Where’s the Fiber?

Most health professionals are aware of the importance of dietary fiber, but the same can’t be said for consumers. We know we should eat more of it, but the beneficial effects it has on weight loss, heart disease, gastrointestinal disorders and even cancer go largely unnoticed. To remedy the situation, let me give you a little background information on fiber, the current daily recommendations, some basic health benefits and a simple plan for meeting a reasonable goal each day.

Fiber is basically the indigestible component of plants. There are actually several different types of fiber and two distinct ways to classify them. The older classification system focuses on their solubility in water. Water-soluble fibers, such as gums, beta-glucans and pectins, actually dissolve or swell in water. These fibers are typically fermented in the large intestine, resulting in a wide variety of beneficial effects on health. Insoluble fibers include cellulose, hemicellulose and lignin, and function to increase fecal bulk, thereby shortening the passage time through the intestinal tract. The newer classification system groups fibers into the “dietary” category or the “functional” category, though some fibers qualify as both. Dietary fibers are those that are consumed intact in plants, while functional fibers are often isolated and added to foods for a physiological purpose.

The current recommendations for fiber are much higher than the average daily intake for most Americans. The National Academy of Sciences set the daily adequate intake at 38 grams for men and 25 grams for women up to age 50, with slightly lower recommendations for older Americans. It’s important to note that there are no specific guidelines based on individual fiber types. The average intake in the United States is somewhere around 12-15 grams per day, so the current guidelines seem somewhat lofty. That said, we know there are numerous health benefits associated with fiber, so increasing your daily intake, even by 5 or 10 grams per day, seems like a prudent step.

Fiber has a number of effects on the body and, subsequently, overall health. First of all, as mentioned earlier, insoluble fiber increases fecal bulk and speeds up transit time, diluting out any potential carcinogens and leaving less time for any remaining pathogens to exert their effects. This mechanism also reduces the incidence of diverticulosis, an inflammatory condition of the large intestine. Fiber also slows down gastric emptying, which may slow the absorption of glucose in the small intestine. The delayed gastric emptying improves satiety or fullness, which can certainly be beneficial for those trying to manage excess weight or obesity. The gradual absorption of glucose may offer better blood sugar control to diabetics as well. Another positive effect is the ability of soluble fiber to bind with bile salts. Bile salts are made from cholesterol, so if some of them are excreted attached to fiber, blood cholesterol levels may drop, thereby reducing the risk of heart disease. Soluble fiber also gets fermented in the large intestine to short-chain fatty acids, which possibly reduce cholesterol production once transported to the liver.

It’s clear that additional fiber offers a myriad of benefits, but how do we increase our intake? It’s really not that difficult to increase your daily fiber consumption. The easiest way is to simply eat more fruits, vegetables and whole grain products. This is basic and obvious, but certainly effective. As an example, it would take 3 servings of fruit, 3 servings of vegetables, 2 slices of whole grain bread, ½ cup beans and 1 serving of a high-fiber cereal to reach 35 grams for the entire day. Easy enough, unless your diet consists of highly processed or refined foods. The best way to start is by incorporating more fiber gradually, adding a few grams here and there. And if you aren’t a big fan of fruits and vegetables, you can always add a fiber supplement as well, though I typically advocate a “food first” philosophy.