After two years of investigation, academic researchers have come to a place that may surprise many close observers: They have found no direct correlation between nutrition and dementia risk.

More study is needed on how diet and nutrition impacts brain function as people age, the scientists declared.

The Nutrition and Dementia Working Group, a team of scientists and researchers led by University of Southern California Professor Hussein Yassine, conducted a two-year study of the existing research on nutrition and dementia and identified several major limitations to existing research on the topic.

“Many trials have not found that making people eat healthy or exercise is translating into benefits in the ways that is expected from the epidemiological research,” said Yassine, MD, associate professor of medicine and neurology at the Keck School of Medicine of USC and the Kenneth and Bette Volk Chair of Neurology of USC, in a news release. “That means either there is no causal connection or that these studies have not been properly designed.”

Yassine noted that one of the limitations of previous studies regarding the relationship between nutrition and dementia risk is that those studies may have not been conducted over a long enough period of time to produce meaningful results. 

“If it takes five to 10 years, then studies that lasted for two years or less are not accurately reflecting the effect of the diet on cognition,” he said in the release.

Much of the previous clinical research does not consider other risk factors that could impact cognition, such as where a person lives, other personal lifestyle choices and whether they have access to proper medical care, study authors said. Also, the working group’s research found there needs to be more research into the dietary preferences of underrepresented groups, who are often disproportionately impacted by dementia.

The working group suggested the use of biomarkers and new technology such as brain imaging may be better indicators than cognition tests of whether nutrition can have positive benefits on cognitive health over time. 

The researchers also suggested future studies should consider using small, personalized trials that take into account participants’ genetic makeup, diet and other factors, rather than relying on randomized controlled trials.

The research was funded by the National Institute of Aging and the Alzheimer’s Association and appeared in The Lancet Healthy Longevity Journal.