Plant Compounds Found to Boost Brain Function in Older Adults

The typical diet in the United States is sorely lacking in fruits and vegetables, but a new study from the University of Georgia a compelling reason why more of us should be eating our kale and spinach.

The research 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.

The study caps more than ten years of work looking at lutein’s role in brain health, says Lisa Renzi-Hammond, an assistant professor of health promotion and behavior with UGA’s Institute of Gerontology in the College of Public Health and corresponding author on the study.

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.

Renzi-Hammond and colleagues from UGA’s department of psychology were interested lutein and how it might affect brain activity because of its high accumulation in retina. “It’s about 1000 times more concentrated there than it is anywhere else in the body,” said Renzi-Hammond. Anatomical studies had shown that lutein accumulates in brain tissue as well.

That struck Renzi-Hammond as odd because Americans on average consume far more pro-Vitamin A carotenoids, like lycopene and beta-carotene, found in foods like tomatoes and carrots, than we do lutein. “Whenever you see something stuck in a tissue in an amount that’s disproportionate to our behavior that tells you that this might really be important,” she said.

In 2016, Renzi-Hammond’s research team and collaborating laboratories were able to show using functional magnetic resonance imaging (fMRI) that older adults who had higher levels of lutein in their brains could perform memory-oriented tasks using less brain power.

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 the same 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.

“The really exciting part of all of this is not only that we were able to change brains themselves, but that we were able to actually change cognitive function in ways that are really meaningful,” said Renzi-Hammond. “If you have improvements in cognitive flexibility, for example, you tend to be able to change the way that you problem solve. You are less likely to be stuck in a mental rut.”

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.
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: http://journal.frontiersin.org/article/10.3389/fnagi.2017.00254/full.