Wednesday, December 1, 2010

Glucose and Aggression ?

The major discovery is that there is a journal called Aggressive Behavior.

Science Daily has reported on a recent work that "Sweetened blood cools hot tempers." The claim is that people who drink lemonade sweetened with sugar show less aggression towards strangers within a short time window after the drink. The experiment is exquisite :

In the study, 62 college students fasted for three hours to reduce glucose instability. They were told they were going to participate in a taste-test study, and then have their reaction times evaluated in a computerized test against an opponent.

Half of the participants were given lemonade sweetened with sugar, while the others were given lemonade with a sugar substitute.

After waiting eight minutes to allow the glucose to be absorbed in their bloodstream, the participants took part in the reaction test.

The reaction test has been used and verified in other studies as a way to measure aggression. Participants were told they and an unseen partner would press a button as fast as possible in 25 trials, and whoever was slower would receive a blast of white noise through their headphones.

At the beginning of each trial, participants set the level of noise their partner would receive if they were slower. The noise was rated on a scale of 1 to 10 -- from 60 decibels to 105 decibels (about the same volume as a smoke alarm).

In actuality, each participant won 12 of the 25 trials (randomly determined).

Aggression was measured by the noise intensity participants chose on the first trial -- before they were provoked by their partner.

Results showed that participants who drank the lemonade sweetened with sugar behaved less aggressively than those who drank lemonade with a sugar substitute. Those who drank the sugar-sweetened beverage chose a noise level averaging 4.8 out of 10, while those with the sugar substitute averaged 6.06.

I can not dispute that a low blood sugar contributes to irritiability (and by extension, aggression.) Just last night, I waited too long between lunch and dinner and was becoming irritated with my surroundings until I was able to eat. But, I have just had a glass of extra-sweetened lemonade and I am still annoyed by the presentation of the study results. The comparison of the means of two populations is meaningless without an error bar on the mean. The numbers of members of each population is only 31, so the error on the mean may be significant relative to the difference of 1.26. Error bars please ! I don't want to pay to see the PDF of this article, so I am not sure if the fault lies with the authors or Science Daily. Did the authors measure their blood sugar? The article's abstract states :

Self-control consumes a lot of glucose in the brain, suggesting that low glucose and poor glucose metabolism are linked to aggression and violence.

Knowing this, it is imperative to know how well each participant metabolizes glucose. Probably more important would be to know the number of men and women in each population. The abstract goes on :

Study 1 found that participants who consumed a glucose beverage behaved less aggressively than did participants who consumed a placebo beverage. Study 2 found an indirect relationship between diabetes (a disorder marked by low glucose levels and poor glucose metabolism) and aggressiveness through low self-control. Study 3 found that states with high diabetes rates also had high violent crime rates. Study 4 found that countries with high rates of glucose-6-phosphate dehydrogenase deficiency (a metabolic disorder related to low glucose levels) also had higher killings rates, both war related and non-war related. All four studies suggest that a spoonful of sugar helps aggressive and violent behaviors go down.

Regarding Study 3 : I wonder what the relative levels of poverty are in these states.

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