You'll find nisin in quite a lot of your food — particularly the food that has to be shelf-stable. Some people look askance at preservatives, but not only is this one all-natural, it has just been shown to kill tumour cells and antibiotic resistant bacteria. A recent article in the Journal of Antimicrobial Chemotherapy, with the refreshing short title of "Biomedical Applications of Nisin" details the work of scientists at the University of Michigan. They have found that nisin might be a way to combat two of the great medical problems of our time.
Nisin is a bacteriocin, a protein put out by bacteria to kill off the competition. Bacteriocins, especially nisin, are common among lactic acid bacteria — the bacteria that are responsible for turning milk into cheese, yoghurt and other dairy products. It's one of the reasons obviously spoiled milk is safe to eat. Nisin was too good a bactericidal agent to keep to the dairy aisle, so food manufacturers added it to processed meats, dips, salad dressings and soups. It's safe, it's natural and now it looks like it could help people stay alive.
The researchers from the University of Michigan gave mice with head and neck tumours a huge dose of a highly purified version of nisin over nine weeks. At the end of the treatment, the nisin had killed between 70 and 80 per cent of the tumour cells.
Nisin also kills off bacteria — including MRSA. First it breaks up biofilms, slimy colonies of bacteria that stick together to protect themselves from other bactericidal influences. When nisin attacks an individual bacterium, it binds to the bacteria and prevents it from pumping up its defences and turning into a "superbug". Just to top things off, the researchers believe that nisin may activate the host's immune response, helping the body itself fight bacterial infections.
So far, the tumour-killing applications of nisin have only been shown to happen in mice. A similar dosage scaled up for humans would be something like twenty to thirty Advil-sized tablets of highly purified nisin. Still, this is good news. We may have a natural, relatively easy-to-get way to fight both cancer and life-threatening bacterial infections.