Dietary fiber. It’s the least sexy macronutrient especially when compared to fat and protein which are always hot topics in the realm of nutritional and food science. However, while fiber is largely under-discussed it indeed plays a vital role in overall health. Unfortunately, as a result of our current food culture in America less than 3% (1) of Americans consume adequate fiber on a regular basis.
What is fiber?
Simply put dietary fiber is the part of plants or other carbohydrates that resist digestion and absorption in the small intestine.(2) It is important to note that there are two kinds of dietary fiber: soluble and insoluble fiber. Soluble fiber is fiber that in the in the presence of water breaks down and forms a gel like substance. Soluble forms of fiber include: pectin, gum and mucilage. Insoluble forms of fiber include: hemicellulose, cellulose and lignin (the materiel that makes wood rigid yet playable). Most foods contain a combination of soluble and insoluble fiber, yet there are exceptions where only form of fiber is found more abundantly in certain foods.
Main benefits of dietary fiber
Both soluble and insoluble fiber play different roles in our health. Soluble fiber is fiber responsible for lowering blood glucose and cholesterol levels.(3) In contrast, insoluble fiber is responsible for increasing the transit time of food through the digestive system as well as decreasing constipation and increasing fecal bulk making passing stool (aka poop) easier.(4) Lastly, while the research is somewhat conflicting insoluble dietary fiber appears to improve satiety.(5) Meaning higher fiber foods are a great way to stay full while trying to loose weight. There are various other health benefits and potential health benefits of dietary fiber including decreased risk of colon cancer, decreased risk of food allergy development, decreasing the risk for coronary heart disease, and longevity) however these will be addressed in a future article.
How much fiber should you eat?
As with just about everything the answer to this question depends context. In this case the context of your diet will determine the appropriate amount of dietary fiber for you. For most, approximately 10-14 grams of fiber per 1000kcal consumed will be appropriate. (6) As you can see the amount of dietary fiber you should consume will vary greatly based on the total amount of food you consume each day. For example, someone consuming 1500kcal a day will need approximately 21 grams of fiber a day. While on the other hand someone like myself eating approximately 4500kcal a day will require closer to 63 grams a day!
Foods High in Fiber
If you find yourself constantly slacking in the fiber department here are some high fiber foods to start eating more of:
- Berries like raspberries and blackberries (7g/per cup)
- Apples with the skin on (4.4 g)
- Pears with the skin on (5.5 g)
- Black beans (15g/cup)
- Lentils (15g/cup)
- Brown Rice (3.5g/cup)
- Oats (5g/cup)
- Pearled barley (6 g per cup)
- Popcorn ( 3.5 g/ 3 cups)
- Broccoli (5 g /cup)
- Green peas (9 g/cup)
- Avocados (9g/cup)
- Flaxseeds (3.3g/tbsp)
- Cocoa powder (2g/tbsp)
My tips for Increasing Fiber intake:
1. Eat more whole foods. Period. If you eat a diet high in whole foods (i.e. fruits, vegetables, whole grains, various forms of plant based starches) then getting adequate fiber should not be a problem. However, the majority of people do not eat a diet rich in whole foods. On the most basic level simply adding more whole foods will instantly increase your fiber intake and do your colon proud. 2. Stop peeling your vegetables and fruit! This is another small dietary adjustment that can make a significant difference in your fiber intake.When you remove the flesh from fruits in vegetables you are basically throwing nutritious fiber away. 3. Eat more COCOA! Yup, this is one of my favorite secret sources of fiber, with a whopping 2 grams/tbsp its a delicious and sneaky way to get more fiber in addition to being high well other healthful nutrients such as minerals, flavanoids, and antioxidants! (7) You can throw cocoa powder in whatever you enjoy the flavor of chocolate in. I personally generally use about 2 tbsp whenever making a protein shake, or mix it into oatmeal in the morning. 4. Start eating beans and legumes weekly. As you can see above beans are basically the one stop shop for fiber. 1 cup of black beans has almost half the daily recommended amount of fiber for someone eating a 2000 kcal diet.
Note that this is just a brief outline of dietary fiber and the role it plays in our health. In the second part of this series I will dive more deeply into the research regarding dietary fiber and the potential negatives of too much fiber.
Agricultural Research Service; U.S. Department of Agriculture. Dietaryfiber (g): usual intakes from food and water, 2003–2006, compared toadequate intakes. What we eat in America, NHANES 2003–2006.
- D Mudgil, S Barak.Composition, properties and health benefits of indigestible carbohydrate polymers as dietary fiber: A review. International journal of biological macromolecules 2013;( 66), 2-4
- Lisa Brown et al. Cholesterol-lowering effects of dietary fiber.American Journal of Clinical Nutrition 1999; 60(1): 30-42
- Yang J, Wang HP, Zhou L, Xu CF. Effect of dietary fiber on constipation: A meta analysis. World Journal of Gastroenterology 2012; 18(48): 7378-7383
- Wanders AJ, van den Borne JJ, de Graaf C, et al. Effects of dietary fiber on subjective appetite, energy intake and body weight: a systematic review of randomized controlled trials. Obesity Review. 2011;12(9):724-739
- U.S. Department of Health and Human Services and U.S. Department of Agriculture. 2015 – 2020 Dietary Guidelines for Americans. 8th Edition. December 2015. Available at http://health.gov/dietaryguidelines/2015/guidelines/
- Ariefdjohan MW, Savaiano DA.Chocolate and cardiovascular health: is it too good to be true? Nutrition Reviews, 2005;63(12):427-30.