Come around 5pm after a long day, you can’t really concentrate on anything and your stomach is grumbling. Everyone is annoying and the anger sets in. So why do we get angry when we are hungry? What is the link between emotion and hunger levels? Experimental research has ranged from quantifiying the amount of stabbing of a voodoo dolls and correlating that with blood sugar levels to sophisticated brain imaging techniques that look at blood flow in the brain. Through this exploration into our criss crossing physiological and psycholoical pathways scientists have discovered two key molecules that could be responsible.
Number one: The hormone ghrelin. It is a potent orexigenic that stimulates hunger. Released by the gut when food intake is low the hormone acts on the hypothalamus, this particular region is also involved in the generation and physical expression of emotions. Concentrations of ghrelin increase just before meal time when nutrients are low and after eating, protein, carbohydrates and fats consumed slow down ghrelin release to varying degrees. A protein and carbohydrate heavy meal will lead to the greatest decrease explaining why these foods keep you fuller longer.
In addition to stimulating feelings of hunger, ghrelin can produce an anxiety response, which can contribute to the feelings of anger. In the hypothalamus ghrelin binds to special neurons that stimulate the release of the neurotransmitter orexin. Binding stops the neurons from producting orexin and low levels are associated with anxiety and sadness.
Number two: The neurotransmitter serotonin. It has many functions in the human body such as controlling memory and the perception of pleasure and pain. Levels of the neurotransmitter rise and fall in correlation with food intake. With low serotonin levels comes anxiety, depression and insomnia making us very, very hangry! A study released by researchers at the University of Cambridge used functional magnetic resonance imaging to reveal that low serotonin made communications between certain parts of the brain weaker than normal which makes it harder for the brain to control emotional responses to anger.
Getting to the bottom of why we get hangry leads to only more questions about the crossing biochemical pathways of physical hunger and emotion. Do you ever experience stracking – stress-snacking? This could be due to high levels of cortisol. The stress hormone is released from adrenal glands and affects the function of the hippocampus. What about brunchies? Bored-munchies. Or chocomotional and drunkies! The list could go on, so a simple solution to avoid this array of emotional discomfort is to make sure to eat regularly even during busy days in the library, lecture theatre and local pub!