Wednesday, May 16, 2012

High sugar consumption reduces intelligence

Eating and drinking a lot of sugary stuff is known to cause diabetes, as the sudden spike in blood sugar level it induces is not very healthy. It causes increased insulin production needed to rid the body of blood sugar levels that are too high, eventually causing insulin insensitivity due to prolonged exposure. Now, scientists from the University of California in Los Angeles have discovered that sugary foods and drinks also affect your brain. Specifically, consuming a lot of sweet stuff affects your intelligence.

To analyse the effect of sugar on the brain, scientists fed rats with fructose, a form of sugar that is often used to make things taste sweet. Of all commonly used sugars, fructose is by far the most sweet tasting. It is usually derived from corn and functions as a preservative as well. Commercially used fructose is processed, and therefore not as healthy as its natural equivalent, which also contains healthy anti-oxidants. Soda is one of the most common examples of being high in fructose content. The body turns fructose into glucose, which is the blood sugar that makes you diabetic if you consistently have too much of it.
Rats, having a similar metabolism to humans, were used as a model by the scientists, and fed with high amounts of fructose. Two groups of rats were analysed, both receiving fructose, but one of the groups got an additional supply of omega 3 fatty acids, which are known to be beneficial for the brain. To assess their intelligence, scientists trained the rats, prior to receiving the fructose diet, to find their way out of a maze. Thereafter, the rats were put on the aforementioned diet and forced to re-do the maze six weeks later.
The scientists found that rats consuming omega 3 in addition to fructose were much faster in completing the maze. Rats lacking omega 3 showed a decrease in brain cell signalling, indicating that their ability to think is impaired. Furthermore, they showed signs of insulin resistance, which is typical for the development of diabetes. Taken together, it seems that fructose consumption, associated with an increase in insulin production, is negatively affecting the brain, influencing memory and learning processes. Additionally, the scientists suspect that insulin is the culprit in causing disruption in the communication between nerve cells.

Free sugars
Fructose and glucose are sometimes referred to as free sugars, meaning they can easily be processed by the body. Sugars, or carbohydrates, can form long chains, such as in starch, which need to be broken down first, before the body can utilize the energy. Because metabolising carbohydrate chains to glucose, the universal form of fuel, takes time, the intestines cannot release it into the bloodstream very fast. That is different when consuming 'single' sugar molecules such as fructose. As it requires far less modification, it can be released much faster than long-chain sugars. The consequence is a bigger spike in blood sugar levels, which is accompanied by a higher release of insulin, the hormone that is tasked with allowing cells to take up the released glucose. It is not an option to keep the insulin levels equal, because keeping glucose levels in the blood high can be dangerous and even lethal.
Structure of fructose: a single molecule, or monosaccharide.
The general idea of a carbohydrate chain, found in starch. Before the body can turn it to glucose and utilize its energy, the bonds between the individual monosaccharides need to be broken down.
The study by the University of California in Los Angeles provides yet another reason to cut down on sweets. They do not only make you diabetic, they also make you less intelligent. It would be much better to consume 'slow' carbohydrates, even though they have less of a sweet taste. Nevertheless, the evidence for harmful effects of sugary stuff is piling up and it indicates consumption of soda and sweets is best avoided. But it does appear that omega 3 fatty acids can prevent damage, which calls for more research regarding this topic. As omega 3 was already hallowed for its beneficial effects on the brain, there is even more reason to start consuming products that contain these healthy fatty acids.


  1. How have the researchers differentiated between the effects of sugar on intelligence and the effects of sugar on memory?

  2. Memory and learning are two things that make up intelligence (among other things), so the rats' declining ability to remember/learn, as seen in the maze experiment, signifies lower intelligence.

    If you'd be studying, it would therefore be unwise to consume a lot of sugar, as it will hamper your ability to learn and memorize, hence lessening your intelligence. Of course, it remains to be seen what the effects of 'normal' sugar consumption are on intelligence. It's likely we need to consume very large amounts before we'd notice it, but it does warrant further investigation.

    1. What I know about science would not fill a thimble, but I do know that you are correct about memory and learning being two of the things that constitute intelligence. Though I have not read the actual study, it appears as if memory retrieval (the rats' ability to recreate the event of navigating the maze) is what was affected. Am I clear in understanding that researchers are indicating that high fructose consumption (with little or no omega 3 to counter its affects) inhibits neurotransmitters from creating the neural pathways required to retrieve learned information and/or experiences? and does this phenomenon affect declarative knowledge as well as procedural knowledge?

    2. I think they did two things seperately: assess intelligence (by maze) in rats with and without omega 3 under the influence of fructose, and make assumptions based on what omega 3 does in the brain, which gives an explanation for the observed effects. But this is a correlation, so far.

      I seem to have omitted the source in this piece... shall add it lader.

  3. Thank you for the infomative posts and the chat. As I said earlier, my knowledge of science would not fill a thimble. I often tell my students, "the only science I know is that those big white fluffy things in the sky ... they're called clouds." It is nice to be able to read posts that explain things in terms "everyday people" can understand.

  4. The test as presented here is flawed. There should be three groups. Control, sugar and omega 3. Feed all the groups an identical base diet and then introduce the fructose to the sugar group and omega 3 to the omega 3 group while training them in the maze.

    What the persons have done here is show only that the omega 3 helped one set of rats. Very poor science.

  5. I think they did include a control group, else there is no way to make these assumptions. Equally, there is no way to get it published without something as basic as controls.

  6. Well, that qualifies as an assumption. No mention of a control group in this article, yet you assume so.

    When Dr. Wakefield published his study linking autism to vaccines, some scientists and physicians supported his findings. They assumed he was right when they should have conducted their own studies. Soon celebrities and politicians got into the fray. As a result, many thousands of children in the United States alone were not vaccinated. Further, diseases such as whooping cough have made a strong resurgence.

    Studies are published every day without proper peer review or other controls. To assume otherwise is extremely naive.

  7. I have sadly not been able to access the full text article, which means I did not see their study setup in full detail, but the abstract does mention this:
    Rats fed on an n-3 deficient diet showed memory deficits in Barnes Maze, which were further exacerbated by fructose intake.
    Such claims cannot be made without a control group, I trust the scientists from a respected university such as the UCLA know that.

    Additionally, I do not share your view about studies published without proper peer review, at least not in the established journals.

    I'd love to verify this by looking at the full text, but it is not available to me. I will try to dig it up later. Until I find solid evidence, I refuse to believe that they did not use a control group :)

  8. I doubt the presumption that consumption of sugar causes diabetes, unless the person was insulin deficient in the first place.