Try not to think with your gut

Sometimes it’s easy when experts step up and eviscerate bad science reporting.

The Verge vs The NESS

The Verge does a story on probiotics and how that may be affecting your mental health.

Gut feelings: the future of psychiatry may be inside your stomach | The Verge.

[A] new understanding of the trillions of microbes living in our guts reveals that this communication process is more like a multi-lane superhighway than a one-way street. By showing that changing bacteria in the gut can change behavior, this new research might one day transform the way we understand — and treat — a variety of mental health disorders.

In one Japanese study, for instance, researchers were only able to change the baseline stress characteristics of germ-free mice until nine weeks of age. After that, no variety of bacterial additions to the mice’s guts could properly regulate stress and anxiety levels. The explanation for this phenomenon might lie in what’s known as “developmental programming” — the idea that various environmental factors, to which we’re exposed early on, greatly determine the structure and function of organs including the gut and the brain.

Although plenty of questions remain, the benefits of using probiotics to treat human behavior are becoming increasingly obvious. Yogurts like Dannon’s Activia have been marketed with much success as a panacea for all of our intestinal ills. Other probiotic supplements have claimed to support immune health. Probiotics’ potential to treat human behavior is increasingly apparent, but will manufacturers one day toss an anxiety-fighting blend into their probiotic brews?

So what does this mean? Not exactly what the writer says it means. Check out the rebuttal.
NeuroLogica Blog » Probiotics for Mental Health?.

There are multiple problems with this style as applied to a science topic. The first is, of course, that the story is anecdotal. We cannot know what the implications of this story are. It is likely highly selected – chosen out of many possible examples to be the most dramatic and emotionally appealing example of whatever story the journalist wants to tell.

What about the topic itself – does the bacteria that colonizes our GI system have a dramatic effect on brain function, including mental illness? At present this is an intriguing idea with some promise and preliminary evidence, but that’s all. It is very unlikely that intestinal flora have as much impact as the article suggests, and there are numerous other factors that are well established, such as genetics and environmental factors.

The research cited in the article is mostly animal research, which essentially shows that mice with certain GI flora have higher levels of stress hormone. That is a plausible simple mechanism – increased levels of cortisol raise the overall level of stress, which could exacerbate things like OCD or anxiety. Exacerbating a pre-existing condition is not the same as causing that condition, however. Even this relatively simple effect is not established in humans, who, it turns out, are not mice. (Animal research is legitimate, but caution is always recommended in extrapolating to humans, especially in psychology studies.)

And, he calls out the ridiculousness of the “Activia” paragraph quoted above. Read one, then read the rebuttal. See?

Just in case anyone asks you about this probiotic stuff, it’s a bit too early to definitive.

  2 comments for “Try not to think with your gut

  1. Chris Howard
    August 26, 2013 at 11:01 PM

    The fact that the writer names Dannon Activia makes me suspect that its a PR piece for Dannon.

  2. Brandon
    August 27, 2013 at 6:58 AM

    I think there is a small error in the last sentence. I think you forgot to add the word “be” before “definitive.”

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