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How Fructose Makes You Stupid and Fish Makes You Smart

A water color of a rat on a computer making a computerized rat run a maze
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“Slap!”

That’s the sound of me high-fiving myself.  After years of telling coworkers and friends that fructose decreases their mental performance, there is finally a study to prove it.  This is yet another study in support of the low fructose, and adequate omega 3 recommendations in Bulletproof Diet.

Not only does excess fructose give you fatty liver disease, high triglycerides, fungal infections, diabetes, gout, and make you obese, it also hurts your brain function.

In this new study, two groups of rats were fed regular rat chow and drinking water for five days.  They also trained in a maze twice a day for five days before starting the experiment.  The researchers tested the rats’ ability to navigate the maze before giving them a very un-bulletproof intervention.  For the next six weeks, both groups of rats had their water replaced with a fructose solution.  However, the researchers decided to also give one group of rats DHA.  DHA is an essential fatty acid that’s needed to transmit signals between brain cells and to make new nerve tissue.  Their hope was that DHA would protect against any drop in mental performance caused by fructose.

“DHA is essential for synaptic function — brain cells’ ability to transmit signals to one another,” said Fernando Gomez-Pinilla, the lead author of the study. “This is the mechanism that makes learning and memory possible. Our bodies can’t produce enough DHA, so it must be supplemented through our diet.”

DHA vs. Fructose

After the six-week trial period, the rats were tested again on their ability to navigate the maze.  The rats that were given fructose without DHA had a significant reduction in brainpower.  It took them far longer to navigate the maze.  Moreover, they were also insulin resistant.  This was especially true for their brain cells, which were less sensitive to insulin than when they were drinking regular water.  This means they were more likely to become fat if the study continued.

“The second group of rats navigated the maze much faster than the rats that did not receive omega-3 fatty acids,” Gomez-Pinilla said. “The DHA-deprived animals were slower, and their brains showed a decline in synaptic activity. Their brain cells had trouble signaling each other, disrupting the rats’ ability to think clearly and recall the route they’d learned six weeks earlier.”

Interestingly, the rats’ insulin resistance and impaired brain function may have both been caused by fructose.  Insulin controls blood sugar, but it also influences brain function and memory.  Being insulin resistant may have decreased the rat’s brain function, “because insulin can penetrate the blood–brain barrier, the hormone may signal neurons to trigger reactions that disrupt learning and cause memory loss,” Gomez-Pinilla said.

What You Do To Your Body, You Do To Your Brain

The good news is that the omega-3 fatty acid DHA given to the other group of rats prevented the drop in brain function suffered by the first group.  In fact, they were also insulin sensitive.  It seems that adding the omega-3s to the rat’s diet protected them against the harmful effects of fructose.

“Eating a high-fructose diet over the long term alters your brain’s ability to learn and remember information. But adding omega-3 fatty acids to your meals can help minimize the damage.”

It’s hard to find a study that supports the Bulletproof Diet more than this one.  Not only did it show that fructose damages your brain function, it also shows that DHA protects your brain.  The Bulletproof Diet supplies ample high quality omega-3s from grass-fed meat, wild-caught/low-mercury seafood, and select fish and krill oil supplements.  If you overdo your fructose intake for a day, these fats will help limit the damage.  On the other hand, if you aren’t consuming enough omega-3s, you’re going to be more sensitive to the negative effects of fructose.

Perhaps the greatest part of this study was how it further validated another key tenet of the Bulletproof Diet – that health is both mental and physical, and what you eat influences both.  As Dr. Gomez-Pinilla said:

“Our study shows that a high-fructose diet harms the brain as well as the body. This is something new.”

To some people, the idea that what you eat affects your brain function is like saying what you wear affects your gas mileage – the two variables are not meaningfully related.  This study shows that eating a lot of fructose decreases your mental performance, and that this can be partially prevented with omega-3s.  If you want to do everything you can to maximize your brainpower, you should limit fructose to less than 25 grams per day.  You should also aim to consume enough DHA from Bulletproof sources like high quality fish and krill oil supplements.  What you eat affects more than your waistline, it also affects who you are.

“Our findings illustrate that what you eat affects how you think.”

If you want to think clearly and be smarter, eat the Bulletproof Diet.

 

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  • leogodin217

    Is the study publicly accessible? I think I found summaries, but not the actual study.

