanding of fiber as a key player in the health of our large intestine, we now know that metabolism of fiber by large intestine bacteria can result in absorption of certain nutrients from that area of the digestive tract. For example, the minerals calcium and magnesium are now included in the list of nutrients likely to be absorbed not only from the small intestine but from the large intestine as well, and in no small part due to the role played by dietary fiber. This recent research is causing new questions to be asked about the relationships between fiber and other nutrients. At least in the case of calcium and magnesium, it might be that case that increased intake of fiber in a whole, natural foods diet can increase availability of these two minerals as well.

As a general rule, research studies on fiber intake do not show problematic interactions with other nutrients. We’ve seen some studies showing small drops (less than 5%) in absorption of select nutrients when fiber intake was significantly increased through a combination of whole, natural foods plus processed food components (like oat bran), but high levels of fiber intake from whole, natural foods in whole population studies of diet and health generally correspond to high levels of nutrient intake overall.

Risk of dietary toxicity

As mentioned earlier, the National Academy of Sciences (NAS) did not set any Tolerable Upper Intake Level (UL) for fiber when its fiber recommendations were updated in 2005. From studies of diets worldwide, we also know that routine dietary intake can average 75-100 grams per day when whole, natural plant foods account for the vast majority of dietary intake. The big picture here appears to be a ringing endorsement of all fiber amounts that correspond to healthy intake of whole, natural foods, even when those foods are particularly fiber-rich.

Incorporating fiber-rich foods into your personal diet, however, can take some patience and some practice. From our perspective, it is often a mistake to try and improve your fiber intake by adding processed food components like purified brans or germs. If you do take this approach, we recommend “baby steps” in the addition of these processed fibers. Cramping, gas, bloating, and other problems are fairly common when processed fibers are added too quickly to a meal plan. (For many persons, “too quickly” might mean as little as one teaspoon per day for one week, and then an increase to two teaspoons the following week.) While these problems might not be considered to involve dietary toxicity risk, we believe they are worth pointing out in this section of a fiber profile. A far better approach—and the approach we recommend—is to gradually replace one or two commonly eaten low-fiber foods (for example, processed grains) or fiber-free foods (e.g., animal foods) on multiple days of the week with a fiber-rich food, and allow your digestive tract to gradually adapt to this increased-fiber intake. For example, it might take several weeks or even several months, for a person accustomed to consuming a 15 gram-per-day meal plan to gradually increase fiber-rich, whole, natural foods intake to a level two or three times that amount.

Finally, we would repeat our previous mention that certain health problems can call for restricted fiber intake. In these situations, high intake of fiber could be thought of as posing a risk of dietary toxicity risk. But in the vast majority of situations, high intake of dietary fiber not only poses no toxicity risk, but has been shown to make possible health benefits that may not be available at minimal intake levels.

Disease checklist

• Constipation
• Irritable bowel syndrome
• Colon cancer
• Breast cancer
• Peptic ulcer
• Heart disease
• Type 2 diabetes
• Inflammatory bowel disease
• Hypertension
• Coronary heart disease
• Insulin resistance
• Metabolic syndrome
• Stroke

Public health recommendations

In 2005, the National Academy of Sciences (NAS) updated its recommendations for fiber intake. These recommendations appear below.

• 0—1 year: Not determined
• 1—3 years: 19 grams
• 4—8 years: 25 grams
• 9—13 years, female: 26 grams
• 9—13 years, male: 31 grams
• 14—18 years, female: 26 grams
• 14—18 years, male: 38 grams
• 19—50 years, female: 25 grams
• 19—50 years, male: 38 grams
• 51+ years, female: 21 grams
• 51+ years, male: 30 years
• Pregnant women: 28 grams
• Lactating women: 29 grams

The NAS chose not to establish a Tolerable Upper Intake Limit (UL) for fiber intake.

The Daily Value (DV) for fiber is 25 grams per day. The DV is the standard that you will see on food labels. The DV is also the standard that we adopted as our WHF recommended minimal daily intake level. However, our meal plans typically provide substantially higher amounts of fiber than the DV. As one example, our Healthiest Way of Eating Plan averages 52 grams of daily dietary fiber.

What can high-fiber foods do for you?

