Looking through a limited lens.
A very limited view of “evidence for an effect of long chain and
shorter chain omega-3 fatty acids” produced an incorrect conclusion that
“long chain and shorter chain omega-3 fats do not have a clear effect on
total mortality, combined cardiovascular events or cancer” (1). The bias
came from evaluating only randomized clinical trials (RCTs), omitting
large amounts of published evidence (2) on how dietary omega-3 fats
compete with omega-6 fats as they maintain healthy tissues and prevent
The biased view failed to interpret the reported estimates of omega-3
fat intakes in relation to existing levels of competing omega-6 fat
intakes, a balance readily seen with gas chromatographic analyses of blood
lipids (3). Such analytical biomarker information would show whether the
reported efforts of the various RCT interventions had actually succeeded
in sufficiently shifting tissue proportions of omega-3 and omega-6 fatty
acids to the extent intended (and whether all subjects complied with the
intended dietary intervention).
An RCT in which tissue proportions of long chain omega-3 and omega-6
fats changed very little has little merit in forming a useful conclusion.
The authors shed little light on such evidence, which is needed for a
truly sound interpretation. The absence of tissue proportions and of
known evidence about n-6 eicosanoids mediating inflammation, thrombosis
and arrhythmia might lead readers to apply Macbeth’s description to this
"meta-analysis": “it is a tale told by an idiot, full of sound and fury,
1 Hooper L, Thompson RL, Harrison RA, Summerbell CD, Ness AR, Moore
HJ, et al. Risks and benefits of omega3 fats for mortality, cardiovascular
disease and cancer: a systematic review. BMJ 2006. [Epub ahead of print;
doi = 10.1136/ bmj.38755.366331.2F].
2 Lands WE. Fish, Omega-3 and Human Health 2005 AOCS Press,
3 Lands WE. Dietary fat and health: the evidence and the politics of
prevention: careful use of dietary fats can improve life and prevent
disease. Ann N Y Acad Sci. 2005 Dec; 1055: 179-92.
The author is a non-employee member of the Board of Directors of Omega Protein.
Competing interests: No competing interests