Hungry men and women with low blood sugar are significantly more likely to angrily lash out at their spouse or romantic partner, according to a new study.
The study, published in the Proceedings of the National Academy of Sciences (PNAS), set out to determine if low blood sugar levels, a determinant of hunger, encouraged aggressive emotional responses and limited patience.
According to the study, researchers asked 107 married couples to keep track of their blood glucose by testing their levels once in the morning and once in the evening for 21 days. At the end of every night, the spouses were asked to privately stick needles into "voodoo dolls" provided by the research team. The number of needles they stuck in the doll served as an indicator of just how angry they were at their spouse that day. There were 51 needles provided to each participant in all - just enough to cover the entire doll with needles.
According to the researchers, even after accounting for influential extraneous variables, such as overall relationship satisfaction, the team was able to determine that on days that people had lower overall glucose levels, they were more likely to stick a high number of pins into the doll, compared to days with high or healthy glucose levels.
In a second experiment, the researchers asked the same couples come into their lab to play a computer game against one another while sitting in different rooms. In reality, the participants were actually playing against a computer player rigged to win and lose an equal number of rounds. After winning a round, victors were given the option to blast an irritating noise at a selected volume into the ears of their perceived opponent. The selected levels were recorded after each victory.
Predictably, the researchers found that people with frequent lower glucose levels, who likewise more often put a high numbers of needles into the voodoo dolls, tended to blast the noise at the highest volumes - an example of aggressive behavior.
With these results, the authors of the study concluded that a defining factor in domestic abuse, physical or emotional, may simply be hunger, as energy is needed by the brain to restrain aggressive tendencies.
"Even though the brain is only two percent of our body weight, it consumes about 20 percent of our calories. It is a very demanding organ when it comes to energy," Brad Bushman, lead author of the study said in a statement. "It's simple advice but it works: Before you have a difficult conversation with your spouse, make sure you're not hungry."
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