They do everything

By way of Over My Med Body, I found this article that finds new virtues for seafood: it reduces anti-social behavior. This is great news! I plan to announce when I'm feeling cranky here at the Myers household, which will prompt an immediate serving of tasty salmon. I'm going to be eating fish every day!

Well, maybe not…I'm really not that cranky. But it is yet another piece touting the virtues of polyunsaturated fatty acids, especially the essential ω-3 fatty acids in which sea food is rich, so it reinforces my preferences, anyway.

Dietary polyunsaturated fatty acids do have a record of positive health benefits, contributing to lower cholesterol levels, reducing inflammation responses (helpful if you have asthma or arthritis), and it is an important component of the diet in the development of that very fatty organ, the brain.

I'm a little disappointed in the study, though. It's a correlational study with rather crude categories, treating whole nations as a bloc. Here's the abstract.

Deaths due to homicide have long been of interest to public health, in part due to their dramatic and tragic nature. Rates of death due to homicide show a more than 20-fold variation across countries in a similar pattern to cross- national differences in mortality from cardiovascular disease, which suggests that similar dietary factors may be important. This ecological relationship may be important because factors such as hostility, depression and anger increase risk of cardiovascular morbidity. A cross-national analysis previously described a robust protective relationship between seafood consumption and lower prevalence rates of major depression indicating that Ï3 fatty acid consumption may have psychotropic effects. Both observational and direct intervention studies have suggested that adequate tissue concentrations of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) may protect impulsive and violent behaviors as well as the closely related parameter of hostility. Virkkunen et al. reported that impulsive and violent offenders had lower plasma concentrations of DHA and higher concentrations of 22:5 ω6 than nonimpulsive offenders and healthy controls. In a double-blind placebo-controlled intervention trial of 2 g of DHA/ day, Hamazaki et al. documented reductions in a measure of hostility among Japanese students under the stress of University exams. Weidner et al. also noted a decrease in measures of hostility in a 5-year dietary intervention study that increased fish intake. It is reasonable to assume that measures of the affective state of hostility are in a continuum that includes violent behavior in the most extreme cases.

There are quite a few studies of this nature out there, and reading a few of them, I'm unconvinced. Here, for example, are some of the data correlating national seafood consumption with the incidence of various mental disorders.

Hmmm. It's suggestive, but there's not much more to say about it. I'm very suspicious of data that lumps "United States" into two numbers, per capita seafood consumption and rates of mental disorders; the US is a big, diverse country, and I know there is wide regional variation in seafood availability—try buying clams or squid or salmon in Morris, Minnesota vs. Seattle—and for all I know there might also be wide variation in the instances of psychiatric diseases. I also see that Canadians and Americans eat about the same amount of seafood, but there's variation between the two that isn't at all consistent.

And man, doesn't Iceland make you suspicious? It's way out there with an astoundingly great seafood diet, and they're also extraordinarily mentally stable (it also has a small population with an exceptional literacy rate and levels of education). It's not clear how much that outlier affected the significance of their statistics, but without it those curves look a lot more fishy…although it does make me want to move to Iceland.

I read the Hamazaki et al. study, which is a direct experimental test—they gave stressed-out students doses of fish oil or a placebo, and saw that aggressive behavior did not rise at final exam time in the students who were supplemented with ω-3 fatty acids compared to the controls. It did not actually reduce aggression: instead, it seems to have prevented a rise in aggression associated with term exams. I'm going to have to suggest to my students that they start loading up on castor oil in the next few weeks.

I'm not persuaded that this one factor, consumption of polyunsaturated fatty acids, plays a significant role in aggression or mental health, although I don't see any reason why it couldn't. The data are just too simplistically analyzed for a phenomenon that we know has multiple causes.

I can say, though, that having seafood for dinner always makes me happy, and I suppose you could argue that that would make me less likely to kill someone. Reading the papers also sparked my appetite and motivated me to cook up a nice salmon fillet tonight. I ate lots, so you can all relax.

Skatje, on the other hand, detests seafood of all forms and didn't eat any. I'm hiding the knives and locking the bedroom door tonight, I think.^*

^*Nah, not really. She never eats seafood, so I think she's learned to control her ω-3-deficiency-induced rage over the years. Hasn't knifed anyone in weeks.