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Omega-3 Fatty Acid Composition
of Habitual Diets
in Australia
Neil J Mann
Department of Food Science
Melbourne Australia
Background
Generally agreed amongst lipid researchers that the
western diet has:
High n-6 : n-3 PUFA intake
Low total n-3 PUFA intake
This leads to an over emphasis of arachidonic acid
(20:4 n-6) derived eicosanoids (TXA2 PGE2 LTB4 etc)
with subsequent increased risk of vascular disease and
inflammatory conditions.
Recommended dietary intakes for n-6
and n-3 PUFA
Workshop on the essentiality of / and recommended dietary intakes for
n-6 and n-3 fatty acids.
(NIH Bethesda Maryland USA, April 1999).
Adequate intakes (AI) for adults
Fatty acid
Linoleic acid
(Upper limit)
a-linolenic acid
EPA (min)
DHA (min)
EPA + DHA
Grams/day
(2000 kcal diet)
4.44
6.67
2.22
0.22
0.22
0.65
% Energy
2.0
3.0
1.0
0.1
0.1
0.3
Determination of n-3 PUFA intake
To
make public health recommendations we need to know what
amounts of fatty acids are being consumed by different dietary
groups.
In many tables of fatty acid content of foods, information is
reported as g fatty acid/100g food (to one decimal place).
Except in certain foods, such as fish, LC PUFA are present in
only trace amounts.
Most fatty acid databases cannot be used to estimate long chain
PUFA intake (AA EPA DHA etc).
Because the trace levels disappear !
But these small (ignored) contributions can accumulate to significant levels of
biological importance in the context of a total diet.
Determination of n-3 PUFA intake (contd)
Due to the low levels of LC PUFA present in foods, composition
tables can round them down to zero when reported to a single
decimal place (g/100g food).
For example 100g lamb chops contain:
(130mg LA, 52mg AA, 44mg EPA, 36mg DPA and 10mg DHA)
This would appear in a composition table as shown:
18:2 n-6
(LA)
20:4 n-6
(AA)
20:5 n-3
(EPA)
22:5 n-3
(DPA)
22:6 n-3
(DHA)
0.1
0.1
0.0
0.0
0.0
Aims
1.
Create a fatty acid database of current food supply to
two decimal places in g/100g
2.
Determine the consumption level of fatty acids in
specific dietary groups
3.
Investigate the main dietary sources of LC n-3 PUFA
in the diets
1. The fatty acid database
 The database consists of 1077 foods with full fatty
acid analysis (at present)
 The reported analytical data contains 11 sat fatty acids,
7 MUFA, 10 PUFA (6 n-6, 4 n-3) and 3 trans fatty acids
 The database concentrates on foods with greater than
1% total fat by weight
2. The dietary study
Healthy male subjects were recruited from 4 habitual diet groups.
Vegan:
Consumed plant foods only.
n=18
Ovolacto vegetarian: Consumed eggs and dairy products
and plant foods.
n=42
High meat eater:
Consumed > 280 g meat/day.
n=17
Moderate meat eater: Consumed 50-260g meat/day.
n=54
2. The dietary study
Characteristics of subjects in the dietary groups (mean + s.d)
High meat
Moderate
meat
Ovolacto
vegetarian
Vegan
Age (y)
34.2 + 9.4ab
38.3 + 7.3a
34.9 + 9.0b
33.0 + 7.7b
BMI
27.0 + 3.4a
26.4 + 3.4a
23.6 + 2.8b
23.3 + 3.5b
Waist/Hip
ratio
0.88 + 0.06ab 0.88 + 0.05a 0.86 + 0.04b 0.85 + 0.05b
Values on the same line with different superscripts are significantly different at (p<0.05).
2. The dietary study
Daily intake of selected items by the 4 dietary groups (mean + s.d)
High meat
Moderate
meat
Ovolacto
Vegans
White meat (g)
109.6 + 51.6a
53.7 + 27.1b
0.2 + 0.7c
0.00 + 0.00c
Red meat (g)
270.4 + 118.0a
108.9 + 41.1b
0.00 + 0.00c
0.00 + 0.00c
Fish (g)
27.7 + 23.9a
26.1 + 18.3a
1.4 + 3.4b
0.7 + 1.8b
Energy (MJ)
1.67 + 3.31a
1.13 + 2.48b
1.15 + 2.46b
1.18 + 2.44b
Protein (% E)
19.4 + 1.3a
17.9 + 2.2b
14.7 + 2.2c
14.1 + 2.4c
Carbo (% E)
40.3 + 4.4a
45.7 + 6.8b
50.9 + 6.4c
57.4 + 5.4d
Total fat (% E)
37.8 + 4.2a
32.8 + 6.1b
32.7 + 6.2b
28.2 + 4.3c
2. The dietary study
LC fatty acid intake (mg/day) for the 4 habitual diet groups.
Group
20:4n-6
(AA)
20:5n-3
(EPA)
22:5n-3
(DPA)
22:6n-3
(DHA)
Total LC
n-3
High meat
240a
70a
90a
120a
290a
Moderate
meat
100b
40b
30b
70a
140b
Ovolacto
30c
0c
0c
10b
10c
Vegans
0d
0c
0c
0c
0c
2. The dietary study
Combining the two meat eating groups into one “omnivore
group” we see the following mean daily intake patterns:
Group
18:2n-6
18:3n-3
LC n-3
n-6:n-3
Omnivores (n=71)
14.2 g
1.5 g
190 mg
9.5 : 1
Ovolacto
(n=42)
18.4 g
1.4 g
10 mg
12.9 : 1
Vegan
(n=18)
21.6 g
1.2 g
0 mg
18.7 : 1
Recommended
< 6.7 g
> 2.2 g
> 650 mg
2. The dietary study
The results for omnivores closely approximate those
reported in an evaluation of the Australian population
based on the National Nutrition Survey (1995) and use
of this fatty acid database.
(Meyer, Mann, Howe, Lewis & Sinclair. Lipids 38[4], 2003)
Australian adult mean daily intakes
Total n-6
11.3 g 1.4 g
Total n-3
8.1 : 1
n-6 : n-3
LC n-6
100 mg
LC n-3
188 mg
2. The dietary study
USA
n-6 : n-3 intake ratio approximately
11 : 1
(Production and consumption data; Hunter, Am J Clin Nutr, 1990)
“Natural” human diets as represented by modeling of
paleolithic diets and current hunter-gatherers give very
different results:
18:2 n-6
18:3 n-3
8.8 g
12.6 g
18:2 : 18:3
0.7 : 1
LC n-6
LC n-3
n-6 : n-3
1.8 g
1.1 g
0.9 : 1
(Eaton, Eaton, Mann, Cordain, Sinclair, World Rev Nutr Diet, 83, 1998)
2. The dietary study
Plasma PL fatty acid concentrations (mg/100ml)
18:2
18:3
20:4
20:5
22:5
22:6
n-6
n-3
n-6
n-3
n-3
n-3
Total n6:n3
LC n-3
H. Meat
24.5
0.3
12.9a 1.4a
1.5a
3.9a
6.9a
6.0:1a
M. Meat
26.9
0.2
12.7a 1.2a
1.5a
3.9a
6.6a
6.5:1a
Ovolacto
27.0
0.3
9.8b
0.7b
1.1b
2.2b
4.0b
9.6:1b
Vegan
25.4
0.3
10.1b 0.6b
1.1b
2.0b
3.7b
9.9:1b
2. The dietary study
Correlation of dietary intake of fatty acids and plasma status
Significant correlation
No correlation
18:0
18:1
20:4 n-6
20:5 n-3
22:5 n-3
22:6 n-3
18:2 n-6
18:3 n-3
18:2 n-6 with 20:4 n-6
18:3 n-3 with 20:5 n-3
3. Dietary sources of LC n-3 PUFA




