Fiber: Why It Matters More Than You Think
It’s famous for improving regularity and helping lower cholesterol. But dietary
fiber also performs other key roles that might surprise you, affecting everything
from your skin to your gallbladder, heart and immunity.
There’s one ingredient that should be part of every meal. There’s no need to make a trip to
a special store to find it: Nature has already thoughtfully prepackaged it in a cornucopia of
vegetables, legumes, fruits and nuts.
The special ingredient? Fiber.
No huge surprise there. We’ve known for decades that fiber-rich foods are good for us.
Many experts have observed that as people in other cultures have given up their traditional
diets and adopted Western eating habits (dominated by processed foods much lower in fiber
and higher in sugar), they’ve become susceptible to weight gain and a host of illnesses.
Meanwhile, a torrent of studies have shown that fiber-rich foods work wonders in the body,
regulating blood-sugar levels, reducing the risk of coronary heart disease, stroke,
hypertension, diabetes, obesity, breast cancer, colon cancer and gastrointestinal disorders
such as reflux, duodenal ulcer, irritable bowel and diverticulitis (inflammation of abnormal
pouches in the wall of the large intestine or colon), and also supporting weight loss.
Today, though, scientists are using newer tools to better understand the various ways fiber
interacts with our bodies’ basic systems. Some of this new work shows that fiber plays an
essential role in a little-known (and critically important) system in our body called
enterohepatic circulation. Entero is Latin for relating to the intestines, or gut; hepatic is
Latin for pertaining to the liver. This system, which has the key job of clearing all fat-soluble
waste from the bloodstream, governs the progression of bile — from the liver, through the
small intestine, and back again.
If we don’t eat enough soluble fiber, our bile, instead of being ushered out of the body and
then replaced with fresh bile produced by the liver, is repeatedly recirculated in our system.
In the process, it becomes more concentrated with toxins, which, in turn, can lead to all
sorts of inflammatory diseases such as gallbladder disease, intestinal inflammation, and
even skin conditions like acne, eczema and psoriasis.
Ultimately, a low-fiber diet can contribute to elevated levels of toxicity throughout the body,
explains Alejandro Junger, MD, director of Integrative Medicine at Manhattan-based Lenox
Hill Hospital and author of Clean: The Revolutionary Program to Restore the Body’s
Natural Ability to Heal Itself (HarperOne, 2009).
“When we don’t eat fiber, the toxins that we should be eliminating through our bowels get
reabsorbed into the bloodstream — and that can cause many problems,” Junger says.
“Unfortunately, Western medicine is toxic-blind,” he says. “In the Western medical world,
toxicity means an acute problem like alcohol toxicity or someone who took too many pills.
This more diffuse toxicity that I am talking about is rarely acknowledged at all in the
Western medical world. And, the end effect of all this toxicity is inflammation — virtually
everybody is inflamed today — which negatively affects various organs in many different
ways.”
Recent research has also focused on the way fiber boosts the immune system. It turns out
that a wide variety of fiber-dependent processes are key to maintaining our resistance both
to infections and to immune-related diseases like cancer. Yet few of us understand
the mechanisms by which dietary fiber works, and why our vitality — not just our regularity —
suffers so much when our fiber intake is inadequate.
Hauling the Body's Trash
Dietary fiber is the part of our plant foods that can’t be
digested. Traditionally, dietary fiber has been divided into two groups: insoluble and soluble.
(For a list of foods in each category see “More Fiber, Please!” below.)
Both bind with the body’s waste products and help move them through proper channels.
Insoluble fiber comes from the hard structural part of a plant, such as wheat bran, the
tough husk around a popcorn kernel or the skins of many fruits and vegetables. Insoluble
fiber makes its way through the digestive system relatively intact, acting as a sort of
sweeping compound and making the stool softer and bulkier.
Soluble fiber, on the other hand, comes from structures within the cells of the plant. As
soluble fiber enters the digestive tract, it absorbs water and dissolves into a thick, viscous
gel. Although both types of fiber affect the body’s ability to circulate bile effectively, soluble
fiber is doing the bulk of the work.
When we eat a meal containing fat, our liver — the largest glandular organ in the body —
begins to produce bile, a liquid comprising acids, cholesterol, lecithin and other substances.
The liver produces around 4 cups of bile every day, all of which is eventually secreted into
the duodenum — the first section of the small intestine — where it helps break down fats
into smaller pieces.
Wisconsin-based nutritionist Karen Hurd, who specializes in resolving chronic digestive
disorders, explains it this way: “Bile works in the small intestine much as a strong dish soap
works in dishwater — to help break up grease and food particles.”
Once broken down into pieces, most nutrients are absorbed in the upper part of the small
intestine. In the ileum — at the lower end of the small intestine — the bile, broken down
into its constituent parts, makes its way back to the liver, carried by the bloodstream.
The liver filters our blood, removing drugs, toxins, fats and fat-soluble waste, and disposes
of these substances by depositing them in newly created bile.
