Hi! Back to the thyroid in a bit… but I've had a few questions about a study that came out earlier this week so I thought I would do a quick post.
Restriction of meat, fish, and poultry omnivores improves mood: a randomized controlled trial
The Strokes: 12:51 (video starts with an ad. Sorry!)
This pilot study was small and interesting and embarked upon to try to answer some questions about diet and mood. Hooray! Specifically the authors speculate that the arachidonic acid (AA) in meat could impact how we feel, and that restricting AA could make us feel better. AA (which is a highly unsaturated omega 6 fatty acid) is situated in the biochemistry to be pro-inflammatory (though WAPF has some issues with this characterization). Specifically, AA eaten directly competes with the desaturating enzymes for EPA (a long chain omega 3 fish oil constituent), so AA could potentially increase pro-inflammatory cytokines such as TNFalpha which are known to have mood altering effects. One question is does fish consumption ameliorate the affects of pro-inflammatory AA, and is that why populations who eat fish tend to have better moods than those who don't? Hey, let's whip up a little experiment and get informed consent and run it by the IRB and test it.
So… 39 adults who ate meat or poultry once daily (thus omnivorous) with no major psychiatric problems, substance abuse, or health problems were randomized to three groups for two weeks. One group was told not to change their diets (OMN). Another group was told to avoid meat and poultry but to eat fish 3-4 times a week (FISH). The last group was told to avoid all animal products except dairy (VEG). (Traditionally in the US eggs are considered dairy for whatever reason but I'm assuming they were left out as the yolks have a nice dose of AA). Diets before and after were assessed by a "validated food frequency questionnaire." The participants were also given a bunch of mood, anxiety, and depression rating scales before and after.
The results! OMN and FISH groups were about the same with no change from baseline, but the VEG group showed a decrease in the psychological ratings scores with respect to tension and stress (anxiety and depression scores were not significantly changed). Dietarily, if one can truly believe a report to a hundredth of a gram of dietary fatty acids based on food frequency questionnaires, EPA and DHA and AA dropped considerably in the VEG group, OMN group was unchanged, and the FISH group managed to increase their dietary long chain omega 3 fatty acid consumption by 100%. They also successfully raised the O6/O3 ratio by 60% in the diet of the vegetarians, which I'm not enthusiastic about long term, by any means.
Hooray! A result. Decreased tension and stress. But what does it mean? I'm hoping this pilot trial is used as evidence to recruit funding for a bigger and more ambitious trial, because what these researchers did not measure is pretty much everything that would tell us anything about what actually happened to decrease those stress scores. There were no measures of tissue fatty acids to tell us how the ratios changed in the body relative to these dietary changes, and no "after" measures of weight. Losing weight from a diet is associated with improved psychological scores, and since vegetarian-geared fare is often healthier than the regular SAD meaty counterparts (tofurky and cheese pizza excepted), I wouldn't be surprised if the most dramatically altered diet caused more weight loss than the others. Or it might have to do with changes in AA. The Seventh Day Adventists study (which the authors if this study did as well!!) showed that "Vegetarian Diets Are Associated with Healthy Mood States."
(My critique of the SDA studies are that being part of a close-knit community that is very pro-vegetarianism is a HUGE confounder when it comes to mood and stress, and boy, it sure would be nice to know the tissue levels of fatty acids because that would tell us a lot more than just food frequency questionnaires and psych scales.)
We need more info to make anything of this little study. I also think the title is misleading (and is leading to misleading news reports, as is typical), as actual mood and anxiety scores were unchanged, only the tension and stress scores (though certainly over the long term tension and stress are associated with more depressed and anxious mood states). Whatever gets you funding, I suppose…