• Support bowel regularity
• Help maintain normal cholesterol levels
• Help maintain normal blood sugar levels
• Help keep unwanted pounds off

What events can indicate a need for more high fiber foods?

• Constipation
• Hemorrhoids if related to straining from constipation
• High blood sugar levels
• High cholesterol levels

Excellent food sources of fiber include turnip greens, mustard greens, collard greens, , navy beans, eggplant, raspberries, and cinnamon.

Even though the most commonly eaten grains are not included in our list of fiber food sources above, whole grains can be helpful in increasing your dietary fiber intake. However, when relying on whole grains for your dietary fiber intake, do not stop at the label information on the front of the package, even if the label says “contains whole grains.” To assure yourself of optimal fiber intake from whole grains, be sure to take one of the following steps: (1) purchase your whole grains in bulk form (raw and unprocessed, and typically found in container bins in the bulk food section of the grocery store); (2) purchase products that stipulate “100% whole grain,” or (3) flip the product over and take a close look at the Nutrient Facts panel for fiber content and make sure that you are getting between 4-14 grams of fiber per cooked cup.

WHF rich in
fiber

FoodCalsDRI/DV

 Navy Beans25576.4%

 Dried Peas23165%

 Lentils23062.5%

 Pinto Beans24561.5%

 Black Beans22759.8%

 Lima Beans21652.6%

 Garbanzo Beans26949.8%

 Tempeh22248%

 Kidney Beans22545.3%

 Barley21742.4%

For serving size for specific foods see the Nutrient Rating Chart.

• Description

• Function

• Deficiency Symptoms

• Toxicity Symptoms

• Cooking, storage and processing

• Factors that affect function

• Nutrient interaction

• Health conditions

• Food Sources

• Nutrient Rating Chart

• Public Health Recommendations

• References

Description

What is dietary fiber?

Dietary fiber is undoubtedly one of the most talked about nutrients for health promotion and disease prevention. In fact, dietary fiber is the focus of two FDA-approved health claims that appear on foods labels touting the benefits of high fiber foods for the prevention of heart disease and certain types of cancer.

Since the early 1950’s, when the term “fiber” first began to be used in scientific journals, there has been considerable controversy among food scientists, nutritionists, and medical experts about the exact definition of dietary fiber.

In fact, even the United States Food and Drug Administration, the federal agency responsible for overseeing food labeling, has no formal, written definition of dietary fiber. For food labeling purposes and the determination of health claims, the FDA has adopted the analytical methods that the Association of Official Analytical Chemists uses for defining dietary fiber.

Although most experts agree that a key defining characteristic of dietary fiber is that it’s derived from the edible parts of plants that are not broken down by human digestive enzymes, many people believe that this definition is too ambiguous and that a more clear, internationally-accepted definition is needed to ensure that the total fiber counts on food labels are consistent and accurate.

In recent years there has been a movement among various organizations to include the physiological benefits of dietary fiber in a new definition. For example, the American Association of Cereal Chemists proposed a new definition of dietary fiber that includes the statement “Dietary fibers promote beneficial physiological effects including laxation and/or blood cholesterol attenuation and/or blood glucose attenuation.”

In addition, the Institute of Medicine at the National Academy of Sciences (the organization responsible for issuing Recommended Dietary Allowances) has proposed a new definition that differentiates between dietary fiber and added fiber. According to this definition, dietary fiber consists of nondigestible carbohydrates and lignin that are intrinsic and intact in plants.

Added fiber, which refers to fiber that is added to foods during food processing, consists of isolated nondigestible carbohydrates that have proven beneficial physiological effects in humans. For food labeling purposes, the Institute of Medicine defines Total Fiber as the sum of Dietary Fiber and Added Fiber.

Despite the controversy surrounding the exact definition of dietary fiber, experts agree on one point: adequate dietary fiber intake is associated with reduced risk of heart disease, colorectal cancer, type 2 diabetes, and obesity.

Categories of dietary fiber

• Cellulose, found in bran, legumes, peas, root vegetables, cabbage family, outer covering of seeds, and apples
• Hemicellulose, found in bran and whole grains
• Polyfructoses (Inulin and Oligofructans)
• Galactooligosaccharides
• Gums, found oatmeal, barley, and legumes.
• Mucilages
• Pectins, found in apples, strawberries, and citrus fruits
• Lignin, found in root vegetables, wheat, fruits with edible seeds (such as strawberries)
• Resistant Starches, found in ripe bananas, potatoes

How it functions

What is the function of dietary fiber?

