What is the relationship between omega-3 and cancer?
A Cancer is less
common in communities that eat large amounts of fish, and the reason is
thought to be the presence in fish of the long chain omega-3 polyunsaturates.
Japanese women, for example, eat a lot of fish, and have a very low rate
of breast, (and other) cancer. Men who eat fish frequently have a lower
risk of prostate cancer. Stomach and intestinal cancers also appear to
be less common in fish eaters. It is difficult to be specific about this
though, because in such studies, there are often several factors that
are different, and which could explain the lower cancer incidence. Laboratory
studies have provided more support to the idea that the omega-3 polyunsaturates
can reduce cancer risk. For example, tests have shown that cancer-treating
drugs work more effectively when there is a good level of omega-3 polyunsaturates
in the diet. Other studies have shown that adding omega-3s to the diet
helps to reduce the level of certain hormone-like substances, which tend
to be present in higher amounts in cancer sufferers. In summary, it can
be said that while there are good grounds for believing that adding omega-3
polyunsaturates to the diet will help to reduce cancer risk, it is not
yet proven beyond doubt.
Q How does omega-3
aid in weight watching?
A The long chain
omega-3 polyunsaturates can aid weight loss by enabling each of the body's
cells to function in the optimal manner. Accumulation of fat is the body's
response to a surplus of energy over needs. When the reverse occurs, as
in a weight loss diet, the stored energy (fat) should be liberated and
burned. However, some people appear to have a problem with this mechanism,
and it has been suggested that a part of the reason for this is that the
membranes which surround each of the body's cells are not functioning
in the way they should because their composition is out of balance. Cell
membranes are made up largely of polyunsaturates. We now know that there
are two families of polyunsaturates which are important in the make up
of cell membranes: the omega-3 family from fish, and the omega-6 family
from vegetable oils like sunflower seed oil. Over the past 50 years, diets
in the West have changed, to supply about twice as much omega-6, and only
half as much omega-3. Thus the balance has changed. Cell membrane composition
has changed too, and some scientists think that this change in membrane
composition has made it more difficult for cells to lose the accumulated
fat they contain. Evidence recently published showed that weight loss
was greater on a calorie-restricted diet when a small amount of fish oil
was added to the diet, compared to the same diet when olive oil was added
instead of the fish oil.
Q What is omega-3?
Which products have it in them?
A The omega-3 polyunsaturates
are a family of polyunsaturated fatty acids. Fatty acids are the building
blocks from which edible oils and fats are made up. The polyunsaturates
are characterised by the presence of certain structural features which
mark them out as being different from other fatty acids. The polyunsaturates
are essential nutrients for humans and indeed most if not all animals.
There are two important families of polyunsaturates, the omega-3 family,
and the omega-6 family. Both are needed in the human diet for optimal
health. The omega-6 family is found mainly in vegetable oils such as sunflower
seed, sesame, corn, soy etc. The omega-3 family is found mainly in fish,
and especially in the oil rich fish such as herring, mackerel, sardines
etc. Small amounts of the omega-3 are found in eggs. Certain vegetable
oils such as linseed (flaxseed), rapeseed (canola) and walnut oil contain
a type of omega-3, known as the short chain type (alpha-linolenic acid).
To be useful to the human body, these short chain omega-3s must first
be converted to their long chain form. While the human body can in theory
do this conversion, in practice, modern diets and lifestyles reduce the
effectiveness of the conversion systems. Roughly 10 times more of the
short chain omega-3s must be consumed to have the same effect as the long
chain form from fish oil.
Q What are the
benefits of EPA? I use this supplement for everyday and one tablet per
A EPA, or eicosapentaenoic
acid, is one of the long chain omega-3 polyunsaturates found mainly in
the oil from fish. Having a small amount of EPA acid is reckoned by those
scientists studying the subject to be a sensible dietary goal. This amount
will provide some protection from heart disease, and perhaps cancer, depression
and other common ills.
Could you give more info on products enriched with omega-3 - e.g. bread,
spread, milk, juices
The availability of ordinary foods fortified with small amounts of fish
oils varies from one country to another, but in general is increasing
all the time, as awareness of the health benefits of the long chain omega-3
polyunsaturates spreads. In the Asian/Pacific region, there are milks,
yoghurts, and fruit juices available containing the omega-3s. In the U.S.
and Europe there are eggs, spreads, and juices available. In Scandinavia
and Australia there are breads and eggs available. In Britain at present
there are only eggs with an enhanced omega-3 level.
