Topic of the Month

Got Fiber? Who Doesn’t Get Enough and Why We Need More

Julia Bird

June 20, 2019

Dietary fiber is part of a balanced and healthy diet. It is found naturally in plant foods. Dietary fiber’s benefits come from not being absorbed: dietary fiber passes through our bodies largely intact, and this is what makes it so helpful. However, many people do not get enough! How can we get more fiber in our diets?

What does dietary fiber do in the body? 

Dietary fiber is good for our gut, good for our heart and good for our waistline1. Fiber holds water as it passes through the large intestine, leading to a soft stool that is easy to pass. Certain fibers, such as those from dried plums2, create an “intestinal hurry” that promotes regularity3. Higher fiber intakes are associated with a lower risk of constipation4.

There are two ways that dietary fiber can help the heart. First of all, dietary fiber in a meal slows the speed at which food leaves the stomach, which helps maintain normal blood glucose levels after eating 5; 6. Secondly, one particular type of dietary fiber such as that found in oatmeal makes a thick gel in the intestines. Bile salts from digestion is trapped in the gel and it passes out of the body. Bile salts are made from cholesterol, so the body uses cholesterol from the blood to make more bile salts, thus reducing cholesterol levels7

Dietary fiber helps us to feel fuller after eating a meal8. Dietary fiber is not absorbed directly so it increases bulk throughout the digestive tract. It slows the speed at which nutrients are absorbed, which means that feelings of hunger are subdued for longer after a meal9.  These effects of fiber on satiety prevent hunger pangs and may have a modest effect on our weight8

How Much Dietary Fiber Do We Need?

The amount of dietary fiber that is recommended varies per country, however most recommend that adults consume at least 25 grams of fiber per day10. Children generally eat less than adults, and the recommendations for children are therefore lower. 

Who Needs More Dietary Fiber?

Despite its many health benefits, many people around the world do not get enough fiber every day, leading to a global “fiber gap”10. Overall, intakes of dietary fiber are less than half of recommendations10. In diverse countries such as China, Iran, the U.S. and many countries in Europe, and in different age groups, studies show that intakes are routinely lower than recommendations11; 12; 13; 14; 15. In the U.S., less than 5 percent of the population has intakes of fiber greater than their age- and gender-based recommendations16. A study in Australia found that adolescents and young adults, girls, men and people of lower socio-economic status were at greatest risk of low fiber intakes17. While women and older adults tended to have better fiber intakes, many people in these groups also fell short of intake recommendations17.

Good Dietary Fiber Sources

The best sources of dietary fiber are from plants because fiber is actually part of the structure of plant cells. Cereals (especially whole grain), legumes, seeds, mushrooms, fruit and vegetables all contain fiber in varying amounts.

Surprising sources of dietary fiber18:

  • Roasted pumpkin seeds (18 g fiber / 100g)
  • Roasted pumpkin seeds (18 g fiber / 100g)
  • Black beans (16 g fiber / 100 g)
  • Popcorn (15 g fiber / 100 g)
  • Almonds (13 g fiber / 100g)
  • Dried apple (9 g fiber / 100g)
  • Whole grain pasta (11 g fiber / 100g)
  • Dark chocolate (11 g fiber / 100g)
  • Peanut butter (8 g fiber / 100g)
  • Baked potatoes with skin (8 g fiber / 100g)
  • White bread (2.4 g fiber / 100g)

How Can We Close the Fiber Gap?

Closing the fiber gap requires us to change what we eat. Low dietary fiber intakes come from low intakes of fiber-rich foods such as fruit and vegetables, nuts, pulses, mushrooms and whole grains. For example, in the U.S., if consumers choose whole grains instead of refined grains, dietary fiber intakes will increase substantially19. Many food producers now make foods containing a higher dietary fiber content. For example, food manufacturers can increase the dietary fiber content of food such as yogurt, breakfast cereals and crackers to help consumers meet the gap20; 21. This can be done either by choosing a whole grain as a basis for grain products such as spaghetti and bread, or by adding fiber to products that do not normally contain fiber such as fruit juices and yoghurt. Increasing nutrition knowledge can also impact food choices, such as increasing fruit and vegetable consumption22.

Dietary fiber is so important in our diets, yet most people do not eat enough. We need to choose more fiber-rich foods to help us close the dietary fiber gap. 

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References

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  2. Piirainen L, Peuhkuri K, Bäckström K et al. (2007) Prune juice has a mild laxative effect in adults with certain gastrointestinal symptoms. Nutrition Research 27, 511-513.
  3. Anderson JW, Baird P, Davis RH, Jr. et al. (2009) Health benefits of dietary fiber. Nutr Rev 67, 188-205.
  4. Shen L, Huang C, Lu X et al. (2019) Lower dietary fibre intake, but not total water consumption, is associated with constipation: a population-based analysis. J Hum Nutr Diet.
  5. Gopirajah R, Raichurkar KP, Wadhwa R et al. (2016) The glycemic response to fibre rich foods and their relationship with gastric emptying and motor functions: an MRI study. Food Funct 7, 3964-3972.
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  7. Surampudi P, Enkhmaa B, Anuurad E et al. (2016) Lipid Lowering with Soluble Dietary Fiber. Curr Atheroscler Rep 18, 75.
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  16. Quagliani D, Felt-Gunderson P (2017) Closing America's Fiber Intake Gap: Communication Strategies From a Food and Fiber Summit. Am J Lifestyle Med 11, 80-85.
  17. Fayet-Moore F, Cassettari T, Tuck K et al. (2018) Dietary Fibre Intake in Australia. Paper I: Associations with Demographic, Socio-Economic, and Anthropometric Factors. Nutrients 10.
  18. USDA national nutrient database for standard reference [electronic resource].
  19. Kranz S, Dodd KW, Juan WY et al. (2017) Whole Grains Contribute Only a Small Proportion of Dietary Fiber to the U.S. Diet. Nutrients 9.
  20. Mhurchu CN, Eyles H, Choi YH (2017) Effects of a Voluntary Front-of-Pack Nutrition Labelling System on Packaged Food Reformulation: The Health Star Rating System in New Zealand. Nutrients 9.
  21. Muth MK, Karns SA, Mancino L et al. (2019) How Much Can Product Reformulation Improve Diet Quality in Households with Children and Adolescents? Nutrients 11.
  22. Pem D, Jeewon R (2015) Fruit and Vegetable Intake: Benefits and Progress of Nutrition Education Interventions- Narrative Review Article. Iran J Public Health 44, 1309-1321.