SALT LAKE CITY Oct 16, 2006 (AP)— Hair strands reveal evidence of a person's diet and can help doctors diagnose eating disorders, researchers at Brigham Young University reported.

Researchers found differences in nitrogen and carbon when samples from females at an eating-disorder clinic were compared with hair from females who didn't have a problem. They said they were able to accurately determine the source 80 percent of the time.

The lead author, Kent Hatch, said hair acts like a "tape recorder."

Just as it can be used to determine if someone has used drugs or has been exposed to harmful amounts of mercury and lead, hair can show what someone has been eating, Hatch said.

Larger studies are planned to possibly develop a test that can be used in clinics. The research was published Monday in a journal, Rapid Communications in Mass Spectrometry.

"This would give a clinician an objective measure to use to diagnose an eating disorder, and we hope it will eventually allow a sound diagnosis at an earlier stage," said Hatch, a professor in BYU's department of integrative biology.

A test is needed in the diagnosis of eating disorders because those who suffer from them tend to be secretive about their problem or may not even know they are ill.

"Their self-evaluation is very impaired," said Jennifer Tolman, clinical director at Avalon Hills, a treatment facility in Cache County, Utah.

"We had a girl who was 5-10 and 98 pounds and she wasn't even sure she had an eating disorder, although she could recognize it in others," Tolman said.

Doctors and therapists often must rely upon patients to report what and how much they eat, information that can be unreliable.

"They are poor historians by nature," Tolman said.

She had not seen the BYU study and declined to comment on the findings. Tolman said damage from eating disorders heart problems, elevated liver enzymes, drops in bone density can be irreversible and sometimes life threatening.

The BYU research was conducted by faculty in integrative biology, communications, statistics and geology.

A co-author, Steven Thomsen, said the project grew from earlier research on the link between eating disorders and exposure to fashion, fitness and beauty magazines. He told his colleagues it would be helpful to biologically determine the same results.

"We have talked about going back and re-exploring some of the things we've studied and adding this variable," Thomsen said of the hair test.

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