Q Could you please
expand on omega-3 and psoriasis
A The relationship
between psoriasis and the long chain polyunsaturates from fish oil is
one which is quite well documented scientifically. Psoriasis is one of
the inflammatory diseases and increasing the amount of the long chain
omega-3 polyunsaturates in the diet is known to aid in bringing about
a more anti-inflammatory state. The first trials in this area were carried
out in the early 1980s and they showed that taking 10g of fish oil daily
for 3 months brought about a lessening of psoriatic symptoms such as itching,
flakiness and redness of skin, as well as a reduction in the amount of
the body affected. Since the, several other trials have been carried out
- all showing much the same thing. The disease is not cured by the omega-3
polyunsaturates, but it does become much easier to live with, and can
be more readily controlled. Another aspect of the situation is that the
omega-3 polyunsaturates can help to counteract some of the adverse effects
of conventional psoriasis drugs.
Q What are the
neurological health benefits of omega-3?
A A significant
part of the structure of brain, nerves and the retina of the eye is composed
of the long chain omega-3 polyunsaturates such as are only found in fish
oil. The long chain omega-3 polyunsaturates are essential for the optimal
development of a healthy brain, eyes and nervous system. Studies have
shown that if the diet does not provide sufficient omega-3, then the formation
and function of these vital organs is impaired somewhat. Depression or
bipolar disorder is one common condition thought to be affected by brain
omega-3 levels. Studies comparing the incidence of depression in different
areas of the world have suggested that depression is less common in areas
where large amounts of fish are consumed. Studies from hospitals have
also recently provided another type of evidence that depression might
well be linked with a shortage of the long chain omega-3 polyunsaturates
from fish. Research published in the Archives of General Psychiatry (199;
56:407-412) reported the results of a study in which severe manic-depressives
(bipolar disorder) patients were treated with long chain omega-3 polyunsaturates
(10g/day) from fish oil. A control group was given olive oil instead of
fish oil. After 4 months, the trial was stopped because the fish oil group
had improved so much that it would have been unethical to continue to
deny the benefits to the placebo group. Other areas in which the long
chain omega-3 polyunsaturates from fish are thought to be involved include
eyesight development in very young children, dyslexia, dyspraxia, hyperactivity,
intelligence, problem solving ability, and even protection from mental
illnesses such as schizophrenia. Research on all these areas is not yet
well developed, but the indications are substantial, and consistent with
epidemiological observations, and the theoretical predictions of experts
in these areas.
Q How much omega-3
can be obtained from fresh water lake fish, if any?
A Freshwater fish
can be a useful source of the long chain omega-3 polyunsaturates, but
the amount is very variable, depending on conditions. The amount depends
on the type of plankton and microscopic plants found in the water in which
the fish are reared. Tropical areas often have different organisms to
those found in more temperate areas and, as a result, can have low omega-3
levels. If the fish are farmed, the type of food they are fed will have
a big influence. For more information relevant to your area, try asking
local universities if they have more detailed information.
Q Are sardines
a good source of omega-3? Does the canning process affect content?
A Sardines are
generally a good source of omega-3s. The canning process does not adversely
affect levels. The processing is carried out under oxygen-free conditions
and so no significant damaged occurs. Similarly with the oil in capsules
- as long as oxygen is kept away, damage is negligible.
Q Is there a
high, or even not so high, concentration of omega-3 in regular tuna? I've
heard albacore tuna has a lot. I eat tuna sandwiches every day, but I'm
not sure that they're albacore tuna. Does it make a difference?
A Fresh and frozen
tuna are excellent sources of long chain omega-3 polyunsaturates, supplying
around 5% total oil of which 20% is omega-3. However, during the canning
process, most of the oil and therefore most of the omega-3 is lost. This
is mainly because tuna is cooked before it is canned, and during the cooking
process much of the oil is separated and lost. The meat that goes in the
tin thus has a low oil content (usually less than 1g per 100g) and a low
omega-3 content (usually less than 0.4g per 100g). It matters little whether
the tuna is albacore or yellow fin because once it is canned there is
little omega-3 left. Some tuna packers do can raw tuna so that the omega-3
content is higher, but it is usually difficult to distinguish such products
from the others in the marketplace. Enquire of the producer to be certain.