Until very recently, the functions of a specific type of fiber were determined by whether or not the fiber was classified as soluble or insoluble. Soluble fibers, such as the type found in oat bran, are known to reduce blood cholesterol levels and normalize blood sugar levels.

On the other hand, insoluble fiber, such as the type found in wheat bran, are known to promote bowel regularity. Many commonly used plant sources of fiber contain both soluble and insoluble fibers. Psyllium husks, for example, contain a mixture of 70% soluble and 30% insoluble fibers. Despite the widespread use of the terms “soluble” and “insoluble” to describe the health benefits of dietary fiber, many medical and nutrition experts contend that these terms do not adequately describe the physiological effects of all the different types of fiber. These experts are now proposing the use of the terms “viscous” and “fermentability” in place of soluble and insoluble to describe the functions and health benefits of dietary fiber.

Reducing cholesterol levels

Like soluble fibers, viscous fibers lower serum cholesterol by reducing the absorption of dietary cholesterol. In addition, viscous fibers complex with bile acids, which are compounds manufactured by the liver from cholesterol that are necessary for the proper digestion of fat. After complexing with bile acids, the compounds are removed from circulation and do not make it back to the liver. As a result, the liver must use additional cholesterol to manufacture new bile acids. Bile acids are necessary for normal digestion of fat. Soluble fiber may also reduce the amount of cholesterol manufactured by the liver.

Normalizing blood sugar levels

Viscous fibers also help normalize blood glucose levels by slowing the rate at which food leaves the stomach and by delaying the absorption of glucose following a meal. Viscous fibers also increase insulin sensitivity. As a result, high intake of viscous fibers play a role in the prevention and treatment of type 2 diabetes. In addition, by slowing the rate at which food leaves the stomach, viscous fibers promote a sense of satiety, or fullness, after a meal, which helps to prevent overeating and weight gain.

Promoting bowel regularity

Certain types of fiber are referred to as fermentable fibers because they are fermented by the “friendly” bacteria that live in the large intestine. The fermentation of dietary fiber in the large intestine produces a short-chain fatty acid called butyric acid, which serves as the primary fuel for the cells of the large intestine and helps maintain the health and integrity of the colon.

Two other short-chain fatty acids produced during fermentation, propionic and acetic acid are used as fuel by the cells of the liver and muscles. In addition, propionic acid may be responsible, at least in part, for the cholesterol-lowering properties of fiber.

In animal studies, propionic acid has been shown to inhibit HMG-CoA reductase, an enzyme involved in the production of cholesterol by the liver. By lowering the activity of this enzyme, blood cholesterol levels may be lowered.

In addition, fermentable fibers help maintain healthy populations of friendly bacteria. In addition to producing necessary short-chain fatty acids, these bacteria play an important role in the immune system by preventing pathogenic (disease-causing) bacteria from surviving in the intestinal tract.

As is the case with insoluble fiber, fibers that are not fermentable in the large intestine help maintain bowel regularity by increasing the bulk of the feces and decreasing the transit time of fecal matter through the intestines. Bowel regularity is associated with a decreased risk for colon cancer and hemorrhoids (when the hemorrhoids are related to straining and constipation).

Deficiency symptoms

What are deficiency symptoms for dietary fiber?

There is no identifiable, isolated deficiency disease caused by lack of fiber in the diet. However, research clearly indicates that low intake of dietary fiber (less than 20 grams per day) over the course of a lifetime is associated with development of numerous health problems including constipation, hemorrhoids, colon cancer:disease, obesity and elevated cholesterol levels.

Toxicity symptoms

What are toxicity symptoms for dietary fiber?

Intake of dietary fiber in excess of 50 grams per day may cause an intestinal obstruction in susceptible individuals. In most individuals, however, this amount of fiber will improve (rather than compromise) bowel health.

Excessive intake of fiber can also cause a fluid imbalance, leading to dehydration. Individuals who decide to suddenly double or triple their fiber intake are often advised to double or triple their water intake for this reason.

