Effects of Hunger on Serotonin

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CAMBRIDGE, England — The consequences of prolonged hunger are blatant and startling. A bloated stomach due to kwashiorkor, perpetual fatigue due to lack of protein and carbohydrates, the general atrophy of the body — these symptoms shock and disturb viewers. There are, however, other symptoms of starvation less blatant than a visible ribcage. Hunger affects the way humans think and act.

The psychological effects of hunger originate in chemical reactions in the brain involving serotonin, a neurotransmitter. Neurotransmitters are chemical messengers sent from neuron to neuron across gaps called synaptic clefts. Serotonin is released from one neuron into this gap to be received by specific receptors on adjacent neurons. This is how brain cells communicate and why we act like we do.

Most of the serotonin in humans–about 90 percent of it–regulates intestinal movements, targeting the gastrointestinal tract. The rest regulates mood, appetite and sleep, and it is also thought to contribute to feelings of well-being and happiness. Serotonin is released when humans begin to consume food.

For this reason, when a person’s intake of food is reduced, so are his or her serotonin levels. The inaction of the intestinal system precludes serotonin release, and there are unfortunate consequences: anxiety, stress, anger and sadness. A lack of nourishment leads to the depletion of this neurotransmitter, which in turn causes chemically determined, depressed feelings.

Cambridge scientists have also shown in experiments that hunger causes rash action: participants given serotonin-activating food showed less aggression than participants given no food at all.

“The varying levels of serotonin affect the parts of the brain responsible for regulating anger, thus making people more likely to act aggressively when hungry,” said scientists.

This phenomena is seen all throughout the animal kingdom. Predators stalk more dangerous prey the more starved they are, and hungry flies ignore their aversion to carbon dioxide if the smell of rotting fruit is present. Humans, if starved for extended periods of time, may act similarly, taking more risks such as eating rotting food or stealing from others.

Grunwald-Kadow, the scientist who headed a study testing the decisions of both hungry and sated drosophila, said, “It is fascinating to see the extent to which metabolic processes and hunger affect the processing systems in the brain. If a fly is hungry, it will no longer reach balanced decisions.” The same can be said of humans.

There are other non-physical consequences of hunger as well. Notably, as described by 30 Hour Famine, a World Vision event organized in 21 countries in which participants must abstain from food for 30 hours to suffer from hunger, scant food intake delays the development of cognitive abilities. Processes including reading, language, attention, memory and problem solving are put at risk by starvation, especially in young and growing neural circuitry. Irreversible eye damage due to vitamin A deficiency and a lowered IQ can also result.

Although extreme poverty and hunger are difficult to look at, some of the most detrimental effects are neurological, chemical and psychological.

Adam Kaminski

Sources: 30 Hour Famine, Things You Didn’t Know, SciTech Daily
Photo: Searching for the Mind

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