Transcript A study to optimise the polyunsaturated fatty acid content

TILAPIAS FROM DIFFERENT
AQUACULTURE SYSTEMS CONTAIN
VARIABLE AMOUNTS OF -3 AND -6
POLYUNSATURATED FATTY ACIDS:
IMPLICATIONS FOR HUMAN NUTRITION
Ioannis T. Karapanagiotidis1*, Michael V. Bell1,
David C. Little1,2, Amararatne Yakupitiyage2
1Institute
of Aquaculture, University of Stirling, UK
2AARM, SERD, Asian Institute of Technology (AIT),
Thailand
Support from the Aquaculture and Fish Genetics Programme, DFID,
UK
Basic Concepts
Fatty acids are the basic units of fats and
oils (lipids)
 The polyunsaturated fatty acids (PUFA) are
a group of fatty acids with great
significance in animal nutrition (including
fish and humans)
 PUFA are categorised according to their
chemical structures, from which the most
important are those of the -3 and -6 fatty
acids.

The Importance of PUFA
 -3
and -6 PUFA are essential (Essential
Fatty Acids or EFA) for normal growth,
development and reproduction of all
vertebrate organisms, including fish &
humans
 Because
of the fact that animals cannot
synthesise -3 and -6 PUFA inside their
body (de novo), these should be provided
from the diet
The Vital Importance of -3 PUFA

Particularly the -3 PUFA (i.e.DHA & EPA) have
beneficial effects on general health and prevent
many health disorders such as:
• Diseases of the heart & of blood vessels
• Diseases of the immune system
• Cancer & respiratory diseases
• Allergic reactions
The Human Diet – A growing
concern

In recent decades, it is fact that the
profiles of fats in Western diets have
become increasingly unbalanced

The intake of saturated fat and -6 PUFA
has increased, whereas -3 PUFA intake
has decreased

Formerly the ratio -3/-6 was 1:5 but it
has now declined to ratios below 1:20
Changes in Fat and Fatty Acid Intake in Western Diets
(source: International Fishmeal & oil Manufacturers Association)
calories
from fat (%)
45
2
40
1.6
35
30
1.2
25
0.8
15
Saturated Fat


10
0.4
5
20
00
19
50
19
00
18
50
B
C
00
10
,0
io
n
18
00
0
B
C
0
m
ill
Total Fat

20
4
   ratio
The Human Diet – A growing concern


These changes in the fat patterns have been
linked with many common health disorders
in the western world (i.e. Coronary Heart
Disease, cancer etc.)
However, these changes appear to be
spreading and influencing diets around the
World
 The incidence of many health disorders is
now increasing in several countries in Asia
The Availability of Fats by economic group (1961-1990,
165 countries) Source: FAO Food balance sheets,
Agrostat PC, 1993
Region
Fat
g/caput/day
Increase between 1961
and 1990
1961
1990
%
Developing countries
28
50
78
Africa
Far East
Near East
Latin America
38
22
46
51
43
45
72
75
13
105
56
47
Developed countries
93
128
38
Former USSR
Oceania
Europe
North America
69
125
104
124
107
138
143
151
55
10
37
22
Fish in the Human Diet:
A Unique Nutritional Role
Fish is not only a high-quality protein food,
for which there are many competing
alternatives in nature
But also
contains high concentrations of -3 PUFA
(i.e. DHA & EPA) for which there are
currently no real competing alternatives
Fish is by far the richest source of -3 in
nature
Linkages between lipids and rural
aquaculture

The inland Asian communities are
traditionally dependent on freshwater aquatic
foods, and especially fish

There is an increasing reliance on farmed fish
as diets and livelihoods change

Is this more better? What are the qualitative
impacts of increasing fish consumption
through intensification of aquaculture?
Impacts of intensification




Most aquaculture production in Asia is semi-intensive
relying on use of both fertilisation and supplementary
feeding
The traditional supplementary feeds are high energy
brans and oilcakes, which are high in -6 PUFA
The increasing trend towards intensive systems is
making use of formulated feeds to satisfy the nutrient
requirements of fish
The fish feeds are using an increasing proportion of
global marine fishmeal (rich in -3 PUFA), but the
least cost formulations, commonly practised, result in
more -6 PUFA.
The current study
 to
determine the fat content and
fatty acid composition of tilapia
(Oreochromis niloticus)
produced in systems across a
range of intensification
Culture Systems
Culture System
Species
Feed Inputs
Wild fish (reservoir)
Nile tilapia
natural food
Extensive Polyculture
in snakeskin gourami
pond
Nile tilapia
natural food &
minimum
inputs
Integrated with chicken
Nile tilapia
natural food &
spilled feed
Semi-Intensive culture
Nile tilapia
fertilised &
supplementary
Intensive pond culture
Nile tilapia
only pelleted
feed
Intensive cage culture
in river
Red tilapia
only pelleted
feed
Total Lipid (%) of wet weight muscle tissue
1.80
1.60
1.40
1.20
TL
1.00
0.80
0.60
0.40
0.20
0.00
wild
polyculture
integrated semi-intensive intensive nile
red Tilapia
The Amounts of FA in edible muscle tissue (mg/g)
5.00
4.50
4.00
3.50
Saturated
MUFA
PUFA
3.00
mg/g 2.50
2.00
1.50
1.00
0.50
0.00
wild
polyculture
integrated
semi-intensive
intensive
red tilapia
 ratios (in edible muscle tissue)
mg FA/g tissue
2.0
1.5 w-3/w-6
1.8
1.6
 
1.4
1.0
1.2
 
1.0
  
0.8
0.5
0.6
0.4
0.2
0.0
0.0
wild
polyculture integrated
semiintensive
intensive red tilapia
Individual Fatty Acids (% of Total FA content)
16.00
14.00
12.00
10.00
EPA
DHA
18:2 n-6
8.00
6.00
4.00
2.00
0.00
wild
polyculture Integrated
Semiintensive
Intensive
Red tilapia
Conclusions of the study

The fat content of tilapia is moderate but
increases as we shift from extensive
production totally dependent on natural
food to more intensive culture systems.

Tilapia contain considerable amounts of
the valuable DHA in the edible muscle
tissue
Conclusions of the study

-3/-6 ratios in tilapia cultured at
different intensities ranged from 1:1 to
1:2, indicating their high lipid nutritional
value

However, higher levels of -6 and lower
ratios of -3/-6 were found in the more
intensively farmed fish compared to the
wild fish and those cultured mainly on
natural food.
General Conclusions

The aquaculture sector has a very important role
to play both in the developing and developed
world by providing food security and ensuring
future fish supplies. Fish is the richest source of
the -3 PUFA in nature and consumption of fish
improves human nutrition and health.

However, since the input of -6 PUFA from other
dietary components is often excessive in humans
it is desirable, or even essential, that fish
continue to supply long-chain -3 PUFA in the
human diet.
Recommendations
 Participation of the feed industry assessing the
potential for developing feed formulations that
enhance -3:-6 ratios to optimal
 a better understanding of the underlying
mechanisms that result in more desirable ratios
observed in less intensively farmed and natural
stocks
Recommendations
 An assessment of the fat quality of other common
aquatic animals, cultured and natural stocks,
consumed by rural communities
 Awareness raised among change agents and
policy makers that production methods can affect
fish quality and that these in turn may have
impacts on human health
Thank you