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March 28, 2024

By: Alyssa Trout, Dietetic Intern

When the word nutrition is mentioned, what comes to mind? Many individuals may think of macronutrients such as carbohydrates, proteins, and fats. One might also think of micronutrients such as vitamins and minerals. These are a few great essential nutrients the human body needs in large and small amounts. Now, where does fiber come in? Fiber is a vital nutrient to the human body, yet it is often overlooked or forgotten.

What is Fiber?

Fiber is a type of carbohydrate, one of the three energy-containing essential macronutrients. In the body, carbohydrates are the body's preferred fuel and energy source 1. However, the human digestive system cannot break down fiber structures. Therefore, fiber serves a unique yet important function aside from being a fuel source within carbohydrate-containing food sources1. There are two types of dietary fiber: soluble and insoluble fiber. Each slightly differs in its function within an advantage to the body. Soluble fiber dissolves in water, and insoluble fiber does not.


The Dietary Guidelines for Americans recommend that 45-65% of all calories come from carbohydrates 2. Furthermore, general recommendations for fiber include 25 grams per day for adult women and 38 grams per day for adult men, or 14 grams of fiber for every 1,000 calories consumed 1.

Role of Fiber

Fiber serves a wide range of functions in the human body, specifically in its role within the digestive tract. These biological functions result in a number of benefits for improving and maintaining optimal health over a lifetime.

Biological functions within the body:

  • Decrease overall intestinal transit time 1
  •  Increase transit time in the stomach 3
  •  Increase satiety 1
  •  Delays glucose absorption into bloodstream 1
  •  Decrease blood cholesterol levels 1
  •  Increase bulk of stool 1

An increased transit time in the stomach is due to the body requiring more time to break down fiber-containing foods. This delays the rate at which glucose enters the bloodstream, supporting stable blood sugar levels. This increased transit time in the stomach is also why increased satiety may occur when consuming fiber-containing foods. Fiber also allows for a decreased transit time in the intestines due to the increased bulk it provides to stool. This allows for regular bowel movements. According to the Academy of Nutrition and Dietetics, fiber may help reduce blood cholesterol levels and prevent heart disease 3.

Benefits of Fiber

After discussing the role fiber has in our body and digestive tract, here are 4 benefits fiber has to our long-term overall health:

  1. Maintain healthy weight 3
  2. Maintain gut health 3
  3. Maintain healthy blood sugar regulation 3
  4. Maintain heart health 3

Fiber-Rich Food Sources

  1. Whole grains: whole wheat products, oats, barley, quinoa, brown rice, farro.
  2. Fruits: apples, pears, plums, bananas, mango, strawberries, blueberries, and dried fruits.
  3. Vegetables: Broccoli, cauliflower, brussels sprouts, kale, spinach, asparagus, corn, and carrots.
  4. Legumes: Lentils, black beans, kidney beans, garbanzo beans, peas, split peas.
  5. Nuts: Almonds, walnuts, pistachios, cashews.
  6. Seeds: Chia seeds, flax seeds, pumpkin seeds, sunflower seeds.

How to Include More Fiber Into Overall Diet

It may appear challenging to determine attainable ways to increase fiber intake. Based on the MyPlate USDA Guidelines, here are three simple ways to improve fiber intake. It is best to consult with a Registered Dietitian Nutritionist (RDN) for personalized nutrition goals and recommendations.

  1. At mealtime, aim for ½ of your plate consisting of fruit and vegetables 4
  2. Between meal and snacks, aim for ½ of your grains to be whole-grain 4
  3. Vary your protein choices 4
    •  Many plant-based protein sources (beans, peas, lentils, nuts, and seeds) also contain fiber.



  1. Hess MA. Review of Dietetics: Manual for the Registration Examination for Dietitians. Culinary Nutrition Publishing; 2022.
  2. Dietary Guidelines for Americans. Home | Dietary Guidelines for Americans. Dietaryguidelines.gov. Published 2020. https://www.dietaryguidelines.gov/
  3. Ellis E. Fiber. www.eatright.org. Published November 3, 2020. https://www.eatright.org/health/essential-nutrients/carbohydrates/fiber
  4. USDA. What is MyPlate? www.myplate.gov. Published 2020. https://www.myplate.gov/eat-healthy/what-is-myplate