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THE NECESSITY OF DIETARY FIBRES
IN HUMAN NUTRITION
THE ROLE OF DIETARY FIBRES IN THE DAILY DIET
Why do we need dietary fibres?
What are dietary fibres?
What is the source of dietary fibres?
Dietary fibres and gastrointestinal function
The general health effects of fibres
Dietary fibres and food transit
How many dietary fibres does food contain?
Why do we need dietary fibres?
Doctors and nutrition specialists recommend
people of all ages to consume more dietary fibres.
Research suggests that fibres help prevent diverticulosis, obesity and constipations.
What are dietary fibres?
Fibres are not a single food or substance. The human
body cannot absorb fibres that have no calories in themselves.
As they are carried through the digestive system and out
of the body, fibres maintain health and lower the risk
of numerous diseases and conditions, including colorectal
and other types of cancer.
What is the source of dietary fibres?
Plants are the unique source of
dietary fibre because of the polysaccharide structure
of their cell wall, as well as the storage and
secretion polysaccharides associated with plant
cells and seeds.
Dietary fibres and gastrointestinal function
Dietary fibres are clearly important for normal gastrointestinal function. This role is well defined in the large intestine, where dietary fibres provide bulk and substrates for microbial activity. Several investigators have proposed that the adequacy of fibres intake can be determined by estimating the amount of fibre needed to maintain an adequate stool weight and transit time.
The general health effects of fibres
Fibres that you eat affect your digestion
in several ways. Fibres help move food and digestive
by-products efficiently through the large intestine
(colon) and out of the body.
The faster food and digestive by-products pass through the gastrointestinal tract, the less time there is for potential cancer-causing agents to do their damage. Fibre is also thought to dilute potential carcinogens, thus lessening their impact. It also helps to alter the metabolism of certain bacteria in the digestive tract, thereby promoting a healthy digestion.
A high-fat diet increases the amount of
bile acids and bacterial enzymes in the colon, where
bacteria can convert them to cancer-causing chemicals.
Increasing the quantity of fibre in the intestines helps
to reverse this effect by diluting or inactivating the
chemicals and reducing the level of bile acids and bacteria.
Dietary fibres and food transit
Another important function of fibres is to quicken the excretion of wastes and their cancer-causing by-products so that they will leave the body before they have much time to come in contact with the sensitive cells which line the inner walls of the bowel. In a typical diet, food needs three or more days to pass through the bowel. Eating even less fibre can allow food to remain in the body still longer. With a high-fibre diet, food is eliminated within a day or two.
How many dietary fibres does food contain?
The maintenance cellulose (fibres) in
the elected products:
On 100 g:
- Apple 2,1 g
- Banana 1,3 g
- Peach 1,4 g
- Fiber and vitamin supplement SANKOM 16 g.
DIETARY FIBRES AND HUMAN HEALTH
Classification
Nutritional importance
Gastrointestinal response
Prevention of diverticulosis
Importance of dietary fibre for gastrointestinal function
Magnesium and human health
Vitamins and human health
Green tea and human health
Classification
The major fibre components are polysaccharides other than starch that include
cellulose, beta-glucans, hemicelluloses, pectins, and gums in addition to the
nonpolysaccharide component, lignin. These polysaccharides are defined by their
sugar residues and links between them. Cellulose and beta-glucans are glucose polymers with beta bonds. In the beta-glucans
bonds are interspersed with beta bonds, and this structure makes the molecule
less linear than cellulose.
In pectins the backbone is predominantly galacturonic acid residues, rhamnose
units are inserted at intervals, and side chains contain predominantly arabinose
and galactose.
Lignin is composed of a mixture of phenolic compounds resulting in a highly
complex molecule. Although most foods contain only small amounts of lignin,
its presence can greatly affect the digestibility of the cell wall structure,
and considerable interest exists in the potential carcinogenic and anticarcinogenic
effects of phenolic compounds derived from plant foods.
Nutritional importance
Several clinical and experimental studies have been conducted on human patients
and on animal models to demonstrate the need of fibre in the diet. These studies
have shown the potential importance of certain sources of dietary fibre for
normal gastrointestinal function, lowering plasma cholesterol, blunting
glycemic response and insulin release.
Gastrointestinal response
For healthy individuals, dietary fibre is clearly important for normal gastrointestinal
function, as summarized in table 1. Several investigators have proposed that
the adequacy of fibre intake can be determined by estimating the amount of fibre
or non-starch polysaccharides (NSP) needed to maintain an adequate stool weight
and transit time.
Prevention of diverticulosis
Increased fibre intake has been suggested for disorders involving the large
intestine such as constipation, diverticulosis, and irritable bowel syndrome.
In all these disorders, numerous factors other than diet can contribute to the
development of the disorder.
In particular, in irritable bowel syndrome, personality and anxiety as well
as dietary factors can be contributing causes. Among identifiable dietary factors,
fibre is the only constituent that appears to affect stool weight.
Hence, in cases of constipation or irritable bowel syndrom in which a low fibre
intake is associated with low stool weight, increasing fibre intake by recommending
dietary modifications may be beneficial.
