(CNN) - Over the years, resveratrol, an antioxidant found in grapes, chocolate and red wine, has been touted as a possible antidote to Alzheimer's disease, cancer, diabetes and many other conditions. Now, the first study in people with Alzheimer's suggests that the compound, when taken in concentrated doses, may actually have benefit in slowing progression of this disease.

Researchers at 21 medical centers across the United States looked at the safety and effectiveness of taking high doses of resveratrol in an experimental pill -- equal to the amount found in 1,000 bottles of red wine -- in people with mild to moderate Alzheimer's.

The researchers looked at several biomarkers of Alzheimer's, and found that people who took up to four pills a day for a year had higher levels of amyloid-beta proteins in their spinal fluid than those who took a placebo (control) pill.

Although accumulation of amyloid-beta in the brain is a hallmark of Alzheimer's disease, patients actually have lower levels of this protein outside of the brain. The study finding suggests that resveratrol could help change the balance from amyloid-beta buildup in the brain to circulating protein in the body.

Even if concentrated forms of resveratrol pills like the kind used in this study were available, it's too soon to recommend going out and getting some just yet.

"The study is encouraging enough that we should certainly go ahead and do a [larger] clinical trial because we showed that it is safe and does have significant effects on Alzheimer's biomarkers," said Dr. R. Scott Turner, professor of neurology at Georgetown University Medical Center and lead investigator of the study, which was published on Friday in the journal Neurology.

The main goal of the current study, which included 119 patients, was to find out whether high doses of resveratrol could be safe. The only small concern they found was that patients taking resveratrol lost about two pounds during the one-year study, and weight loss is already a problem with Alzheimer's, Turner said. In comparison, the control group gained about 1 pound.

Much more research is needed

The study was not big enough to answer some important questions, such as whether patients taking resveratrol actually had lower levels of amyloid-beta plaques in their brain, and most importantly, whether they experienced less decline in their mental faculties.

A large, phase 3 clinical trial getting at these issues could start in as soon as a year, Turner said. (The current study was a phase 2 trial, typically meant to evaluate safety and get an early look at efficacy of a new drug.)