New Study: High-Fructose Diet Makes You Stupid

You gotta love scientists. They never seem to believe anything unless or until they scientifically prove it. Even if it’s obvious. Fernando Gomez-Pinilla, a professor of neurosurgery and integrative biology at UCLA recently had this to say after completing a study on how a high-fructose diet affects your brain: “Our findings illustrate that what you eat affects how you think.”

Duh! Even I could have told you that. Yet I can’t help feeling a little justified by the rest of the findings of their study. I feel confirmed as a mother and as a lover of traditional, Real Food. While past studies on high levels of fructose consumption concentrated on the effect fructose had on the development of diabetes, fatty liver disease, and weight gain, this is the first study published to concentrate on the effect fructose has on the brain.

Turns out, it makes you stupid.

That’s right. High levels of fructose inhibit learning and memory retention.

Gomez-Pinilla and study co-author Rahul Agrawal, a UCLA visiting postdoctoral fellow from India, studied two groups of rats that each consumed a fructose solution as drinking water for six weeks. The second group also received omega-3 fatty acids in the form of flaxseed oil and docosahexaenoic acid (DHA), which protects against damage to the synapses — the chemical connections between brain cells that enable memory and learning.

“DHA is essential for synaptic function — brain cells’ ability to transmit signals to one another,” Gomez-Pinilla said. “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.”

The animals were fed standard rat chow and trained on a maze twice daily for five days before starting the experimental diet. The UCLA team tested how well the rats were able to navigate the maze, which contained numerous holes but only one exit. The scientists placed visual landmarks in the maze to help the rats learn and remember the way.

Six weeks later, the researchers tested the rats’ ability to recall the route and escape the maze. What they saw surprised them.

“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.”

The DHA-deprived rats also developed signs of resistance to insulin, a hormone that controls blood sugar and regulates synaptic function in the brain. A closer look at the rats’ brain tissue suggested that insulin had lost much of its power to influence the brain cells.

“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.

He suspects that fructose is the culprit behind the DHA-deficient rats’ brain dysfunction. Eating too much fructose could block insulin’s ability to regulate how cells use and store sugar for the energy required for processing thoughts and emotions.

“Insulin is important in the body for controlling blood sugar, but it may play a different role in the brain, where insulin appears to disturb memory and learning,” he said. “Our study shows that a high-fructose diet harms the brain as well as the body. This is something new.”


Does this mean you should stop eating fruit or other foods naturally high in fructose?

No way! When fructose occurs in nature, it’s usually part of a whole food full of anti-oxidants, fiber, pectin, and other goodies that can slow the digestion of fructose and mitigate it’s damage. Given the packaging, you’re not likely to eat all that much fructose anyway. Who sits down and eats a dozen apples?

But what about that fructose in table sugar? The fructose in corn syrup?

These, you should certainly avoid. They’re refined and concentrated unnaturally, and they’re easily consumed in excess.

I also appreciate that the study confirms the protective nature of wild caught seafood, eggs from pastured hens, and organ meats — nature’s most concentrated sources of DHA.

So, rather than reaching for the caramel macchiato or other sugary snack when it’s time to cram for finals or learn something new, we should be reaching for real brain food like fish roe or fermented cod liver oil! (Where to find fermented cod liver oil.)

What’s your favorite brain food? And how often do you eat it?

(photo by jennifertomaloff)


  1. says

    Thanks for sharing, Kristen! I love to add chia and a raw pastured egg yolk to my morning fruit smoothies (along with a Kombucha base) to get my brain super charged for the day! Appreciate you bringing us this important information! Like you said, it’s just validation for what we already know! Blessings, Kelly

  2. Jen says

    This is sad, considering what they feed children for breakfast and lunch in public schools… a steady diet of HFCS.

    I do think the study would have been more interesting and telling if there was a non-high fructose control group. This experiment seems to study the effects of DHA more than high fructose.

    • KristenM says

      Yeah. I was hoping to see that, too.

      But it’s still telling that both groups of rats started out with no added fructose OR DHA (just a standard rat chow diet). They were fed this “normal” diet and trained in the maze first to establish a base line. So, they’re comparing not just DHA+fructose to fructose, they’re also comparing both of these to the no-fructose diet established at the beginning. At least, that’s what I understood from the researcher’s summary.

