A new Science Advisory report from the
American Heart Association recommends
that omega-6 polyunsaturated fatty acids (PUFAs), as found in vegetable
oils, nuts and seeds, are beneficial when part of a heart-healthy
eating plan.(1) Consumers should aim for at least 5-10% of energy
(calories) from omega-6 PUFAs, and will derive most benefit when
omega-6 PUFAs replace saturated or trans fats in the diet. Precise
recommended daily servings will depend on physical activity level, age
and gender, but range between 12 and 22 grams per day.
The AHA report also addresses the recent controversy that omega-6
fatty acids, via linoleic acid, which accounts for 85-90% of dietary
omega-6, may actually increase inflammation and thereby increase rather
than reduce cardiovascular risk. Any link between omega-6 and
inflammation, says the AHA, comes from the fact that arachidonic acid,
which can be formed from linoleic acid, is involved in the early stages
of inflammation, but anti-inflammatory molecules are also formed; these
suppress the production of adhesion molecules, chemokines and
interleukins, all of which are key mediators of the atherosclerotic
process. Thus, concludes the report, it is incorrect to view the
omega-6 fatty acids as pro-inflammatory.
The report also reviewed epidemiological data and found that, in
randomised controlled trials, those assigned to the higher omega-6
diets had less heart disease. A meta-analysis of several trials
indicated that replacing saturated fats with PUFA lowered risk for
heart disease events by 24%. Reducing omega-6 intakes, said the report,
would be more likely to increase than to decrease the risk of CHD.
Professor Heinz Drexel from the VIVIT Research Institute at
Feldkirch, Austria, speaking on behalf of the European Society of
Cardiology, adds that the report not only recommends the consumption of
at least 5-10% of energy from omega-6 PUFAs but indicates that intakes
higher than 10% of energy appear safe and may even be even beneficial.
This latter statement, says Professor Drexel, “is somewhat discordant
with earlier recommendations made by other authorities”.
Commenting on the report, Professor Drexel adds: “This advisory is a
resurrection of older recommendations on omega-6 PUFAs, in particular
on linoleic acid. It is based on new ecological, case-control,
prospective cohort and randomised controlled studies. Concerns raised
in the past decade that omega-6 PUFAs may be pro-inflammatory are
dispelled with evidence that omega-6 PUFAs have anti-inflammatory
properties at the level of vascular endothelial cells. On balance, the
advantages outweigh the disadvantages.
“However, the effects of Omega-6 PUFAs appear weak and require
long-term interventions. Many studies in the past were not long enough
for a nutritional intervention. Moreover, in the intervention studies
other nutrients were changed along with the enrichment of omega-6
PUFAs.”
