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There has been a long association between humans and bacteria,
particularly those that colonize the gastrointestinal tract. Over 300 of different species of
microflora have been identified in the human digestive tract. Most bacteria in the gut do not
pose any harm, they just feed off the material that passes through. There is a group of bacterial
species, the so-called "friendly bacteria" that have health-promoting effects.
They belong to the Lactobacillus species and were shown to significantly
limit the growth of putrefactive and pathogenic bacteria. The latter group produce toxins that poison the body and in so doing weakens
the immune system by putting a strain on the immunocompetent cells such as macrophages, monocytes
and others. In fact, the lactobacilli microorganisms were suggested to have a beneficial effect on humans
in the early twentieth century by the Russian microbiologist Elie Metchnikoff. He believed that by eating
plenty of yogurt, which contains several lactobacillus species one could offset the balance between
"good" and "bad" bacteria in the gut towards the former. This would protect those consuming yogurt on a
daily basis against disease and premature aging promoted by the putrefactive and pathogenic bacteria
in the colon.
The most important lactobacilli in the gut are: L. acidophilus, L. bifidus, L. brevis, L. casei,
L. cellobiosus. The first two in this group are widely used in nutritional supplements because of
their potent action against many pathogens. Some of the pathogenic bacteria inhibited by L. acidophilus
are: E. coli, Klebsiella pneumoniae, Proteus vulgaris, Pseudomonas aeruginosa, Salmonella typhosa, Shigella
dysenteriae, Staphylococcus aureus, Candida albicans. The lactobacillus group exert their inhibitory activity
against pathogens through:
- competition for nutrients
- release of acids that lower the pH in the colon and create a less favorable environment for the pathogens
- production of antimicrobial factors, e.g. bacteriocins (proteins that have lethal effect on related bacteria).
Some people believe that by eating lots of yogurt is sufficient to ensure that the friendly lactobacilli
in this dairy product will prevail over the "unfriendly bacteria" and thus keep them in check. What these people
do not know is that most commercial yogurts are made using strains of L. bulgaricus and Streptococcus thermophilus.
These bacteria, although friendly to us do not colonize the colon and therefore are of little value as a weapon
against pathogens. Unless fortified with L. acidophilus and L. bifidus the supermarket yogurt cannot protect us
against the nasty bacteria that occur in the colon.
In conclusion, by having L. acidophillus and L. bifidus in our daily food, either from enriched yogurt or supplements
(capsules containing billions of active bacteria) we benefit because these bacteria:
- release B vitamins that get absorbed in the gut
- produce the enzyme lactase that helps digest the disaccharide lactose
- help in food digestion and correct digestive disorders and as a consequence prevent bad breath
- produce lactic and acetic acids, hydrogen peroxide and antimicrobial factors that limit the growth of
pathogens
- reduce the risk of yeast infections by inhibiting the growth of candida albicans and related yeasts
- may help reduce the risk of colon cancer.
A discussion on the health benefits of having friendly bacteria in our diet would not be complete
without mentioning a food component that actually promote the growth of lactobacillus species.
These food components, called fructo-oligosaccharides (FOS)
are short-chain polysaccharides from plants that were shown to be an excellent nutrient
for the bifidobacteria and lactobacilli. Good food sources are onions, asparagus,
garlic and Jerusalem artichokes. However, we only get approximately 0.8 grams of
FOS from food alone, whereas the recommended daily dose for pure FOS is 2-3 grams.
It is obvious that we need to make up for the difference in the amount of FOS required for
optimal health by supplementation. It is worth mentioning that reputable manufacturers of
nutritional supplements always add FOS to their lactobacilli products. Recent clinical studies
have shown that adding FOS to our diet can:
- selectively feed and promote the growth of beneficial bacteria such as bifidobacterium. Up to 1 gram of FOS
per day can increase the number of bifidobacteria by 5-fold.
- relieve constipation and improve liver function
- improve the elimination of toxic compounds and help reduce the reabsorption of cholesterol
into circulation (part of bile cholesterol in the colon is reabsorbed into the blood stream)
- reduce the formation of cavities and help lower blood sugar levels in diabetics.
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Dietary fibers
- Background: Dietary fibers are plant compounds found mostly in the cell walls and are not broken down
by the acid/enzymatic secretions of our digestive tract. The wall compartment of planr cells contain 30-40% insoluble fiber,
40-50% soluble fiber, some 20% various fiber compounds, 2-5% protein and a small amount of minerals.
- Wheat bran is a typical example of insoluble fiber. It has a high content of cellulose that is glucose polymer, which is able to
bind water. This property makes the content of the colon bulky and speeds up its transit through that segment of the digestive tract.
Thus, a cellulose-rich diet promotes regular bowel movement and decreases the chance of toxic substances being absorbed through the
intestinal wall into the circulation.
- The soluble fiber category includes hemicelluloses, gums, mucilages and pectins. Hemicelluloses have the remarkable property
of binding the cholesterol excreted through the bile thus preventing its reabsorption in the colon.