Because the bile that has been absorbed in the ileum enters the bloodstream in its
constituent parts, it reverts back to fats, toxins, drugs and fat-soluble waste — all the little
pieces that made up the bile. The liver must again filter these components out of the
bloodstream. They are added to the waste that has been newly collected from the
bloodstream. The old bile, in its constituent parts, is combined with the new bile carrying its
toxic load, which makes for an increasingly toxic bile that is secreted once again into the
small intestine.
As long as you have adequate fiber in your diet, this doesn’t pose a problem for your body:
That fiber forms a tight bond with the bile in the intestine, binding up all the harmful toxins,
cholesterol and fat that it contains. Since the soluble fiber cannot be absorbed by the
intestinal wall, neither can the bile attached to it. This fiber-bound bile ultimately leaves the
body in a bowel movement, with its load of toxins, cholesterol and fat in tow.
But if we’re eating a fiber-poor diet, our supply of bile can become increasingly concentrated
with toxins and fats as it recycles back to the liver.
“I call bile the body’s trash truck,” says Hurd. “It’s as if the truck dumps its load in the
bloodstream and the liver has to clean it all up again. Then you have old trash mixed in with
the new.”
Among other problems, inadequate fiber consumption can contribute to elevated blood
cholesterol levels, notes Todd Rideout, PhD, adjunct professor at the University of Manitoba
and research scientist at the university’s Richardson Centre for Functional Foods and
Nutraceuticals.
When bile is being properly escorted by fiber and carried out of the body by our stool, he
explains, “there are fewer bile acids recycling to the liver and being stored in the
gallbladder.” That means the next time we eat a meal with fat in it, the liver has to make
fresh new bile. It manufactures this new bile by pulling cholesterol (one of the key
components of bile) out of the blood, thereby reducing blood cholesterol levels. Under lowfiber
conditions, though, that process doesn’t happen as readily, and thus cholesterol has an
opportunity to increase in the bloodstream and accumulate in our arteries.
A Dangerous Sludge
Another problem with inadequate fiber intake, Hurd says, is that it
results in a change of consistency in our bile. As bile becomes more polluted, she explains,
“the physical state of bile is not as liquid as before,” she says. “It becomes sludgy, like mud.
Eventually, it can turn into a solid substance we call gallstones.”
Moreover, Hurd explains, the trashier and sludgier your bile becomes, the more acidic and
irritating it becomes to your tissues. This can lead to a host of problems, including swelling
and inflammation in your colon, duodenum and all the way up in your esophagus.
“Inflammation in the esophagus includes all kinds of things like Barrett’s esophagus, where
you have this thickening of the opening, so things feel like they get stuck in your throat,”
says Hurd.
Sludgy bile causes not only various diseases of the gallbladder, explains Hurd, but also
tertiary skin conditions, such as acne, eczema and psoriasis, which depend upon a properly
functioning gallbladder to help bile break down into little pieces, or emulsify, the fats. The
results, says Hurd, are predictable: “If you don’t have the right types of fats in your skin,
you’ll have skin problems.”
Worse, if the fats are not successfully emulsified via the bile, the body falls back on a
second, less desirable chemical process capable of breaking these long-chain fatty acids into
usable short-chain fatty acids. That process is called oxidation, and it can lead both to
premature aging and to inflammatory diseases of all kinds, including heart disease.
“If your bile is so sludgy that you cannot adequately emulsify the fat, and it dumps back in
your body these long chains that have not been broken down properly, they will enter into
your bloodstream by way of the ileum, travel through the lymphatic system and deposit into
the circulatory system behind the heart,” explains Hurd. “The heart is one of the most
oxygen-rich environments in the human body, and what happens is you will have immediate
fat oxidation, which makes nasty little foam cells that are extremely sticky and build up
inside the arteries. And then your arteries can become 50 percent blocked or 80 percent
blocked or 100 percent blocked,
For example. When you have 100 percent blockage, you have what’s known as a myocardial
infarction — a fancy phrase for heart attack.”
The idea that a lack of dietary fiber can be a root cause of atherosclerosis and heart attack
is shocking to many people, notes Hurd. Yet there are other dire consequences of a faulty
recycling system that may surprise us even more — like cancer, especially hormonally
caused cancers such as estrogen types.
“Estrogen is made from fats. It’s an example of a fat-soluble waste that is cleared by the
liver,” Hurd explains. “But if you don’t
properly eliminate polluted bile, that estrogen goes
back into your bloodstream, and the estrogen levels in your bloodstream mount,” she
continues. “Then those estrogens can stimulate the growth of abnormal cells, which can
lead to the growth of cancerous cells. And, then we have estrogen-type cancers, such as
breast cancer, uterine cancer, fallopian tube cancer, ovarian cancer and vaginal cancer. Why
are these cancers being stimulated? Because estrogen is stimulating their growth. Why do
we have so much estrogen? Because we never threw it away via elimination when we had
the chance.”
The encouraging news, says Hurd, is that one of the most promising ways to help end this
vicious cycle — and to eliminate many painful and frustrating conditions whose symptoms
are commonly treated with drugs or surgery — is simply to eat an ample supply of fiber-rich
foods.
Boosting Immunity
We’ve seen that dietary fiber plays a huge part in keeping our bodies’
filtration and elimination systems working properly, but that’s really only part of the story.
