Getting to Know Fiber… Again (Part 1)

Doctors, dietitians, and television commercials constantly tell us to eat more fiber, and many of us are tired of hearing it. But it’s one message that doesn’t seem to go away — and for good reason. Most Americans don’t get enough fiber. If we did, we might not be dealing with as many health issues.


No, fiber isn’t a cure-all or even a medicine, but when you stop and think about it, it’s pretty remarkable what fiber can do. By the time you read this, the US Department of Agriculture and the US Department of Health and Human Services will just have announced the new 2010 Dietary Guidelines for Americans, which come out every five years. We’ll see what they have to say about fiber. In the meantime, let’s revisit our old friend that does more for us than we realize.

What Is Fiber, Anyway?
Fiber is kind of a standalone in the world of nutrition. It’s actually a carbohydrate, but (unlike starches and sugars) we can’t digest it very well. Fiber is made up of glucose units similar to those in starches and sugars, but in fiber, the units are bonded in such a way that we can’t break them apart in the digestive tract. We don’t have the enzymes to do this. So this means that fiber pretty much stays intact as it travels through the gut.

However, once fiber reaches the large intestine, it can be metabolized or fermented by intestinal bacteria, the “friendly flora” that use fiber for energy. (You can thank the bacteria for any feelings of [ahem] “gassiness” that you might experience after eating that bowl of bran flakes.) Some fiber isn’t fermented by bacteria, however, and simply passes right through us.

Insoluble Fiber: Nature’s Broom
Dietitians generally talk about two types of fiber: insoluble and soluble. That breakdown is actually not quite accurate, but we’ll get to that another time. Insoluble fiber is usually what most people think of when they hear the word “fiber.” Here are the different types of insoluble fiber:

What it does. I’ve heard insoluble fiber referred to as “nature’s broom.” As insoluble fiber travels through your digestive tract, it binds to water. This makes stools bulkier and softer, helping to prevent constipation and diverticulosis, a condition in which pouches form in the intestinal wall. Diverticulosis can lead to diverticulitis, which is a painful inflammation of these pouches. Here’s what insoluble fiber can do for us:

Food sources. It’s pretty easy to get insoluble fiber in your diet. And chances are you like at least some of these foods!

How much? Your total daily fiber intake should be about 14 grams of fiber per 1,000 calories, or somewhere between 25 and 35 grams per day. Most people take in only about 13 grams per day, so there’s room for improvement.

More fiber fun next week!

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Amy Campbell: Amy Campbell is the author of Staying Healthy with Diabetes: Nutrition and Meal Planning and a frequent contributor to Diabetes Self-Management and Diabetes & You. She has co-authored several books, including the The Joslin Guide to Diabetes and the American Diabetes Association’s 16 Myths of a “Diabetic Diet,” for which she received a Will Solimene Award of Excellence in Medical Communication and a National Health Information Award in 2000. Amy also developed menus for Fit Not Fat at Forty Plus and co-authored Eat Carbs, Lose Weight with fitness expert Denise Austin. Amy earned a bachelor’s degree in nutrition from Simmons College and a master’s degree in nutrition education from Boston University. In addition to being a Registered Dietitian, she is a Certified Diabetes Educator and a member of the American Dietetic Association, the American Diabetes Association, and the American Association of Diabetes Educators. Amy was formerly a Diabetes and Nutrition Educator at Joslin Diabetes Center, where she was responsible for the development, implementation, and evaluation of disease management programs, including clinical guideline and educational material development, and the development, testing, and implementation of disease management applications. She is currently the Director of Clinical Education Content Development and Training at Good Measures. Amy has developed and conducted training sessions for various disease and case management programs and is a frequent presenter at disease management events.

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