By Mayo Clinic staff
http://www.mayoclinic.com/
Eat more fiber. You've probably heard that before. But do you know why
fiber is so good for your health?
Dietary fiber — found mainly in fruits, vegetables, whole grains and
legumes — is probably best known for its ability to prevent or relieve
constipation. But fiber may also provide other health benefits, including
reducing your risk of several diseases such as diabetes and heart disease.
So how much fiber do you need each day? National Academy of Sciences'
Institute of Medicine, which provides national dietary guidelines, gives
the following daily recommendations for adults:
38 grams for men and 25 grams for women 50 and younger
30 grams for men and 21 grams for women 51 and older
Do you need to eat more fiber? Read on to learn more about fiber and how
you can incorporate more of this beneficial compound into your meals and
snacks.
What is fiber?
Fiber — also known as roughage or bulk — includes all parts of plant foods
that your body can't digest or absorb. Fiber is classified into two
categories: Those that don't dissolve in water (insoluble fiber) and those
that do (soluble fiber).
Insoluble fiber. This type of fiber moves through your digestive system
more quickly than its counterpart. Insoluble fiber can help promote soft,
bulky stools. Whole-wheat flour, nuts, vegetables, bran and fruits with
edible seeds, such as raspberries, are good sources of insoluble fiber.
Soluble fiber. This type of fiber dissolves in water to form a gel-like
material. It can help lower blood cholesterol and glucose levels. You can
find generous quantities of soluble fiber in oats, legumes, barley,
apples, citrus fruits, carrots and psyllium.
The amount of each type of fiber varies in different plant foods. To
receive the greatest health benefit, eat a wide variety of high-fiber
foods.
Benefits of bulking up
Digestive enzymes can't break down fiber, unlike other food components
such as fats, proteins or carbohydrates, which your body breaks down and
absorbs. Fiber passes virtually unchanged through your stomach and small
intestine and into your colon.
In the colon, bacteria ferment some forms of fiber. Other forms of fiber
resist fermentation and pass in stool unchanged, which increases the
weight and size of your stool in addition to softening it. A bulky stool
is easier to pass, decreasing the chance of constipation. If you have
loose, watery stools, fiber may also help to solidify the stool because it
absorbs water and adds bulk to stool.
A high-fiber diet may lower your risk of specific disorders, such as
hemorrhoids, irritable bowel syndrome and the development of small pouches
in your colon (diverticular disease). Fiber may also lower blood
cholesterol levels and slow the absorption of sugar, which, for people
with diabetes, may decrease the need for insulin. A high-fiber diet may
also reduce the risk of developing type 2 diabetes (formerly called
adult-onset or noninsulin-dependent diabetes).
In addition, fiber may reduce the risk of colon cancer. Insoluble fiber
speeds movement of digested food through your intestine. This may reduce
the amount of time your colon is exposed to cancer-promoting substances
formed during digestion. But it's not yet clear whether other ingredients
in fibrous foods or fiber alone helps protect against cancer.
Eating a high-fiber diet may also help with weight control. High-fiber
foods generally require more chewing time, which gives your body time to
register when you're no longer hungry, so you're less likely to overeat.
Also, a high-fiber diet tends to make a meal feel larger and linger
longer, 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.
Boost your fiber intake
The best sources of fiber are whole-grain products, raw or cooked fruits
and vegetables, and dried beans and peas. Refined or processed foods —
such as fruit juice, white bread and pasta, and non-whole-grain cereals —
are lower in fiber content. The refining process removes the outer coat
(bran) from grain, which lowers its fiber content. Similarly, removing the
skin from fruits and vegetables decreases their fiber content.
Whole foods rather than fiber supplements are generally best. Fiber
supplements — such as Metamucil, Citrucel and Fibercon — don't provide the
vitamins, minerals and other beneficial nutrients that high-fiber foods
do. However, some people may still need a fiber supplement if the dietary
changes aren't sufficient or if they have certain medical conditions, such
as irritable bowel syndrome. Check with your doctor if you feel you need
to take fiber supplements.
So where's the fiber? This list shows the amount of dietary fiber in
several types of foods.
Food item
Fiber content in grams
Apple, medium with skin
3.7
Broccoli, boiled, 1 cup
4.5
Brown rice, cooked, 1 cup
3.5
Carrots, raw, one medium
2.2
Kidney beans, red, boiled, 1 cup
13.1
Oat bran muffin, medium
5.2
Oatmeal, quick, regular or instant, cooked, 1 cup
4.0
Popcorn, air popped, 2 cups
2.4
Raspberries, raw, 1 cup
8.4
Split peas, cooked, 1 cup
16.3
Whole-wheat bread, one slice
1.9
Other foods are good sources of fiber as well. Read food labels to find
the amount of dietary fiber in each product, or search the U.S. Department
of Agriculture (USDA) National Nutrient Database Web site.
High-fiber foods are good for your health. But too much fiber too quickly
can cause intestinal gas, abdominal bloating and cramping. Increase fiber
in your diet gradually over a period of a few weeks. This allows the
natural bacteria in your digestive system to adjust to the change. Also,
drink plenty of water. Fiber works best when it absorbs water, making your
stool soft and bulky. Without the added water, you could become
constipated.
Tips for fitting in fiber
Need some ideas for high-fiber meals and snacks? Try these suggestions:
Start your day with a high-fiber breakfast cereal — 5 or more grams of
fiber per serving. Opt for cereals with bran or fiber in the name. Or add
a few tablespoons of unprocessed wheat bran to your favorite cereal.
Add bran cereal or unprocessed wheat bran to baked products such as
meatloaf, breads, muffins, casseroles, cakes and cookies. You can also use
bran products as a crunchy topping for casseroles, salads or cooked
vegetables.
Switch to whole-grain breads. These breads list whole wheat, whole-wheat
flour or another whole grain as the first ingredient on the label.
Ideally, look for one with at least 3 grams of dietary fiber per serving.
Substitute whole-grain flour for half or all of the white flour when
baking bread. Whole-grain flour is heavier than white flour. In yeast
breads, use a bit more yeast or let the dough rise longer. When using
baking powder, increase it by 1 teaspoon for every 3 cups of whole-grain
flour.
Eat more whole grains and whole-grain products. Experiment with brown
rice, barley, whole-wheat pasta and bulgur.
Take advantage of ready-to-use vegetables. Mix frozen broccoli into
prepared spaghetti sauce. Snack on baby carrots.
Eat more beans, peas and lentils. Add kidney beans to canned soup or a
green salad. Or make nachos with refried black beans, baked tortilla chips
and salsa.
Eat fruit at every meal. Apples, bananas, oranges, pears and berries are
good sources of fiber.
Make snacks count. Fresh and dried fruit, raw vegetables, and low-fat
popcorn and whole-grain crackers are all good choices.