Fiber also plays a vital role in improving the effectiveness of the gastrointestinal system,
which contains more than half the body’s immune system.
After some dietary fibers pass through the small intestine undigested, they arrive in the
large intestine, or colon, and serve as fuel for the friendly bacteria living there. These socalled
prebiotic fibers help friendly bacteria grow and triumph over bad bugs in the colon.
“Fiber feeds good bacteria, so a lack of fiber actually kills the good bacteria in your gut —
and the good bacteria in your gut is yet another thing that Western medicine does not clue
into in terms of its importance,” says Junger. “In fact, very few gastrointestinologists even
deal with what kind of bacteria you have in your gut.”
According to some experts, a flourishing corps of friendly intestinal flora can help protect
the lining of the intestine and prevent leaky gut syndrome, a condition that allows toxins,
fungi and undigested proteins to get into the bloodstream. Leaky gut syndrome can cause a
host of autoimmune diseases and allergies. (See “Good Bacteria Welcome” in the
July/August 2007 archives at experiencelifemag.com.)
Of course, there’s one other benefit of a high-fiber diet. The foods that are naturally high in
fiber — beans, vegetables, whole grains and fruits — are precisely the foods that are high in
phytonutrients, vitamins, minerals and antioxidants. They tend to be lower-glycemic foods,
too — the kind that naturally support steady energy and good weight management.
Given fiber’s multiple benefits, it’s clear that many of us practice the wrong nutritional
math. Instead of trying to subtract calories, we should concentrate on adding grams of fiber
(Hurd recommends 5 grams of soluble fiber — the equivalent of a half-cup cup of beans —
at each meal). The best part? You can see and feel the results from eating more fiber
almost immediately. When introduced to a properly designed fiber-boosting regimen, says
Hurd, many of her clients find that certain digestive troubles can vanish the same day.
She’s seen entrenched skin conditions clear up within a week and gallstones dissolve within
six weeks. So, eat those beans! It’s all part of a winning strategy for better health.
The Fiber-Bile Connection
Fiber and bile play little-understood but important roles in
digestion and toxin elimination. Here’s an overview of how they work together in your body.
Bile is an acidic substance made by the liver, primarily to aid your body’s digestion of fats
and to help transport heavy metals out of the body.
The bile travels down two biliary ducts [A].
One duct dumps directly into the duodenum [B] (first section of the small intestine), where
there is a slow, constant dripping of relatively dilute bile.
The other duct leads to the gallbladder, where the bile is concentrated to 10 times its
strength. When food moves from the stomach into the duodenum, the gallbladder
contracts and squirts concentrated bile into the duodenum. There, the bile mixes with the
fats you have consumed and helps breaks them down. Any gallbladder problems leading to
reduction in bile quality or supply may lead to digestive troubles.
In the duodenum, recently consumed soluble fiber binds with the mixture of bile, toxins and
other undigested material. This mixture then travels through the small intestine to the
ileum.
Bile and waste products that are bound to fiber proceed through the large intestine and
are eliminated though the rectum in a bowel movement. Bile not bound to fiber is
reabsorbed into the bloodstream through the wall of the terminal ileum [C]. The
bloodborne bile then returns to the liver for filtering.
The liver extracts the bile from the blood and re-secretes it back into the intestines for
reuse. Any suspended toxins in the bile are carried back through the system, increasing the
body’s toxic burden. Bile goes through this recycling process several times a day. But when
we don’t eat enough fiber, we don’t eliminate enough polluted bile or produce enough fresh
bile. As our recycled bile grows sludgier, it introduces more inflammatory compounds into
our bloodstream, contributing to a wide array of potentially serious health problems.
More Fiber, Please! Recommendations for daily fiber intake range from 20 to 40 grams,
but by some estimates, the average American eats only 8 grams. But we don’t just need
more fiber, experts say: We need more fiber distributed in small meals and snacks
throughout the day.
“If you have all your fiber in one serving, it only acts on the food you eat then, not on the
food you eat hours later,” says Christine Gerbstadt, MD, RDRN, a spokesperson for the
American Dietetic Association. “Fiber doesn’t hang around waiting for the next meal. If you
want fiber to regulate your blood sugar all day, you have to eat it all day.”
Real, whole foods are your best source for fiber. Beans, in particular, are the richest source
of soluble fiber we have, says Wisconsin-based nutritionist Karen Hurd, who recommends
everyone eat three half-cup servings of legumes daily as part of a whole-foods eating plan.
But if you’re getting sick of beans, she suggests substituting 2 teaspoons of psyllium husk
powder (for those who are not allergic to psyllium husk) mixed in a glass of water for one or
more of those servings. Here are some other good fiber sources:
Soluble fiber: dried beans, lentils, oat bran, oatmeal, rice bran, barley, citrus fruits,
strawberries and apple pulp.
Insoluble fiber: whole grains (including wheat, rye, rice, barley and most other grains),
cabbage, beets, carrots, Brussels sprouts, turnips, cauliflower and apple skin.
Prebiotic fiber: legumes, wheat, barley, potatoes, rice, bananas, artichokes, onions and
No comments:
Post a Comment