Title: The Omega 6:Omega 3 Ratio

Key words: fatty acids, prostaglandins, linoleic acid, linolenic acid, fish oils, seed oils, coronary heart disease (CHD),

Date: August 2000

Category: 4. Food Data

Type: Article

Author: Dr Mark Draper

The Omega 6:Omega 3 Ratio

Cause for concern in the UK?

Introduction

It is now considered optimum to consume no more than 20% of our total calories in the form of fat. The current average in Britain is above 40% compared to 15% in countries like Japan, Thailand and the Philippines that have a low incidence of fat-related diseases.(1)

The structures and metabolic pathways of the fatty acids are in the attached appendix.

The Omega 6 and Omega 3 compete for the same pathways and an excess of Omega 6 can lead to an increase in the levels of arachidonic acid and eicosanoid synthesis. The higher levels of prostaglandin PGE2, Prostacyclins (PG12) and thromboxanes may increase inflammations and coaguability. It appears that the Omega 3s increase the levels of Prostaglandin PGE3 and also reduces eicosanoid synthesis.(2)

There are two essential fatty acids: Linoleic acid (LA 18:2w6) and Alpha -linolenic acid (LNA18:3w3). The optimum daily intakes may be 9 to 18 gms and 2 to 9 gms per day respectively (3). The ideal balance between Omega 6 and Omega 3 is thought to be 2:1.

Oily fish contain large quantities of the long chain Omega 3 polyunsaturated fatty acids (EPA and DHA see table unsaturated fatty acids). The low rates of coronary heart disease in various populations with high intakes of fish suggest that these fatty acids possess health preserving properties (4).

The Types Of Fats Consumed In The British Diet

Apparently 42% is in the form of Saturated fatty acids (SFA) ; 40% in the form of Monounsatured fatty acids (MUFA); 16% as Omega 6 Polyunsaturated fatty acids (PUFA) and 2.5% as Omega 3 PUFA (a ratio of 6.4 Omega 6:Omega 3).

If a calculation was performed assuming the average UK person ate 140 gms of fat per day then 3.5 gms would be in the form of Omega 3. The Greenland Inuits consume 14 gms per day (3).

In the ideal diet, fat intake should, perhaps, be in equal proportions (33%) SFA , MUFA and PUFA. In North America, the Omega 3 intake in the diet has fallen to one sixth of that in the 1850's and the Omega 6 intake has doubled, changing the ratio of Omega 6 to 3.

 

The Optimum Ratio of Omega 6 to Omega 3

The ratio varies between 1:2.5 (Inuit diets) through 6:1 (UK) to 20:1 (contempary safflower and corn oil diets). Although their overall incidence of cardiovascular disease is low, the Inuits do suffer from strokes. This may, however, be due to deficiency of vitamin C and E rather than an increased bleeding tendency due to the effect on thromboxanes and prostacyclins. The Inuits also have a high incidence of osteoporosis. This may be due to their relatively high protein intake.

The ratio in different tissues in the body is as follows; brain 1:1, fat tissues 5:1 and other tissues 4:1. Our enzymes convert Omega 6 only one fourth as quickly as Omega 3. To get equal conversion the ratio should be 4:1 but Omega 6 oils are associated with degenerative conditions so the ratio should favour Omega 3. Perhaps the ideal Omega 6: 3 ratio would be 2:1. If the UK fat intake was halved then 70 gms would have PUFA 24gms with 16 g Omega 6 and 8g Omega 3.

With the present difficulties in obtaining good quality fish and fish oils we should, perhaps, be looking towards organically grown seed oils to increase our levels of intake of Omega 3 (See Table 1: Fat content and fatty acid composition of seed oils). The Omega 3 content of flax (linseed) oil is about 57% and the ratio 1:3. To decrease the dietary ratio of Omega 6 to 3 and to increase the levels of Omega 3, using the uncooked blends of various oils may be the way forward . Another option is to feed hens flax, so that their eggs are Omega 3 enriched.(5) A reduction in dietary animal fats and the trans fatty acids in margarines should also be advised .

 

Table 1:

Fat content and fatty acid composition of seed oils.

Seed oil

Fat content (%)

Fatty Acid Composition

(% of total oil)

Potential Problems

   

18:3w3

18:2w6

18:1w9

18:0

16:0

 

almond

54.2

 

17

78

5

   

avocado

12

 

10

70

20

   

beech

50

 

32

54

8

   

brazil

66.9

 

24

48

24

   

cashew

41.7

 

6

70

18

   

chia

30

30

40

       

coconut

35.3

 

3

6

 

91

 

corn

4

 

59

24

17

   

cottonseed

40

 

50

21

25

 

toxic ingredients

evening primrose

17

 

81*

11

2

6

 

filbert

62.4

 

16

54

5

   

flax

35

58

14

19

4

   

grape

20

 

71

17

12

   

hemp

35

 

60**

12

2

 

may fail drug screens

hickory

68.7

 

17

68

9

   

kukui (candlenut)

30

29

40

       

macadamia

71.6

 

10

71

12

   

neem

40

1

20

41

20

 

very bitter

olive

20

 

8

76

16

   

palm kernel

35.3

 

2

13

 

85

 

peanut

47.5

 

29

47

18

 

toxic fungus

pecan

71.2

 

20

63

7

   

pistachio

53.7

 

19

65

9

   

pumpkin

46.7

0-15

42-57

35

0

9

 

rape (canola)

30

7

30

54***

7

   

rice bran

10

1

35

48

17

   

safflower

59.5

 

75

13

12

   

sesame

49.1

 

45

42

13

   

soybean

17.7

7

50

26

6

9

 

sunflower

47.3

 

65

23

12

   

walnut

60

5

51

28

5

11

 

wheatgerm

10.9

5

50

25

18

   

* Incudes 9% GLA

** Includes up to 23% GLA

*** Includes up to 5% erucic acid

 

 

 

References

  1. Holford, P. The Optimum Nutrition Bible 1997; p.45 - Piatkus
  2. Ferretti, A. Flanygan, V. P. Prostaglandins Leukut. Essential Fatty Acids: 1996; 54 451-455
  3. Erasmus, V. Fats that Heal, Fats that Kill p.51-52, Alive Books,1999
  4. Prichard, B. N. C., Smith, C. C. T. et al. Fish Oils and Cardiovascular Disease. - British Medical Journal. 1995; 310 (6983): 819
  5. Winnipeg, M. B. Nutrition Advisory Panel Meeting Executive Summary - Flax Council of Canada. 1995