Here’s a quiz for you. The Dietary Guidelines Advisory Committee states that this dietary component is a nutrient of strong public health interest because so few people consume enough of it. Do you know what it is?
No, it’s not a vitamin or mineral – but another dietary component that’s critically lacking in the standard American diet – fiber. In fact, less than 3% of Americans meet the dietary recommendations for fiber. Yes, fewer than 3%. Those are shocking statistics if you think about it!
How much fiber should you get each day? Institute of Medicine recommends that men get at least 38 grams of fiber daily and women at least 25 grams. But, the average person gets only an average of 15 grams daily. We’re falling WAY short!
What is Fiber, Anyway?
Fiber is a type of carbohydrate, but unlike other carbs that your body converts into energy, fiber isn’t digested when it enters the upper digestive tract. Instead, it makes its way into the lower digestive tract or colon where some sub-types of fiber are ingested by bacteria. When bacteria take in fiber, they can ferment certain types and form by-products. Some of these by-products appear to have health benefits.
For example, bacteria in the lower digestive tract convert a type of fiber called resistant starch into short-chain fatty acids. An example of a short-chain fatty acid is butyric acid. Butyric acid helps keep the lining of the colon healthy by reducing inflammation. In turn, this reduction in inflammation may, in turn, lower the risk of colon cancer, although more research is needed in humans. Foods high in resistant starch include legumes, uncooked potato starch, cooked & cooled potatoes, unripe bananas, cooked and cooled rice, and hi-maize flour.
Another reason fiber is an important dietary component is that some fiber is “prebiotic,” meaning it fosters the growth of healthy, gut-friendly bacteria that keep your intestinal tract healthy.
The Three Types of Fiber: Indirect, Soluble and Insoluble Fiber
Fiber comes in three different types. The two types in whole foods are soluble fiber and insoluble fiber. As you might expect, soluble fiber dissolves easily in water whereas insoluble fiber does not. Each type has slightly different health benefits.
Soluble fiber is the type most closely linked with a lower risk of cardiovascular disease. Soluble fiber forms a thick gel once it enters the digestive tract and this thick, jelly-like material delays movement of food through the digestive tract. Because the food moves more slowly when a meal is high in fiber, blood sugar rises less. That’s why healthcare professionals recommend a fiber-rich diet for diabetics and people with pre-diabetes.
Then, there’s insoluble fiber, a form of fiber that helps you stay “regular.” Insoluble fiber works by increasing stool bulk so that you’re less likely to become constipated. Finally, there’s functional or isolated fiber. This fiber that food manufacturers add to products, so they can say it has a high fiber content. Examples of this type of fiber are inulin, guar gum, dextrins, polydextrose, and more. It’s not clear whether this type of fiber has the same health benefits as fiber from whole foods.
What Foods Are High in Fiber?
Only plant-based foods contain fiber. The best sources, as you might expect, are fruits, vegetables, whole grains, nuts, and seeds – foods derived from plant life. Most fruits and vegetables contain a combination of soluble and insoluble fiber, but soluble fiber is highest in legumes, barley, oats, fruit, and non-starchy vegetables, whereas wheat, rye, and other grains are the best sources of insoluble fiber.
Lower Risk of Death?
If you still aren’t convinced that you need more fiber in your diet, maybe this will sway you. A meta-analysis of seventeen studies looking at fiber intake and health found a 10% reduction in the risk of all-cause mortality with each 10-gram per day increase in fiber consumption. That’s pretty powerful! To be able to potentially lower your risk of death by boosting the fiber content of your diet.
It’s not surprising if you think about it. You only find fiber in plant-based foods and plants are the richest source of phytonutrients, non-nutritive compounds that have antioxidant and anti-inflammatory activity. In fact, the word “phyto” comes from the Greek word for plant. You find an abundance of phytonutrients in fruits, vegetables, nuts, seeds, and whole grains, and all of these foods are high in fiber.
What we don’t know is whether isolated or functional fiber added to foods to increase its fiber content has the same health benefits as natural, soluble and insoluble fiber from plant-based sources. Since you find isolated fiber in packaged and processed foods that are typically less nutritious than whole foods.
Fiber Helps with Appetite Control
Another benefit of fiber is it helps curb hunger. Soluble fiber is the type that aids in satiety. But, not all soluble fiber equally subdues appetite. The kind that most effectively curbs the desire to eat is viscous fiber, the type that best interacts with liquids in your stomach to form a thick gel. Once this gel-like material forms, it slows down the movement of food out of your stomach. Unless a soluble fiber can easily form this gel, it won’t have as much impact on appetite.
Two of the best examples of viscous soluble fiber is pectin, a fiber abundant in fruit, particularly apples, and beta-glucan, in substantial quantities in barley and oats. No wonder that bowl of oatmeal in the morning keeps you full for hours! Studies show that barley also suppresses appetite and reduces calorie consumption. Some produce that’s rich in viscous fiber includes asparagus, Brussels sprouts, sweet potatoes, mangoes, apricots, lentils, and beans.
Viscous fiber also slows the rise in blood sugar you get in response to a meal. That’s important for metabolic health. Studies also show that a diet rich in viscous fiber helps lower cholesterol. One precaution – slowly increase the amount of viscous fiber in your diet to avoid bloating. Give your digestive tract a chance to adapt to it.
References:
WebMD.com. “Phytonutrients”
Today’s Dietitian. Vol. 15 No. 12 P. 16.
The Journal of Nutrition, Volume 130, Issue 2, 1 February 2000, Pages 272S–275S,
Healthline.com. “9 Foods That Are High in Resistant Starch
WebMD.com. “Fiber: How Much Do You Need?”
J Nutr. 2012 Jul;142(7):1390S-401S. doi: 10.3945/jn.112.160176. Epub 2012 May 30.
Am J Epidemiol. 2015 Jan 15;181(2):83-91. doi: 10.1093/aje/kwu257. Epub 2014 Dec 31.
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The Two Types of Fiber and How to Get More of Each in Your Diet
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