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Longer Life Span in Rats Linked to Chromium

October 20, 1992|THOMAS H. MAUGH II | TIMES SCIENCE WRITER

Dietary supplements of the metal chromium can extend the life span of rats by more than one-third and may hold promise in humans, a Minnesota researcher said Monday.

Biochemist Gary W. Evans of Bemidji State University in Minnesota gave a special chromium supplement to 10 rats and compared them to 20 rats that received chromium in a form less readily absorbed. After 41 months, he reported Monday at a San Francisco meeting of the American Aging Assn., 80% of the rats that received the supplement were alive, while all others were dead. The rats getting the supplement lived an average of one year longer than the others.

"That's a real departure from the usual life expectancy patterns," said gerontologist Caleb E. Finch of USC. Evans seems to have found "a new and unexpected potential variable in life span that deserves serious consideration in longer-lived species," Finch said.

Previous research has found that the only factor that could produce substantial increases in life span in animals is a significant reduction in caloric intake. But the chromium supplements can produce an equally large increase without any such restrictions, Evans said.

More than 90% of U.S. adults have a dietary deficiency of chromium, in part because it is not readily absorbed from many foods, said biochemist Richard Anderson of the U.S. Department of Agriculture in Beltsville, Md.

USDA researchers have developed and patented a form of chromium, called chromium picolinate, that is more easily absorbed by the body. That is the form used by Evans.

"This could potentially be a major finding," Anderson said, "but whether it is reproducible remains to be established. . . . There's no reason not to believe it, however."

Because chromium has other beneficial effects as well, Evans said he would "very definitely suggest that people take a multivitamin-multimineral supplement containing chromium picolinate" on a regular basis.

Researchers have been searching for centuries for a magic elixir that would extend human life span. They have found no such elixir, but 60 years ago researchers observed that rats fed a diet containing only 60% to 65% of their normal caloric intake live as much as 50% longer.

Over ensuing decades, researchers have observed similar results in other species ranging from one-cell protozoa to fish and perhaps to primates. One proponent of the theory, UCLA pathologist Roy L. Walford, has nearly doubled the life span of laboratory mice and has gone so far as to start consuming a low-calorie diet himself.

Physiologist Edward Masoro of the University of Texas Health Sciences Center in San Antonio has argued that restricted calorie intake works because it reduces the amount of the sugar glucose circulating in the animals' bloodstreams--a theory that is becoming widely accepted. High levels of glucose damage proteins, a process called glycation, and are responsible for many of the ill effects associated with diabetes.

Masoro and others believe that this accumulation of damaged proteins is one of the major factors that accelerate aging and lead to death.

Evans started his longevity study because he and other researchers have observed in humans that chromium picolinate supplements reduce blood glucose levels and inhibit glycation, apparently by enhancing the activity of the hormone insulin. Preliminary studies suggest that chromium picolinate could thus be very useful in treating Type 2 diabetes, in which naturally occurring insulin is not as effective at controlling blood sugar levels as it should be.

"Because we had seen this decrease in humans, we decided to do an experiment in rats," he said. He found that rats given chromium picolinate had a median life span of 45 months, compared to a median of 33 months for rats receiving less available forms of chromium. Previous studies have shown that rats severely deficient in chromium typically live less than 24 months.

In addition to the increased life span of the rats fed chromium picolinate, Evans reported that their blood glucose levels were reduced about 25% and that the occurrence of glycated proteins in their blood was reduced about 60% by day 1,000 of the experiment.

Evans concedes that the number of animals in his study was small. "This is basically just a pilot study," he said. But he is hopeful that his preliminary success will allow him to obtain funding for a larger study. Such studies are "very expensive," he added.

Because chromium picolinate acts through its influence on insulin, it has a number of other effects on the body.

Studies Evans conducted with Dr. Jack Geller and Dr. Raymond I. Press at Mercy Hospital and Medical Center in San Diego show that it reduces blood cholesterol levels in humans by reducing the concentration of "bad" low-density lipoproteins and increasing the concentrations of "good" high-density lipoproteins.

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