Probiotics & Prebiotics - Do they really work?
Our first impression of bacteria is how deadly or infectious
they are bit it is only a very small amount of them that are bad.
For instance, out of 2500 strains of Salmonella only two of them
cause trouble. Moreover, some bacteria such as E Coli, only causes
havoc when ingested through the mouth. It normally lives in our
guts' micro flora.
Things go wrong if they become too comfortable and over populate
the micro flora. Here is where the bacteria in probiotics come to
the rescue. These 'good' bacteria help keep the population of the
others in place. Overpopulation produces excessive gases (hydrogen
sulphide, H2S) hence bloating, diarrhoea, cramps and other symptoms
of great discomfort.
What are Probiotics and Prebiotics?
Schrezenmeier & De Vrese (Am J Clin Nutr 73 (Suppl) 361s-364s
2001) define a probiotic as: 'A preparation or product containing
viable, defined micro organisms in sufficient numbers, which alter
the micro flora of the host intestine and, by that, exert beneficial
health effects on the host'. Meanwhile, prebiotics are nutrients
and constituents of food which our gut flora feed upon, thus increasing
their numbers. Prebiotics include fructo-oligosaccharides, which
are found naturally in many plants including leeks, onions, wheat,
garlic, chicory root and artichokes.
The 1908, Nobel Prize-winning scientist Elie Metchnikoff of the
Pasteur Institute in Paris provided the first evidence that microorganisms
may be responsible for the health-promoting effects of fermented
milks. After observing that Bulgarian peasants lived to ripe, old
ages, Metchnikoff became convinced that their health and longevity
were linked to microbes in the soured milk they copiously drank.
He suggested that disease-causing 'bad' bacteria could be eliminated
by ingesting large amounts of Bulgarian sour milk, which contained
a beneficial 'good' bacterium later identified as Lactobacillus
Probiotics may be found in live yoghurts or specially formulated
powders, supplement pills or probiotic drinks which contain one
or more of the strains of these bacteria. With food processing,
pollution and antibiotic therapy, the numbers of bacteria living
naturally in our gut are reduced, and research has shown that active
consumption of bacteria increases the size of intestinal colonies,
thereby improving digestion of food. Moreover, numerous studies
have also shown that with optimal numbers of 'good' bacteria, the
immune system is improved, increasing our ability to fight disease.
Probiotics may also have a role in reducing the severity of food
allergies and intolerances, and may help reduce severity of symptoms
in both osteo- and rheumatoid arthritis.
Health Benefits of Probiotics
- Managing Lactose Intolerance:
Because Lactic Acid Bacteria (LAB) convert lactose into lactic acid, their ingestion
helps lactose intolerant individuals tolerate more lactose than
what they would have otherwise.
- Prevention of Colon Cancer:
In laboratory investigations, LAB have demonstrated anti-mutagenic
effects thought to be due to their ability to bind with (and
therefore detoxify) carcinogenic substances formed in cooked
meat. Lower rates of colon cancer among higher consumers of
fermented dairy products have been observed in some population
Animal studies have demonstrated the efficacy of a range
of LAB to be able to lower cholesterol levels, presumably by
breaking down bile in the gut, thus inhibiting its re-absorption
(which enters the blood as cholesterol).
Several small clinical trials have shown that consumption
of milk fermented with various strains of LAB can result in
modest reductions in blood pressure.
Improving Immune Function and Preventing Infections:
Probiotics are thought to have several beneficial effects
on immune function. They may protect against harmful bacteria
overgrowth and there is evidence to suggest that they may improve
immune function by encouraging production of cells in our body
whose main function is to protect us against infections and
cancers. Clinical trials have also demonstrated that probiotics
may decrease the incidence of respiratory tract infections and
dental caries in children. LAB foods and supplements have been
shown to be effective in the treatment and prevention of acute
diarrhoea; decreasing the severity and duration of rotavirus
infections in children as well as antibiotic associated and
travellers diarrhoea in adults.
Probiotic foods and supplements have been found to modulate
inflammatory and hypersensitivity responses, an observation
thought to be at least in part due to the regulation of cytokine
function. Clinical studies suggest that they can prevent reoccurrences
of Inflammatory Bowel Disease in adults, as well as improve
milk allergies and decrease the risk of atopic eczema in children.
Improving Mineral Absorption:
It is hypothesized that probiotic lactobacilli may help correct
mal absorption of trace minerals, found particularly in those
with diets high in phytate content from whole grains, nuts,
Prevents Harmful Bacterial Growth Under Stress:
In a study done to see the effects of stress on intestinal flora, rats that were fed probiotics had no occurrence of harmful bacteria latched onto their intestines compared to rats that were fed sterile water.
Dead or Alive! Alive better
In one of its surveys the independent magazine 'Which?'
reported that only 5-15% of bacteria in products tested survived
all the way to the consumer! So is this a waste of money and false
Luckily it is not an entirely 'yes' answer, because scientists
demonstrated that the immune system in subjects given dead 'good'
bacteria still responds. In California and Jerusalem irradiated
probiotics (irradiation kills all living bacteria) where given to
mice with gut inflammation.
The treatment reduced the inflammation in a similar way to giving "live"
bacteria, and the researchers concluded that irradiated probiotics
were just as effective.
According to the BBC, Professor Eyal Raz, one of the study authors,
said: "Our goal was to address whether the metabolic activity
of probiotics was mandatory for their protective effect." The
team believes that part of the body's immune system called the "innate"
immune system responded to the bugs, regardless of whether they
were dead or alive. This immune response might be damping down the
overactive response within the gut.
However, experts say that the presence of live rather than inactivated
bacteria in the gut has several advantages. Firstly, the simple
fact that they are occupying space and attached to the gut wall
denies that space to harmful bacteria, particularly if their numbers
increase over time.