KANSAS CITY, MISSOURI. There is overwhelming evidence that omega-3 fatty acids or, more specifically, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), the main components of fish oils, are highly effective in preventing sudden cardiac death, death from heart disease, and certain arrhythmias. Investigations involving individual heart cells have shown that EPA and DHA prolong the refractory state of the cells by interacting with fast-acting sodium channels and L-type calcium channels. It is thus clear that the cardioprotective effect of EPA and DHA is intimately associated with the degree to which these two fatty acids are actually incorporated into the heart tissue (myocardium). The ultimate test of the extent of incorporation is, of course, analysis of the heart tissue itself; however this, for obvious reasons, is not terribly practical.
Researchers at the Mid America Heart Institute now report that the EPA and DHA content of red blood cells (RBCs) almost exactly mirrors the concentration in the myocardium. Their study involved 20 heart transplant patients whose EPA and DHA level was measured in heart tissue and red blood cells. The researchers found an almost perfect correlation (r = 0.82) between the content in cardiac tissue and the content of RBCs.
In a subsequent experiment involving 25 heart transplant patients, the researchers measured EPA and DHA in biopsied myocardial tissue, plasma lipids, cells scraped from the cheek (buccal tissue), and red blood cells before and after 6 months of supplementation with 300 mg EPA + 200 mg DHA. The supplementation resulted in a 272% increase in EPA and a 94% increase in DHA in the heart tissue itself. The corresponding increases in plasma lipids, buccal tissue, and RBCs were 365% and 104%, 124% and 95%, and 279% and 84% respectively. The best correlation was between myocardial tissue and RBCs followed by myocardial tissue and buccal tissue. The researchers conclude that EPA and DHA levels in RBCs give an accurate indication of the content in heart cells. Buccal tissue is also a good indicator, but more cumbersome and exacting to obtain than a blood sample. The researchers also point out that RBC content is a good indicator of long-term intake, whereas plasma lipids vary depending on the food consumed on the day immediately preceding the test.
Harris, WS, et al. Omega-3 fatty acids in cardiac biopsies from heart transplantation patients: correlation with erythrocytes and response to supplementation. Circulation, Vol. 110, September 21, 2004, pp. 1645-49