The Role of Probiotics in Health.

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The Role of Probiotics in Health


Probiotic bacteria are micro-organisms that have the specific property of transforming
sugars almost exclusively into lactic acid. They are abundant in nature and
extremely useful. Lactic bacteria have been used for centuries in the production
of cheese, yogurt, cultured buttermilk, kefir and other fermented foods. Lactic
bacteria are essential for human and animal survival. They are normally present
in the skin, the digestive tract and the vaginal mucosa, where they fulfil numerous
functions and assure the protection of tissues against the action of harmful

Beneficial bacteria include Lactobacillus acidophilus, Lactobacillus casei,
Lactobacillus rhamnosus, Lactobacillus plantarum 299v and Bifidobacterium longum.
The bifidobacteria species of bacteria can survive without oxygen (anaerobic)
and are beneficial for the well-being of humans both during infancy and in the
later years. Bifidobacteria are the predominant friendly bacteria present
in the colon of breast fed infants and bifidobacterium longum is one of the
major strains of friendly bacteria found in infants.

Colonisation of the digestive tract by a population of micro-organisms specific
to each person takes place in the first few days of life. The most significant
changes in the intestinal flora take place from birth until weaning and again
in the later stages of life. In between, the microbial population of the dominant
flora remains relatively stable and prevent potentially pathogenic bacteria
from adhering to the intestinal wall. This has been termed the barrier effect.

The most natural way of obtaining good bacteria is through food. However, the
processing and preparation of food can be detrimental to the lactic bacteria
found in fresh foods. Camembert cheese, sauerkraut and yoghurt are naturally
rich sources of these beneficial bacteria.

The balance of bacteria in the digestive tract remains fragile and susceptible
to lifestyle changes. Factors such as stress, change in the diet and medicine
intake can upset this balance. An imbalance can result in various disorders
including bloating, intestinal pains, nutritional deficiencies and constipation.
A disruption in the barrier effect will lead to a colonisation of the digestive
system by pathogenic bacteria which may result in intestinal disorders. Diarrhoea
is an example of the barrier effect being disrupted by the pathogenic bacterium
Clostridium difficile.

In later years (around fifty and over) it is particularly important to maintain
the levels of bifidobacterium in the colon because the body does not produce
them to the same extent as after infancy. The consumption of fructo-oligosaccharides
(FOS) can help to maintain these friendly bacteria levels. FOS are found in
fruits, vegetables and plant based foods; they are particularly abundant in
Jerusalem artichokes, chicory root, leeks, onions and asparagus.

Healthy digestion

The process of digestion begins when the smell of food reaches the olfactory
tissue (sense of smell), this stimulates the production of saliva. The process
of chewing mixes food with amylase, a carbohydrate digesting enzyme found in
saliva. The chewing stage is critical for good digestion. Some people recommend
chewing each mouthful of food forty times before swallowing (it is worth trying
this, it is quite surprising what happens to the food). In the stomach, hydrochloric
acid mixes with the well-chewed food to aid the breakdown of protein and to
help prevent any incoming pathogenic bacteria travelling further into the intestine.

The intestine is one of the most important lymphoid organs in the human body.

The primary site of action for probiotics is the intestinal wall where they
interact with immune cells, whether by direct contact or by the production of
cytokines, a type of molecule that interacts and co-ordinates with communication
and immune cell response.

The intestinal immune system has two significant functions for health. Firstly,
to suppress the immune response against foreign proteins from bacteria or food
found in the digestive tract. This helps prevent oversensitivity to food and
minimises chronic digestive tract inflammation such as Crohns disease. Secondly,
to promote protective immune responses against pathogenic bacteria, the synthesis
of antibodies is a key component of protective immunity in the gut.

