Fiber is indigestible – and also irreplaceable

Your grandmother called it roughage; nutritionists call it fiber. Dietary fiber is an age-old nutrient in our diets that is getting new play today because of its myriad health benefits.

Fiber is the indigestible portion of plant foods. It’s found mainly in fruits, vegetables, whole grains, nuts, and dried peas and beans. It wouldn’t seem as if something that passed virtually unchanged through your digestive tract, literally from mouth to colon, could be helpful, but fiber definitely is.

In its most basic role, dietary fiber increases the weight and size of your stool. A soft stool is easier to pass, decreasing your risk of constipation. On the other side of the coin, dietary fiber also firms loose, watery stools owing to its ability to absorb water.

Beyond this, a fiber-rich diet may lower your risk of specific health problems, everything from hemorrhoids and irritable bowel syndrome to the development of small pouches in your colon known as diverticular disease.

Fiber, especially soluble fiber found in foods such as oats, peas, beans, apples, citrus fruits and barley, can lower blood cholesterol levels and slow the absorption of sugar in your diet, which is a boon for people with diabetes. Eating a high-fiber diet is also thought to reduce the risk of developing type 2 diabetes. There is some evidence that dietary fiber can help to prevent colorectal cancer.

What many people really like about dietary fiber is its use as a weight loss aid. High-fiber foods generally require more time to chew, which gives your body time to register when you’re no longer hungry, so you’re less likely to overeat at mealtime. A high-fiber diet also tends to make a meal feel larger and linger longer in your stomach, so you stay full for a greater amount of time. And, high-fiber diets tend to be less "energy dense," which means they have fewer calories for the same volume of food.

The 2005 Dietary Guidelines for Americans, the most recent, recommend that we should eat between 20 and 35 grams of dietary fiber each day. To reach this amount, if you’re not eating it already, it’s important to start slowly when adding more fiber to your diet. That means gradually eating more fiber over a couple of weeks. This lets the natural bacteria in your gut adjust to the change. Eating too much fiber when you’re unaccustomed can produce problems such as intestinal gas, abdominal bloating and cramping.

Increase your water intake as you eat more fiber, too. Fiber works best when it absorbs water, making your stool soft and bulky. Without the added water, you could become constipated.

What foods are specifically high in fiber?

In the vegetable group, 1 cup of cooked green beans, peas, sweet potato and winter squash all provide 4 or more grams of dietary fiber. Other good choices include beets, carrots and corn.

Fruits like berries are high in fiber. A one-cup serving of blackberries, for example, provides nearly 8 grams of dietary fiber. Apples, dates, oranges, peaches and dried fruits such as raisins and prunes are also good fiber sources.

One-cup of plain canned baked beans provides over a third of your fiber quota for the day. Cup size portions of lentils and split peas serve up half of your daily fiber needs.

On the bread and cereals front, a slice of whole grain bread has three times the fiber as white bread. Bran cereals are among the highest in fiber; a half cup of 100 percent All Bran provides one-quarter of the daily fiber goal. Shredded wheat and oatmeal are also high fiber choices.

Nuts are high in calories, but they do serve up 2 to 3 grams of dietary fiber per 1-ounce serving.

More is not necessarily better. Eating too much fiber, much more than the Dietary Guidelines recommend, can prevent the absorption of nutrients such as calcium, iron, zinc, copper and magnesium.

To make sure you’re getting the right amount of fiber, and reaping fiber’s benefits, aim to eat a high-fiber food at each meal and snack. For example, spoon into a bowl of oatmeal with raisins for breakfast, lentil soup with a whole-grain roll for lunch, tossed green salad with dinner, and an apple or bag of peanuts through the day.

Carol Bareuther is a registered dietitian and a regular contributor to The Triton. Comments on this column are welcome at editorial@the-triton.com .