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H E A LT H
Beneficial bacteria
Bacteria are not something we normally think of as having a positive function. But there are different types
of bacteria, and some of them are extremely beneficial to our health.
AT A GLANCE
Good bacteria.
Gut microflora.
Probiotics.
Probiotics can be defined as ‘live
microbial food ingredients that have a
beneficial effect on human health’. The
term probiotic comes from the Greek
‘for life’. This links with the actions of
probiotics. They promote the growth of
good bacteria in the body.
Some bacterial microorganisms can
cause illness or are pathogenic. Bacterial
pathogens, or what we might call ‘bad’
bacteria such as salmonella and E.coli,
can cause gastro-intestinal upset.
Probiotics are non-pathogenic bacteria
that do not cause illness. They are also
referred to as ‘good’ or ‘friendly’ bacteria.
When we are born our digestive
system is free of bacteria, but bacteria
start to take up residence in our body
immediately after birth. There are over
four hundred species of probiotic
bacteria that can inhabit our digestive
tract. Healthy adults will have three to
four hundred bacteria species
inhabiting their intestines.
(Lactobacillus or Bifidobacterium) and
then by the specific strain of bacterium
(Lactobacillus casei or Bifidobacterium
bifidum). See our table on p134 for a
list of common lactic acid bacteria used
in probiotic products. Some of these
bacteria live in our intestines and are
classed as resident, while others are
transient. They do not take up
permanent residence in the digestive
tract, but form temporary colonies.
Lactic acid bacteria are commonly
used in the production of fermented
foods such as yoghurts, cheeses and
pickled foods such as sauerkraut. Their
growth lowers the pH of the food,
preventing food spoilage by inhibiting
other microbes from developing. This is
what gives dairy products, such as
cheese and yoghurt, a longer shelf life
than milk itself. While these bacteria are
used in fermented foods, not all of
these are probiotic. Yoghurt is probiotic,
but cheese is not (see Probiotic foods).
Types of good bacteria
Benefits
Lactic acid bacteria are the most
Report by
common bacteria used in probiotic
Aisling Murtagh cc foods. They can be classified by species
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APRIL 2008 HEALTH
A balance of good bacteria helps our
digestive system to function at it best.
They can assist the breakdown of fat
and protein and in the manufacture of
certain B vitamins in the gut. They can
increase our body’s uptake of certain
nutrients by improving their
bioavailability.
It has been suggested that many
gastro-intestinal problems are related to
an imbalance of microflora. When we
have a healthy level of microflora in our
intestines it helps our body deal with
pathogenic bacteria if exposed to them.
Some good bacteria produce
bacteriocins, which are antibiotic-like
substances that suppress the growth of
non-beneficial, pathogenic bacteria in
the gut. Good bacteria can therefore act
as a barrier to pathogenic bacteria.
Rather than just looking at probiotics
on a general level, particular strains of
probiotic bacteria have more specific
benefits. L. casei and L. acidophilus have
been found to have immune enhancing
properties. L. acidophilus also
encourages the production of substances
that inhibit the growth of the yeast
Candida, and is useful in the treatment
of constipation. B. bifidum has been
found to be anti-pathogenic; it can
prevent the growth of undesirable
bacteria that can cause digestive upset.
Flora imbalance
Bacteria inhabit our gut from birth, and
it is important to have the right balance
of good bacteria for digestive health.
Many factors can disrupt our gut flora,
such as a bout of gastroenteritis, and
even high stress levels. Taking a course
of antibiotics kills most bacteria in the
gut, whether good or bad. A low fibre
diet can result in low levels of good gut
microflora. Probiotic foods can help to
rebalance gut flora and help repopulate
the gut with good bacteria.
It is not just bacteria that affect the
microflora balance. Other
microorganisms, such as yeasts or
viruses, also occupy the digestive tract.
For example, the yeast Candida, which
can lead to infections such as thrush,
can also inhabit our digestive tract.
Problems occur when this
microorganism increases in number
and disrupts the balance of microflora.
Prebiotics
Prebiotics stimulate the production of
probiotics. They are indigestible fibres
that are fermented by probiotic bacteria
in the colon. This then stimulates the
growth of good bacteria. Prebiotics
include fructo-oligosaccharides (FOS),
inulin and citrus pectin.
Research in 2007 in the British Journal
of Nutrition found that when the nondigestible fibres in wholegrains reach the
intestine they have a prebiotic effect. This
effect does not occur when the fibre
alone is consumed (e.g. wheatbran), but
was found to result from consumption of
the wholegrain itself.
