Why public health strategy should promote plant oils in
preference to fish oils
by Laura Scott (MSc Nutrition) VVF Snr Nutritionist
Fish is seemingly promoted as the new penicillin. VVF uncovers
the science to show that it is plant oils and a plant based
diet, not fish oils, that are the real way forward for lifelong
People are encouraged to believe that a healthy diet is
one which includes fish. The reason being that some fish
contain the types of ‘good’ fat that our bodies
need. There is a widespread misconception amongst the general
public and health professionals that fish is the only source
of these good fats.
There are two reasons why these ideas have become so well
established. Firstly, much has been made of the healthiness
of the Mediterranean diet, which is based on generous servings
of fruits and vegetables, cereals and olive oil and where
fish is served in preference to meat or dairy products. Mealtimes
tend to be very social and this may have profound implications
for health. Secondly, a number of studies have examined the
effect of fish in helping to prevent a second heart attack
in people who have already had one attack and these show
some protection benefits.
Fats in the Diet
There’s a lot of confusion about fat and diet, but
the truth is that our bodies can’t function without
it. Eating the right kind of fat is, however crucial.
What we don’t need are saturated fats, found mainly
in meat, dairy and animal products, but also in many processed
foods. These are strongly linked to high blood cholesterol,
hardening of the arteries, coronary heart disease, some cancers
and other degenerative diseases. We do need unsaturated fats
– especially polyunsaturated fats.
Within polyunsaturated fats are substances called essential
fatty acids, or EFAs – namely omega-6 (linoleic acid -
LA) and omega-3 fats (linolenic acid – LNA). Although olive
oil is not an EFA it is another type of unsaturated fat which
has some healthy properties and it is good to include it
in the diet. EFAs – particularly the omega-3 fats – help
keep the heart healthy.
Fish is a source of EFAs, particularly omega-3 fats, but
not all fish contain them. Those that do are principally
oily fish such as herring, salmon, mackerel, sardines and
fresh tuna. White fish, such as cod, haddock and plaice,
don’t and nor does tinned tuna.
However, the richest sources of omega-3 fats are not fish
at all but plants. Seed oils such as linseed (flax) and rapeseed
(canola) as well as soya oil are rich sources as are seeds
and nuts themselves particularly walnuts (1). Green leafy
vegetables are also a source (2).
Omega-3 and Heart Disease
It’s been known for a long time that people whose
diet is based largely on fish and is rich in omega-3 have
low rates of heart disease. This led researchers to investigate
whether giving fish to people who had already suffered a
heart attack would prevent them from having another attack.
These are ‘secondary prevention trials’ and two
of the largest are the DART and GISSI trials, which both
used fish-based omega-3 fats. They did show a reduced risk,
but much less publicised was the LYON trial, which used plant
oils as a source of omega-3 fats. The results of this study
showed that plant oils reduced the risk of a secondary heart
attack by at least twice that of fish oils!
It found that males who had been advised to eat as much
as 400g of oily fish per week showed a reduction of almost
30 per cent in mortality (death) over two years. Although
there were fewer fatal heart attacks, the total number of
heart attacks wasn’t reduced. It is thought that fish
oils help to normalise heartbeat rhythms and prevent blood
from becoming too sticky and ‘clumping’ (3).
Despite this apparent reduction in risk, a follow-up study
10 years later found there were no long-term survival benefits
This trial looked at people on a Mediterranean diet who
had had a heart attack and survived it. Fish oil supplements
equivalent to a whopping 100g of oily fish per day were given
and showed a 20 per cent reduction in mortality (5).
This was another secondary prevention trial, but instead
of fish or fish oils, plant-derived omega-3 fatty acids were
used. Amazingly, a 70 per cent reduction in mortality was
achieved – more than double that of the fish trials! There
was also a significant reduction in coronary ‘events’ and
these protective effects were found to start quickly (6).
Four years on, patients were still following the diet and
their hearts were still being protected (7). Subsequent studies
have confirmed the power of plant omega-3 fatty acids in
protecting the heart (8,9).
Plant Oils Better than Fish Oils
Comparing the three main trials shows that:
- plant oils are far more effective than fish oils in reducing
the chance of cardiac death in high-risk patients;
- plant oils reduce the risk of dying from secondary heart
attack by more than double that of fish oils;
- plant oils reduce the number of painful, non-fatal heart
- there are long-term survival benefits from consuming
No Gain for Low-Risk
The trials we’ve written about all looked at people
who were at high risk of a heart attack. Because people are
termed ‘low-risk’, it doesn’t mean they
will never have an attack, it simply means they are further
down the risk scale. They are those who eat low levels of
saturated fat and therefore can include vegetarians and vegans
(10,11). When researchers looked at low-risk groups they
found that eating fish had no effect on reducing their chances
of dying from a heart attack (12).