    • SaraBeth says

      Yes, I read this twice and am still not sure that this study really has anything at all to say about fructose consumption – it seems to be all about DHA. The author suspects the fructose is harmful, but he really doesn’t know. What if they had compared a rat chow diet with DHA-enhanced diet? I’d bet the DHA-enhanced rats would still do better – but thanks to this incomplete study it’s all supposition. In the meantime, it does make sense to stick with pastured egg yolks and cod liver oil!

  3. Bev Senevey Snabl via Facebook says

    That must be what happened to my brain! I used to drink tons of Pepsi! I have been off of it for over 2 years…will I ever get my brain back?

  4. says

    So many negative effects comes out but why are foods and drinks at the grocery stores are still populated with products with high fructose corn syrup? I hope they pull out those products and only sell natural and organic products.

  5. Hannah says

    I know this post is a few days old, but I’d like to come to the defense of those scientists. That feeling after you hear the results of a study where you go “Duh! I knew that already!” is actually a pretty well known bias in our brains, called hindsight bias. Things always seem so much more obvious after they’ve happened. For example, people’s estimated risk of a terrorist attack was way higher right after 9/11 than it was a year after the attack. It had just happened, so they predicted that it would be more likely to happen.

    So to say “Duh! That’s so obvious!” to the results of this study, you’d have had to make a prediction that HFCS would impair learning and memory retention BEFORE the study came out. Otherwise, it’s just your brain editing your memories (which, studies say, are way less reliable than we think) to make you seem more right than you actually were.

    Here’s a great article on hindsight bias:

    Have a great day!
    – one of those crazy scientist folk

  6. Loriel says

    This is kind of off subject but I heard if you scramble your eggs (even pastured) the nutritional value drops. Is this true? I feed my 13 month old scrambled pastured eggs and I want to make sure I’m not ruining the eggs by scrambling them. Help please!

  7. Kristen Cyr says

    I’m not sold here. I don’t consume HFCS but this study doesn’t put a nail in the coffin. It seems strange that both groups were given HFCS solution to drink and one group was also given a DHA supplement and because that group did better, the conclusion was drawn that it must be the fault of the fructose. How did we get there? How can one make that conclusion if there is no non-fructose consuming group? It can easily be false attribution and I could just as easily conclude that DHA makes me smarter. Then I can go one step further and conclude that I can consume all the fructose I want as long as I also take a DHA supplement.

    I absolutely believe that consuming too much sugar is not healthy whether it is processed in factories, labs or made by bees. I just dislike these types of studies that make hasty generalizations and seem to oversimplify the matter. You can’t look at a few rats and then apply a broad stroke to suit your intent, which appears to be, villifying fructose.

    • Kristen says

      I meant to say “both groups were given a fructose solution…” Also, to clarify that I agree that consuming fruits is great because it is nature’s fructose and it is nicely packaged for us but things like HFCS, sugar, honey, molasses etc should be consumed in very limited quantities because they are not nicely packaged to slow down the digestion of fructose.

  8. Anon says

    And remember to keep your total sugar consumption below 20-36g (20g/day women and 36g/day men) as recommended by the AHA. Even a single apple has up to 23g of sugar.

  9. DePAw says

    Where’s the rats just given flax+DHA and no fructose, and rats given neither?

    All this study shows is that omega-3s are good for us, it can shown nothing about fructose as no group of rats weren’t eating fructose.

  10. Jean-François Lepage via Facebook says

    Interesting. Although the study is not being shown. Nevertheless, rule of thumb, everything in excess is bad, usually. And if you have a high level of sugar, more insulin will be created, and as long as you are within range of normalities, you are fine. We all know the effects of hyper and hypoglycemia. Which are especially counterproductive to emotions and neuro-physiological pattern. New study, ok, new knowledge? I doubt so.

  11. Christopher A. Gilbert via Facebook says

    Tuna, probably because of all the dolphin in it! hahaha ahhh sometimes the old jokes are the best

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>