Irritable. Cranky. Impatient.
Are these the signs of an unhappy partner or a hungry partner? New evidence suggests that low blood sugar may indeed be linked to relationship disputes (Bushman, DeWall, Pond, & Hanus, 2014).
In a scientific study using glucose measurements and, yes, voodoo dolls, researchers showed us empirically what many of us have guessed for years: Being "hangry"—angry because you're hungry—doesn't make for a happy marriage. The idea that hunger corresponds with a short temper is not just in your imagination. Bushman and colleagues (2014) suggest that reduced blood sugar (i.e., glucose) might lower self-control, one of the most powerful tools for successfully navigating relationship conflicts.
So grab a cookie and read on: Staving off hunger may be a key to peaceful relationships.
What Is Self-Control?
Self-control is often conceptualized like a muscle, a limited resource that can be used up in the same way that muscles become tired (Muraven & Baumeister, 2000; for an alternative perspective, see Beedie & Lane, 2012). Many everyday behaviors dip into our self-control resources. And any action that requires self-discipline—quitting smoking; resisting sweets; dealing with an annoying boss; herding unwieldy children; refraining from saying what you actually think—has the potential to deplete your self-control.
When people are low in self-control, they tend to act more impulsively instead of carefully regulating their own behavior. Such failures in self-regulation can result in unintended shopping sprees or late-night Oreo binges, but they might also have interpersonal consequences. For example, temporary self-control deficits are linked to aggressive behavior (DeWall, Baumeister, Stillman, & Gailliot, 2007), especially for individuals who have less self-control to begin with.
How Is Eating Related to Self-Control?
Feel like you’re lacking willpower? Maybe you’re really just low in blood sugar.
In a series of nine studies, Gailliot and colleagues (2007) suggested that exerting willpower takes energy, in the form of glucose. They observed that after individuals do a difficult task that requires self-control, they have lower levels of glucose. These lower levels of blood sugar correspond with less exertion of self-control in subsequent activities. Gailliot and colleagues (2007) also demonstrated that after a demanding activity (the kind that depletes willpower), consuming sugary lemonade instead of lemonade made with artificial sweetener seemed to lessen the negative effects of the depletion task.
In other words, self-control seems to require sugar to operate effectively, and the taste alone of real glucose might be enough to do the trick (Hagger & Chatzisarantis, 2013).
Food for Love
Now let’s think about romantic relationships. In their recent study, Bushman and colleagues (2014) focused on the intersection between biological needs and social interactions. Their idea was simple and compelling: Low blood sugar might inhibit self-control and thereby produce anger and aggression in even the most intimate relationships.
To begin, the researchers taught approximately 100 couples how to measure their own glucose levels, and then asked them to take these measurements twice a day (after breakfast and after dinner). These couples were also given voodoo dolls and a set of 51 pins. The researchers asked participants to stick pins in their doll each evening to the extent that they were angry at their spouse. Naturally, they were asked to do this privately, away from their spouse. The pins served as a measure of aggressive impulses.
After the 21 days of glucose measuring and voodoo-doll stabbing, couples paid a visit to the lab. They then played a game and thought they were competing against each other, but they were really playing against a computer. The winner of each round won the chance to blast his or her partner with a horrible, nails-on-chalkboard, crying-babies sound. So the question was: How loud and long did they blast their partner? The sound volume and duration served as a measure of aggressive behavior.
If You’re Hangry and You Know It
So what did the researchers find? People with lower levels of glucose tended to stab their voodoo dolls with more pins (i.e., had more aggressive impulses) and also tended to give longer and louder noise blasts (i.e., showed more aggressive behaviors).
Grab a granola bar and contemplate this idea: Sometimes angry fighting and bickering doesn’t originate within the couple dynamic itself, but rather emerges from situational states (i.e., like hunger) that could potentially be resolved through a yummy snack.
Does this really mean everyone should feed their partners candy bars at the first sign of a quibble? No—but maybe. Assuming self-control is glucose driven, gnawing on a candy bar may deliver a sugar rush, but that rush might be followed later by a sugar crash. Such a rollercoaster might be worse than having stable, if slightly low, blood sugar. Perhaps a simple take-away is to make sure you’re not hungry before sitting down as a couple to discuss an important issue.
Will glucose solve all marital conflicts? Definitely not. We need to be careful about the inferences we draw from this one study. While it reveals important connections (i.e., less blood sugar, more partner anger and aggression), we need more evidence to support the idea that lower blood sugar causes interpersonal aggression and that self-control is the mechanism that explains this potential association. Self-control is by many, many accounts a central component to successful interpersonal relations, and every bit of knowledge we can gain about its origins and influences has important implications for psychological health and well-being.
Beedie, C. J., & Lane, A. M. (2012). The role of glucose in self-control another look at the evidence and an alternative conceptualization. Personality and Social Psychology Review, 16, 143-153.
Bushman, B. J., DeWall, C. N., Pond, R. S., & Hanus, M. D. (2014) Low glucose relates to greater aggression in married couples. PNAS.
DeWall, C. N., Baumeister, R. F., Stillman, T. F., & Gailliot, M. T. (2007). Violence restrained: Effects of self-regulation and its depletion on aggression. Journal of Experimental Social Psychology, 43(1), 62-76.
Gailliot, M. T., Baumeister, R. F., DeWall, C. N., Maner, J. K., Plant, E. A., Tice, D. M., ... & Schmeichel, B. J. (2007). Self-control relies on glucose as a limited energy source: willpower is more than a metaphor. Journal of Personality and Social Psychology, 92, 325-336.
Hagger, M. S., & Chatzisarantis, N. L. (2013). The sweet taste of success the presence of glucose in the oral cavity moderates the depletion of self-control resources. Personality and Social Psychology Bulletin, 39, 28-42.
Muraven, M., & Baumeister, R. F. (2000). Self-regulation and depletion of limited resources: Does self-control resemble a muscle? Psychological Bulletin, 126, 247-259.