In addition, excessive intake of nonfermentable fiber, typically in supplemental form, may lead to mineral deficiencies by reducing the absorption or increasing the excretion of minerals, especially when mineral intake is too low or when mineral needs are increased such as during pregnancy, lactation, or adolescence.

Factors that affect function

What factors might contribute to a deficiency of dietary fiber?

Even though fiber is often defined as the “undigestable” part of food, a certain amount of healthy digestive function is important for realizing the health benefits of this nutrient.

Inadequate chewing can prevent the health benefits of fiber from being realized, since fibers that cannot be solubilized (like lignins, celluloses, and some hemicelluloses) require extra chewing in order to participate in biochemical processes.

Nutrient interactions

How do other nutrients interact with dietary fiber?

Foods high in nonfermentable fiber, or the fiber that passes all the way through the intestines unchanged, may reduce the absorption and/or increase the excretion of several minerals, including calcium and iron.

Health conditions

What health conditions require special emphasis on dietary fiber?

A diet high in fiber may play a role in the prevention and/or treatment of the following health conditions:

• Breast cancer
• Cardiovascular disease
• Colon cancer
• Constipation
• Diabetes
• Diverticulitis
• Gallstones
• High cholesterol
• Irritable bowel syndrome
• Obesity
• Syndrome X

Food sources

What foods provide dietary fiber?

Excellent food sources of fiber include turnip greens, mustard greens, collard greens, , navy beans, eggplant, raspberries, and cinnamon.

Very good sources of dietary fiber include romaine lettuce, celery, Swiss chard, spinach, fennel, asparagus, cabbage, Brussels sprouts, green beans, cauliflower, carrots, tomatoes, green peas, beets, bell peppers, broccoli, shiitake mushrooms, kale, pinto beans, black beans, kidney beans, dried peas, lentils, strawberries, pear, cranberries, strawberries, oranges, whole wheat, barley, flax seeds, coriander seeds, cloves, and oregano.

Good sources of dietary fiber include apricots, grapefruit, banana, figs, pineapple, cantaloupe, avocado, plums, papaya, kiwifruit, blueberries, apple, sweet potato, summer squash, onions, shiitake mushrooms, yam, leeks, olives, crimini mushrooms, potatoes, corn, beets, rye, quinoa, buckwheat, oats, spelt, garbonzo beans, soybean, miso, sesame seeds, rosemary, black pepper, cayenne pepper, dill, and turmeric.

