FRIDAY, Sept. 11, 2015 (HealthDay News) -- High doses of resveratrol, a compound found in red wine and berries, may have some activity against Alzheimer's disease, a preliminary clinical trial suggests.
Resveratrol is an antioxidant that certain plants produce to shield against stress from the environment. People ingest small amounts when they eat red grapes, red wine, berries or dark chocolate.
Lab research has suggested that resveratrol might have some powers against the diseases of aging -- including Alzheimer's disease. But evidence from human studies has been lacking.
The new study, published Sept. 11 in Neurology, offers the first evidence that high-dose, "pharmaceutical-grade" resveratrol can get into the brains of people with mild to moderate Alzheimer's.
What's more, it seems to stabilize levels of a protein that is linked to Alzheimer's progression.
The study did not, however, show whether people's symptoms actually stabilized, experts cautioned. The trial was primarily designed to see whether it's even safe and feasible to give Alzheimer's patients such high doses of resveratrol.
Larger, longer trials are still needed to see whether the treatment can slow Alzheimer's progression, said senior researcher Dr. R. Scott Turner, director of the Memory Disorders Program at Georgetown University in Washington, D.C.
"It does appear to be safe, and we did find evidence that resveratrol can get into the brain," Turner said.
However, he added, "we're not ready to recommend it as a treatment for Alzheimer's."
That's not only because the research is ongoing: The product used in the study -- a synthetic, purified version of resveratrol -- is not commercially available.
Resveratrol supplements have long been a staple at health food stores. But there's no telling how much of the compound, if any, is actually in those products, Turner pointed out.
Nor will red wine do the job. "The doses we used were equivalent to what you'd get in about 1,000 bottles of red wine a day," Turner noted.
James Hendrix, director of global science initiatives for the Alzheimer's Association, said the findings are "encouraging" and warrant larger studies.
But he agreed that only time will tell if resveratrol can help slow the dementia process.
Scientists first became interested in resveratrol as an Alzheimer's therapy based on "calorie restriction" research, Turner said. In animals, reduced-calorie diets seem to stall the effects of aging and increase longevity -- at least partly because calorie restriction boosts activity in a gene called SIRT1.
It turns out that resveratrol also activates SIRT1. "So resveratrol essentially mimics calorie restriction," Turner said.
But only small amounts of natural resveratrol from food actually become "bioavailable" in the human body.
So Turner's team tested a pharmaceutical-grade version among 119 older adults with mild to moderate Alzheimer's. All were already taking standard medications for slowing the disease's progression. About half the patients were randomly assigned to add resveratrol capsules, while the rest were given placebo (inactive) capsules.
Over one year, the resveratrol group showed a stabilization in the level of a protein -- called amyloid-beta 40 -- in their spinal fluid. In contrast, those levels declined in the placebo group.
That's important, Hendrix explained, because levels of amyloid-beta 40 in the spinal fluid normally decrease as Alzheimer's worsens. The theory is that more of the protein is being deposited in the brain, where it contributes to the abnormal "plaques" that mark Alzheimer's.
"So this may be an indicator that resveratrol slows disease progression," Hendrix said.
"But," he added, "this is an early finding, and larger, longer studies are still needed."
As for safety, the most common symptoms included nausea and diarrhea, which affected 42 percent of resveratrol users and one-third of placebo users. Some resveratrol users also lost weight -- an average of 2 pounds.
That's potentially concerning, according to Turner. "You don't like to see that," he noted, "because Alzheimer's disease itself also causes weight loss."
A larger, advanced-stage trial of resveratrol is being planned. Until then, Hendrix recommended that Alzheimer's patients stick with their treatment plans -- and speak with their doctor before adding any kind of supplement.
As for preventing Alzheimer's in the first place, Hendrix doubted that there's any "magic pill," resveratrol or otherwise.
But, he said, there is evidence that lifestyle choices can help prevent Alzheimer's, or delay its onset. A healthy diet, regular exercise and staying mentally active could all help.
"What's good for your heart," Hendrix said, "is also good for your brain."
The Alzheimer's Association has more on lowering Alzheimer's risk.