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An interesting article was published earlier this week on the website of the journal Medical Hypotheses, suggesting that the current obesity epidemic may be caused by salt addiction. The article is provocatively titled "Salted Food Addiction Hypothesis may explain overeating and the obesity epidemic" and as you might expect given the journal that published it, it is wildly speculative.  Now I'm just going to say this upfront - I think the authors are probably wrong.  But it can be fun to speculate, and I did learn some interesting things from the paper, so I think it could make for some interesting discussion.

The authors do their best to build a case that people can become addicted to salt.  Despite my original expectations, the study was quite a challenging read, so I will do my best to summarize what I felt were their main points:

1. Once people are exposed to sodium, they tend to crave more of it.
2. Our current environment exposes us to very large amounts of sodium.
3. Once people become "addicted" to sodium, they are likely to seek out ever increasing amounts, which will almost certainly mean an ever increasing caloric intake.

The authors suggest that dietary sodium may affect reward centers in the brain, just like other addictive behaviors. Or, as they put it:

‘‘Salted food craving” may be a neuropsychiatric manifestation of severe dysphoria resulting from a high tolerance and severe withdrawal at mu-s opioid receptor sites, while overeating may be a neuropsychiatrically based maladaptive attempt to self-medicate mood destabilization.

In other words, salt intake may affect opiate receptors, just like certain drugs.  To test this theory, the authors performed a truly novel experiment - they examined whether people going through opiate withdrawal increased their intake of salty food.  Unfortunately, as far as I can tell they didn't actually measure salt intake, which seems like a bit of an oversight.  As you might expect, this is where the paper goes seriously off the tracks.  While going through opiate withdrawal, subjects gained an average of 11 lbs, and self-reported that they increased their intake of fast food.  How much more fast food did they consume?  They don't say, nor do they provide any statistics.  Luckily, the authors don't let this stop them from interpreting their findings!  Since fast food tends to be high in sodium, the authors interpret this anecdotal increase in fast food intake to suggest that the subjects were trying to self-medicate their opiate deficiency by consuming higher amounts of sodium.  WHAT???

This is one of the best examples of over-interpretation that I've ever seen.   It is unclear if there was any measure of the primary outcome (sodium consumption), and their proxy (fast food intake) was self-reported.  What's more, we have no information on how the self-report was done, or even basic statistics.  It's almost too bad that they included the "experimental" data in the paper, because the hypothesis they put forward in the first half of their paper is interesting and at least somewhat plausible, but this "experiment" is so strange that it leaves a bad (and somewhat salty) taste in my mouth.

So what's the take-home message?  Most of us consume far too much sodium, which is almost certainly bad for our health and longevity.  Is it behind the obesity epidemic?  Almost certainly not.

Travis

Cocores, J., & Gold, M. (2009). The Salted Food Addiction Hypothesis may explain overeating and the obesity epidemic Medical Hypotheses DOI: 10.1016/j.mehy.2009.06.049

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4 Response to "Salted Food Addiction Hypothesis may explain overeating and the obesity epidemic"

  1. Helen Krummenacker Said,

    Salt cravings don't have to mean calories.

    I've had times where I suddenly desperately needed salt, due to signs (low blood pressure, for one). Salt water or even pouring table salt into one's hand and licking it does the trick. Even someone who didn't think of that would just tend to shake salt onto already salty food if they want it saltier. Eating more food goes beyond a desire for sodium.

    Posted on August 8, 2009 at 7:20 AM

     
  2. Alan Said,

    I'm a bit of a hedge scientist. When trying to find correlations in my operational research, I'm regularly torn to shreds by more capable scientists - sometimes, I'll admit, to the point where I'll just give up in frustration - reasoning that I don't have the quantitative chops to do anything with my data.

    So imagine my surprise, that a paper with the kind of grotesque research design flaws you describe, can get into a peer-reviewed journal. What gives?

    Posted on August 8, 2009 at 8:03 AM

     
  3. Travis Saunders, MSc Said,

    @ Helen,

    Thanks for the thoughtful comment. I've had a real craving for salt after some long runs on hot days as well, although I can't say I've ever enjoyed the taste of salt water!

    @ Alan,

    The journal where this research was published (Medical Hypotheses) takes a "deliberately different approach" to peer review. Their papers tend to be very speculative, and their peer-review process seems to focus on ideas more than anything else. So just because the paper made it into this journal, doesn't mean it would make it into any conventional (and more widely read) journal. I wouldn't take it too personally :)

    Posted on August 8, 2009 at 10:13 AM

     
  4. brtkrbzhnv Said,

    Reading about this hypothesis, all I could think about was that South Korea and Japan are among both the absolute slimmest (according to NationMaster, obesity is almost 10 times less common there than in the US) and the absolute saltiest of industrialized nations. Scandinavia is also quite high in sodium consumption and low in obesity, though not as extreme as East Asia. The simple fact is that noöne has ever become obese because of a kimchi addiction – and the same cannot be said for low-sodium products such as candy bars and ice cream.

    A competing hypothesis would be that a high-sodium meal makes people full faster by 1) a signal from their bodies that they've gotten enough sodium, and 2) an increased consumption of water.

    Posted on October 8, 2010 at 6:37 AM

     

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We are PhD students in the School of Kinesiology and Health Studies at Queen's University in Kingston, Ontario. Our research focuses on the relationships between obesity, physical activity, and health risk. This blog is our attempt to consider the many "cures" for obesity that we read about on a daily basis. Enjoy.

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The opinions expressed here belong only to Peter and Travis and do not reflect the views of any organization. Any medical discussion on this page is intended to be of a general nature only. This page is not designed to give specific medical advice. If you have a medical problem you should consult your own physician for advice specific to your own situation.

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