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Fiber - Friend or Foe? |
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(READING TIPS: For fast reading, scan through the topic headings in BOLD BLACK, important conclusions in BOLD BLUE, and " Must Know " in BOLD RED. To jump to specific sections in this article, click on the respective LINKS in the Contents.)
| Before You Begin Information presented here is for general educational purposes only. Each one of us is biochemically and metabolically different. If you have a specific health concern and wish my personalized nutritional recommendation, write to me by clicking here. |
Contents
Introduction
Basics of Dietary Fiber
Soluble Fiber
Insoluble Fiber
Fiber - Which Kind Do You Need?
Psyllium As the Source of Soluble
Fiber
Psyllium and Cholesterol
Psyllium and Digestive System
Function
Soluble Fiber - Friend or Foe?
Should 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 hypotheses true?
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.
- Lentils.
- Oats.
- Barley.
- Psyllium laxatives
- Sesame seed
- Fruit, especially bananas,
apple pulp, citrus, grapes, apricots, cherries
- Vegetables, especially potatoes,
cabbage, carrots
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 Fiber:
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 insoluble fibers:
- Wheat bran
- Apple and pear skins
- Peas and carrots
- Bran cereals
- Whole-grain breads
- Vegetables.
- Pears
- 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.
Psyllium 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 mucilages.
Psyllium's total 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 (AHA) Diet.
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 compared 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.
Soluble fibers appear to reduce blood cholesterol in two ways. First, they prevent the reabsorption of vital bile acids from the small intestine. To replace the lost bile acids, cholesterol is drawn from the body, thereby reducing its cholesterol supply. Second, the fermentation of soluble fibers in the intestine produces short-chain fatty acids which block the synthesis of cholesterol.
Studies suggest that soluble fibers also may help control the rise in blood sugar following a meal and reduce insulin requirements in some patients with diabetes mellitus. By increasing the viscosity of gastrointestinal contents, soluble fibers retard gastric emptying, slowing the absorption of glucose in the process.
Psyllium and Digestive System Function
People
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 system.
Soluble Fiber - Friend or Foe?
To many, soluble fiber is a close friend that keeps them away from constipation
by increasing 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 cancer.
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 cancer.
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 heart disease."
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 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 bowel
motility, you may want to reduce Psyllium intake and increase your digestive
enzymes intake while maintaining a high water intake of 8-10 glasses a day.
If you can get all the fibers from your diet alone, that is best. The Mediterranean
diet (with a heavy focus on dense vegetables) provides both soluble and
insoluble fibers from whole foods, not to mention antioxidants and other
nutrients that have benefits of which are still undiscovered.
| Message from Dr. Lam I hope you have enjoyed reading this article. If you have areas you don’t understand, comments (good or bad), or if you have a specific health concern, feel free to write to me by clicking here. |
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 www.LamMD.com. Feel free to email
Dr. Lam at dr@LamMD.com if you have any questions.
Reprint Information
This article may, in its unabridged, unaltered form and in its entirety only,
be reprinted and republished without permission provided that it is for personal
and non commercial education use only and further provided that credit be given
to the author, with copyright notice and www.LamMD.com
clearly displayed as source. Written permission from Dr. Lam is required
for all other use.
©2000 Michael Lam, M.D. All Rights Reserved.
References
Ames BN et al. "Oxidants, Antioxidants, and the Degenerative Disease of Aging" Proc Natl Acad Sci 1993; 90:7915-7922.
Gaziano, JM et al "Antioxidant Vitamins and Coronary Artery Disease Risk" Am J Med 1994; 97 ( suppl 3A): 18S-21S.
Hodis, NH, Mack WJ, LaBreeL, Cashin-Hemphill L, Sevanian A, Johnson R, and Azen SP. JAMA 1995l; 273:1849-1854.
Rimm, EB et al "Vitamin E Consumption and the Risk of Coronary Heart Disease in Men" N Engl J Med 1993: 328;1450-1456.
Stephens, NG , Parsons A, Schofield, PM, Kelly F, Cheesman, K and Mitchinson, MJ. Lancet 1996; 357:781-786.
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