Do Sugar and/or Saturated Fat Make You Stupid?

Another article from by Emily Deans, M.D and can be found on her blog at

Do Sugar and/or Saturated Fat Make You Stupid?

Two more heavily publicized papers came out in the past week or so, just in time to be fodder for questions at my talk on Evolutionary Psychiatry and Alzheimer’s Dementia in the upcoming week.

Have you ever heard the Adagio from Spartacus? Hang in there for a little bit. Around 1:09 you get the early rendition of one of the more romantic themes in classical music, repeated with greater power later in the ballet (2:47 and 7:04). The Russian composers really knew how to sock it to you with a good theme.

Can we say the same of rat researchers from UCLA? Well, excepting our own good friend and AHS president Aaron Blaisdell, the jury is still out… These researchers pulled out some interesting things, though, in their little study on 24 rats.

“‘Metabolic syndrome’ in the brain: deficiency in omega-3 fatty acid exacerbates dysfunctions in insulin receptor signaling and cognition.”

This paper combines everything awesome and evil all at once. Rat study. Fructose! DHA. Mazes. The authors even begin the paper not with an abstract but with highlighted Key Points: We provide novel evidence for the effects of metabolic dysfunctions on brain function using the rat model of metabolic syndrome induced by high fructose intake. Etc.

So… we have some rats. There are two diets and two drinks. Group 1 gets regular rat chow with omega 3 and water to drink. Group 2 gets regular rat chow with omega 3 and a 15% fructose drink instead of water. Group 3 gets water and omega 3 deficient diets (and I doubt it is so easy to make a human in the wild quite so omega3 deficient as these rats), and group 4 gets the double whammy of an omega 3 deficient diet and the 15% fructose solution. The diets go for 6 weeks, and in that time, we have a pretty remarkable change in the fructose-slurping rates.

The fructosed rats drink a lot more than the plain water-drinking rats, and even though they eat less food than the plain water rats, they take in more calories. By the end of the 6 weeks, the fructosed rats have high glucose and insulin levels, and the triglyceride levels of poor group 4 (given fructose and omega 3 deficient diet) are over twice the levels of group 1 (omega 3 food + water). The researchers found that the omega 3 in the diet seemed to protect the group 2 rats a little from the fructose, with less weight gain and less rat metabolic syndrome.

These rats had also been trained to go through a maze, and the fructose-poisoned omega 3 depleted rats did worse than any of the other groups in remembering how to get through the maze. They lost the maze race, big time. Again, the rats who had fructose and omega 3 had relatively preserved maze-solving abilities.

The researchers measured very specific elements in the rats’ bodies and brains after the experiment. Measures of energy metabolism were decreased in poor group 4, whereas omega 3 seemed to increase energy metabolism. Other chemicals known to be important in the ability of the nerves to adapt and change according to different stimuli (called synaptic plasticity) were very decreased in the omega 3 deficient rats, and very much decreased in the fructose-poisoned omega 3 deficient rats. Group 2 rats (+ omega 3, + fructose) had, again, some protection from the bad effects of the fructose.

And, not surprisingly, the omega 3 deficient rats had a decreased amount of DHA in the brain and an increased amount of omega 6 fats and their metabolites, like arachidonic acid.

Fructose in excess is well known to cause metabolic syndrome (hypertension, hypertriglyceridemia, and hyperinsulinemia are typical symptoms). Did you know that metabolic syndrome affects the brain as well? Of course you do. There are plenty of rat studies showing that downing vast quantities of coca-cola fructose is a pretty lousy idea, if one cares about one’s liver or brain. (I recommend this segment of the HBO Weight of the Nation series about the liver, and a good bit halfway through the next segment about sugar-sweetened drinks.)

So, we’ve now proven that fructose is bad (in the context of an excess calorie diet), and omega 3 is protective, and the main point is to not deprive your rats of omega 3.

Sugar can indeed make you dumb (in the context of an excess calorie diet). Eating lab rat chow completely devoid of omega 3 can make you even dumber. I don’t recommend it. But you can see how a modern processed food diet can mimic these changes. Soda or juice or red bull or sweetened beverage of your choice and a lack of omega 3 does not a happy liver or brain make, and the changes occur quickly.

And now the second diet and dementia study of the week (involving actual humans! However, it is another observational study from the hospital where I’m academically attached). Participants in the Women’s Health Study (about 39,000 female health care professionals) filled out a food frequency questionnaire at baseline, and beginning five years later, an older sub cohort (about 6000 women over 65) underwent serial cognitive testing via telephone over the course of an additional four years. Data was gathered and statisticians went to work.

The women underwent cognitive testing three times, with the time between the 1st and 3rd test being an average of 4 years. Women tended to do better the second time than the first time (having learned what the tests were going to be), but at the end of the four years, the scores dropped for most women from the second to the third test. It declined the most for women who ate the most saturated fat, and actually test scores continued to improve for women who consumed the most monounsaturated fat.

There were no associations between total fat, trans fat, and polyunsaturated fat (which is mostly omega 6) and cognitive change.

By the time you pull out covarites you have a mell of a hess. Saturated fat intake was associated with lower rates of high cholesterol, by the way (statinization?? This part of the study occurred from 1998-2002. Statins came out in the late 80s and lipitor, the biggest-selling one I believe, was released in 1998. Though it is hard to tell if women on statins would have automatically been put into the “hypercholesterolemia” group or if just total cholesterol was used to make this group. There are many frustrating things about the way the data is presented in this study). MUFA (olive oil) consumption was also correlated with lower total cholesterol. Women with known cardiovascular disease (history of a myocardial infarction, stroke, coronary artery bypass or stenting) were taken out of the data and the trend remained similar. More total fat intake was associated with lower exercise, smoking, and higher BMI. Previous epidemiology studies all linked saturated fat intake to poorer cognitive function over time. The main difference in this study is that these health care professionals had much lower total trans fat intakes than the average American. Trans fats have been previously associated with poorer cognitive function in other epidemiological studies, and trans fat consumption tracks with saturated fat consumption.

The paper is a little too brief and too heavy on statistical mumbo-jumbo to bother much with coming up with any mechanisms. It does recommend a Mediterranean diet at the end, and immediately classifies PUFAs and MUFAs as “good fats” and saturated fats and trans fats as “bad fats” in the discussion.

I think when it comes down to it, we will find that these women who were chowing down on the saturated fats in the 1990s are going to be women who were less likely to take care of their health in other ways. The olive oil fans were also more educated (even then olive oil was starting to be popular) and likely to take the best care of themselves. I’m not surprised to see these correlations. I still can’t figure out how saturated fat all on its own can cause cognitive decline, mechanistically. I find it very interesting that the highest saturated fat eaters had lower levels of hypercholesterolemia in this large group, and the paper makes no attempt whatsoever to explain this finding. Hmmmm.


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