Spouses Grouse as Low Blood-Sugar Level Spurs Crankiness

Apr 14, 2014 5:45 pm ET

(Updates with professor’s comments in 10th paragraph.)

April 14 (Bloomberg) -- Serious discussions between spouses shouldn’t take place on an empty stomach, a study suggests.

Husbands and wives reported being most unhappy with their spouses when their blood-sugar levels were lowest, usually at night, according to research released today in the Proceedings of the National Academy of Sciences. Missing a meal, dieting or just being hungry may be the reason, researchers said.

Sugar, or glucose, is used by the brain as fuel to help regulate self-control. Without the fuel, it is more difficult for people to control emotions like anger and aggression, researchers said. Today’s findings are among the first to show how low sugar levels in the body may play a part in marital arguments, confrontations and even domestic violence, said Brad Bushman, the lead study author.

“Self-control comes in part from the fuel we give our brains. This is one of the few physiological aspects we can control,” said Bushman, a professor of communication and psychology at Ohio State University in Columbus, in a telephone interview today. “People who are hungry are often very cranky.”

Researchers in the study included 107 married couples who for 21 days had to test their blood-sugar levels before breakfast in the morning and before bed in evening. They were also given voodoo dolls representing their spouses and told to insert as many as 51 pins daily depending on how angry they were with their partner. The researchers were testing aggressive impulses.

Measuring Aggression

Those with the lowest nighttime blood-sugar levels inserted the most pins, while those with the highest glucose levels inserted the least, the study found. Women tended to stick more pins into their husband voodoo doll, but the finding wasn’t significant. The authors only found the association for nighttime blood glucose levels as the amount of sugar in the body drops throughout the day, Bushman said.

After 21 days, the couples went into a laboratory where they were told they would compete with their spouse to see who could press a button the fastest to test aggressive behavior. The winners could blast their spouse with a loud noise through headphones. The spouses in reality were playing against a computer, not each other.

The researchers found that those with the lowest average nighttime blood-sugar levels sent louder and longer noises to their spouse no matter how good their relationship was or whether they were male or female.

Timing Important

“If couples have a sensitive topic to discuss, it would be really smart to do it over dinner or better yet after dinner,” Bushman said. “They should definitely not do it on an empty stomach.”

Low blood sugar can trigger hormones that activate the body’s “fight or flight” system and cause people to become more aggressive, anxious and irritable, said Timothy Graham, who wasn’t an author of today’s study.

For families with someone who has diabetes, where swings between highs and lows can occur more often, he suggests counseling. For others, regular, small meals throughout the day may help keep blood sugar levels consistent and help prevent dips that can cause aggression.

“Probably more regular and healthy meals could improve the dynamics of a relationship,” Graham, an assistant professor of medicine at the University of Utah in Salt Lake City, said in a telephone interview.