For the study, the team collected dietary data from the participants -- all of whom were either obese or overweight. In addition, they were also screened for their medical history and subjected to adiposity tests during the initial appointment. On their second appointment, the researchers asked the participants to complete a spatial reconstruction test and collected fasting blood levels. The latter, in particular, helped determine the participants' regular carotenoid intake.
After analysis, the researchers found that lutein seemed to enhance memory function in the participants. They noted a direct relationship between higher lutein blood levels and improved accuracy in object binding – the ability of a person to recall various features of an object as a logical whole. They also found an inverse link between lutein and misplacement error, which was not seen in other carotenoids. (Related: Study shows lutein can boost heart health.)
“Our results revealed that serum lutein was significantly related to two metrics of relational memory performance even after adjusting for significant covariates,” the research team concluded in their report. “While this study was correlational, it lays the groundwork for subsequent research in this area.”
Lutein is a carotenoid, that is, a pigment that gives plants their bright colors. It's found in many vegetables – spinach smoothies are great sources.
While many studies have linked lutein to better eyesight, an increasing pool of literature has showed its ability to contribute to brain health. Scientists have shown that lutein is present in brain tissue, comprising around 60 percent of total carotenoids. However, data from the National Health and Nutrition Examination Survey reveals that lutein makes up only 12 percent of dietary carotenoids. This shows an apparent preference for lutein in the brain.
An earlier study on rhesus macaques also showed how adding lutein to infant formula positively impacted brain development. The team reported selective increases in the brain's carotenoid levels, with the highest concentrations seen in the occipital cortex, which processed visual information.
For the current study, the team looked at the participants' carotenoid intake by measuring it in blood samples. Additionally, the participants took tests on relational memory – their ability to store and remember associations and relationships between two different objects.
The research team found that serum lutein, in particular, positively affected memory function. They theorized that the carotenoid achieved its beneficial effects through its antioxidant and anti-inflammatory properties.
“Participants with overweight or obesity are more susceptible to oxidative and inflammatory stress due to the higher levels of chronic inflammation associated with excess adipose tissue,” the researchers reported. “Inflammation and oxidative stress can be mitigated by fruit and vegetable intake, foods that are often rich in carotenoids.”
Inflammation disrupts the proper function of the hippocampus. It prevents the process of long-term potentiation, the molecular means by which the brain forms memories. Lutein helps prevent age-related macular degeneration in the retina. By scavenging harmful molecules, the antioxidant decreases the oxidative stress that harms the eyes.
The researchers concluded that lutein performed the same antioxidant role in the hippocampus. They recommended that future studies check carotenoid levels in the macula and blood.
They published their findings in the scientific journal Nutrients.