Have you noticed that all kinds of foods are suddenly “good source of fiber?” Fiber is now in yogurt, ice cream, beverages, cookies, sweetened cereal, and other foods that previously had not contained fiber. Could it be that someone is pulling a fast one on us? Let's find out.
You probably know that dietary fiber is exclusive to plant foods: whole grains, fruit and vegetables, beans, seeds, and nuts. Fiber forms the structure of a plant: the skin, seeds, germ, stems, veins, roots, and pulp.
There are two kinds of fiber: insoluble and soluble. Insoluble fiber, such as bran, moves wastes out quickly to prevent some GI diseases. Soluble fiber slows digestion which stabilizes blood sugar, lowers blood cholesterol and creates a feeling of fullness. Fiber doesn't provide many calories because it is not absorbed. Carbohydrate from sugar and starch yields 4 calories per gram, while fiber yields 1 - 1.5 calories.
In addition to dietary fiber, insoluble and soluble, we now have “functional fiber.” Functional Fiber is non-digestible carbohydrates that are man-made or extracted from plants in the lab. Pectin from citrus and cellulose from trees are extracted functional fibers.
Functional fibers are ingredients that are added to food. They replace sugar and fat, add bulk to low calorie food, increase fiber without the grit, and improve the mouth feel, stability and taste of food (today’s consumers want it all: taste, health and convenience).
Polydextrose is a functional fiber made by man in the lab from dextrose, sorbitol and citric acid through the wonders of vacuum thermal polymerization (Wow!). In 2007, the U.S. Food and Drug Administration (FDA) expanded the approved use of polydextrose in a broad range of food products. In addition, natural polydextrins from inulin and oligofructose extracted from chicory root has been refined. These polydextrins meet the scientific definition of a fiber because they resist digestion. The polydextrins are the fibers we see in all kinds of foods today.
What's the Difference?
Polydextrins are not bad for you. They seem to confer the health benefits of soluble fiber. Animal studies show that they stimulate the growth of beneficial bacteria in the colon and they improve the absorption of calcium and magnesium too. But Slate reports the Institute of Medicine's (IOM) position on polydextrose; the IOM says, “polydextrines may have beneficial effects, but they are not well understood.” In the US, the FDA allows polydextrose to be labeled as dietary fiber, but Health Canada does not permit the fiber designation.
When thinking about fiber, consider that whole wheat bread contains vitamins B1, B2, B3, E, folic acid, and the minerals calcium, phosphorus, zinc, copper, iron, manganese and magnesium, plus amino acids and phytonutrients, like phenols, ellagic acid, catechins, and others yet to be discovered. On the other hand, polydextrose gives you - well, fiber, along with mouth feel, etc. It truly is "a good source of fiber," but what about the other nutrients?
Do you have a favorite faux fiber food?