Fish Consumption Reduces All-cause Mortality? - Maybe Not

[Dean Pomerleau]

All,

 

I'm not a big proponent of eating fish, being a vegan myself. But in the interest of presenting the fact, here is a new meta-analysis [1] from Al (thanks Al!) that seems to show eating more fish is associated with reduced all-cause mortality. Specifically, among the almost 700,000 subjects across 12 prospective cohort studies, those who ate the most fish were 6% less likely to die during the follow-up period than those who ate the least fish (RR=0.94, 95% confidence interval (CI): 0.90, 0.98; I(2)=39.1%, P=0.06). Here  from the full text is the forest plot of mortality risk across the 12 studies:

 

 

As you can see, for most of the studies the confidence interval spans the centerline, and several are actually right of center (higher death risk for fish eating). Nevertheless, the center of mass is left of center - meaning reduced mortality risk when the studies are all combined together. 

 

Before you get too excited Saul and other fish-eating enthusiasts, consider the following.The authors did several additional sensitivity analyses to see how much the apparent benefits of eating fish depended on various factors. I think what they found was telling. Here is the table with the results, with a few items highlighted:

 

 

What these sensitivity analyses show is that the mortality benefit of eating fish was attenuated to the point of being non-significant in:

• The six studies that were large (40,000+ subjects)
• The six studies that had long follow-up periods (12+ years)
• The four studies that compensated for differences in red meat intake between fish eaters and fish abstainers
• The eight studies that compensated for differences in fruit and veggie intake between fish eaters and fish abstainers

Given the small (6%) benefit to start with, coupled with all these attenuating factors, it appears to me that the purported benefits of eating fish for all-cause mortality are probably marginal at best.

 

--Dean

 

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[1] Eur J Clin Nutr. 2016 Feb;70(2):155-61. doi: 10.1038/ejcn.2015.72. Epub 2015 May 13.

 

Fish consumption and all-cause mortality: a meta-analysis of cohort studies.

 

Zhao LG, Sun JW, Yang Y, Ma X, Wang YY, Xiang YB.

 

full text: http://www.nature.com.sci-hub.io/ejcn/journal/v70/n2/full/ejcn201572a.html

 

Abstract12 

 

BACKGROUND/OBJECTIVES:

 

Although fish consumption may have an influence on specific mortality of major chronic diseases, the relationship between fish consumption and all-cause mortality remains inconsistent.

 

SUBJECTS/METHODS:

 

We performed a systematic search of publications using PubMed and Web of science up to 31 December 2014. Summary relative risk (RR) for the highest versus lowest category of fish consumption on risk of all-cause mortality was calculated by using a random effects model. Potential nonlinear relation was tested by modeling fish intake using restricted cubic splines with three knots at fixed percentiles of the distribution.

 

RESULTS:

 

Twelve prospective cohort studies with 672 389 participants and 57 641 deaths were included in this meta-analysis. Compared with the lowest category, the highest category of fish intake was associated with about a 6% significantly lower risk of all-cause mortality (RR=0.94, 95% confidence interval (CI): 0.90, 0.98; I(2)=39.1%, P=0.06). The dose-response analysis indicated a nonlinear relationship between fish consumption and all-cause mortality. Compared with never consumers, consumption of 60 g of fish per day was associated with a 12% reduction (RR=0.88, 95% CI: 0.83, 0.93) in risk of total death.

 

CONCLUSIONS:

 

These results imply that fish consumption was associated with a reduced risk of all-cause mortality.

 

PMID: 25969396

 

[mikeccolella]

http://www.washingtonpost.com/wp-dyn/content/article/2009/06/02/AR2009060200772.html

 

For those concerned about environmental or toxicity issues a better fish choice may be the dreaded sardine.

[Saul]

Good choice, Mike.

 

BTW, most salmons are an excellent choice, too. (My favorite salmons:  wild Pacific sockeye salmon; and my new farmed favorite:  farmed New Zeeland chinook (aka King) salmon (this farmed fish has won green awards -- and is delicious and nutritious).

 

NOTE:  Chinook salmon grows wild in the North American Pacific NorthWest, if I'm not mistaken, and I'm sure is great too -- but not available in my supermarket,and probably expensive.

 

NOTE ALSO:  Chinook salmon might be the largest salmon.  That would probably make it the salmon highest on the food chain -- a negative -- the higher on the food chain, the more mercury.  (Consider the MUCH larger Ahi Tuna:  High mercury.  But Ahi Tuna is a monster; chinook salmon is much smaller.)

 

However, the award winning FARMED version of Chinook salmon of course has a controlled diet -- therefore virtually no mercury.

 

(BTW, since I'm a fish eater, when I have my semi-annual bloodwork done, I always have it tested for mercury.  Mercury is always very low.)

 

 

  -- Saul