Note to Reporters: The following column was written by Melissa Wdowik, PhD, RDN, an assistant professor at Colorado State University in the Department of Food Science and Human Nutrition, and director of the Kendall Reagan Nutrition Center.
Have you given much thought to the fiber in your diet? Probably not, if you are like most Americans. While recommended intakes of dietary fiber range from 21-25 grams per day for women to 30-38 for men (depending on age), average intake in this country is about 15 grams for both genders. It may be a bigger deal than you think.
Dietary fibers are complex carbohydrates in plants that your body cannot digest or absorb. Instead, they either form a gel when mixed with water in the gut, or move quickly to the large intestine, where they speed up the elimination of waste. These characteristics have historically placed fibers into one of two groups: soluble and insoluble, respectively. However, research indicates that solubility does not tell the whole story of physiological effects; besides, plant-based foods have mixtures of soluble and insoluble fiber. I prefer to encourage intake of a variety of fiber types, with attention to fiber’s many benefits and dietary sources.
Heart health is one of the best-known benefits of fiber intake. Eating more oat products, legumes (dry beans, peas and lentils) and psyllium (often added to cereal) decreases triglycerides, total cholesterol and LDL cholesterol in the blood. An increase of just 10 grams per day appears to be beneficial; you can get this amount by adding ½ cup navy beans to your dinner, or ½ cup black beans and ½ cup brown rice.
Blood sugar and insulin responses are also improved after a meal containing fiber. Most beneficial are whole grains, legumes, nuts, fruit and non-starchy vegetables. A favorable intake might include oatmeal with nuts and berries for breakfast, a large colorful tossed salad for lunch and lentil tomato soup for dinner.
Digestive issues such as irritable bowel syndrome, diverticular disease and slow-moving bowels can be prevented or treated with a fiber-rich diet. The key is to increase fiber intake gradually and increase fluid intake at the same time. For example, swap a donut for a cup of psyllium-enriched breakfast cereal on days 1 and 2, continue this and replace fast food with a whole wheat tortilla wrap on days 3 and 4, and continue both of these while adding ½ cup vegetables to dinner on days 5 and 6, adding a glass of water to each meal as well. Since the gut reacts differently in each of us, consult your doctor or dietitian for additional information.
Fermentation is a process that breaks down some fibers into beneficial end products. These fermentable fibers are called prebiotics, and contribute to the health of the gut by stimulating good bacteria to promote both digestion and immunity. Notable sources include bananas, onions, leeks, garlic, fruit, soybeans, asparagus and chicory root. Chicory is a significant source of inulin, the fiber that is artificially added to foods to increase their fiber content; examples include Fiber One 90 calorie bars and Chobani 100-calorie yogurt, each with 5 grams of fiber from chicory. But beware! This form of fiber causes gastric discomfort, bloating and gas in many people, and is a perfect example of the advantage of real food over supplementation.
Weight loss is another benefit of a high-fiber diet because of its tendency to make you feel full and eat less, while also slowing digestion. Try to replace processed snacks such as chips and pretzels with fruit, seeds and nuts. At meals, incorporate vegetables, barley and beans while cutting back on meat and white pasta.
The easiest way to increase your fiber intake is to eat more fruit, vegetables, legumes and whole grains. Aim to eat a wide variety of different types of fiber, and remember, add fiber gradually while increasing the amount of water you are drinking. The benefits are almost endless.
Melissa Wdowik, PhD, RDN, FAND, is an assistant professor at Colorado State University in the Department of Food Science and Human Nutrition, and director of the Kendall Reagan Nutrition Center.