Functional food
Foods that are marketed as having a
specific health benefit, over and above
their nutritive value, are deemed
functional foods. Probiotic foods can be
classed as functional foods. Some may
claim they will benefit the immune
system or assist digestion.
Other probiotic foods, such as biolive yoghurts, may just state they are
probiotic and not promote the specific
benefits of the bacteria they contain.
Even if a probiotic product makes no
particular health claims, it will generally
promote a good microflora balance and
depending on the bacteria present, may
have more specific benefits.
Research carried out by the European
consumer group BEUC, of which the
CAI is an active member, found that
consumers read and trust health claims
used in the marketing of functional
foods. BEUC also suggests that health
claims are often based on one attribute
of the product, which does not reflect
its overall health value. In relation to
probiotic drinks there is an element of
truth in this statement. Some probiotic
drinks can have a high sugar content,
so it is important to check the
ingredients if concerned about sugar
intake. A sweet taste can assist
consumer taste acceptance of a product.
However, this can take away from its
overall health value. It is also thought
that a diet high in sugars can support
the growth of unfavourable
microorganisms that disrupt microflora
balance, such as yeasts like Candida.
Probiotic drinks that are high in sugar
thus seem somewhat contradictory.
Safety
Probiotic foods are not new. These
bacteria have been used in certain foods
since the beginning of civilisation. They
even got a mention in the Bible. But
new strains of probiotic bacteria have
been developed for use in foods.
Consumers may be familiar with the
lactic acid bacteria such as those found in
Danone Actimel L. casei defensis or
Danone Activia Bifidus ActiRegularis.
These strains are developed, patented and
owned by the manufacturer.
Recent research from Holland has led
to some questioning of the safety of
probiotics. They were used in the
treatment of patients with pancreatitis
and more patients died from the group
where probiotics were used. In this case
probiotics were used as a drug
(introduced directly into intestine
through feeding tube). This can be
alarming for consumers, but we
consume probiotics very differently.
They are consumed as a food or food
supplement and not used as a drug.
The novel food legislation (Regulation
258/97/EC) governs the introduction of
a food or food ingredient that has not
been available on the EU market prior to
1997. Because probiotic foods have been
around for a long time, they are not
considered novel foods. If they are used
in a non-traditional way, they must be
assessed under the novel food regulation.
PROBIOTIC YOGHURTS AND DAIRY DRINKS
Manufacturer
Product
Size
Price
(€)
Price per
100g (€)
Bacteria
Danone
Actimel drink
12x100g
4.99
0.42
orange
L. casei
defensis
Danone
Activia yoghurt
500g
1.99
0.40
Bifidus
ActiRegularis
L. bulgaricus
Streptococcus
thermophilus
Glenisk
Organic natural
yoghurt wholemilk
500g
1.84
0.37
L. casei
B. bifidum
(bifidus)
L. bulgaricus
Streptococcus
thermophilus
Old
McDonald
Functional live
low fat yoghurt
plain
500g
1.99
0.40
L. acidophilus
B. longuum
L. bulgaricus
Streptococcus
thermophilus
Onken
Natural yoghurt
500g
1.41
0.28
L. acidophilus
B. longuum
Streptococcus
thermophilus
Rachel’s Dairy
Organic yoghurt
vanilla low fat
450g
1.99
0.44
L. acidophilus
Bifidobacterium
L. bulgaricus
Streptococcus
thermophilus
Yakult
Probiotic drink
7x65g
3.99
0.88
L. casei shirota
B. breve
B. infantis
Useful contacts
Irish Nutrition and
Yeo Valley
Organic natural
yoghurt
500g
1.69
0.34
L. acidophilus
Bifidobacterium
Dietetic Association
Yoplait
Everybody drink
8x100g
3.95
0.49
L. rhamnosus GG
Kill Avenue
Yoplait
Essence healthy
digestion drink
6x60g
3.99
1.10
Bifidobacterium
BB 12r
Dun Laoghaire
Yoplait
Essence immunity
boost drink
6x60g
3.99
1.10
Bifidobacterium
BB 12r
email [email protected]
HEALTH APRIL 2008
consumer choice
Ashgrove House
Co. Dublin
www.indi.ie
133
But some new strains of probiotic
bacteria have been developed. The novel
food regulation is currently being
revised. It has been questioned by some
European consumer organisations
whether new strains of probiotic
bacteria should be subject to approval
under the revised novel food regulation.
The European Food Safety Authority
does not currently assess the safety of
probiotics used in food.
