The search for a cure for Alzheimer's disease has been elusive. A new study explored whether taking high doses of some B vitamins could slow its progression.

Researchers studied 340 people with mild to moderate Alzheimer's disease. The issue was whether large doses of three vitamins – B6, B12 and folic acid – might slow disease progression, including cognitive decline.

“In Alzheimer's disease, the aspect of cognition that is most obviously affected is memory,” said Dr. Paul Aisen with the UC-San Diego School of Medicine.

The study appears in the Journal of the American Medical Association. It focused on reducing levels of an amino acid called homocysteine, which tends to be higher in people with Alzheimer's.

The high dose of B vitamins lowered homocysteine levels, but without slowing disease progression.

The four-year study showed that not only do the high doses of vitamins fail to halt progression of cognitive decline, they might actually result in increased depression in some Alzheimer's patients.

“Unfortunately, the results were disappointing in the sense that this intervention – the high dose of vitamins – did not have a favorable effect on the disease,” Aisen said.

Gary and Mary Paun have been married for 31 years. Their lives changed forever three years ago when Mary began experiencing symptoms of Alzheimer's disease.

“I’m doing the best I can do,” Mary Paun said.

“It just disrupts mostly what we thought was normal life, but it's also brought us a lot closer together,” Gary Paun said.

With every bit of research comes hope for progress.

“I'm frustrated in only the fact that they haven't found a cure yet, but I think the cure is close. I really do,” Gary Paun said.