I am convinced digestion is the great secret of life.

--Sydney Smith (1771-1845), British clergyman and author

Few issues in medicine and nutritional science evoke general consensus among the experts. fiber is one of the exceptions.

fiber plays an essential role in overall good nutrition and is necessary to achieve optimum health. It helps to prevent a broad range of diseases, including the two responsible for most deaths: heart disease and cancer. A fiber deficiency, on the other hand, contributes to a multiplicity of common health problems--several of which can deprive you of maximum life span.

Most folks in the United States consume far too little fiber. For starters, the standard American diet still emphasizes foods of animal origin. Meat, poultry, fish, dairy products, and eggs contain no fiber whatsoever. Then, too, our diet features an abundance of packaged foods, which have had their fiber stripped away. Like vitamins, minerals, and essential fatty acids, fiber is often a casualty of modern refining and processing.

Actually, the practice of removing fiber from foods has its roots in the earliest years of nutritional science. Back then, nutritionists deemed fiber expendable because it contains no nutrients, has no calories, and is indigestible. fiber, they believed, does nothing.

Of course, they couldn't have been more wrong. As any student of Zen knows, even doing nothing amounts to doing something. Such is the case with fiber.

Nutritionists now realize that fiber quickly ushers noxious chemicals and other waste products from the intestinal tract. This benefits not just the digestive system but the entire body in a variety of ways, which I'll discuss a bit later.

The combination of a high-fiber diet and daily fiber supplements fosters a cleaner, healthier internal environment. It primes your insides to withstand the life-shortening ravages of toxins and time.

A Checkered Past

For a substance that can do the body so much good, fiber has generated its share of controversy. Perhaps the first to cast doubt on the substance's value was the Greek physician Hippocrates, who stated that "white bread is more nutritious, as it makes less feces." The Father of Medicine, being a hygiene-oriented guy, equated more feces with more filth and therefore with less health. He apparently failed to realize that abundant bowel movements actually keep the intestinal tract clean. In doing so, he set the tone for the debate that was to come.

Centuries later, American Sylvester Graham (of graham cracker fame) challenged Hippocrates' pronouncement by launching a campaign in support of whole-grain foods. Although he failed to persuade folks on this side of the Atlantic, he did make a believer out of Britain's Queen Victoria. She switched to whole-grain bread in 1847, at age 28. She lived 54 more years, to age 82--quite remarkable for those times.

None of this persuaded the American Medical Association, which in 1936 officially condemned the use of bran. The organization's move effectively stifled fiber research for three decades. When John Harvey Kellogg--who "invented" dry breakfast cereals with his brother, Will--began preaching the health benefits of whole grains and bran, the American Medical Association condemned him, too.

It wasn't until the 1960s that fiber once again became the center of attention in medical and scientific circles. This time, several investigators announced that they had observed striking health differences between populations who consumed high-fiber diets and those who didn't. In affluent Western countries, where people ate mostly refined and processed foods, degenerative conditions--including heart disease, colon and rectal cancer, diverticulitis, appendicitis, gallstones, hemorrhoids, hiatal hernias, and varicose veins--had reached epidemic proportions. These ailments were almost unheard of in Third World countries, where people ate primarily whole (unprocessed) foods.

Based on their findings, the investigators speculated about a possible link between a low intake of fiber and the development of disease. They noted that the refined and processed foods common in Western diets were made with fiberless white flour. Plus, fiber-rich plant-derived foods--the whole-food staples of Third World diets--were all but gone from Western diets, having been replaced by fiber-poor animal-derived foods.

Soon after, Denis Burkitt, M.D.--a British surgeon best known for his discovery of Burkitt's lymphoma, a cancer associated with the Epstein-Barr virus--corroborated the investigators' theory with his own findings. During his 20 years of practicing medicine in Africa, Dr. Burkitt observed that the people there seldom developed the degenerative conditions prevalent in Western countries. He, too, attributed the disparity to the lack of fiber in Western diets. Because his reputation was firmly established, Dr. Burkitt persuaded others in the medical and scientific communities to rethink their position on fiber.