Drug-nutrient interactions

Form in dietary supplements

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References

1. Costa GT, Guimaraes SB, and Sampaio HA. Fructo-oligosaccharide effects on blood glucose: an overview. Acta Cir Bras. 2012 Mar;27(3):279-82. Review. https://doi.org/10.1590/s0102-86502012000300013
2. Dhingra D, Michael M, Rajput H, et al. Dietary fibre in foods: a review. J Food Scie Technol 2012;49:255-66. https://doi.org/10.1007/s13197-011-0365-5
3. Enright L, Slavin J. No effect of 14 day consumption of whole grain diet on antioxidant measures in healthy, young subjects: a pilot study. Nutr J 2010;9:12-20. https://doi.org/10.1186/1475-2891-9-12
4. Eswaran S, Muir J, Chey WD. Fiber and functional gastrointestinal disorders. Am J Gastroenterol 2013;108:718-27. https://doi.org/10.1038/ajg.2013.63
5. Fechner A, Fenske K, Jahreis G. Effects of legume kernel fibres and citrus fibre on putative risk factors for colorectal cancer: a randomised, double-blind, crossover human intervention trial. Nutr J 2013;12:101-12. https://doi.org/10.1186/1475-2891-12-101
6. Fukii H, Iwase M, Ohkuma T, et al. Impact of dietary fiber intake on glycemic control, cardiovascular risk factors and chronic kidney disease in Japanese patients with type 2 diabetes mellitus: the Fukuoka Diabetes Registry. Nutr J. 2013; 12: 159. Published online 2013 December 11. doi: 10.1186/1475-2891-12-159. https://doi.org/10.1186/1475-2891-12-159
7. Hugenholtz F, Mullaney JA, Kleerebezem M, et al. Modulation of the microbial fermentation in the gut by fermentable carbohydrates. Bioactive Carbohydrates and Dietary Fibre 01/2013; 2(2):133—142. https://doi.org/10.1016/j.bcdf.2013.09.008
8. Inman M. How bacteria turn fiber into food. PLoS Biol 2011;9:e1001227. https://doi.org/10.1371/journal.pbio.1001227
9. Johansson EV, Nilsson AC, Ostman EM, et al. Effects of indigestible carbohydrates in barley on glucose metabolism, appetite and voluntary food intake over 16 h in healthy adults. Nutr J 2013;12:46-58,. https://doi.org/10.1186/1475-2891-12-46
10. King DE, Mainous AG, Carnemolla M, et al. Adherence to healthy lifestyle habits in US adults, 1988-2006. Am J Med 2009;122:528-34. https://doi.org/10.1016/j.amjmed.2008.11.013
11. King DE, Mainous AG, Lambourne CA. Trends in dietary fiber intake in the United States, 1999-2008. J Acad Nutr Diet 2012;112:642-8. https://doi.org/10.1016/j.jand.2012.01.019
12. Kutos T, Golob T, Kac M, et al. Dietary fibre content of dry and processed beans. Food Chem 2003;80:231-5. https://doi.org/10.1016/s0308-8146(02)00258-3
13. Laurentin A and Edwards CA. Fiber: Resistant Starch and Oligosaccharides. https://doi.org/10.1016/b978-0-12-375083-9.00109-4
14. Encyclopedia of Human Nutrition (Third Edition), 2013, Pages 246-253.Leonel AJ, Alvarez-Leite JI. Butyrate: implications for intestinal function. Curr Opin Clin Nutr Metab Care 2012;15:474-9. https://doi.org/10.1016/j.aninu.2017.08.010
15. Mudgil D and Barak S. Composition, properties and health benefits of indigestible carbohydrate polymers as dietary fiber: a review. Int J Biol Macromol. 2013 Oct;61:1-6. doi: 10.1016/j.ijbiomac.2013.06.044. Epub 2013 Jul 2. https://doi.org/10.1016/j.ijbiomac.2013.06.044
16. National Research Council. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients). Washington, DC: The National Academies Press, 2005.
17. Nilsson AC, Ostman EM, Granfeldt Y, et al. Effect of cereal test breakfasts differing in glycemic index and content of indigestible carbohydrates on daylong glucose tolerance in healthy subjects. Am J Clin Nutr 2008;87:645-54. https://doi.org/10.1093/ajcn/87.3.645
18. Ning H, Van Horn L, Shay CM, et al. Associations of dietary fiber intake with long-term predicted cardiovascular disease risk and C-reactive protein levels (from the National Health and Nutrition Examination Survey Data [2005-2010]). Am J Cardiol 2014;113:287-91. https://doi.org/10.1016/j.amjcard.2013.09.020
