October 2001
We have developed an orange flavoured drink premix containing 4 gms of Psyllium seed husk and 2.7 gms of Oligofructose.
Most dietary fibre sources promote laxation by increasing colonic contents, which stimulates propulsion. Unfermented or incompletely fermented fibre and the accompanying moisture it holds are two contributors to this increased stool mass (1). Slowly or incompletely fermented fibres also contribute to stool weight by providing substrate for microbial growth. The greater bacterial mass and accompanying water further increase stool weight (2,3). In most studies, the additional stool mass produced by consumption of more dietary fibre contains the same proportion of moisture as do low-fibre stools (4).
Psyllium seed husk is a partially fermented dietary fibre from Plantago ovata that increases stool weight and promotes laxation by its presence in stool and by increasing the moisture content of stool (5-8). In a study by Cummings et al (2000), they proposed that the unfermented gel isolated from psyllium containing stools functions as an emollient and lubricant. The greater ease of passage, gentleness, and softness reported by the subjects and the isolation of a very viscous fraction supports this hypothesis.
All studies involving psyllium report increases in wet and dry stool weights both in healthy subjects (5-8, 9-11) and in subjects with gastrointestinal disease (12-17). Psyllium appears to increase stool mass more effectively than do other common laxative fibre sources. In the Cummings study , each gram of psyllium seed husk increased stool weight an average of 5.9 gms, compared with 4.9-5.4 gms for wheat bran fibre and 3.4-4.5 gms for oat bran fibre (1,3).
Consumption of viscous soluble fibres significantly lowers serum total and LDL cholesterol concentrations (18,19), and may provide an alternative to drug therapy for some patients (20-22). Of the viscous soluble fibres, psyllium husk fibre appears to be one of the most effective (23,24) with the least adverse effects (25).
Short term placebo-controlled studies showed that consumption of 7-10 gms psyllium/day lowers serum total cholesterol concentrations 4-11% and serum LDL cholesterol concentrations 6-18% below placebo control concentrations (19-23, 26-31). The mechanism of action of psyllium's hypocholesterolemic effects has not been fully elucidated. Psyllium was shown to stimulate bile acid synthesis ( 7 alpha hydroxylase activity) in animal models (32,33) and in humans (27), which leads to reduction of serum cholesterol. Additional mechanisms, such as inhibition of hepatic cholesterol synthesis by propionate (34) and secondary effects of slowing glucose absorption (35) may also play a role.
Other soluble fibre sources, such as guar gum (36), locust bean gum (37), pectin (38), oat bran 39), and legumes (40), have also been reported to decrease serum total and LDL cholesterol concentrations. However the practical uses for many of these fibres are limited by a lack of palatable forms (28). In a study in which the effects of 10 different fibres were compared in rats, psyllium fed rats had the lowest serum and liver cholesterol concentrations (24).
Ingestion of prebiotics (non-digestible food ingredient that selectively stimulates bacteria in the colon) results in a different spectrum of fermentation products, including the production of high concentrations of short chain fatty acids, leading to a decrease in pH. A low pH in faeces was associated with a reduced incidence of colon cancer in various populations (41,42).
Butyrate is associated with many biological properties in the colon (43). One of the first observed effects of butyrate on the degree of DNA methylation is probably associated with modified gene expression, the consequences of which are yet unknown, particularly in relation to colon cancer. However, butyrate may also directly enhance cell proliferation in normal cells and suppress proliferation in transformed cells by improving cell differentiation. This is an important step in suppressing cancer cells. In addition, apoptoses may be increased in transformed cells but inhibited in normal cells when butyrate is present (44-46).
Colon cancer, which in a high proportion of the population is due to somatic mutations occurring during the lifetime of an individual, could be retarded by preventing these mutations. Prebiotics have been shown to deactivate genotoxic carcinogens. DNA damage had been prevented and chemopreventive systems may be stimulated in vivo in colon tissues.
The colon of the human gastrointestinal tract contains a large population of resident bacteria. In fact, approximately 55% of the solids in faeces is microbial biomass. In adults, these bacteria are balanced in a complex ecosystem consisting of more than 40 major species and more than 400 species in total (47).
In a healthy individual, most of these species are advantageous or benign to the host, but some are potentially pathogenic if their numbers are allowed to increase to high levels. Disturbances to the ecological balance in the intestinal microflora caused by, for example, changes in diet, stress or antibiotic treatment can lead to the overgrowth of deleterious bacteria, and subsequently to gastrointestinal disorders (48). These disorders may be as minor as intestinal discomfort or increased flatulence, or relative serious health problems such as severe diarrhoea, irritable bowel syndrome and colitis. Undesirable bacteria in the colon have even been implicated in the development of colon cancer (49).
Oligofructose is derived from a plant source (usually chicory or sucrose) and consists of fructose chains of up to several units. It is a resistant starch, or soluble dietary fibre, that is not absorbed in the small intestine and passes into the large intestine where it is partly fermented, producing an energy value of 6 - 8 kilojoules/gm.
Carbohydrates are normally absorbed in the small intestine and directly metabolised in the liver, generating 17 kilojoules/gm. Complex fibres produce little or no energy and are broken down by bacteria to some degree in the large intestine.
Resistant starches are neither fibres or complex carbohydrates, and were for many years a dilemma for the Food Authorities. They are now recognised under the carbohydrate banner and are listed on nutritional panels as soluble dietary fibre.
Oligofructose is a tremendous substrate for bifidus bacteria, stimulating its activity by several hundred percent. This is called prebiotic activity, referring to stimulation of health promoting bacteria in the intestinal tract. Short chain fatty acids are produced, lowering pH levels and providing an energy source for the growth and maintenance of large intestine cells. This process leads to differentiation of cancer cells, a vital step that is required before cancer cells can be killed.
The ideal environment for healthy bacteria is quite different to the environment preferred by pathogens and gram negative putrefactive bacteria. Consequently the undesirable bacteria diminish in number as the healthy bacteria proliferate in the presence of oligofructose.
One type of undesirable bacteria are faecal bacteria that thrive in the presence of unabsorbed iron. This leads to the production of oxygen radicals that are known to damage protein, lipids and DNA. This damage has been implicated in the induction of somatic cell mutations that may favour the development of several forms of cancer (50).
There is some limited evidence that habitual intake of dietary fibre may suppress the production of reactive oxygen species (51).
A colon high in faecal iron levels would benefit substantially from oligofructose consumption, creating an environment unfavourable for the growth of iron loving bacteria. The microflora balance would gradually shift from the putrefactive to the healthy, increasing the growth of probiotic bacteria such as lactobacillus, bifidus, acidophilus and enterococcus.
Moreover, probiotics might prevent infection because they compete with pathogenic viruses or bacteria for binding sites on epithelial cells (52). Diarrhea due to the growth of pathogenic bacteria is the most common side effect of antibiotic use. Probiotics might inhibit this growth by releasing inhibitory substances, as indeed has been shown in vitro by some strains (53).
Desirable bacterial numbers can also be increased by consuming cultured products such as yoghurt but in many cases they are not very effective because many bacteria are destroyed in the stomach and small intestine. Upon reaching the colon or large intestine the surviving bacteria are often present is such low numbers that any likely benefit is doubtful. This especially happens with commercial yoghurt that has a shelf life of several weeks, with bacterial numbers possibly already low before consumption. Yoghurt manufacturers have addressed the problem by including oligofructose in the yoghurt so that surviving bacteria are rejuvenated once they reach the colon.
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Page created: Nov 11, 2001. Page last updated: May 27, 2006. |
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