Australians are not big fish eaters (approx 26 g/day).
Australians are moderate to high red meat eaters
(approx 170 g/day).
Australian sheep / cattle are almost entirely pasture
fed, hence accumulate 18:3 n-3 from grass and
produce appreciable levels of EPA and DPA.
Grain fed animals tend to accumulate 18:2 n-6 and
and have very low levels of LC n-3 PUFA.
3. Dietary sources of LC n-3 PUFA
Selected fatty acid levels in beef rump (mg/100g lean meat)
Total
fat
18:2
n-6
18:3 20:5 22:5 22:6
n-3 n-3 n-3 n-3
Grass fed
Grain fed*
2800 a
4800 b
190 a
255 b
49 a 40 a 58 a
21 b 21 b 48 b
7.7
6.5
USDA
4900
200
17
0
0
0
* Pasture then 200 days grain fed
a,b data in columns with differing superscripts significantly different (p<0.05)
Concluding Comments

A comprehensive, accurate fatty acid composition database is
needed to assess dietary LC n-3 intake.

Non-meat/fish eaters consume virtually no LC n-3 PUFA

Omnivores are consuming 190 mg LC n-3 PUFA per day

This is well below the recommended 650 mg/day

Omnivores have higher plasma PL n-3 PUFA levels than
vegetarians and a lower n-6 : n-3 plasma ratio

Red meat from pasture fed animals is a major contributor to
LC n-3 PUFA intake in Australia
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