Dr. Burkitt's work had been limited to Africa's rural populations. When other populations were studied, however, the same general pattern emerged. Countries in which the typical diet was high in fiber, low in fat, and devoid of refined and processed foods had the lowest rates of degenerative disease.

Subsequent research uncovered yet another interesting phenomenon: When people move from a country in which refined and processed foods are scarce to one in which these foods are standard fare, their risk of degenerative disease rises considerably. For example, Japanese citizens who move to the United States and adopt American eating habits are much more likely to develop heart disease, cancer, and other health problems than Japanese citizens who remain in their homeland.

Fiber Demystified

fiber--or the lack of it--clearly has a profound influence on your health. So just what is the stuff, and how does it work in your body?

The term fiber actually encompasses an array of substances: celluloses, gums, hemicelluloses, lignins, mucilages, and pectins. All are remnants of plant cell walls, and all resist the action of digestive enzymes and so move through your system unaltered.

Each of the various types of fiber falls into one of two general categories, based on its solubility in water. The natural gel-forming fibers--gums, mucilages, and pectins as well as certain hemicelluloses--are soluble. The structural fibers--celluloses, lignins, and the remaining hemicelluloses--are insoluble.

Plant-derived foods contain various combinations of soluble and insoluble fibers. (Remember, animal-derived foods have no fiber at all.) Often, either the soluble or insoluble types are dominant. Oats, for example, supply an abundance of soluble fibers, while wheat offers mostly the insoluble variety.

Once inside your body, soluble and insoluble fibers perform different but complementary functions. Soluble fibers act like tiny sponges, sopping up water as well as toxins that would otherwise irritate the intestinal lining or be absorbed into the bloodstream. Insoluble fibers act like tiny brooms, sweeping away stagnant waste and keeping the intestinal environment clean. Together, the fibers police your intestines, making sure that toxins and other waste vacate the premises as quickly as possible. Otherwise, these poisons can slip through the intestinal wall and into your bloodstream, along with food and water. Once there, they contaminate your blood and can travel anywhere in your body.

A Diamond in the Roughage

You may not think of it this way, but your intestinal tract serves as an internal containment system. It protects the rest of your body from the toxic soup that it holds. Its highly selective mucous membrane lining allows only nutrients and water to pass through the intestinal wall and into your bloodstream.

Should the toxins become excessive or should their journey through the intestines slow considerably, they're more likely to slip into your bloodstream. They then place an extra burden on your liver and kidneys, the organs responsible for cleansing your blood.

You can easily prevent this sort of toxic overload just by following a high-fiber diet. Toxins simply don't stand a chance in the presence of optimum amounts of fiber.

For starters, fiber promotes peristalsis, the muscular contractions along the intestinal wall that move waste through the intestines. Here's what happens: Soluble fiber absorbs water in the intestines, causing it to swell to several times its original size. As the fiber expands, it adds bulk to the waste. Stools become larger and softer, exerting a gentle pressure on the intestinal wall that prompts the muscles of the wall to contract. (An interesting fact: Populations that consume high-fiber diets have an average fecal weight of 500 grams, compared with 100 grams for populations that consume low-fiber diets.)

What's more, the combination of increased bulk and enhanced peristalsis shortens the amount of time required to digest food and process waste--what the experts call transit time. In population studies, high-fiber diets consistently produce rapid transit times of 24 to 36 hours, while low-fiber diets produce much slower transit times of 72 to 96 hours.

Of course, the faster waste moves through your system, the less opportunity toxins have to irritate the intestinal wall or to escape through the wall and into the bloodstream. Allowing toxins to linger in your body any longer than absolutely necessary is not to your advantage. In populations with slow average transit times, colon and rectal cancers rank second only to lung cancer in frequency. But colon and rectal cancers are almost unheard of in populations with rapid average transit times.

The fast transit time associated with a high-fiber diet has another benefit as well. It limits the exposure of the beneficial bacteria that live in your intestinal tract to toxins. As long as these "good bugs" are plentiful and healthy, they prevent disease-causing bacteria and fungi from making themselves at home. (You'll learn more about your intestinal ecosystem and its inhabitants in chapter 31.)

