Dietary Fiber Benefits
Dietary fiber benefits are needed for everyone. If you are not getting enough fiber then the dietary fiber benefits you are missing out on could be detrimental to your health. Dietary fiber, formerly unrecognized for its health benefits, has received much attention in the past decade. Dietary fiber benefits are widely accepted as playing a significant role in reducing total blood cholesterol, thereby decreasing the risk of coronary heart disease. Dietary fiber benefits also include help in alleviating 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. So which dietary type offers the most dietary fiber benefits? Keep reading to learn more. 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 dietary fiber benefits are 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, 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 dietary fiber benefits 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
- 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 dietary fiber benefits, 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 a 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 week.
Numerous landmark studies have been conducted to validate this. One is cited in the December 1, 1996, issue of the publication OBGYN News. 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 dietary fiber benefits 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.
Soluble Fiber: Friend or Foe?
To many, soluble fiber is a close friend that keeps them away from constipation by increasing ease of bowel 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 bowel 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 bowel 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 about 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.
Other dietary fiber benefits include 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 are 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, the 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 between 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. It’s 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 fledged 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 insoluble 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 lesson 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 soluble and insoluble fibers from whole foods, not to mention antioxidants and other nutrients that have benefits of which are still undiscovered.
© Copyright 2016 Michael Lam, M.D. All Rights Reserved.