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We all know dietary fiber is good for us, but many of us don’t know what it is. And if my patients’ misconceptions are indication of what most people think, dietary fiber is one of the most confusing dietary terms out there. For some, it simply conjures up the unappetizing image of eating the equivalent of shredded corrugated cardboard. This is a shame because fiber is an important part of our diet.
Most Americans don’t get enough fiber in their diets. The recommended intake is between 20 and 38 grams of total fiber per day, depending on your age and gender, with 25 grams being a realistic goal for most people. This is about the same amount of fiber that is found in five servings of either fruits or vegetables and one or two servings of either whole grains or beans. Unfortunately, the average American consumes a mere 14 grams — and many eat even less. Since fiber helps you digest food, if you don’t get enough in your diet, you can become constipated, develop hemorrhoids, or be prone to illnesses like diverticulosis (inflammation in your digestive tract).
And contrary to popular beliefs, you can’t simply substitute fiber supplements, such as Metamucil, for healthy eating habits. When you take ingest a large amount of fiber at once, you have to make sure that you drink plenty of water. If you don’t, the fiber will act as a sponge and absorb liquids in your body. This, in turn, can cause constipation, and bloating. The best way to get enough fiber is to eat fruits, vegetables, whole grains, and beans. They’re one-stop fiber shopping: they contain moderate amounts of fiber and water.
Since fiber is important to our health and yet is so misunderstood, I’d like to go through what I call “Fiber 101.” Whether you just need a refresher on this nutrient or are a fiber novice, these basics should get you up to speed and show you how to add more fiber-rich foods, which are both tasty and low in calories, to your diet. With a little planning, you’ll see that it’s actually pretty easy to maintain your fiber needs.
What is fiber and where does it come from?
Fiber is a carbohydrate that is not digested by our bodies. It is only found in plant foods — no animal products contain fiber — such as fruits, vegetables, whole grains, beans, seeds, and nuts. Since our bodies can’t digest and break down fiber, it has practically no calories.
Is all fiber the same?
No. There are two kinds of fiber and each one has a different health effect. Here’s a breakdown of these fiber types:
- Insoluble fiber: This type of fiber does not dissolve in water and is known as a “bulking agent” – it’s kind of like a Roto-Rooter for the digestive tract. It’s good for bowel regularity and elimination, since it absorbs water and makes stools softer. Insoluble fiber also tends to speed up the movement of food in the digestive tract. It can help prevent hemorrhoids and diverticulosis, and it may help prevent colon cancer.
- Soluble fiber: This fiberdoes dissolve in water and it forms a gel-like substance in the stomach, which slows down the rate at which the stomach empties. This type of fiber tends to slow down the movement of food throughout the digestive tract and is not related to regularity. Instead, it’s been shown to help lower blood cholesterol and help control blood sugar levels in diabetics.
What are good dietary sources of fiber?
It’s important to eat both soluble and insoluble fiber because both are vital to your health. A good source of fiber contains at least three grams of fiber per serving and a high-fiber source has at least five grams per serving.
Some good choices for foods containing insoluble fiberinclude: wheat and corn bran, whole-grain products (such as bread, pasta, and cereals), fruits, and vegetables. If you’re looking for soluble fiber, choose foods that contain oats and oat bran, beans (chick peas, kidney beans, baked beans, and black beans), and fruits, and vegetables.
Notice that fruits and vegetables do “double duty” and are a great source of both types of fiber. Avoid fruit and vegetable juices; stick with the whole fruit or vegetable to maximize your fiber intake. It’s best to eat the peels (after thoroughly washing them, of course) and edible seeds. When shopping for fiber-rich foods, choose those that are less processed. These will contain more fiber, since refining processes strip away foods’ natural fiber. Finally, if you’re cooking a dish with meat, consider substituting some of the meat with beans.
How much fiber do you need each day?
The recommended intake is about 20 to 25 grams per day of total fiber from food sources, depending on your age and gender. Most people can handle up to 35 grams a day without any ill effects. The good news is that it’s not hard to get enough fiber into your diet. Eating five servings of fruits and vegetables a day plus a serving or two of whole grains or beans will easily get you to 20 grams of fiber a day. A serving of most fruits, vegetables and whole grains contains anywhere from three to six grams of fiber. New dietary guidelines recommend seven to nine servings of fiber a day, depending on age, gender, and physical activity.
What’s the best way to increase my fiber intake?
I always recommend adding fiber to your diet very gradually, as your body needs time to adjust. Adding fiber too quickly can produce excess gas, bloating, and diarrhea. A good rule of thumb is to add a serving (containing three to five grams of fiber) a week. Read the labels on foods carefully to calculate your daily fiber intake — the grams can add up quickly.
Remember to also drink plenty of water along with increasing your fiber intake, since fiber helps prevent constipation by acting like a big colon sponge — it holds on to water to push the waste through and keep it moving.
Why can’t I just take a fiber supplement?
The best sources of fiber are dietary, since you get the added value of ingesting the other nutrients in that food, including vitamins and minerals. Our bodies are built to digest nutrients obtained from the food supply, not those that have been isolated and put into concentrated supplements.
Fiber supplements may have a role in your diet if you really struggle with reaching the daily recommendation, but you should check with your doctor before taking them. You can also sprinkle some fiber into soups, pasta sauce, or other liquids to boost your daily fiber intake, but remember to add no more than three grams per serving. Some foods on the market, such as yogurt and orange juice, actually contain added fiber.
Why do people say that fiber is good for weight loss?
A fiber-rich diet contributes to effective weight management for a number of reasons. These include:
Many fiber-rich foods are also low in calories. Fiber is good at binding to water, which tends to provide a greater sense of fullness in the stomach and great sense of feeling satisfied after eating. High-fiber foods usually require a person to chew more, which slows down the rate of eating. When you eat slower, biological signals from the stomach have a chance to tell your brain that you’re content (this takes about 15 to 20 minutes to happen).The body does not absorb fiber, so fiber is essentially calorie-free.
Dr. Fernstrom’s Bottom Line: Whether you are looking for help with your cholesterol, blood sugar, constipation, or weight control, increasing your daily fiber intake might just be the missing link to a healthier lifestyle. If you make the commitment to eating less processed foods and plenty of fruits and vegetables, you’ll meet your fiber needs without extra effort.
Madelyn Fernstrom, Ph.D., CNS,is the founder and director of the An associate professor of psychiatry, epidemiology, and surgery at the University of Pittsburgh School of Medicine, Fernstrom is also a board-certified nutrition specialist from theAmerican College of Nutrition.
PLEASE NOTE: The information in this column should not be construed as providing specific medical advice, but rather to offer readers information to better understand their lives and health. It is not intended to provide an alternative to professional treatment or to replace the services of a physician.