Hidden Assets

fiber certainly does an outstanding job of keeping your intestinal tract healthy. But its benefits extend far beyond gut level. In fact, the relationship between fiber intake and disease risk is so strong that nutrition-minded doctors routinely prescribe high-fiber diets and fiber supplements as preventive and therapeutic measures.

To be honest, nutrition researchers have just barely scratched the surface in understanding the effects of fiber on human health. Here are some of the conditions that they have found fiber to be helpful in combating so far.

Cardiovascular diseases. Atherosclerosis--the hardening and clogging of arteries that leads to heart attacks, strokes, and other so-called vascular incidents--usually begins with high cholesterol. According to at least one study, fiber and prescription drugs work equally well in lowering cholesterol. People who took 60 to 90 grams of oat bran a day showed just as much improvement in their cholesterol readings as people taking medication. But fiber costs much less, and it produces no side effects.

Other research suggests that fiber influences cholesterol levels in several ways. It nabs saturated fat and cholesterol in the intestines, before they get absorbed into the bloodstream. (Saturated fat, you'll recall, is converted into cholesterol by the body.) It binds with bile acids, substances that are synthesized from cholesterol by the liver and that eventually excrete into the small intestine, and prevents them from getting absorbed, too. (If the bile acids get into the bloodstream, they can be used to make more cholesterol.) It reduces "bad" low-density lipoprotein cholesterol and raises "good" high-density lipoprotein cholesterol, thus improving your total cholesterol profile.

fiber also blocks atherosclerosis by escorting toxins from the body. Otherwise, these poisons can pass through the intestinal wall and into the bloodstream, where they generate free radicals. And when free radicals attack arterial cells, the damage results in artery-hardening plaque.

Cancer. A Dutch study, published in the British medical journal Lancet, found that death rates from all types of cancer were three times higher among men with poor fiber intakes than among men with optimum fiber intakes. Once again, fiber moves cancer-causing compounds out of the body before they can do any harm--either in the intestines or elsewhere.

The Anti-Aging Diet, with its emphasis on organically grown plant-derived foods, can substantially reduce your body's carcinogen load. But it can't eliminate carcinogens completely. Nothing can. That's because cancer-causing compounds occur naturally, as by-products of your body's routine processes.

During digestion, for example, the gallbladder releases stored bile acids from the liver into the small intestine. These acids emulsify fats to make them more absorbable. If the acids are not promptly removed from the small intestine once they've done their job, they're transformed into cancer-promoting substances by harmful intestinal bacteria. The likelihood of actually developing cancer from these substances, regardless of their source, increases both with their concentration and with the duration of their contact with the intestines.

You can keep concentration and "contact time" from exceeding safe limits simply by following a high-fiber diet (like the Anti-Aging Diet) and supporting it with daily fiber supplements. This nutritional one-two punch minimizes your cancer risk.

Blood sugar problems. White sugar, white flour, and other refined grains have simple molecular structures that allow them to be rapidly digested and absorbed. When consumed, these so-called simple carbohydrates cause blood sugar to rise rapidly. In response, the pancreas releases large quantities of the hormone insulin, which clears the excess blood sugar by storing it in the liver and muscles. Just like that, blood sugar dips downward.

This roller-coaster effect--blood sugar skyrocketing, then plummeting--is known as rebound hypoglycemia. It reaches its lowest point two to four hours after a meal. When it does, you start to feel hungry. And if you happen to eat a simple carbohydrate such as white sugar or white flour, the roller-coaster ride starts all over again. Over time, fluctuating blood sugar can contribute to a host of health problems, including atherosclerosis and diabetes (the result of pancreatic burnout).

Complex carbohydrates--whole grains, legumes, potatoes, and the like--help the body to regulate its own blood sugar level. The starches in these fiber-rich foods have complicated molecular structures, so they take longer to be broken down into simple sugars. Plus, the fiber slows the rate at which the simple sugars are absorbed. As a result, insulin is released in a slow and controlled manner. This prevents rebound hypoglycemia as well as post-meal hunger pangs. In other words, no more roller-coaster ride.

