"I joke to people they get up and do the macarena," said Bruce Ames, a professor of molecular biology at the University of California at Berkeley, and lead author of the report. "They're much livelier."

Not only that, but 24-to-28-month-old rodents who ate the antioxidant alpha-lipoic acid in their chow and drank the amino acid known as acetyl-L-carnitine in their water showed marked improvements in short-term memory after only a month on the diet, researchers announced in the current issue of the Proceedings of the National Academy of Sciences. The average life span of a lab rat is two to three years.

In a maze designed to test how fast they learned a routine that rewarded them with food, the elderly rats that did not get diet supplements often went hungry.

"They weren't doing very well. They didn't really seem to know where they were. They were pretty senile rats," said co-author Tory Hagen, an assistant professor of biochemistry and biophysics at Oregon State University.

"We were seeing, over time, that the older animals (on the supplement) seemed to learn faster and their short-term memory and cognitive skills seemed to improve markedly."

Hagen, who is 40, started taking acetyl-L-carnitine and alpha-lipoic acid about a year ago, as soon as he saw what it did to the rodents in his care.

"I feel much more energetic, I'll say that," said Hagen, a biochemist.

The two compounds are made by the body, but they are also found in food: acetyl-L-carnitine in red meats, particularly beef and pork, and alpha-lipoic acid in green leafy vegetables such as broccoli and spinach. Hagen thinks it may be essential to obtain some of the compounds from the diet to augment what the body can produce.

Ames, who is "73, and getting younger every year," and his wife have also been taking the pills for a few months as part of a small clinical trial on humans. The molecular biologist has not noticed much difference in his energy levels or memory, although his wife thinks her skin feels smoother.

Both researchers emphasize their experiences are anecdotal and more research needs to be done before they can draw the same conclusions about the effect of the two compounds on humans.

But both are optimistic that the two compounds, taken together as a diet supplement, will be proven to be a viable way to protect human cells from the ravages of time.