(CNN) Taking a daily multivitamin might be associated with improved brain function in older adults, a new study says, and the benefit appears to be greater for those with a history of cardiovascular disease.
The findings did not surprise the researchers -- rather, they were shocked, said Laura Baker, an author of the study and professor of gerontology and geriatric medicine at Wake Forest University in North Carolina.
"I have to use the word 'shocked,' " Baker said.
The researchers -- from the Wake Forest University School of Medicine, in collaboration with Brigham and Women's Hospital in Boston -- analyzed cognitive function in older adults who were assigned to take either a cocoa extract supplement containing flavonoids, a multivitamin or a placebo every day for three years. No one, not even the researchers, knew who was assigned to which daily routine until the results were revealed.
"We really believed that the cocoa extract was going to have some benefits for cognition based on prior reports of cardiovascular benefit. So we're waiting for that big reveal in our data analysis -- and it was not cocoa extract that benefited cognition but rather the multivitamin," Baker said. "We are excited because our findings have uncovered a new avenue for investigation -- for a simple, accessible, safe, inexpensive intervention that could have the potential to provide a layer of protection against cognitive decline."
But she added that she and her team are not ready to recommend that older adults immediately add a daily multivitamin to their routine based on these results alone.
The findings, published Wednesday in Alzheimer's & Dementia: The Journal of the Alzheimer's Association, are not definitive and cannot be generalized to the public. More research is needed to confirm them.
"It's too soon to make these recommendations," Baker said. "I feel like we need to do this in one other study."
The new study included 2,262 people, 65 and older, who were enrolled between August 2016 and August 2017 and followed for three years. The participants completed tests over the phone annually to evaluate their cognitive function. They were scored on recalling stories, showing verbal fluency and ordering digits, among other tests.
The researchers analyzed function, based on test scores, among those who took cocoa extract daily compared with a placebo, and among those who took the daily multivitamin compared with a placebo.
The researchers found that three years of taking the multivitamin appeared to have slowed cognitive aging by 1.8 years, or 60%, compared with the placebo. Daily cocoa extract supplementation for three years did not affect cognitive function, the researchers wrote.
The study -- supported by the National Institute on Aging of the National Institutes of Health -- also found that multivitamins were most beneficial for older adults who had a history of cardiovascular disease.
"It's well-known that those with cardiovascular risk factors could have lower levels in their blood of vitamins and minerals. So supplementing those vitamins and minerals could improve cardiovascular health and, by virtue of that, improve cognitive health -- and we know that there's a strong connection between cardiovascular health and brain health," said Dr. Keith Vossel, a professor of neurology and director of the Mary S. Easton Center for Alzheimer's Research and Care at the University of California, Los Angeles.
Thanks to that connection between cardiovascular and brain health, taking steps to prevent cardiovascular disease or other chronic diseases -- such as maintaining a healthy diet and exercise -- can benefit the brain too, said Vossel, who was not involved in the new study.
"If we can really eliminate or really prevent chronic diseases, we could prevent dementias," he said. "Roughly up to 40% of dementia could be prevented with just better preventative measures throughout life's span."
The specific factors driving this link between a multivitamin and cognitive function are unclear and require more research, but Baker and her team think the findings might be connected to the way multivitamins can benefit people who might be lacking in micronutrients such as vitamin C, vitamin E, magnesium or zinc.
"With aging, the situation can get worse. A lot of our older adults do not have adequate nutrition for a number of reasons," Baker said.
"As we get older, we are more likely to have medical conditions that can compromise micronutrient sufficiency," she said. "The medications that we take for these conditions can also affect micronutrient sufficiency by interfering with the body's ability to absorb these essential nutrients from the diet."
Other studies have had mixed results in the association between certain vitamins and supplements and dementia risk, Vossel warned.
"We've been down this road a little before with vitamins and dementia research. For many years, dementia specialists were recommending vitamin E based on some early promising results with vitamin E and cognition, and especially those with Alzheimer's disease. But then, the results have been mixed since then," Vossel said.
Older adults should talk to their primary care physician before starting a vitamin or supplement routine, he added.
"Supplementing is usually safe, but it needs to be monitored carefully, especially for those who have memory loss, because overdosing with vitamins can be very dangerous," Vossel said. "Even with vitamin E overdosing or taking high levels of vitamin E can increase the risk of bleeding. So these are just some considerations."
Overall, the new study's findings are encouraging, said Heather Snyder, vice president of medical and scientific relations at the Alzheimer's Association.
"There's certainly follow-up work that we need to see happen -- particularly independent confirmation in studies that are in larger and more diverse populations -- but this is encouraging," she said. "There is more research that needs to be done to understand what it might be in the multivitamin that may have a benefit."