Fish Oil and Heart Health

ADELAIDE, AUSTRALIA. There is ample evidence that increased fish or fish oil consumption is associated with a reduced risk of cardiac mortality, especially sudden death. It is believed that this benefit arises from the incorporation of the long-chain omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) into the phospholipid membrane of cardiomyocytes (heart cells).

Australian researchers recently reported some very exciting findings regarding the actual mechanism and effectiveness of increasing the EPA + DHA content of myocytes and erythrocytes (red blood cells) by daily supplementation with fish oil. Their study involved 60 patients scheduled for on-pump bypass surgery and/or valve repair. The patients were divided into six groups of 10 patients and received supplements as follows:

  • Group 1 - 6 grams/day EPA + DHA (50:50) for 7 days prior to surgery
  • Group 2 - 6 grams/day EPA + DHA (50:50) for 14 days prior to surgery
  • Group 3 - 6 grams/day EPA + DHA (50:50) for 21 days prior to surgery
  • Group 4 - 6 grams/day of alpha-linolenic acid (ALA) in the form of flax oil for 21 days prior to surgery
  • Group 5 - 6 grams/day of olive oil for 21 days prior to surgery
  • Group 6 - no supplements

Blood samples and biopsy specimens from the right atrium were taken during surgery. The samples were analyzed for fatty acid content and the following results obtained:

Fatty acid Content - % of Total Fatty acids
Component
Baseline – Control
Fish oil – 21 days
Flax Oil – 21 days
Olive Oil – 21 days
Myocytes
EPA
0.49
2.97
0.75
0.55
DHA
4.83
8.52
5.18
5.39
EPA+DHA
5.31
11.50
5.93
5.94
ALA
0.13
0.15
0.34
0.13
Arachidonic acid
20.84
15.99
20.01
20.02
Erythrocytes
EPA
0.71
3.14
1.20
0.84
DHA
4.44
7.56
4.53
5.25
EPA+DHA
5.15
10.70
5.73
6.09
ALA
0.11
0.09
0.30
0.11
Arachidonic acid
14.21
11.67
14.36
14.51

The above results lead to the following observations:

  • Fish oil supplementation for 21 days resulted in a substantial increase in both EPA (500%) and DHA concentration (76%) in cardiomyocytes. This was mirrored by a proportional increase in red blood cells (340% for EPA and 70% for DHA).
  • The increase in EPA + DHA was at the expense of a decrease in pro-inflammatory omega-6 arachidonic acid of 23% in the fish oil group (21 days). Supplementation with flax or olive oil had no effect on arachidonic acid levels.
  • Supplementation (for 21 days) with flax oil (alpha linolenic acid) increased myocyte EPA concentration by a statistically insignificant 53% and DHA concentration by only 7% indicating that the efficiency of ALA conversion to EPA, and especially DHA, is low.
  • No significant differences were found between the olive oil group and the control group.
  • Analysis of data obtained after an average 10 days of fish oil supplementation showed that DHA is initially incorporated into heart cells at a rate twice that of EPA.
  • No excessive bleeding during surgery was observed for any of the groups involved in the study.

The researchers conclude that daily supplementation with 6 grams of EPA + DHA rapidly increases the EPA + DHA content of cardiomyocyte phospholipid membranes at the expense of a decrease in arachidonic acid level. They point out that these optimal rates of EPA + DHA incorporation are not likely to be matched at lower doses of fish oil. They also make the interesting suggestion that high-dose fish oil supplementation could be beneficial for patients recovering from a heart attack.
Metcalf, RG, et al. Effects of fish-oil supplementation on myocardial fatty acids in humans. American Journal of Clinical Nutrition, Vol. 85, 2007, pp. 1222-28

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