UK News
Is oily fish really healthy?
Friday, 24th March 2006, 07:52
Category: Healthy Living

LIFE STYLE EXTRA (UK) - Eating oily fish
may not be as good for you as doctors thought,
according to new research.

A study does not find evidence of a clear health
benefit of the omega 3 fats found in fish such as
mackerel and salmon.

The findings published online by the British
Medical Journal do not rule out an important
effect of the fatty acids, but suggest that the
evidence should be reviewed regularly, say
the researchers.

Consumption of long chain omega 3 fatty acids,
found in oily fish and fish oils, and a shorter
chain omega 3 found in oily fish and fish oils,
and another type of omega 3 found in some
plant oils, is believed to protect against heart
disease.

UK guidelines encourage the general public
to eat more oily fish, and higher amounts are
advised after a heart attack.

Researchers analysed 89 studies to assess
the health effects of the omega 3 fats on total
death rates, heart disease, cancer, and strokes.

Each study involved a treatment group and
a control group and investigated the effect of
omega 3 intake on health for at least six months.

Pooling the results showed no strong evidence
that omega 3 fats have an effect on total
mortality or combined cardiovascular events.

Other recent reviews of omega 3 trials found
the fats decrease mortality, but the publication
of a large contradictory trial has changed the
overall picture.

The authors cannot say exactly why the
results of this trial differ from the other large
studies in this field.

They therefore conclude that it is not clear
whether omega 3 fats reduce or increase total
mortality, heart disease, cancer, or strokes.

UK guidelines advising people to eat more
oily fish should continue at present but the
evidence should be reviewed regularly, say
the authors.

Added dietitian Dr Lee Hooper, of the
University of East Anglia: "But it is probably
not appropriate to recommend a high intake
of omega 3 fats for people who have angina
but have not had a heart attack.

"To understand the effects of omega 3 fats
on health, we need more high quality
randomised controlled trials of long duration
that also report the associated harms."

In an accompanying editorial epidemiologist
Eric Brunner, of the Royal Free and University
College London Medical School, London,
warned: "We are faced with a paradox. Health
recommendations advise increased consumption
of oily fish and fish oils.

"However, industrial fishing has depleted the
world's fish stocks by some 90% since 1950,
and rising fish prices reduce affordability
particularly for people with low incomes.

"Global production trends suggest that,
although fish farming is expanding rapidly,
we probably do not have a sustainable
supply of long chain omega 3 fats."

http://www.lse.co.uk/ShowStory.asp?story=WU2423768O&news_headline=is_oily_fish_really_healthy

J Membr Biol. 2005 Jul;206(2):155-63.

Is fish oil good or bad for heart disease?
Two trials with apparently conflicting results.
Burr ML, Dunstan FD, George CH.

Department of Epidemiology, Statistics and
Public Health, Cardiff University, Wales, UK.

Two successive randomized trials examined
the effect of an increased intake of fatty fish,
or the use of fish oil supplements, in reducing
mortality in men with heart disease. The Diet
and Reinfarction Trial (DART) was conducted
in 2033 men who were recovering from acute
myocardial infarction (MI). Those who were
advised to eat fatty fish (or who opted to take
fish oil capsules instead) had a 29% reduction
in all-cause mortality over the following two
years compared with those not so advised.
The effect appeared in the first few months
of the trial. The Diet and Angina Randomized
Trial (DART 2) involved 3114 men with stable
angina. Advice to eat fatty fish did not reduce
mortality, and taking fish oil capsules was
associated with a higher risk of cardiac and
sudden death. The adverse effects of fish or
fish oil were restricted to men not taking
beta-blockers or dihydropyridine calcium-
channel blockers, and were greater in those
taking digoxin. Evidence from other sources
strongly suggests an anti-arrhythmic action of
fish oil, particularly after MI or in the presence
of acute ischemia. The apparently conflicting
results of the two trials may reflect different
actions of n-3 fatty acids in acute and chronic
conditions, together with different effects of
eating fish and taking fish oil capsules. A
mechanism is proposed that could account
for these findings.

PMID: 16456725 [PubMed - indexed for MEDLINE]

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=16456725&dopt=Abstract

Clin. Cardiol. 22, (Suppl. III), III-11-III-15 (1999)
Nut Consumption, Lipids, and Risk of a Coronary Event
Gary E. Fraser, M.B. Ch.B., Ph.D.
Center for Health Research, School of Public Health,
Loma Linda University, Loma Linda, California, USA

Summary: In the past, many have avoided nuts
because of their high fat content. The Dietary
Approaches to Stop Hypertension (DASH) diet,
however, recommends regular consumption of
this food along with seeds and dried beans
(4-5 servings per week) as part of a diet to
control hypertension. Nuts are nutrient-dense
and most of their fat is unsaturated. They are
also perhaps the best natural source of vitamin E
and are relatively concentrated repositories of
dietary fiber, magnesium, potassium, and arginine,
the dietary precursor of nitric oxide. Human
feeding studies have demonstrated reductions
of 8-12% in low-density lipoprotein (LDL)
cholesterol when almonds and walnuts are
substituted for more traditional fats. Other
studies show that macadamias and hazelnuts
appear at least as beneficial as fats in commonly
recommended diets. Whether consuming
modest quantities of nuts daily may promote
weight gain is not known with certainty, but
preliminary data suggest that this is unlikely.
Four of the best and largest cohort studies in
nutritional epidemiology have now reported
that eating nuts frequently is associated with a
decreased risk of coronary heart disease of
the order of 30-50%. The findings are very
consistent in subgroup analyses and unlikely
to be due to confounding. Possible
mechanisms include reduction in LDL
cholesterol, the antioxidant actions of
vitamin E, and the effects on the endothelium
and platelet function of higher levels of nitric
oxide. Although nuts may account for a
relatively small percentage of dietary calories,
the potential interacting effects of these
factors on disease risk may be considerable.
.....'
http://www.clinicalcardiology.org/productcart/pc/supplements/CC22S3/CC22-3.fraser.html