ISSFAL Official Statement Number 6: The importance of measuring blood omega-3 long chain polyunsaturated fatty acid levels in research
Introduction
It is becoming increasingly clear that n-3 LCPUFA play an important role in human health [2]. N-3 LCPUFA have been shown to be important for neurological development [3,4], cardiovascular health [5,6] and there is emerging evidence of their beneficial role in other disease states, including mental health conditions [7].
Several mechanisms have been suggested for these potential health benefits [8], including effects on cell membranes which can influence signal transduction, promotion of neuronal growth, altering neurotransmitter release, and facilitating glucose uptake from the endothelial cells into the brain. N-3 LCPUFA are also important precursors of the eicosanoids and docosanoids, which have anti-thrombotic and vasodilatory effects [8].
The evidence for the above-mentioned potential health benefits are derived from a large number of studies, including both epidemiological/observational studies and baseline data from randomised, controlled trials (RCT). However, many of these studies have failed to include measurements of n-3 LCPUFA levels. This may have serious implications for their ability to draw correct conclusions about the effects of omega-3 on the measured outcome/s.
The recently published systematic literature review [1] highlights that there are many factors associated with the n-3 LCPUFA levels of an individual. Therefore, the aims of the current statement paper are to: 1. recommend that researchers should measure n-3 LCPUFA levels at baseline and post-intervention; 2. report on the full fatty acid results in future research and 3. analyse the results as intention to treat, but also to analyse by the effect of the change of n-3 LCPUFA levels and the change in the outcome variable(s) where possible.
Section snippets
Methods
Professors Barbara Meyer and Renate de Groot proposed to the ISSFAL executive board to write a statement about the importance of measuring n-3 LCPUFA levels in research. After receiving a positive reply from the executive board and support from the ISSFAL board, the procedure for writing ISSFAL statements, as described on the ISSFAL website (http://www.issfal.org/statements/procedures-for-policy-statements), was followed. After a review by the ISSFAL Board, it became clear that a systematic
Terminology
Various terminologies exist in the literature when describing n-3 LCPUFA levels (defined as n-3 PUFA not containing alpha-linolenic acid (ALA, 18:3n-3)) in an individual; including the Holman index; the Lands Highly Unsaturated Fatty Acids (HUFA) [9]; long chain omega-3 PUFA [10] and the HS-Omega-3 Index [11]. The n-3 LCPUFA levels are similar to the afore-mentioned terminologies, and hence n-3 LCPUFA levels are used in the current statement.
Factors affecting n-3 LCPUFA levels
The n-3 LCPUFA levels in an individual are associated
Conclusions
- 1
Factors positively associated with the n-3 LCPUFA levels are: age, sex (women less than 50 years of age).
- 2
Factors negatively associated with the n-3 LCPUFA levels are: genetics, BMI (if erythrocyte EPA and DHA is less than 6%), smoking and alcohol.
- 3
There is inconclusive evidence for the association of waist girth and physical activity with n-3 LCPUFA levels.
- 4
There is no convincing evidence that krill oil versus fish oil, or the chemical form of n-3 LCPUFA matters in terms of bioavailability.
- 5
It is
Recommendations
The recommendations below are for people of all ages, however the systematic literature review [1] focussed on adults.
- 1
It is essential that in all types of research, including cross-sectional, cohort and clinical research, the n-3 LCPUFA levels are measured in biological samples, and this should be done according to appropriate study protocol. So, for cross-sectional studies the biological samples must be measured at one time point and for cohort and clinical intervention studies the biological
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