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 Grams/day % Energy
(2000 kcal diet)
Linoleic acid 4.44 2.0
(Upper limit) 6.67 3.0
a-linolenic acid 2.22 1.0
EPA (min) 0.22 0.1
DHA (min) 0.22 0.1
EPA + DHA 0.65 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 20:4 n-6 20:5 n-3 22:5 n-3 22:6 n-3
(LA) (AA) (EPA) (DPA) (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 n=42
and plant foods.
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 Ovolacto Vegan
meat vegetarian
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 0.88 + 0.06ab 0.88 + 0.05a 0.86 + 0.04b 0.85 + 0.05b
ratio
Values on the same line with different superscripts are significantly different at (p 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 Total n-3 n-6 : n-3 LC n-6 LC n-3
11.3 g 1.4 g 8.1 : 1 100 mg 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 18:2 : 18:3 LC n-6 LC n-3 n-6 : n-3
8.8 g 12.6 g 0.7 : 1 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 Total n6:n3
n-6 n-3 n-6 n-3 n-3 n-3 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 18:2 n-6
18:1 18:3 n-3
20:4 n-6
20:5 n-3
22:5 n-3 18:2 n-6 with 20:4 n-6
22:6 n-3 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 18:2 18:3 20:5 22:5 22:6
fat n-6 n-3 n-3 n-3 n-3
Grass fed 2800 a 190 a 49 a 40 a 58 a 7.7
Grain fed* 4800 b 255 b 21 b 21 b 48 b 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