University of Illinois at Urbana-Champaign
A study of older adults links consumption of a pigment found in
leafy greens to the preservation of "crystallized intelligence," the
ability to use the skills and knowledge one has acquired over a lifetime.
The study is reported in the journal Frontiers in Aging
Neuroscience.
Lutein (LOO-teen) is one of several plant pigments that humans
acquire through the diet, primarily by eating leafy green vegetables,
cruciferous vegetables such as broccoli, or egg yolks, said University of
Illinois graduate student Marta Zamroziewicz, who led the study with Illinois
psychology professor Aron Barbey.
Lutein accumulates in the brain, embedding in cell membranes, where it likely plays "a neuroprotective role," she said.
"Previous studies have found that a person's lutein status
is linked to cognitive performance across the lifespan," Zamroziewicz
said. "Research also shows that lutein accumulates in the gray matter of
brain regions known to underlie the preservation of cognitive function in
healthy brain aging."
The study enrolled 122 healthy participants aged 65 to 75 who
solved problems and answered questions on a standard test of crystallized
intelligence. Researchers also collected blood samples to determine blood serum
levels of lutein and imaged participants' brains using MRI to measure the
volume of different brain structures.
The team focused on parts of the temporal cortex, a brain region
that other studies suggest plays a role in the preservation of crystallized
intelligence.
The researchers found that participants with higher blood serum
levels of lutein tended to do better on tests of crystallized intelligence.
Serum lutein levels reflect only recent dietary intakes, Zamroziewicz said, but
are associated with brain concentrations of lutein in older adults, which reflect
long-term dietary intake.
Those with higher serum lutein levels also tended to have
thicker gray matter in the parahippocampal cortex, a brain region that, like
crystallized intelligence, is preserved in healthy aging, the researchers
report.
"Our analyses revealed that gray-matter volume of the
parahippocampal cortex on the right side of the brain accounts for the
relationship between lutein and crystallized intelligence," Barbey said.
"This offers the first clue as to which brain regions specifically play a
role in the preservation of crystallized intelligence, and how factors such as
diet may contribute to that relationship."
"Our findings do not demonstrate causality,"
Zamroziewicz said. "We did find that lutein is linked to crystallized
intelligence through the parahippocampal cortex."
"We can only hypothesize at this point how lutein in the
diet affects brain structure," Barbey said. "It may be that it plays
an anti-inflammatory role or aids in cell-to-cell signaling. But our finding
adds to the evidence suggesting that particular nutrients slow age-related
declines in cognition by influencing specific features of brain aging."