Fiber: Does It Matter? by Lisa Njoroge, MS, RD, LD

Fiber is a common topic in nutrition discussions, but what is it? Fiber is a component of plants, found in fruit, vegetables, grains, and seeds, however it is not digested and absorbed like other nutrients (i.e. vitamins and minerals). So, if it is not absorbed, why do humans need it? 
Health benefits of having adequate fiber intake include reduced risk of mortality from cardiac disease, colon cancer, stroke, and type 2 diabetes mellitus (1). Other benefits include regularity of bowel movements and promotion of variety of microflora in the large intestine (2). The recommended amount of fiber varies with age, sex, and national health guidelines, but a general guideline for fiber intake is between 21 – 38 grams per day depending on the individual, according to the USDA. 
What is the difference between soluble and insoluble fiber? Soluble fiber attracts and absorbs water, forming a gel in the digestive tract. It is soluble fiber that supports heart health by reducing cholesterol. Insoluble fiber does not dissolve in water or form gel, but rather passes through the digestive tract intact, adding bulk to stools and promoting regular bowel movements. Most plant foods contain some of both types of fiber (3), but you’ll find more soluble fiber in oats, apples, carrots, barley, and psyllium. 
Higher amounts of insoluble fiber can be found in foods such as wheat bran, whole-wheat flour, beans, potatoes, and nuts. 
Although most Americans are not meeting the recommended daily amount of fiber, caution should be taken when changing fiber intake. Adding fiber too quickly can cause digestive upset such as gas, bloat, and constipation. Another important factor to consider is increasing hydration and water intake while increasing fiber intake. Adding fiber should be done gradually and should be discussed with a health care provider such as a Physician or Registered Dietitian.

1. McManus, Katherine D. Should I be eating more fiber? Harvard Health Publishing, Harvard Medical School, February 2019. https://www.health.harvard.edu/blog/should-i-be-eating-more-fiber-2019022115927#:~:text=Fiber%3A%20how%20much%20is%20enough,and%2030%20daily%20grams%2C%20respectively​
2. Lattimer JM, Haub MD. Effects of dietary fiber and its components on metabolic health. Nutrients. 2010;2(12):1266-1289. https://www.mdpi.com/2072-6643/2/12/1266​
3. Julia M. W. Wong , David J. A. Jenkins, Carbohydrate Digestibility and Metabolic Effects, The Journal of Nutrition, Volume 137, Issue 11, November 2007, Pages 2539S–2546S, https://doi.org/10.1093/jn/137.11.2539S