Probiotic foods
Common probiotic products include
yoghurts and dairy drinks. These
products contain different strains of
probiotic bacteria. See our table for an
overview of a range of probiotic
products on the market and the bacteria
they contain. But not all yoghurts are
probiotic. Consumers will see bio-live,
live or probiotic on the label if they are.
The transient bacteria, L. bulgarius
and Streptococcus thermophilus, often
act as starter cultures in the yoghurt
making process. These bacteria can be
listed as ‘active bacteria’ in the
yoghurts ingredients as they are not
thought to survive passage through the
digestive tract to the gut. Other
probiotic cultures can be added to
probiotic yoghurts, such as L.
acidophilus, L. casei, B. bifidum and B.
longum. These probiotic cultures can
survive better, and the yoghurt itself
protects them from damage during
digestion. The specific bacteria that the
yoghurt contains can be shown on the
yoghurt label, or in the ingredients
lists, but is not always displayed.
Probiotic yoghurts listed in the table
are slightly more expensive than nonprobiotic yoghurts. On average, a 125g
pot of yoghurt costs about sixty cents
and a 500g pot around €1.80. Some of
the probiotic dairy drinks were more
expensive than the yoghurts. There are a
number of organic yoghurts listed in
the table. It seems that organic yoghurts
are also often probiotic.
For a product to claim it is probiotic
it must have a minimum concentration
of colony forming units (CFUs). Most
probiotic products will name the
probiotic cultures present, but do not
give the exact concentration. The greater
the concentration of probiotic bacteria,
the greater the chances of their survival
when they reach the gut. Testing of
yoghurts that claim to be probiotic and
the inclusion of the number of bacteria
that should be present in the yoghurt
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APRIL 2008 HEALTH
choice comment
If consumers wish to consume probiotics, it can be hard to know which products are best.
Some companies who produce probiotic products emphasise the benefits of a specific
probiotic in their product, when consumed regularly. While these claims are often supported by
research, let us be clear that this is also a defined sales strategy. Regular consumption means
increased sales and profits.
could provide consumers with clearer
information on the quality of a
probiotic product.
Specific bacteria have specific proven
benefits, but a balance seems to be
more beneficial to overall health.
Consuming a range of different
probiotic products could help this
balance, as these products will often
contain different probiotic cultures.
We may also see the term ‘synbiotic’
on yoghurts. These products combine
prebiotics and probiotics that work in
symbiosis to encourage the growth of
good gut bacteria.
Beneficial bacteria enter a
hostile environment
When we ingest probiotic bacteria, they
have to survive an environment where
digestive juices, such as acids and bile,
can damage them. An important
function of our digestive juices is to
destroy pathogenic bacteria that can
cause illness, but this can also lead to
the destruction of good bacteria.
However, some are more resistant to
digestive juices than others. More
resistant bacteria will often be chosen
for use in probiotic products. It is
recommended that probiotic bacteria
which are used in probiotic foods
should be acid and bile tolerant,
capable of withstanding technological
processes and have a long shelf life.
Probiotic supplements
Probiotics can also be purchased in
supplement form. Probiotic
supplements will most often state the
number of bacteria present. This
number is usually measured on
manufacture of the product. The
number of probiotic bacteria present
will decline with time. Some
manufacturers will differentiate between
the number of bacteria at manufacture
and the number expected to be present
by the products expiry date.
Consumers may find that probiotic
supplements are kept refrigerated in
retail outlets. Probiotic bacteria are
living microorganisms. Storing them at
lower temperatures will prevent the
number of each probiotic bacteria in the
supplement from declining.
There is debate as to how well
probiotics survive digestion when
taken in this form. It is best to take
probiotic supplements on a full
stomach. Some probiotic supplements
can be enteric coated, which protects
them from being damaged by digestive
juices. They should then reach the
intestine more efficiently.
No RDA
There is no recommended amount of
probiotic bacteria that we should
consume on a daily basis. If we never
consume probiotics this does not mean
we will have low or no gut flora. There
are many factors that influence the
development of the correct balance of
gut flora. Sometimes gut flora need
rebalancing, such as after taking
antibiotics. In some instances they can
be more important than others.
LACTIC ACID BACTERIA
Species
Strain
Resident or Transient
Lactobacillus
L. acidophilus
Resident
L. casei
Resident
L. rhamnosus
Resident
L. bulgaricus
Transient
L. salivarius
Resident
B. bifidum
Resident
B. breve
Resident
B. infantis
Resident
B. longum
Resident
Streptococcus
thermophilus
Transient
Bifidobacterium
Other lactic acid bacteria