Scientists have discovered why a diet high
in oily fish like salmon and mackerel may help improve inflammatory
conditions such as arthritis.
They have found a key anti-inflammatory fat
in humans is derived from a fatty acid found in fish oil.
The researchers, from Harvard Medical School
and Brigham and Women's Hospital, found the diet worked best
when combined with low aspirin doses.
Details are published in the Journal of Experimental
The inflammatory response protects the body against infection
and injury, but when it goes wrong it can lead to conditions
such as arthritis, and cardiovascular disease.
The Harvard team identified a new class of
fats in the human body, called resolvins, which they showed
can control inflammation.
They do this both by stopping the migration
of inflammatory cells to sites of inflammation, and the turning
on of other inflammatory cells.
Resolvins are made from the omega-3 fatty
acids, found in high concentration in oily fish.
Their production also appears to be stimulated
by taking aspirin.
One form of resolvin - E1 - is thought to
play a particularly significant role in controlling inflammation.
The researchers identified this specific
fat in blood plasma samples taken from volunteers given omega-3
fatty acids and aspirin.
Lead researcher Dr Charles Serhan told the
BBC News: "Since we obtained these results I started to encourage
my own children to eat foods rich in omega-3 fatty acids."
The study also reveals a potential pitfall
of COX-2 inhibitors, drugs designed to block inflammation,
which have been shown to have negative cardiovascular side
The enzyme COX-2 is involved in making resolvin
E1, and the researchers suspect that taking the drugs may
disrupt the body's ability to synthesise the fat.
Thus, while the drugs are designed to reduce
inflammation, it is possible that they actually undermine
one of the body's most important methods for achieving the
However, the researchers stress the experiment
to prove this idea has yet to be done with humans.
A spokesperson for the Arthritis Research
Campaign said: "A number of studies have suggested that oily
fish can help people with inflammatory arthritis, and this
new study appears to confirm this.
"Our charity has also funded a small preliminary
study which shows that oily fish or fish oil capsules can
also play a part in reducing the pain and inflammation in
osteoarthritis - a degenerative type of arthritis.
"We always suggest that people with arthritis
eat two or three portions of oily fish a week, or take 1,500mg
fish oil capsules a day."