“All fiber is the same, right?”
As more definitions and categories for fiber emerge, it is getting confusing for us to know what to eat and what actually counts toward to our daily fiber intake.
Most of us are familiar with fiber being either soluble or insoluble, but we can never seem to remember the differences between the two. The important thing to note is that both are good for you. Dietary fiber is a plant-based carbohydrate nutrient that is minimally digested and most of it passes through the body.
Soluble fiber is the kind that attracts water and turns to gel during digestion; insoluble fiber does not do this. Soluble fiber is found in oat bran, barley, nuts, seeds, beans, lentils, peas, and some fruits and vegetables. It slows down digestion.
Insoluble fiber helps food move through the digestive system, thus promoting regularity and preventing constipation by adding bulk to stool, helping food pass more quickly through the stomach and intestine. You can find it in foods like wheat bran, whole grains, and vegetables. Most plant foods contain both soluble and insoluble fiber, but the amounts of each vary depending on the type of food. Both are important for health, digestion, and disease prevention. Some examples of foods that have both types are oatmeal and beans. These natural fibers are referred to as intact.
“It sounds like fiber is in a lot of the foods I already eat. Should I make an effort to eat more fiber?”
Even as fiber has become more complex to define, the research is clear on the wealth of health benefits of a high fiber diet, including weight management, a lowered risk of diabetes and heart disease, and promotion of regularity. Fiber is important to our daily diet for these reasons and many more. Despite the benefits, research shows that 90 percent of Americans consume an average of only 15 grams of dietary fiber each day. This number is a far below the recommended levels of 25 grams per day for adult women and 38 grams per day for adult men.
“So how do we close this gap?”
Well, food manufacturers have recognized the consumer interest in increasing dietary fiber intake and they are adding fiber to foods that previously contained none. So if you wonder why the Greek yogurt you just bought has fiber in it, it’s because food companies are adding isolated (as opposed to intact) fibers to foods like energy bars, juice, water, ice cream, yogurt, and sugary cereal.
“What exactly are isolated fibers?”
Isolated fibers are either extracted from other starchy foods or chemically synthesized and added to non-fiber containing foods to give them a higher fiber content. They can be found on nutrition labels in the form of inulin, maltodextrin, polydextrose, polyols, cellulose, oat fiber, resistant starch, pectin, and gum, just to name a few. They can contribute to our total fiber, but may not offer the same effects as eating foods naturally high in fiber.
“Is isolated fiber basically the same as intact fiber?”
There is a debate in the nutrition community as to whether these commercially produced fibers provide the same health benefits as intact fiber. (Keep in mind that when you choose foods with ingredients like oats or wheat bran, you are eating intact fiber.) The research is mixed, but recent studies suggest that isolated dietary fiber is less beneficial than the intact fiber found in plants. This may be due in part to the way natural fiber works with other biologically active compounds found in whole foods that help in disease prevention. Just to be clear: intact fiber is natural whole plant fiber such as the kind found in whole grains, fruits, and vegetables, and includes both soluble and insoluble fiber.
“What is the downside to fake fiber?”
When consumed in large amounts, some isolated fibers may cause gas, bloating, and a laxative effect in some people. These tend to happen with fibers such as oligofructose, polydextrose, and inulin. In addition, some isolated fibers, like maltodextrin, fail to help you stay regular.
“Are there any benefits of added fibers?”
An upside to the rise of functional foods is that prebiotics, along with isolated fiber, are now being added to many common foods, such as cereals, biscuits, breads, drinks, and yogurts. One common type is inulin. Prebiotics are a healthy non-digestible food ingredient that allows good bacteria to flourish in the gut, promoting good digestive health. These functional foods prompt metabolic activity, leading to health improvements. Healthy bacteria in the intestine can combat unwanted bacteria, providing a number of possible health benefits including help with disease prevention through strengthening the immune system, reducing inflammation, enhancing bioavailability and absorption of minerals, decreasing risk factors for cardiovascular disease, and promoting satiety and weight loss.
“So should I avoid foods with isolated fiber?”
In time, studies will show if isolated fibers have the same benefits as the intact fiber found in naturally occurring foods, but for now the research is inconsistent. Every fiber is different and functions slightly different in the intestinal tract. When incorporated into a well-balanced diet, fiber-added foods can boost your overall fiber intake, but these foods may lack the nutrition of foods containing natural fiber. However you are getting fiber into your diet, there will be benefits.
Lela Iliopoulos is a Registered Dietitian and Certified Diabetes Educator and an expert in nutrition therapy, health promotion, and education. She is passionate about impacting nutritional health through the practical application of science-based informatio