No wonder a high-fiber diet has such great value in the treatment of hypoglycemia as well as Type II (non-insulin-dependent) diabetes. As one of my patients put it, "I don't get hungry between meals anymore--and my sweet tooth has disappeared, too."

Overweight. Although many people consider overweight an issue of appearance, it is in fact a serious, life-shortening health problem. It affects more folks in the United States than in any other country in the world.

One of the reasons we Americans tend to weigh too much is that we eat too much. Overeating is the most common nutritional disorder in the United States. That's because our diet features lots of fiberless refined and processed foods, which require little "chew time" and fail to fill us up.

A high-fiber diet, on the other hand, supports weight loss. fiber-rich foods take longer to chew, so they do a better job of stimulating the flow of digestive juices in the mouth and stomach. You can eat less and still feel satisfied. And as the fiber absorbs water and expands, it delays emptying of the stomach. This creates a sense of fullness and contentment while buying time for more thorough digestion in the stomach.

Constipation. Proper elimination is of vital importance to every aspect of health. Indeed, we Americans spend millions of dollars each year on the more than 700 laxative products now on the market--all in an effort to keep things moving, so to speak.

But laxatives treat only the symptoms of constipation, not its cause: a low-fiber diet based on animal-derived foods and refined grains, which increase transit time and generate huge quantities of toxins. The feelings of stuffiness, fuzzy-headedness, and general ill health that accompany constipation are physical manifestations of internal toxicity.

The immobilizing effects of a low-fiber diet can be compounded by inactivity. Some scientists have concluded that lack of exercise, rather than old age per se, causes the constipation common among the elderly. Walking, jogging, tennis, and other activities stimulate the abdominal and back muscles to literally massage the intestines, which increases peristalsis.

When the intestines must struggle and strain to push through hard, dry stools, weak areas along the intestinal wall can bulge out over time. The tiny pouches that form signal the onset of diverticulosis. Should these pouches become infected, diverticulosis turns into diverticulitis, an extremely painful abdominal condition.

Both diverticulosis and diverticulitis are entirely preventable. In countries where the traditional diet consists primarily of fiber-rich plant-derived foods, people just plain don't get these diseases.

Hemorrhoids, varicose veins, and hiatal hernias. Without sufficient fiber to hold water, the contents of the intestines become dry and compacted. The resulting stool moves along very slowly and is difficult to pass. Straining to expel the hardened feces forces blood downward, engorging blood vessels in the lower body.

When you repeatedly strain to pass stool, the stress produces bulges in the rectal veins--what you may know as hemorrhoids. The extreme downward pressure can also damage the leg veins, causing the familiar swelling and distention of varicose veins. Any upward pressure created by straining may contribute to a hiatal hernia (when part of the stomach protrudes through the diaphragm, the muscular wall that separates the chest from the abdomen).

Tooth decay and periodontal disease. Refined carbohydrates--fiberless foods such as sugar and white flour--are key players in the development of cavities. They provide nourishment for the bacteria that foster tooth decay and dental plaque. And because refined carbs contain no vitamins or minerals, they contribute to nutrient deficiencies, which further encourage cavity formation.

Complex carbohydrates, on the other hand, are vitamin and mineral powerhouses. And they're rich in fiber, which means that they require more chewing. In these ways, complex carbs help keep teeth and gums healthy and strong. (Incidentally, both tooth decay and periodontal disease are rare in Third World countries, where diets consist primarily of whole, unprocessed, unrefined foods.)

Getting Your Fill

Of course, to reap all the health benefits of fiber, you need to make sure that you're getting enough of the stuff. A person following the typical American diet consumes 5 to 15 grams of fiber daily. Although no Recommended Dietary Allowance exists for fiber, health organizations such as the American Cancer Society, the American Diabetes Association, the American Heart Association, the National Cancer Institute, and the American Medical Association agree that this intake is woefully inadequate. Optimum intake from all sources--foods and supplements--ranges from 40 to 60 grams daily.