Research Using Probiotics

Lactobacillus and diarrhoea

A meta-analysis of randomised control studies was conducted to assess the efficacy
of lactobacillus in improving clinical outcomes in children with acute infectious

Studies that satisfied the selection criteria were adequately randomised, blind
control trials in which the case subjects were treated with lactobacillus and
the control group was given a suitable placebo. The results revealed that lactobacillus
reduced the duration of diarrhoea by 0.7 days and reduced the frequency of diarrhoea
on day two of treatment, compared to placebo. It concluded that lactobacillus
is safe and effective in the treatment of acute infectious diarrhoea in children

Lactobacillus plantarum 299v and IBS

Treatment of IBS can be frustrating to the clinician and the sufferer. The practitioner
should offer concise, appropriate diagnosis, reassurance and education that
IBS is a functional disorder without significant long-term health risks. Probiotic
therapy using Lactobacillus plantarum 299v has demonstrated superiority to placebo
in improving pain, regulating bowel habits, and decreasing flatulence (1).

The survival of probiotics

To be effective, a probiotic must enter the intestine alive, where its beneficial
effects occur. Scientific in vitro tests have demonstrated the resistance of
B. longum, L.rhamnosus, L.acidophilus and L. plantarum to stomach acid which
ensures their safe passage into the intestines. These bacteria have also been
found to be highly resistant to bile. Bile secretion from the liver serves as
a defence mechanism against foreign intestinal micro-organisms. The ability
of a probiotic bacterium to survive in the presence of bile is a major factor
in the growth and development of friendly bacteria in the intestines.

Probiotics and lifestyle

The balance of bacteria in the digestive tract remains fragile and susceptible
to lifestyle changes. Factors such as stress, change in diet and drug intake
(antibiotics), can disturb this balance. Any imbalance can result in various
disorders including bloating, intestinal pains, nutritional deficiencies and
constipation. Also, a disruption of the barrier effect will lead to colonisation
of the digestive system by pathogenic bacteria which may result in intestinal
disorders. These disorders can be very severe, such as in the case of pseudomembraneous
colitis (a serious type of diarrhoea) induced by the pathogenic bacteria Clostridium
difficile due to the elimination of the barrier effect following a course of
antibiotics. One of the most important characteristics for a probiotic bacterium
is the ability to inhibit the growth of pathogens.

Hydrochloric acid, secreted by the stomach in order to aid protein digestion,
has a very low pH of around 3 (water is 7). This is harmful for the probiotic
bacteria in supplements if they are not protected from this acid. Such protection
is usually achieved by consuming probiotic supplements with or immediately after
a meal.

The meal acts as a buffer against the stomach acid; increasing the pH of the
stomach environment to a more tolerable level, therefore allowing safe passage
of the bacteria into the intestine where they can exert their effects. Alternatively,
consuming probiotic supplements with a glass of milk will have a similar effect.
The milk will dilute the acid, and the calcium content (being a natural alkali)
will further increase the pH. However, more recently developed probiotic strains
are resistant to stomach acid.

The human digestive system has always been host to probiotic bacteria, they
are part of the make-up of the human body just as the liver or the heart is.
The change in dietary habits from eating naturally produced, home-grown, home-cooked
foods to eating forced grown pre-prepared convenience foods, and food high in
refined carbohydrates and sugar has depleted the levels of probiotic bacteria
in the digestive system and created a need for probiotic supplementation.

The biological roles of the lactobacillus family of bacteria are numerous and

" Helping immune function in the digestive tract

" Creating bacterial barrier protection for the intestinal wall

" The production of acidic compounds that kill pathogenic or bad bacteria

" Regulation of intestinal transit time

" Production of vitamin K, some B vitamins and certain growth factors

Bifidobacteria are important members of the micro biota and are considered
to contribute to maintaining health. However, the level of bifidobacteria colonising
the intestine of elderly people tends to be lower than in younger adults. Particular
strains of Bifidobacterium longum have been noted to be well tolerated by older
humans and are safe to use as food supplements (3).

It may be prudent to bear in mind ones age and increase the daily consumption
of fresh fruit and vegetables and reduce the amount of convenience foods and
food high in refined carbohydrates and sugars in the diet. A twenty minute walk
every day will also help to reduce stress levels, thereby helping to maintain
the correct pH of the intestine, keep the cardiovascular system in good order
and relax both mind and body.

General Reference Source:

Institut Rosell, Lallemand.

Other References:

1. Curr Treat Options Gastroenterol. 2002 Aug;5(4):267-278

2. Pediatrics 2002; 109: 678-84.

3. Microbiol Immunol. 2003;47(12):911-4.

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