Table 1. Importance of dietary fibre for gastrointestinal function
| Gastric emptying |
Water-holding capacity; viscosity |
Slower delivery of nutrients |
| Lower bile acid reabsorption |
Bile acid binding capacity |
Bile acid and cholesterol metabolism |
| Digestion and absorption of nutrients |
Water holding capacity; binding capacity |
Slow fat and carbohydrates absorption |
| Bulk and transit time |
Fermentability of the polysaccharides; water-holding capacity |
Stool weight; concentration in stool |
| Microbial growth |
Fermentability; water- holding capacity |
Short-chain fatty acid production; microbial metabolism |
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Magnesium and human health
What magnesium is?
Magnesium is one of the minerals that we require in relatively large amounts.
It is particularly abundant in green vegetables, and it is also available in natural
supplements.
What magnesium does?
Magnesium plays many roles in the body. It promotes absorption and use of other
minerals such as calcium, helps to move sodium and potassium across the cell membranes;
it is involved in the metabolism of proteins, and turns an essential enzymes.
Why do you need magnesium?
Magnesium helps bones to grow and teeth to remain strong. It enables nerve impulses
to travel through the body, keeps the body's metabolism in balance, and helps
the muscles — including the heart — to work properly. Small amounts of magnesium
work as an antacid; large amounts of magnesium work as a laxative.
Up to three-quarters of the US population get less than recommended amount
of magnesium (400 milligrams a day). Those most likely to be deficient in magnesium
include the elderly, diabetics, moderate or heavy drinkers, and people taking
diuretics.
Doctors use magnesium to treat heart rhythm abnormalities and it may help prevent
clogging of the arteries.
Besides, Magnesium plays a necessary role in: -
- regulation of the muscular activity of the heart;
- supports a normal hearts rhythm;
- stabilized blood pressure;
- provides an absorption of such minerals as calcium, potassium, phosphate, etc.;
- provides an absorption of important vitamins from group B,C,E;
- participates in processes of metabolism for proteins;
- strengthens bones and teeth;
- reduces cramps;
- regulation nervous system;
- avoid stress.
Vitamins and human health
| Powerful antioxidant. Adjusts coagulability of blood, formation of bone tissue, formation of steroid hormones, carbohydrate metabolism. It is necessary for preservation of healthy bones, teeth and blood vessels. Participates in absorption of iron. Stimulates development of the interferon constraining duplication of viruses. Reduces influence of allergens. |
| It is irreplaceable for normal metabolism, health of skin and nervous system. |
| Antioxidant. Stabilizes nonsaturated fat acids and cellular membranes and promotes prevention of sedimentation of atherosclerotic plaques in vessels, strengthens immunity. Reduces need of cardiac muscles in oxygen, favorably influences for peripheral blood circulation. Possessing diuretic effect, reduces blood pressure. It is necessary for healthy functioning of muscular tissue. Improves genital function and potency. |
| Participates in synthesis of nucleinic acids and proteins, is effective for prevention of atherosclerosis, diabetes mellitus, premenstrual syndrome, depressions. |
| Takes part in processes of growth, hemapoesis, energy metabolism, metabolism of proteins, fats, carbohydrates, regulates the state of central and peripheral nervous systems, together with vitamin A provides normal vision. Participates in maintenance of tissues of organism and skin. |
| Normalizes the activities of nervous and cardiovascular systems, influences on metabolism of carbohydrates (sugars, starch) and fats. Normalizes acidity of gastric juice, peristalsis of stomach and intestines. Participates in processes of producing of energy. |
| Normalizes carbohydrate, protein metabolism, digestion, function of liver, heart, stomach and intestines. Participates in metabolism. Reduces the level of cholesterol. Influences on synthesis of sexual hormones, cortison, tiroxin, insulin. Regulates the state of central and peripheral nervous systems, work of adrenal glands, takes part in synthesis of hemoglobin, antibodies. Prevents tiredness, removes stress. It is formed by intestinal microflora. |
| Participates in synthesis of nucleinic acids, hemapoesis of bone marrow, promotes prevention of developmental anomalies of nervous system of fetus. Participates in formation of a spinal cord of fetus. |
| Participates in metabolism, influences on nervous system, sexual function, state of skin. Biotin plays the important role in metabolism of carbohydrates and fat and amino acids. |
| Normalizes the processes of hemapoesis, function of liver and nervous system. Regulates the metabolism of fats, carbohydrates and proteins. It is synthesized by microflora of intestines, but in insufficient quantity. |
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Green tea and human health
The human body constantly produces unstable molecules called oxidants, also
commonly referred to as free radicals. To become stable, oxidants steal electrons
from other molecules and, in the process, damage cell proteins and genetic material. Antioxidants are substances
that allow the human body to scavenge and seize oxidants. Like other antioxidants,
the catechins found in tea selectively inhibit specific enzyme activities. They may also target and repair DNA aberrations caused by oxidants.
All varieties of tea come from the leaves of a single evergreen plant, Camellia
sinensis. All tea leaves are picked, rolled, dried, and heated. With the additional
process of allowing the leaves to ferment and oxidize, black tea is produced.
Possibly because it is less processed, green tea contains higher levels of antioxidants
than black tea.
Although tea is consumed in a variety of ways and varies in its chemical makeup,
one study showed that steeping either green or black tea for about five minutes releases
over 80 percent of its catechins. Instant iced tea, on the other hand, contains
negligible amounts of catechins.
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