A common food preservative - Nisin - that is used in over 50 countries, has been found to be effective in slowing down a type of cancer.

Nisin is added in many foods like cheese, meats and beverages. It prevents the food from spoiling by inhibiting the growth of certain bad bacteria.

Researchers from the University of Michigan found that the chemical was effective in slowing down and sometimes even stopping the growth of squamous cell head and neck cancers.

Head and neck cancers account for 3 percent of all cancers in the U.S, says the National Cancer Institute. These cancers begin in the squamous cells that line the moist surfaces of head and neck (inside the mouth, nose or throat).

"The poor five-year survival rates for oral cancer underscore the need to find new therapies for oral cancer. The use of small antibacterial agents, like nisin, to treat cancer is a new approach that holds great promise. Nisin is a perfect example of this potential because it has been used safely in humans for many years, and now the laboratory studies support its anti-tumor potential," Yvonne Kapila, and professor at the University of Michigan School of Dentistry and lead investigator of the study.

Researchers say that the anti-bacterial agent slows down the cancer cells by activating a protein called CHAC1 in cancer cells. This protein is associated with cell death in cancer cells. They speculate that the cell must be dying because Nisin creates pores in the cell membranes that allow calcium to get into the cell. How the calcium mediates cell death, however, isn't clear.

Nisin doesn't harm the normal cells, but only acts on the cancerous cells. The chemical is a strong candidate for further drug trials because millions are consuming Nisin through food every day and the safety of the chemical is well established.

The study is published in the journal Cancer Medicine.