Fiber - Friend or Foe?
of Dietary Fiber
- Which Kind Do You Need?
As the Source of Soluble Fiber
and Digestive System Function
Fiber - Friend or Foe?
You Take Fiber Supplements?
Dietary fiber, formerly unrecognized for its
health benefits, has received much attention in the past decade.
It is widely accepted as playing a significant role in reducing
total blood cholesterol, thereby decreasing the risk of coronary
heart disease. It has also been credited in helping to alleviate
numerous bowel disorders, including colon cancer. Are these two
Basics of Dietary Fiber
Dietary fiber can be divided into two basic groups, soluble and
insoluble. Soluble fiber dissolves in water, and insoluble fiber,
as the term describes, does not. Both soluble and insoluble fiber provide bulk in the
large intestine and encourage bowel regularity. However, there
are important differences between the two.
The job of soluble
fiber is to absorb water in the intestinal tract and slow down
the amount of time needed to empty the intestine. Eating these
fibers makes you feel full and may help in weight loss.
These are also the fibers which are credited with helping to lower
bad cholesterol levels in the blood. Examples of foods that contain
soluble fibers include:
- Dried beans and peas.
- Psyllium laxatives
- Sesame seed
- Fruit, especially bananas, apple pulp,
citrus, grapes, apricots, cherries
- Vegetables, especially potatoes, cabbage,
Remember that fruits
and oats are primary sources of soluble fibers. Psyllium is the
most convenient and readily available form of soluble fiber supplementation.
Insoluble fibers draw water into
the intestinal tract, but rather than slowing down digestion,
they actually speed it up and increase the amount and frequency
of bowel movements. Examples of foods that contain
- Wheat bran
- Apple and pear skins
- Peas and carrots
- Bran cereals
- Whole-grain breads
- Toasted whole-grain breads
- Browned potatoes
Remember that vegetables
and wheat bran are the primary sources of insoluble fiber.
Fiber - Which Kind Do You Need?
In order to achieve the maximum amount of benefit from fiber, you
should try to get both
types into your diet.
Plant foods all contain both types of fiber - although some are
particularly rich in one or the other. Think
of vegetables and wheat bran as the primary sources of providing
insoluble fibers. Think of fruits, oats, and psyllium laxatives
as sources of soluble fibers. Following the anti-aging
Mediterranean diet will give you both.
As the Source of Soluble Fiber
Psyllium (Metamucil), a natural, water-soluble, gel-reducing fiber,
which is extracted from the husks of blond psyllium seeds (plantago
ovata), is a member of a class of soluble fibers referred to as
dietary content - 86 percent - is made up of 71 percent soluble
fiber and 15 percent insoluble fiber. This compares to
15 percent total fiber and only five percent soluble fiber for oat
bran. The soluble
fiber in one tablespoon of psyllium is equal to 14 tablespoons of
oat bran, another soluble fiber. For this reason, in
contrast to oats, psyllium is added in relatively small quantities
to other cereal grains to make food products.
Psyllium and Cholesterol
Through the years, researchers have found that patients
with mild to moderately elevated cholesterol levels can achieve
a sustained reduction of about 10% in cholesterol level by consuming
psyllium twice a day and adhering to the American Heart Association's
Numerous landmark studies have been conducted to validate this.
One is cited in the December 1, 1996 issue of the publication
<I>OBGYN News</I>. This study was led by Dr. James
Anderson, professor of medicine at the University of Kentucky
College of Medicine in Lexington. For six months, Dr. Anderson
followed 248 patients who were all instructed to follow the AHA
diet. Some patients were given Psyllium while others were given
a placebo. The average cholesterol level for the study population
was 229 mg/dl, with an LDL of 154 mg/dl. After six months, members
of the Psyllium plus diet group lowered their total cholesterol
by 8.6% and their LDL by 11.1%, versus those in the diet group
who showed only a 4% reduction in both these levels. The researchers
further note that the Psyllium worked
best for those people with the highest cholesterol
levels, with reductions of up to 25%.
Another well-designed, controlled study followed more than 100
adults with high blood cholesterol (levels greater than 220 mg/dl).