- An important class of fiber compounds, found in certain seeds
such as flaxseeds but also in grains and legumes is the lignan precursor. This highly complex carbohydrate
(chemically related to lignin, present in the trees' bark) is enzymatically modified by the gut flora to
compounds that exhibit antibacterial, antifungal and antiviral activity.Some of the physiological effects
of dietary fibers are presented in the table below.
|
Fiber Class |
Chemical Structure |
Source |
Physiological Effect |
|
Cellulose |
Unbranched b(1-4) -D-glucose
polymer |
Main plant well component; wheat bran |
Increases fecal weight and size |
|
Hemicelluloses: non cellulose polysaccharides |
Mixture of 5 and 6 carbon sugar molecules in branching chains |
Plant cell wall;
Oat bran |
Increases fecal weight and size;
Binds cholesterol in bile so that it prevents its reabsorption in the colon |
|
Gums |
Branched-chain uronic acid containing polymers |
Karaya; gum arabic |
Same as above |
|
Mucilages |
Contain mixtures of 5 and 6 carbon sugar molecules with a structure similar to hemicelluloses |
Occur in plant seeds, legumes and psyllium |
Form large colloidal particles in the gut that delay gastric emptying; act as heavy metal chelating agents |
|
Pectins |
Mixtures of esterified galacturn, galactan and arabinose in varying proportions |
Citrus rind, apple, pear, onion skin |
Same as above |
|
Algal polysaccharides |
Polymers of uronic acids of glucose and mannose |
Algin, carrageenan |
Same as above |
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*Adapted from "Encyclopedia of Nutritional Supplements",
Michael T. Murray, N.D., 1996,
Prima Publishing, Rocklin, CA. |
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One should bear in mind that different fibers have different effects(see table above) and that so far
no RDA for fiber has been set. Typically, the North American diet contains some 20-30 g of fiber per day, which according
to some nutrition experts is far from adequate. People in the regions where chronic
degenerative diseases are very rare consume over 100 grams of fiber daily. Since fiber swells, high-fiber diet must include plenty of liquid (1.5-2.0 liters/day).
It is also important to remember that large amounts of fiber may impair the absorption of some minerals such as
iron, zinc, copper and calcium. That is why fiber supplementation is only a part of
a properly balanced diet. |
- Health benefits: There is an overwhelming body of evidence that diet is an important factor in the development
of a host of degenerative illnesses. Thus, a diet poor in fiber can lead to conditions such as autoimmune disorders,
cardiovascular disease, cancer, multiple sclerosis and others. In
the table below some of the diseases associated
with low fiber diets are shown.
|
| Type of Disease |
Specific Condition |
| Metabolic |
Obesity, diabetes, gout, kidney stones |
| Cardiovascular |
High blood pressure, atherosclerosis, varicose veins, thrombosis |
| Colonic |
Constipation, diverticulitis, appendicitis, hemorrhoids, colon cancer,
irritable bowel syndrome, ulcerative colitis |
| Others |
Autoimmune disorders, dental caries, multiple sclerosis,
skin conditions |
*Adapted from "Encyclopedia of Nutritional Supplements",
Michael T. Murray, N.D., 1996,
Prima Publishing, Rocklin, CA. |
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For your information the table below presents the fiber content in some foods. Always drink plenty of water
when taking supplemental fiber. |
| Food |
Serving |
Grams of fiber |
Cereals(breakfast type)
All-Bran
Cornflakes
Oatmeal
Shredded Wheat |
1 cup
1 cup
1 cup
1 cup
|
2.5
0.5
2.0
3.0
|
Breads, Pastas, Nuts
Whole wheat bread
White bread
Rye
Spaghetti, whole wheat, cooked
Peanuts |
4 slices
4 slices
4 slices
1 cup
10 nuts
|
5.0
2.0
6.5
8.0
1.5
|
Crackers
Rye |
10
|
10.0
|
Fruits(skin included)
Apple
Pear
Orange
Grapefruit
Peach
Strawberries
Raspberries
Raisins |
1 medium
1 large
1 medium
1 medium
1 large
1 cup
1 cup
1/2 cup |
3.8
6.0
2.5
3.4
2.4
3.0
5.5
6.0 |
Vegetables
Asparagus
Cellery, diced
Lettuce
Spinach
Tomato
Broccoli
Cabbage, red
Carrots
Cauliflower
Corn(cooked)
Peas(cooked)
Kidney beans(cooked)
Lentils(cooked)
Potato, no skin(cooked)
Potato, with skin(cooked)
Rice, brown(cooked)
Rice, white(cooked) |
1 cup
1 cup
5 leaves
5 leaves
1 large
1 cup
1 cup
1 cup
1 cup
1 cup
1 cup
1 cup
1 cup
1 medium
1 medium
1 cup
1 cup
|
2.2
2.0
5.5
6.0
1.9
4.7
3.5
5.0
2.5
6.0
9.6
15.0
7.8
1.5
2.5
2.1
0.8
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