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Fructose makes you stupid; DHA makes you smart

by Dr. Randy


Breakthrough study

A recent study in rats examined the effect of omega-3 fats (particularly DHA) and fructose on memory. Rats were trained to solve a maze and then given either a diet with omega-3 fats (DHA and flax seed oil) or one deficient in omega-3 fats. Each group was further divided into those also fed high-dose fructose in their drinking water or not. The group that was fed the fructose showed impairment of memory and took a longer time to solve the maze than prior to eating fructose. Those fed an omega-3 deficient diet and fructose fared the worst in the memory task. The rats fed fructose and omega-3 fats did better.

The conclusion of this study was that rats fed fructose had impairment of their ability to solve a maze because of memory deficits. Those given DHA and fructose had an improvement in their memory. The mechanisms involved in the memory impairment seemed to be a direct result of brain insulin resistance induced by fructose and ameliorated by taking DHA.

This study is the first to document insulin resistance and metabolic syndrome effects in the brain. And it suggests that taking DHA improves insulin metabolism, even with a diet containing fructose that induces insulin resistance.

Conclusions from the study

We can derive several take home messages from this simple study. We already know that the epidemic of obesity, insulin resistance, and diabetes is in large part due to the consumption of high fructose corn syrup in the American diet. This study tells us that fructose also results in dysfunction in the brain associated with insulin metabolism. It also confirms the importance of DHA for brain function.

Here are the words of the authors. “These findings expand the concept of metabolic syndrome affecting the brain and provide the mechanistic evidence of how dietary habits can interact to regulate brain functions, which can further alter lifelong susceptibility to the metabolic disorders.”

What you should do

Obesity and metabolic syndrome play a huge part in the epidemic of chronic inflammatory diseases including heart disease, cancer, and diabetes. Now we see that mental impairment is another part of this picture. Studies like this warn us that high fructose corn syrup should not be an ingredient in any foods in our diets. Unfortunately, corn syrup is a primary ingredient in many packaged and processed foods. Read labels and choose products sweetened with other sources of sugar or more natural sweeteners like stevia, sorbitol, or xylitol. It is always better to choose foods sweetened with sugar than corn syrup. Assume that any sweetened drinks from vending machines or restaurants will have corn syrup. Of course, it is best to eat unprocessed whole foods and avoid processed foods and juices. The natural fructose in fruit is not harmful in moderate amounts. And supplements like omega-3 fats along with antioxidants can provide extra benefit for mental functions as well.


Agrawal R and Gomez-Pinilla F. ‘Metabolic syndrome’ in the brain: deficiency in omega-3 fatty acid exacerbates dysfunctions in insulin receptor signalling and cognition. The Journal of Physiology, May 1, 2012, 590, 2485-2499.

  • Erica Etelson

    Do you have a fish oil supp brand you recommend? The Weston Price foundation recommends some very expensive cod liver supps b/c they think the ratio of vitamin A to vitamin D is very important, and most fish oil supps don’t have much vitamin A and also have too much omega 9 which we get enough of in our diet.

    • Dr. Neustaedter OMD

      I don’t use cod liver oil that contains A and D. I think using Nordic Naturals or Carlson is fine, thought the fermented is best.