New UGA study describes why more of us should be eating our kale and spinach

Athens, Ga. – Research from the University of Georgia is the first to show that adding lutein and zeaxanthin, compounds found in dark leafy greens, to the diets of older men and women improves cognitive function in a randomized controlled trial.

Lutein and zeaxanthin are part of the carotenoid family, the pigment compounds that give plants and vegetables their color. The body doesn’t produce lutein and zeaxanthin on its own, so they must be consumed from food.

“We are very dependent on our dietary intake to maintain our biology,” said Billy R. Hammond, psychology professor in the Franklin College of Arts and Sciences and lead author on the study.

Every tissue in our body, he said, relies on various components of our diet, and phytochemicals such as lutein and zeaxanthin seem to be particularly important.

The study caps more than 10 years of work looking at lutein’s role in brain health, said Lisa Renzi-Hammond, an assistant professor of health promotion and behavior in UGA’s College of Public Health and study co-author.

The randomized controlled trial was designed to test whether supplementing lutein and zeaxanthin in the diet would improve brain function over time, thus suggesting that cognition and brain speed can be protected as we age.

The researchers randomly assigned 62 adults over age 60 into two groups, one taking a lutein and zeaxanthin supplement and one taking a placebo. Participants completed a series of cognitive tests to determine their baseline brain function and repeated same series of tests at 4-month intervals.

After one year of supplementation with lutein and zeaxanthin, participants who took the supplement had improved complex attention, executive function and mental flexibility compared to those who took the placebo. These functions, according to Renzi-Hammond, can lead to improvements in activities of daily living that are meaningful to participants.

“If you have improvements in cognitive flexibility, for example, you tend to be able to change the way that you problem solve,” she said. “You are less likely to be stuck in a mental rut.”

The effects are particularly significant, said Hammond, because nutrition studies can never truly control behavior.

“Everyone in the entire trial still ate food, so they’re still being exposed to lutein and zeaxanthin in their food,” he said. “This effect that we found is above and beyond the fact that everybody was somewhat exposed to the treatment.”

In addition, the research team has measured brain function in a myriad of ways over the course of its investigation – with cognition, with visual processing speed, with fMRI, with electroencephalogram, which measures the electric pulses that fire between brain cells – and they all showed that high levels of lutein and zeaxanthin correlate with better brain function.

The mechanism behind lutein and zeaxanthin’s ability to improve brain health is still unknown, and the team plans to tackle that question in future research. But, perhaps an equally important next step, said Renzi-Hammond is figuring out how to encourage people to consume more lutein.

“We say ‘Remember to eat your greens,’ but we don’t do it,” she said. “At the end of the day, when we are deciding what to eat for dinner, it’s more often convenience and cost that play a factor.”

This work illustrates that we really are what we eat, said Renzi-Hammond.

“You need new, raw material all the time, and parts of whatever you just ate are going to end up in your brain, literally,” she said. Putting more dark greens on your plate may be one way to protect your brain against decline.

To Renzi-Hammond this message empowers consumers. “It’s the ability to say ‘I can eat differently and do something meaningful to reduce my risk and keep myself functioning at peak condition for as long as I can.’”

The study “Effects of Lutein/Zeaxanthin Supplementation on the Cognitive Function of Community Dwelling Older Adults: A Randomized, Double-Masked, Placebo-Controlled Trial” published in Frontiers in Aging Neuroscience and is available online at

Additional authors included Medina O. Bello, Cutter A. Lindbergh, and Catherine M. Mewborn, all with the department of psychology at the University of Georgia; and L. Stephen Miller with UGA’s psychology department and Bio-Imaging Research Center.