  • JonO

    I wonder how Ray Peat would dispute this..I’m sure he will argue that it was the sugars that displaced the harmful polyunsaturated fat (DHA) and those rats performed better (probably reduced seratonin as well), but this wouldn’t explain why the non-DHA fed mice did worse ;) However, I do admit I am skeptical of studies that has the words “fed regular rat chow” in them. The “rat chow” the scientists use is very un-bulletproof (for the rats), loaded with industrial oils, cheap GMO corn derived mush..YIKES!

    • Dave Asprey

      That’s a fair point about chow. I’d love to hear what Peat would say too!
      Sent from my nobile phone. You understand….

  • http://www.facebook.com/zhuk0v Sasha Zhukov

    Dave, can you please give us a link to this study? What “regular rat chow” means? Didn’t they have to have another glucose-group? Also it’s intersting to know how regular glycogen depliting exercises effect high fructose consumption.

  • Gabriel

    What is special about Greek yogurt?
    “Gomez-Pinilla, a native of Chile and an exercise enthusiast who
    practices what he preaches, advises people to keep fructose intake to a
    minimum and swap sugary desserts for fresh berries and Greek yogurt,
    which he keeps within arm’s reach in a small refrigerator in his office.
    An occasional bar of dark chocolate that hasn’t been processed with a
    lot of extra sweetener is fine too, he said.”

    • nthmostfit

      Greek yogurt is strained to remove whey, lactose, and sugar, and typically doesn’t contain any added sugar. (If you see low-fat “Greek” yogurt, laugh and then run away.)

  • David Despain

    Dave, there were several problems with the analysis of a plethora of news reports that came out when this study’s press release was first published. For example, your article might’ve been better titled “Insulin resistance makes you stupid and fish makes you smart”. The fact is the rats were overfed, leading to weight gain and insulin resistance (same could have happened with any other caloric source like fat). See my report here: http://evolvinghealthscience.blogspot.com/2012/05/confusing-messages-about-sugar-are.html

    • Xagave

      I could not have said it better. :)

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  • Lou

    Dave,

    What do you think of Ray Peat — who would argue the exact opposite of this?

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  • http://twitter.com/RyanCritchett Ryan Critchett

    INSANE! But I kind of knew this too. I could tell at some level, just in my cognitive performance, that a lot of fructose impairs my thinking. It’s like a disruptive feeling.

  • http://www.facebook.com/amritrosell Amrit Rosell

    I’m not a rat, and I eat far better than whatever “rat chow” is made of. ;)
    Are there any studies of how fructose affects actual human brains which are fed various diets?

  • http://fitnessprohealth.com/ Nick_FPH

    Dave! I’m trying to pinpoint what is causing my Dad’s “severe” arthritis in his hands. He’s 57 and a construction worker. We have been eating paleo for 15 months, but he cheats daily by having wine/alcohol, chocolate covered almonds from trader joes, and bryers ice cream with fruit at night (and fruit in the morning). My recommendations to him were: try cutting out alcohol, the choc covered almonds, and ice cream, reduce fruit (fructose) intake and nuts high in omega 3, and ramp up healthy fats, omega 3 supplements, take more vit d (he’s only getting 3,000 IU @ 165lbs), and just eat more bulletproof foods.

    But I fear this won’t be enough, or it may be irreversible. Is inflammation the underlying cause? The only thing that seems to help is ibuprofen, but we don’t think that’s a good solution. Any insight into what BIG changes he has left to make, please let us know!

    Nick

    • Dave Asprey

      He should look at eliminating wheat and all nightshade vegetables (potato, eggplant, tomato, peppers) for at least 2 months to see what happens. Miracles sometimes. ?

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  • Tommy

    Hey Dave, which krill oil would you recommend?

    Thanks

  • OurWorldChange

    So in regards to humans, how much fructose are we talking here to qualify as ‘excess’?? One of my fave supplements has fructose. About the amount you would find in two grapes per serving. Depending on the day I can have as many as six servings.

  • Hunter Michael Kelley

    Rat studies aren’t credible sources for evidence in regards to human function. The proportions used in their studies are ridiculous and unrealistic. They often cut out essential foods in place of one substance pushed to toxic levels. We don’t have the same metabolism or immunities, and they can manipulate the outcomes to support whatever result they prefer. It’s not accurate experimentation. It’s just a selling ploy to misinform a, sadly and purposely, poorly educated public, in order to boost sales in their respective industries. Corporations are the ones who fund research. Research, that can say whatever they want it to. I’m not saying that I agree or disagree with this topic, but Rat Studies are NOT going to give you an accurate answer.

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