"Fish Consumption and Suicide"
Depression is a serious and common mental disorder
responsible for the majority of suicides,
but as I already covered intakes of fruits, vegetables,
and naturally occurring antioxidants have been found
to be protectively associated with depression so,
they concluded, it may be possible to prevent depression
or to lessen its negative effects through dietary intervention.
But not so fast.
This was a cross-sectional study, meaning a snapshot in time,
so you don’t know whether the poor dietary pattern
precedes the development of depression
or if depression causes poor dietary intake.
Depression and even treatments for depression,
can affect appetite and dietary intake.
Maybe people who feel crappier, just eat crappier,
instead of the other way around.
What you need is a prospective study,
a study performed over time where you can start out
with people who are not depressed
and follow them for 6 years
and those with higher carotenoid levels in their bloodstream,
which is considered a good indicator of fruit and vegetable intake,
was associated with a 28% lower risk
of becoming depressed within that time.
So they conclude that having low blood levels
of those healthy phytonutrients may predict the development
of new depressive symptoms. But what about suicide?
Worldwide, a million people kill themselves every year.
In this comparison of European countries
Greece had the lowest rates of suicide.
Maybe it’s the balmy weather, but maybe
it has something to do with their diet.
10,000 people followed for years,
and those following a more Mediterranean diet pattern
were less likely to be diagnosed with depression.
What was it about the diet that was protective?
It wasn’t the red wine, or the fish.
It was the fruit and nuts and effectively
higher plant to animal fat ratio and beans
that appeared protective.
Conversely, significant adverse trends were observed
for dairy and meat consumption.
A similar protective dietary pattern was found in Japan,
a high intake of vegetables, fruit, mushrooms and soy products
was associated with a decreased prevalence of depressive symptoms.
It was not characterized by a high intake of seafood.
100,000 Japanese men and women were followed for up to 10 years,
and they didn’t find evidence of a protective role
of higher fish consumption or the long chain omega 3’s
EPA and DHA against suicide.
In fact, they found a significantly increased risk of suicide
among male nondrinkers with high seafood omega 3 intake.
This may have just been due to chance,
but a similar result was found in the Mediterranean.
High baseline fish consumption
together with an increase in consumption were
associated with an increased risk of mental disorders.
One possible explanation could be the mercury content of fish.
An accumulation of mercury compounds
could increase the risk of depression.
We know that mercury in fish
can cause neurological damage,
such as negative effects on Alzheimer disease,
memory loss, autism, as well as depression,
So the increased risk of suicide
among persons with a high fish intake
might be attributable to the harmful effects
of mercury in fish.
The big Harvard cohorts found similar results,
hundreds of thousands followed for up to 20 years,
and no evidence that taking fish oil or eating fish
lowered risk of suicide, with a trend towards
even higher suicide mortality.
What about for the treatment of depression?
Neither EPA or DHA appeared more effective than sugar pills,
and the same can be said
when one puts all the trials done to date together.
We used to think omega-3 supplementation was useful,
but several recent studies have tipped
the balance the other way.
It seems that nearly all of the treatment efficacy
observed in the published literature may be attributable
to publication bias, meaning the trials
that showed no benefit tended not to get published at all,
and so all one saw was a bunch of positive studies,
but only because a bunch of the negative ones were buried.