19. Phillips GO. Dietary fibre: a chemical category or a health ingredient? Bioact Carbohydr Diet Fibre 2013;1:3-9.
20. Russell WR, Gratz SW, Duncan SH, et al. High-protein, reduced-carbohydrate weight-loss diets promote metabolite profiles likely to be detrimental to colonic health. Am J Clin Nutr 2011;93:1062-72. https://doi.org/10.3945/ajcn.110.002188
21. Shah M, Chandalia M, Adams-Huet B, et al. Effects of a high-fiber diet compared with a moderate-fiber diet on calcium and other mineral balances in subjects with type 2 diabetes. Diabetes Care 2009;32:990-6. https://doi.org/10.1177/0148607115621863
22. Shiga TM, Lajolo FM, Filisetti TMCC. Changes in the cell wall polysaccharides during storage and hardening of beans. Food Chem 2004;84:53-64. https://doi.org/10.1016/s0308-8146(03)00166-3
23. Slavin J. Fiber and prebiotics: mechanisms and health benefits. Nutrients. 2013 Apr 22;5(4):1417-35. doi: 10.3390/nu5041417. Review. https://doi.org/10.3390/nu5041417
24. Sundar Raj AA, Rubila S, Jayabalan R, Ranganathan TV (2012) A Review on Pectin: Chemistry due to General Properties of Pectin and its Pharmaceutical Uses. 1:550 doi:10.4172/scientificreports.550
25. Threapleton DE, Greenwood DC, Evans CE, et al. Dietary fibre intake and risk of cardiovascular disease: systematic review and meta-analysis. BMJ. 2013 Dec 19;347:f6879. doi: 10.1136/bmj.f6879. Review. https://doi.org/10.1136/bmj.f6879
26. Zhu Y, Hsu WH, and Hollis JJ. The Impact of Food Viscosity on Eating Rate, Subjective Appetite, Glycemic Response and Gastric Emptying Rate. PLoS One. 2013; 8(6): e67482. https://doi.org/10.1371/journal.pone.0067482
27. American Association of Cereal Chemists. The definition of dietary fiber. Cereal Foods World 2001; 46(3), 112-127. 2001.
28. American Dietetic Association. Health implications of dietary fiber - - Position of the ADA. Journal of the American Dietetic Association 1997; 97:1157-1159. 1997. https://doi.org/10.3390/foods10102452
29. Burton-Freeman B. Dietary fiber and energy regulation. J Nutr 2000 Feb;130(2S Suppl):272S-5S. 2000. PMID:15360.
30. Cohen LA. Dietary fiber and breast cancer. Anticancer Res 1999 Sep-1999 Oct 31;19(5A):3685-8. 1999. PMID:15370.
31. Davy BM and Melby CL. The effect of fiber-rich carbohydrates on features of Syndrome X. J Am Diet Assoc 2003 Jan;103(1):86-96. 2003. https://doi.org/10.1053/jada.2003.50005
32. De Moura FF, Lewis KD, and Falk MC. Applying the FDA Definition of Whole Grains to the Evidence for Cardiovascular Disease Health Claims. The Journal of Nutrition. Bethesda: Nov 2009. Vol. 139, Iss. 11; p. 2220S-2226S. 2009. https://doi.org/10.3945/jn.109.112383
33. Fernandez ML. Soluble fiber and nondigestible carbohydrate effects on plasma lipids and cardiovascular risk. Curr Opin Lipidol 2001 Feb;12(1):35-40. 2001. https://doi.org/10.1097/00041433-200102000-00007
34. Flamm G, Glinsmann W, Kritchevsky D, et al. Inulin and oligofructose as dietary fiber: a review of the evidence. Crit Rev Food Sci Nutr 2001 Jul;41(5):353-62. 2001. PMID:15310.
35. Garcia Peris P, Camblor Alvarez M. [Dietary fiber: concept, classification and current indications]. Nutr Hosp 1999 May;14 Suppl 2:22S-31S. 1999. PMID:15380.
36. Groff JL, Gropper SS, Hunt SM. Advanced Nutrition and Human Metabolism. West Publishing Company, New York, 1995. 1995.
37. Institute of Medicine. Dietary Reference Intakes: Proposed Definition of Dietary Fiber. National Academy Press, Washington DC, 2001. 2001.
38. Lininger SW, et al. A-Z guide to drug-herb-vitamin interactions. Prima Health, Rocklin, CA, 2000. 2000.
39. Mahan K, Escott-Stump S. Krause's Food, Nutrition, and Diet Therapy. WB Saunders Company; Philadelphia, 1996. 1996.
40. McIntosh M, Miller C. A diet containing food rich in soluble and insoluble fiber improves glycemic control and reduces hyperlipidemia among patients with type 2 diabetes mellitus. Nutr Rev 2001 Feb;59(2):52-5. 2001. https://doi.org/10.1111/j.1753-4887.2001.tb06976.x
