In the quest to determine why some people remain in good physical and mental health until a very old age and others don't, scientists working with fruit flies suggest that a factor of healthy aging could be found in the gut.

Other recent studies have begun connecting diseases such as diabetes and Parkinson's to changes in gut bacteria, although they have not pinpointed the ideal composition.

"Age-onset decline is very tightly linked to changes within the community of gut microbes," says senior author David Walker of the University of California, Los Angeles in the US. "With age, the number of bacterial cells increase substantially and the composition of bacterial groups changes."

The research team used fruit flies because of their short life span -- which lasts an average of eight weeks -- and the diverse ages at which they die.

"One of the big questions in the biology of aging relates to the large variation in how we age and how long we live," says Walker.

What's more, scientists have identified all the genes of the fruit fly, and are able to switch them on and off individually.

Springboarding off previous research in which they observed that the flies develop leaky guts within days before dying, they analyzed the gut bacteria -- collectively referred to as the microbiota -- of more than 10,000 female flies.

They isolated a group of flies to which they gave antibiotics to reduce the number of species found in the intestinal tract, resulting in improved digestive function as they aged.

"When we prevented the changes in the intestinal microbiota that were linked to the flies' imminent death by feeding them antibiotics, we dramatically extended their lives and improved their health," says Walker.

After leaking began, flies that had been given antibiotics lived an average of 20 days, which represents a substantial chunk of time considering their average lifespan.

"The health of the intestine -- in particular the maintenance of the barrier protecting the rest of the body from the contents of the gut -- is very important and might break down with aging," says lead author Rebecca Clark of Durham University in the UK.

In collaboration with professors at the Scripps Research Institute in Florida, the team produced a group of germ-free flies, whose guts were barren of microbes.

These flies lived for an estimated average of 80 days, about one and a half times longer than the un-doctored flies.

The study, which follows on the heels of another in which scientists mapped out how microbiota change over the course of a lifetime, was published in the journal Cell Reports.