This post just furthers this line of thinking out loud: How much fish oil is "enough"?
Observations over the last 30 years followed this path: If a little bit of omega-3 fatty acids from fish are beneficial in reducing cardiovascular events, and a moderate intake is even better, is even more better? When have we reached a plateau? When do adverse effects outweigh the benefits?
Some insight can be gained through studies that examined blood levels of omega-3s. Let's take a look at some data from 2002, a comparison of men dying from heart disease vs. controls in the Physicians' Health Study, Blood Levels of Long-Chain n–3 Fatty Acids and the Risk of Sudden Death.
This is a table that shows the blood levels of various fatty acids Group with sudden death vs Control Group :
Several observations jump out:
--The total omega-3 blood content differed significantly, 4.82 vs 5.24% ("Total long-chain n-3 polyunsaturated")
--Total omega-6 content did not differ
--Arachidonic acid (AA) content did not differ
--Linolenic acid content did not differ (i.e., plant sourced omega-3)
The fact that neither omega-6 nor arachidonic acid content differed counters the argument that Simopoulos has made that the omega-6 to omega-3 ratio (intake, not blood levels) is what counts. It also argues against the EPA to AA ratio (and similar manipulations) that some have argued is important. In this study, only the omega-3 level itself made a difference; no ratio was necessary to distinguish sudden death victims vs controls.
Further, quartiles of omega-3 blood levels showed graded reductions of risk:
An omega-3 blood level of 6.87% conferred greatest risk reduction. Depending on the model of statistical analysis, risk reductions of up to 81-90% were observed. Wow.
Taken at face value, this study would argue that:
--An omega-3 fatty acid blood level of 6.87% (or greater?) is ideal
--The omega-3 fatty acid blood level stands alone as a predictor without resorting to any further manipulation of numbers, such as relating EPA and/or DHA to AA levels.
Of course, this is just one study, though an important one. It is also not a study based on any intervention, just an observational effort. But it does add to our understanding.
We will develop these issues further in our upcoming Track Your Plaque Webinar on Wednesday, August 20th, 2008.