41. Meseguer Soler I, Martinez Para MC, Farre Rovira R. [Dietary fiber (and II). Metabolism and physiologic implications]. Med Clin (Barc) 1998 Jan 17;110(1):32-7. 1998. PMID:15390.
42. Pereira MA, Ludwig DS. Dietary fiber and body-weight regulation. Observations and mechanisms. Pediatr Clin North Am 2001 Aug;48(4):969-80. 2001. PMID:15320. https://doi.org/10.1097/00007611-197704000-00029
43. Pereira MA, Pins JJ. Dietary fiber and cardiovascular disease: experimental and epidemiologic advances. Curr Atheroscler Rep 2000 Nov;2(6):494-502. 2000. PMID:15350.
44. Swanson KS, Fahey GC. New developments in the area of dietary fiber. Nutrition in Complementary Care Newsletter 2001; 4(1):5,12. 2001.
45. Zhao X, Yang Y, Song Z et al. Effect of superior fiber complex on insulin sensitivity index and blood lipids in non-insulin dependent diabetes mellitus rats. Zhonghua Yu Fang Yi Xue Za Zhi 2002 May;36(3):184-6. 2002.
46. American Association of Cereal Chemists. The definition of dietary fiber. Cereal Foods World 2001; 46(3), 112-127 2001.
47. American Dietetic Association. Health implications of dietary fiber - - Position of the ADA. Journal of the American Dietetic Association 1997; 97:1157-1159 1997.
48. Burton-Freeman B. Dietary fiber and energy regulation. J Nutr 2000 Feb;130(2S Suppl):272S-5S 2000. PMID:15360.
49. Cohen LA. Dietary fiber and breast cancer. Anticancer Res 1999 Sep-1999 Oct 31;19(5A):3685-8 1999. PMID:15370.
50. Davy BM and Melby CL. The effect of fiber-rich carbohydrates on features of Syndrome X. J Am Diet Assoc 2003 Jan;103(1):86-96 2003. https://doi.org/10.1053/jada.2003.50005
51. Fernandez ML. Soluble fiber and nondigestible carbohydrate effects on plasma lipids and cardiovascular risk. Curr Opin Lipidol 2001 Feb;12(1):35-40 2001. https://doi.org/10.1097/00041433-200102000-00007
52. Flamm G, Glinsmann W, Kritchevsky D, et al. Inulin and oligofructose as dietary fiber: a review of the evidence. Crit Rev Food Sci Nutr 2001 Jul;41(5):353-62 2001. PMID:15310.
53. Garcia Peris P, Camblor Alvarez M. [Dietary fiber: concept, classification and current indications]. Nutr Hosp 1999 May;14 Suppl 2:22S-31S 1999. PMID:15380.
54. Groff JL, Gropper SS, Hunt SM. Advanced Nutrition and Human Metabolism. West Publishing Company, New York, 1995 1995.
55. Institute of Medicine. Dietary Reference Intakes: Proposed Definition of Dietary Fiber. National Academy Press, Washington DC, 2001 2001.
56. Lininger SW, et al. A-Z guide to drug-herb-vitamin interactions. Prima Health, Rocklin, CA, 2000 2000.
57. Mahan K, Escott-Stump S. Krause's Food, Nutrition, and Diet Therapy. WB Saunders Company; Philadelphia, 1996 1996.
58. McIntosh M, Miller C. A diet containing food rich in soluble and insoluble fiber improves glycemic control and reduces hyperlipidemia among patients with type 2 diabetes mellitus. Nutr Rev 2001 Feb;59(2):52-5 2001. https://doi.org/10.1111/j.1753-4887.2001.tb06976.x
59. Meseguer Soler I, Martinez Para MC, Farre Rovira R. [Dietary fiber (and II). Metabolism and physiologic implications]. Med Clin (Barc) 1998 Jan 17;110(1):32-7 1998. PMID:15390.
60. Pereira MA, Ludwig DS. Dietary fiber and body-weight regulation. Observations and mechanisms. Pediatr Clin North Am 2001 Aug;48(4):969-80 2001. PMID:15320. https://doi.org/10.1097/00007611-197704000-00029
61. Pereira MA, Pins JJ. Dietary fiber and cardiovascular disease: experimental and epidemiologic advances. Curr Atheroscler Rep 2000 Nov;2(6):494-502 2000. PMID:15350.
62. Swanson KS, Fahey GC. New developments in the area of dietary fiber. Nutrition in Complementary Care Newsletter 2001; 4(1):5,12 2001.
63. Zhao X, Yang Y, Song Z et al. Effect of superior fiber complex on insulin sensitivity index and blood lipids in non-insulin dependent diabetes mellitus rats. Zhonghua Yu Fang Yi Xue Za Zhi 2002 May;36(3):184-6 2002.