Lower levels of blood sugar may make married people angrier and more aggressive towards their spouses, a new study has found.
Researchers found that people who had generally lower levels of glucose were willing to blast their spouses with unpleasant noises at a higher volume and for a longer time than those who had higher glucose levels.
The study shows that hunger caused by low levels of blood glucose may play a role in marital arguments, confrontations and possibly even some domestic violence, said Brad Bushman, lead author of the study from The Ohio State University.
Blood glucose levels can be brought up most quickly by eating carbohydrates or sugary foods.
"People can relate to this idea that when they get hungry, they get cranky," Bushman said.
It even has a slang term: "hangry" (hungry + angry), researchers said.
"We found that being hangry can affect our behaviour in a bad way, even in our most intimate relationships," he said.
The study involved 107 married couples. It started with the couples completing a relationship satisfaction measure.
All participants were given a voodoo doll that they were told represented their spouse, along with 51 pins.
At the end of each day, for 21 consecutive days, the participants inserted 0 to 51 pins in the doll, depending on how angry they were with their spouse.
They did this alone, without their spouses being present, and recorded the number of pins they stuck in the doll.
Each person also used a blood glucose meter to measure glucose levels before breakfast and every evening before bed for the 21 days.
The lower the participants' evening blood glucose levels, more pins they stuck in the doll representing their spouse.
This association was present even after the researchers took into account the couples' relationship satisfaction.
"When they had lower blood glucose, they felt angrier and took it out on the dolls representing their spouse," Bushman said.
"Even those who reported they had good relationships with their spouses were more likely to express anger if their blood glucose levels were lower," said Bushman.
Bushman said that glucose is fuel for the brain. The self-control needed to deal with anger and aggressive impulses takes energy, and that energy is provided in part by glucose.
"Even though the brain is only 2 per cent of our body weight, it consumes about 20 per cent of our calories. It is a very demanding organ when it comes to energy," he said.
The study appears in the journal PNAS.