These comments only apply to tuna. Other canned fish are just as good
as the raw fish as sources of long chain omega-3 polyunsaturates.
Q I would like
to know if it's OK for children to take omega-3 and how much?
A Omega-3 is perfectly
safe for children to take, though practical problems can make it difficult
for children under 5. As far as amounts are concerned, for children between
5 and 10 years of age, I suggest you try to get an intake of around 300mg
per day of long chain omega-3 (from fish oil). If you want to use vegetable
omega-3, you must increase this by 10 times to have the same effect. For
children over 10, I suggest about 500mg per day.
Q Have there
been studies showing the relationship between omega-3 and such conditions
as Tourette syndrome, ADD and OCD?
A To date there
have been no published studies looking at the relationship between omega-3
intake and Tourette's syndrome or OCD. Some studies have been reported
on ADD (ADHD) but so far these are only observational studies which suggest
that ADHD sufferers have low omega-3 levels. There are currently two studies
underway in which patients with ADHD are being given omega-3 supplements,
but so far the results have not been published, though they are due sometime.
Q I am interested
in starting to take omega-3 and was wondering whether there are any drug
or vitamin interactions. Also, do I have to take the fish oil with a vitamin
A The omega-3 polyunsaturates
are components of foods and as such not likely to interact with drugs,
though it is difficult to be exact since there are so many drugs being
launched all the time. If you are taking any drug on the recommendation
of a physician it would be wise to inform him or her when next you visit.
There are no known interactions with vitamins or minerals. It is a good
idea to ensure a good intake of vitamin E if you are going to take an
omega-3 supplement. Fortunately reputable manufacturers all add an adequate
level of vitamin E to their products, so you need not take any extra.
If the supplement you take does not provide vitamin E, then change it
for one that does!
Q Which is better
for heart health - fish or fish oil supplements?
A If you are happy
eating a least two good-sized portions of oil fish a week, this should
provide you with sufficient omega-3 oils to maintain a healthy heart and
circulation. However, if you cannot guarantee you will eat this amount,
fish oils in supplement form may be a safer option. One piece of research
conducted over two years showed that there were no differences between
the effects of eating oil-rich fish twice a week and taking fish oil capsules
daily for two years (DART sub-group analysis). Supplements offer the additional
benefit of supplying a measurable amount of omega-3 whereas the amounts
in fish vary.
Q Why do doctors
recommend aspirin for heart rather than fish oils?
A Although a nutritional
approach to heart health maintenance is better than drug treatment in
most cases, there are no comparative data to show that a certain amount
of omega-3 long chain polyunsaturates is as effective as routine use of
low-dose aspirin in secondary prevention of heart attack, although there
is certainly a body of evidence to suggest it has a role in heart health.
If aspirin is prescribed then it is important that you do not switch to
fish oil supplements without first consulting your doctor. If you are
in good health, then fish oil supplementation will help keep you that
way. The side effects of fish oil (improved skin condition and joint mobility
to name just two) are bonuses!
Q Could you explain
why I should take fish oil supplements? I need convincing as I eat a healthy
diet and feel fit.
A If you eat plenty
of oily fish (e.g. mackerel, herring, sardine, pilchard, salmon) then
you don't need to take a supplement. The reason most people (90% of the
population according to the Institute for Optimum Nutrition) are deficient
in omega-3s is that the typical Western diet has changed so much since
the turn of the century. Our reliance on processed foods, meat and dairy
produce means that most of us eat less fish (particularly the oily fish
which made regular appearances in the traditional British diet) and fewer
of the nuts and seeds that provide vegetable-source omega-3 (which although
not as good as fish oils are certainly better than no omega-3s at all).
The Department of Health, through its Committee on the Medical Aspects
of Food Policy (COMA) recommendations, advises increasing oily fish consumption
as does the British Nutrition Foundation. You may not notice the deficiency
now (skin condition is a good indicator - are you sure your skin is as
velvety, plump and blemish-free as it could be?), but as you age your
body will feel the lack and you will be less able to fend off diseases
associated with growing older. Fish and fish oils supply omega-3 nutrients.
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