Washington, Aug 24 (IANS): US prisons have seen a change in trend with instant noodles replacing cigarettes as the most popular commodity there, a new study shows.

Study author Michael Gibson-Light said due to the worsening quality of food provided by the prisons, inmates found themselves craving for a tastier substitute that's cheap and durable, whose features are owned by Ramen noodles, Efe news reported .

As the hard currency in the closed economy of the prison, the noodle packs can be used as exchange for other food items, clothing or hygiene products.

Gibson-Light admitted that his research was done on a limited sample, but said the result is logical as prison budgets have not kept up with their exploding populations.

According to news reports, the number of convicts grew 343 per cent from 1980 to 2013, while the budgets for services were stagnant.

"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," Gibson-Light said.