Toxins in Fish
Human beings have been so successful at spreading pollution
that environmental contamination is widespread and all oceans
now contain toxic chemicals. Persistent organic pollutants
(POPs) are now part of most food chains and they become more
concentrated the higher up the chain you go. Mercury, organophosphates,
PCBs, dioxins, and radioactive pollution in some fish, are
all highly toxic to life.
Fatty foods have a tendency to ‘soak’ up toxins
and so oily fish are particularly prone to absorbing them
– the toxins are actually stored in the fatty part of the
fish. By eating smaller fish, oily fish take on their toxic
load and become ever more toxic themselves! POPs are implicated
in heart disease, infertility and can harm developing foetuses.
Responding to a Food Standards Agency 2002 survey, the Consumers’ Association
warned that high levels of dioxins and PCBs in fish and fish
oil supplements could “put millions at risk” (13).
Mercury in Fish
Humans should avoid mercury in their diet as it acts like
a poison, affecting their kidneys, heart and central nervous
system (CNS). Exposure to mercury is a particular risk for
unborn children where the main organs, especially the CNS,
are still developing. According to a government agency, fish
eating is responsible for the majority of mercury in people’s
diets (14). Following a Food Standards Agency survey of mercury
levels in fish, official advice is now for pregnant and breastfeeding
women to limit how much tuna they eat and for them and children
under 16 not to eat shark, swordfish or marlin at all. (15)
Other studies have found that over 60 per cent of bluefin
tuna caught in the Mediterranean exceed EC ‘safety’ figures.
Researchers have calculated that some of those people who
eat high levels of these oily fish will far exceed the World
Health Organisation’s (WHO) ‘safety’ levels
(16, 17). A 2000 government study failed to detect any mercury
in vegetarian diets and concluded, “it is reasonable
to assume that because participants in this study did not
eat fish, their dietary exposures to mercury will be substantially
less than those of the general population” (18).
Protect and Survive
One way mercury harms the body is by acting as a potent
free radical. Free radicals are unstable molecules that damage
body cells and the body’s main defence against them
are antioxidants – beta-carotene (converted to vitamin A),
and vitamins C and E. Plant foods are rich in these antioxidants
and plant oils are particularly rich in vitamin E, which
stops EFAs from deteriorating or going off. Only plant oils,
not fish oils, contain protective vitamin E.
How Much Fish?
The FSA seem as muddled as everyone else about how much
fish people should eat each week. Some of its publications
say two servings and others say at least two servings. But,
in any case, surveys show the vast majority of people are
unaware of the official advice and most people are confused
by what is meant by oily fish (13).
Public Health Failure
The average UK consumption of oily fish is 53g per person
per week (19). This meagre quantity represents only about
a third of a single portion and is a tiny amount compared
to the 400g weekly intake of oily fish which have been used
to produce heart benefits in research studies. This shows
that all the attempts to get the British public to eat fish
is a spectacular failure.
Alternatives to Fish Oils
Seeds, nuts, beans and their oils are the richest-known
sources of the ‘good’ fats. Green leafy vegetables
also contain these essential fats. Walnuts, linseed (flaxseed)
and rapeseed oil (canola) are all exceptionally rich in omega-3
The best way to buy and store nuts, seeds and their oils
is in very small quantities and to keep them in the fridge.
This helps to ensure that they are as fresh as possible.
These oils are not suitable for heating as it destroys the
beneficial EFAs. Most healthfood shops and supermarkets sell
packets of nuts and seeds and blended plant oils – usually
marketed as oils rich in omega-3 and omega-6 fats. They contain
information on how much oil to use each day. With whole seeds
and nuts, a handful each day is normally sufficient. Olive
oil can be used for cooking.
Fish-like substitutes are available thanks to food technologists
who have produced imitation fish fingers, scampi, tuna and
salmon patZ that actually taste of fish. They are available
in most healthfood shops.
Intelligent Public Health Promotion
Adding fish to the diet will not bring about long-term good
health. Plant-based vegetarian and vegan diets are the best
choice for optimum health.
- Plant oils are a far healthier source of the essential
fats we need.
- Plant oils halve the risk of heart disease compared with
- Fish is a spectacularly unpopular food in the UK.
- Fish is likely to be contaminated with harmful chemicals.
- Plant oils are far less likely to turn rancid than fish
- Plant oils as nuts and seeds are the ultimate fast food.
- Plant-based diets offer protection against many diseases.
Our hearts don’t need fish, our brains don’t
need fish and our health is far better served by plant oils
and a well-balanced plant-based diet.
1 Buttriss J, 1999. n-3 Fatty Acids And Health. p.1. (BNF)
Pereira C et al, 2001. The Alpha-Linolenic Acid Content of
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3 Burr ML et al, 1989. Effects
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8 Singh RB et al, 1997. Randomised,
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14 COT Statement
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of mercury in fish and shellfish.
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