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18:3n-3

1 ± 0.1

1 ± 0.1

20:5n-3

5 ± 0.2

5 ± 0.1

22:6n-3

10 ± 2

7 ± 0.1'

Other n-3 (18:4n-3 + 20:3n-3 + 22:5n-3)

3 ± 0.5

4 ± 0.1

18:2n-6

1 ± 0.1

3 ± 0.1

Other n-6 (20:4n-6 + 22:4n-6)

0.2 ± 0.1

0.5 ± 0.1

Total n-3

20 ± 2

17 ± 0.2

Total n-6

2 ± 0.1

3 ± 0.1

Ratio of n-3 : n-6

11 ± 2

Significantly different from wild, p < 0.01. Significantly different from wild, p < 0.05. Source: Modified from van Vliet and Katan, 1990.

Significantly different from wild, p < 0.01. Significantly different from wild, p < 0.05. Source: Modified from van Vliet and Katan, 1990.

3.3. Imbalance of Omega-6: Omega-3 and Its Biological Significance

It is evident that food technology and agribusiness provided the economic stimulus that dominated the changes in the food supply (Dupont et al., 1991; Hunter, 1989; Litin and Sacks, 1993; Raper et al., 1992). From per capita quantities of foods available for consumption in the US national food supply in 1985, the amount of EPA is reported to be about 50 mg/capita/d and the amount of DHA was 80 mg/capita/d. The two main sources of EPA and DHA are fish and poultry (Raper et al., 1992). It has been estimated that the present Western diet is "deficient" in omega-3 fatty acids with a ratio of omega-6 to omega-3 of 15-20 : 1, instead of 1 : ,1 as is the case with wild animals and presumably human beings (Crawford, 1968; Crawford et al., 1969; Eaton and Konner, 1985; Eaton et al., 1998; Ledger, 1968; Simopoulos, 1991; Simopoulos, 1999a; Simopoulos, 1999b; Simopoulos, 1999c). Before the 1940s, cod-liver oil was ingested mainly by children as a source of vitamins A and D, with the usual dose being a teaspoon. Once these vitamins were synthesized, the consumption of cod-liver oil was drastically decreased.

Thus, an absolute and relative decrease of the omega-6 : omega-3 fatty acid ratio has occurred in the food supply of Western countries over the last 100 yr (Tables 8-10). Eaton et al. (1998) have estimated the intake of EFA from animal and vegetable sources, assuming 35% of energy came from animals and 65% from plants. In the Late Paleolithic Period, Table 8 shows that the ratio of LA : LNA was 0.70, whereas the ratio of longer chain omega-6 : omega-3 was 1.79, with a total omega-6 : omega-3 ratio of 0.79. In the United States, again considering the same subsistence ratio of animal sources : plant sources of 35 : 65, the current diet would provide a ratio of 16.74 (Table 9), which is close to the estimates of 15-20:1 of other investigators (Simopoulos, 1991; Eaton et al, 1998). Considering other populations (Table 11), in Japan, the omega-6 : omega-3 ratio is 4 : 1 (Sugano and Hirahara, 2000), and in the United Kingdom, this ratio is 15 : 1, whereas 20 yr ago it was 10 : 1 (Sanders, 2000). Similar ratios have been suggested for northern Europe and Holland, with lower ratios in southern Europe because of a higher consumption of

Table 6

Fatty Acid Levels (mg/g Yolk) in Chicken Egg Yolks

Fatty acid

Greek egg

Supermarket egg Fishmeal egg

Flax egg

Saturates

Total 100.7 Monounsaturates

18:1 120.5

Total 142.8 n-6 Polyunsaturates

Total 23.1 n-3 Polyunsaturates

Total 17.7

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