The study, set to begin in South Carolina in January, is part of the Defense Department's heightened focus on suicide prevention as the number of service members attempting to take their own lives has risen.

There were 17,754 suicide attempts among veterans last year - about 48 a day - up from 10,888 in 2009, according to data from the Department of Veterans Affairs. In July of this year, 26 active-duty soldiers were believed to have committed suicide, the most ever recorded in a month since the U.S. Army began tracking such deaths.

The first part of the new clinical trial will examine the effects of daily omega-3 fatty acid supplements on about 320 at-risk military personnel and veterans, said researcher Ron Acierno, director of the post-traumatic stress disorder clinic at the Veterans Affairs medical center in Charleston.

Omega-3 fatty acids, which are found in fish oil and not produced by the human body, are instrumental in repair and regeneration of brain cells, Acierno said.

"The thinking is that the areas of the brain that are affected by this lack of a regenerative advantage of omega-3 also play a role in depression and other emotional disorders, and by proxy, suicide," he said.

Those considered to be at risk have talked about suicide, he said. Researchers will also include people with alcohol problems, post-traumatic stress disorder and depression.

They will be given two commercially available "juice boxes" of omega-3 fatty acids a day, Acierno said.

"It doesn't taste like medicine at all," he said. "Here you have a very cheap intervention with very few side effects that could have significant impacts."

The study will be funded by taxpayer dollars allotted by the Defense Department. It will be conducted by researchers at the Medical University of South Carolina, the Ralph H. Johnson VA Medical Center in Charleston and the National Institute on Alcohol Abuse and Alcoholism.

On average, about 100 Americans die each day from suicide, officials said. More that 8 million U.S. adults seriously thought about suicide in the last year, according to the Substance Abuse and Mental Health Services Administration.

Among military members, the rate of suicide in non-combat personnel is slightly higher than the rate of combat personnel, Acierno said.

"The problem of suicide is big," Acierno said. "But the problem of suicidality is massive, and that is having these suicidal thoughts. We don't want people to even have these thoughts or, if they are having them, to not have them as frequently." (Editing by Colleen Jenkins and Paul Simao and Andre Grenon)

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