This doesn't mean that you have to tally every gram of fiber you eat over the course of a day. In fact, I advise you not to even try it, since it's a frustratingly difficult task. Besides, you automatically maximize your dietary fiber intake just by adopting the Anti-Aging Diet. Based on the New Four Food Groups--grains, legumes, fruits, and vegetables--the Anti-Aging Diet is naturally high in fiber and low in calories.

To ease into the diet and notch your fiber intake upward, begin by cutting back on (and eventually eliminating) fiberless foods: red meat, poultry, fish, dairy products, eggs, baked goods made with white or enriched flour, and anything containing sugar. Then gradually add in high-fiber foods such as almonds, apples, beans, broccoli, corn, oatmeal, prunes, raspberries, spinach, whole oats, and whole wheat.

You can also increase the fiber content of meals and snacks by substituting one food for another. Some examples: Choose whole-grain cereals over toaster pastries, brown rice over white, popcorn (sans butter) over potato chips, whole fruits over juices, and hummus or bean dip over sour cream dip.

Supplements for Insurance

Even a healthy diet like the Anti-Aging Diet can vary in the quantity and quality of fiber that it supplies from one day to the next. Then, too, diet alone cannot provide the amount of fiber required for maximum disease prevention. For both of these reasons, I recommend daily fiber supplementation.

If you are over age 30 and have been consuming the standard American diet for most of your life, I suggest you start by supplementing with two to five grams of fiber once or twice daily to clean and restore your intestinal tract. (One gram of fiber equals two 500-milligram capsules.) Then, after a few months, you can cut back to one to three grams daily as a maintenance dosage--a sort of fiber insurance policy. Trial and error is the best way to determine the exact amount of fiber you need.

You'll find many excellent fiber supplements on the market. The one I prefer is Yerba Prima's Daily fiber, which contains psyllium, oat bran, apple pectin, guar gum, and rice bran. Everyone is different, however, so you may want to try a few different products until you find one that you like. Steer clear of any product that contains sugar, fructose, or aspartame.

Some people experience intestinal discomfort, bloating, or gas when they first increase their fiber intakes. These symptoms occur as the fiber is fermented by gas-forming bacteria in the intestines. Don't take these symptoms as a sign that a high-fiber diet and fiber supplements are not for you. Your intestines just need time to adjust. Eventually, the gas-forming "bad bugs" will die off and be replaced by beneficial bacteria.

If you're bothered by symptoms, reduce your fiber supplementation to a dosage that you can better tolerate. Give your body a chance to get used to the supplements. After a while, you can try increasing your dosage again, but do it very gradually.

If your symptoms continue despite these measures, you may be allergic to psyllium, oat bran, or another ingredient in your fiber supplement. In this case, I suggest discontinuing the mixed-fiber product and trying each type of fiber as a single supplement until you find the one that best agrees with you.

As you increase your fiber intake, be sure to increase your fluid intake, too. fiber needs water to do its job in the intestines. Plus, water is necessary for efficient detoxification and elimination. Most experts recommend drinking at least eight eight-ounce glasses of H₂O a day.

A Friend for Life

fiber is just one ingredient in the Renewal "recipe." But without it, the Renewal process would collapse. You need fiber to soak up and sweep away damaging toxins and to keep your insides clean.

There are other ways that you can limit your exposure to toxins. For instance, you can choose only organically grown foods, drink only chemical-free water, and take other daily supplements in addition to fiber (as recommended in the Anti-Aging Supplement Program). Together, these strategies can safeguard your cells against toxic contamination.

Remember: The cleaner the cellular environment, the healthier the cells. And healthy, long-lived cells translate into a healthy, long-lived you.

*

fiber has a partner in protecting your intestinal wellness. It's called acidophilus, which is a fancy name for a supplement that may contain not one but several different types of bacteria. Don't worry, though: These bacteria are actually good guys. And as the next chapter explains, you'll want to have plenty of them around.