The study followed men and women who ate a high-fat diet (40 percent
or more of total calories) as compare to those who ate a low-fat
diet (no more than 30 percent of total calories). Researchers
then compared the effects of adding 1 1/2 packets of Psyllium
(Metamucil) twice a day on blood cholesterol levels with the effects
of not taking the soluble fiber supplement.
After eight weeks, supplementation with Psyllium showed a small
but significant decrease in total cholesterol and LDL cholesterol
levels, regardless of the type of diet. Total cholesterol levels
dropped a weighted average of 4.7 percent; LDL cholesterol levels
showed a 6.6 percent decrease.
Psyllium and Digestive System Function
also use Psyllium to treat chronic, not acute, constipation as
well as acute diarrhea, diverticulosis (asymptomatic infection
of large intestine), diverticulitis (infection/inflammation of
lower large intestine), and irritable bowel syndrome. Psyllium is a laxative that promotes
bowel movements by absorbing water and electrolytes,
producing a bulk fluid that is easy to pass. It is contained in
fiber supplements, such as Metamucil, Effer-syllium, Perdiem Fiber,
Konsyl and Hydrocil, and in Kellogg's Bran Buds ready-to-eat cereal.
For constipation, Psyllium is often
taken as 1-2 teaspoons or 1-2 packets, 1-3 times daily. It
needs to be mixed with water or juice, and should be accompanied
by a lot of fluids
throughout the day. Side effects are most commonly bloating, flatulence,
and cramps. People with intestinal ulceration, bowel adhesions,
or stenosis should use caution when taking Psyllium. For these
people, Psyllium could cause more harm than good to their digestive
Soluble Fiber - Friend or Foe?
To many, soluble fiber is a close friend that keeps them away
from constipation and increases ease of bowl movement. This is
especially true among many that have a high tendency of getting
constipated easily. Those over 50 years old are particularly affected
by slowing motility of the gastrointestinal tract and resultant
constipation. Taking soluble fiber
two to three times a day is a simple way to solve this problem.
Many people with normal digestive functions still take Psyllium
on the hypothesis that a faster and softer bowl movement improves
transit time. This theoretically translates into less time the
feces and its contaminants stay in the body. Ultimately, this
is postulated to enhance bowl health and prevents the formation
of polyps, some of which can lead to colon cancer.
However, three landmark studies,
including one carried out on more than 88,000 nurses and published
in the New England Journal of Medicine, showed that a high fiber
diet seemed to offer no protection specifically against colon
Another study published in the British Medical Association journal
Lancet (October, 2000) raises questions over previous studies
showing the benefits of fiber in preventing colorectal cancers
as well. This particular study was lead by the European Cancer
Prevention Organization Study Group and found dietary fiber (by
Psyllium supplement) can actually increase the risk of colorectal
The efficacy of dietary supplementation of calcium and fiber on
the recurrence of cancer was studied by researchers from nine
European countries and Israel. They assigned 665 people to groups
that randomly receive calcium, soluble fiber (3.5 to 5 grams of
Psyllium) or a placebo. They were then examined with a colonoscopy
after three years.
Of the 665 that participated, 552 received the follow-up exam.
At least one cancer developed in 16 percent of the calcium group,
29 percent in the fiber group and 20 percent in the placebo group.
They say while the benefit of the calcium was not statistically
significant, the increase in the soluble fiber group was.
The findings of this study is consistent with two earlier American
studies that suggest a low-fat,
high-fiber diet may not be an effective strategy to prevent colorectal
cancer recurrence in those who have a history of polyps.
Dr. Bonithon-Kopp, author of the study, pointed out, "However,
our findings should not prevent recommendations for high consumption
of vegetables, fruits and cereals, because this approach has potentially
beneficial effects on other chronic diseases, especially coronary
It is important to put such studies into perspective. So far,
three major studies were published that looked at the relationship
of dietary fiber and cancer. Only the early stages of the adenoma-cancer
sequences were studied. It was found that soluble fiber did not
have a benefit in preventing recurrence of small polyps. This
should not come as a surprise. Soluble
fiber's main action is in lowering of cholesterol and reduction
of cardiovascular disease. Its colon cancer prevention properties
have been under investigation and merely hypothesized for years
without concrete evidence. The latest three studies provide good
evidence that indeed the role of soluble fiber in preventing colon
cancer is probably not well founded.
