NEW YORK (CBSNewYork) — Cigarettes are out, ramen is in.

The noodles are replacing cigarettes as a form of currency in prisons, but it’s not because of a ban on tobacco products, according to a recent study.

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According to University of Arizona School of Sociology doctoral candidate Michael Gibson-Light, the ramen trade is booming behind bars because inmates are getting hungry.

Ramen’s popularity comes as a result of ‘punitive frugality’ which means the burden of care is moving from the system to prisoners and their support networks, Science Daily reported.

“Punitive frugality is not a formal prison policy, but rather an observable trend in prison administration practice in institutions throughout the country,” Gibson-Light said. “Services are cut back and many costs are passed on to inmates in an effort to respond to calls to remain both tough on crime and cost effective.”

As Science Daily reported, the U.S. Bureau of Prisons spent $48.5-billion on corrections in 2010, which marked a 5.6 percent decline from 2009. Since 1982 state corrections expenditures have not kept up with the prison population.

Gibson-Light studied 60 inmates and prison staff members between May 2015 and May 2016. He found that the rise in the ramen trade came as prisoners became unhappy with their food choices and sought a cheap, tasty, high calorie alternative.

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“Prisoners are so unhappy with the quality and quantity of prison food that they receive that they have begun relying on ramen noodles — a cheap, durable food product — as a form of money in the underground economy,” he said. “Because it is cheap, tasty, and rich in calories, ramen has become so valuable that it is used to exchange for other goods.”

The dorm room –and apparent prison staple — has been used to trade for “other food items, clothing, hygiene products, and even services, such as laundry and bunk cleaning… as bargaining chips in gambling when playing card games or participating in football pools.”

Gibson-Light said the study — which will be presented at 111th Annual Meeting of the American Sociological Association (ASA) — highlights the connection between prison practices and the lives of inmates.

“What we are seeing is a collective response — across inmate populations and security levels, across prison cliques and racial groups, and even across states — to changes and cutbacks in prison food services,” he said.

He said similar trends can be found even where prisons have not banned tobacco products, and that a deeper study is needed as changes in prison currency are far from common, and that inmate quality of life could be at stake.

“The form of money is not something that changes often or easily, even in the prison underground economy; it takes a major issue or shock to initiate such a change,” he said. “The use of cigarettes as money in U.S. prisons happened in American Civil War military prisons and likely far earlier. The fact that this practice has suddenly changed has potentially serious implications.”

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In addition to cigarettes, ramen has also started to replace stamps and envelopes as a form of prison currency.