Ruminations: Ravenous, Are We?

"We've discovered that you really need that gut signalling to have long, sustained reduction in AgRP activity."
"In the absence of that gut signalling, you really don't shut off these hunger neurons."
"[Hanger researchers identify neuron activity in the hypothalamus, a brain region co-ordinating hunger and emotion. Hunger activates these brain cells known as AgRP neurons for the proteins they express. These neurons are colloquially spoken of as 'hangry neurons']."
Amber Alhadeff, researcher, Monell Chemical Senses Center, Philadelphia

Scientists asked participants to record their emotions and hunger levels five times a day for three weeks. Pexels

Researchers are now beginning to make biological sense of how our brains and emotions are affected by what we eat, or what we fail to eat when we should. A study out of Britain concludes that the feeling of hunger is associated with emotions on the negative scale. The word "hangry" was added to the Oxford English Dictionary in 2018 in recognition of its acceptance as a real phenomenon. Not everyone becomes angry when they are hungry, but many do.

And the very link between hunger and mood has long been known, but never before ascribed to biological connections with hormones. Messages are hormonally sent everywhere in the body, travelling through the bloodstream. Research being undertaken at present focuses for the most part on the body communication system through hormones and neurons. Hunger coincides with a drop in glucose linking to hormonal changes affecting brain functioning.

Eating something can raise low blood glucose; a combination of protein, fibre and complex carbohydrates works best to raise blood glucose. Low blood glucose instructs the body to release adrenalin and cortisol, hormones that naturally raise blood sugar, enabling function even with a drop in blood sugar. On the other hand, cortisol and adrenalin flooding the bloodstream creates a natural reaction of alertness to threats. High alert in combination with hunger can result in irritability associated with hanger.

Dr. Alhadeff's laboratory at the Monell Chemical Senses Center studies food intake behaviour and how gut-brain communication influences what we eat. When lack of food activates AgRP neurons in mice, a signal of hunger is sent by the neurons. The cells also signal a "negative valence"; an emotion of discomfort generally associated with fear, anxiety and anger. Once the mice eat, AgRP neurons calm and both hunger and negativity signals abruptly halt.

Dr. Alhadeff hypothesizes hungry neurons to represent remnants of a era in distant human history when people foraged for food and more than just hunger was needed to motivate us to find food. This neuron group still has a lasting impact.