For prevention of colon cancer,
insoluble fiber is the diet of choice. Insoluble fiber
is not what was supplemented in these studies. Subjects in the
last study were given Psyllium, which consists of 71% soluble
and 15% insoluble fiber.
Furthermore this last study did not address the issue of the progression
of adenoma into full fledge cancer. Soluble fiber may still prevent
the progression of these polyps into tumors. That type of study
has yet to be done, especially as it relates to the malignant
transformation of adenoma.
It is well known that fiber's health enhancing activities is maximized
in the presence of high volume of water, which acts to soften
the bulk of the stool. It is also unclear in this study whether
the participants have increased their water intake in conjunction
with the soluble fiber intake.
Should You Take Fiber Supplements?
The average American diet is low in fiber (5-15 grams). For
optimal anti-aging purposes, 25-30 grams of fiber is needed. This
can be achieved by taking in half a cup of bran, one cup of legume,
2 cups of vegetables, 3 fruits, whole grain bread and cereal on
a daily basis. If you are not, consider fiber supplementation together with digestive enzymes
and higher intake of water to enhance gastrointestinal health.
All fiber supplements are best taken one hour before
a meal so as not to interfere with absorption of nutrients.
If you are currently on soluble fiber for
cholesterol control, there is no reason to stop, for
the simple reason that soluble fiber does lowers cholesterol.
If your primary objective is to prevent colon cancer, then it
is wise in view of the last 3 major studies to take additional
vegetables and whole grain products such as wheat bran, which
will provide you with insoluble fiber, instead of taking fiber
supplements such as Psyllium as a way to prevent cancer.
Regardless of whether you are taking soluble or insoluble fiber,
do remember to make sure your water intake is at least 8-10 glasses
a day, especially if you are on any fiber supplement program.
If you have high cholesterol and want to totally stay away from
Psyllium as a way to reduce cholesterol level, some natural alternatives
to consider include garlic, niacin (in therapeutic dosages), and
statin drugs (prescription required).
The take home lesion is simple: take insoluble fibers,
which come from whole foods such as vegetables, wheat, and grain
products, for cancer prevention. For cholesterol control, take
soluble fibers, which are abundant in fruits, oat bran, legumes,
apple pectin, and guar gum. Take Psyllium as a supplement for
cholesterol control and not for cancer prevention. For
those who are using Psyllium to enhance bowl motility, you may
want to reduce Psyllium intake but increase intake in digestive
enzymes while maintaining a high water intake of 8-10 glasses
If you can get all the fibers from diet alone, that is the best.
The Mediterranean diet (with a heavy focus on dense vegetables)
provides both soluble and insoluble fibers from whole food, not
to mention antioxidants and other nutrients that have benefits
of which are still undiscovered.
About The Author
Michael Lam, M.D., M.P.H.,
A.B.A.A.M. is a specialist in Preventive and Anti-Aging Medicine. He is currently
the Director of Medical Education at the Academy of Anti-Aging
Research, U.S.A. He received his Bachelor of Science degree from
Oregon State University, and his Doctor of Medicine degree from
Loma Linda University School of Medicine, California. He also
holds a Masters of Public Health degree and is Board Certification
in Anti-aging Medicine by the American Board of Anti-Aging Medicine.
Dr. Lam pioneered the formulation of the three clinical phases
of aging as well as the concept of diagnosis and treatment of
sub-clinical age related degenerative diseases to deter the aging
process. Dr. Lam has been published extensively in this field.
He is the author of The Five Proven Secrets to Longevity
(available on-line). He also serves as editor of the Journal
of Anti-Aging Research.
For More Information
For the latest anti-aging related health issues,
visit Dr. Lam at http://www.drlam.com/. Feel free to
email Dr. Lam at dr@DrLam.com
if you have any questions.
© 2001 Michael Lam, M.D. All
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