New theory on aging says popping pills and drinking orange juice no guarantee you'll live longer

In direct contrast to previous reports, researchers now say that drinking gallons of orange juice and popping vitamin pills may not be a guarantee that you will live longer.

Scientists in the past have suggested that taking antioxidants to combat free radical cell damage might delay ageing.

But a study by a University of Wisconsin-Madison team has found no proof that highly reactive oxygen molecules are involved, and at least in rodents, the key may be that some cells are committing early suicide.

Both ageing theories do however agree on the involvement of damage to the cell's genetic material - DNA.

The U.S. researchers looked at mice which were genetically engineered to age prematurely, and found that this was because they lacked a protein that effectively proof reads DNA for mistakes.

They found that as mutations or DNA damage accumulates, critical cells die.

Researcher Dr Tomas Prolla says that as a consequence, the altered mice had far more DNA errors within the power houses of cells - structures called mitochondria, and this in turn, prompted cells to die off.

When compared with normal mice, the altered mice were also seen to have developed the obvious signs of ageing, such as gray hair and muscle wasting, but at a much quicker rate.

Dr Prolla says he believes the key to what is happening in ageing is that as mutations or DNA damage accumulates, critical cells die, and these critical cells might include adult stem cells that are essential for replacing the cells that die.

Therefore if these critical stem cells are lost, tissue structure and the ability of tissue to regenerate is damaged.

Dr Prolla has apparently seen similar evidence in tissues such as bone marrow, intestine and hair follicles.

Dr Aubrey de Grey, an expert in ageing research at the University of Cambridge, says the study is important, and supports similar work by other groups over the past few years.

He adds that it would be premature to say that these studies are conclusive, but they certainly imply that cell death, especially of stem cells, can make a big difference to the rate of ageing.

He says caution is necessary because it is impossible to be conclusive about something which shortens life if you accelerate it as it is also lifespan-limiting when it proceeds at its natural rate.

He says in an ideal situation they would develop mice that had better mitochondrial DNA repair and maintenance and lived longer as a result, but as yet they don't have that result.

The study is published in the journal Science.