January 28, 2020

A meta-analysis and a randomized trial add evidence to the previously researched benefits of lutein and zeaxanthin supplementation for the eyes as well as reveal new data concerning the carotenoids’ positive effects on brain structure.

On December 30, 2019, the journal PLoS One published a meta-analysis of randomized trials that examined the effects of lutein supplementation on macular pigment optical density and other factors. Macular pigment optical density is related to the amount of the carotenoids lutein and zeaxanthin in the eyes’ macula, the central area of the retina. Macular lutein filters potentially damaging blue light as well as helps to prevent oxidative damage, thereby aiding in the prevention of age-related macular degeneration (AMD) and cataracts.

“Since lutein must be obtained from the diet, principally from leafy green vegetables, fruits, and egg yolk, researchers have explored whether dietary supplementation with lutein might prevent AMD in healthy people or improve the condition of patients with AMD,” writes Liwen Feng of Sichuan University and colleagues. “Several studies support these possibilities and have demonstrated that lutein supplementation can improve visual acuity.”

For the meta-analysis, Dr Feng and associates selected nine randomized, placebo-controlled trials that included 855 AMD patients. Trial duration ranged from three to 24 months. Supplementation with 10 or 20 milligrams lutein per day was associated with 7% higher macular pigment optical density, 28% greater visual acuity and 26% greater contrast sensitivity than the placebo. The increase in macular pigment optical density was more rapid in association with higher lutein doses and longer treatment.

In another investigation, reported on December 1, 2019 in the Journal of Aging Research, 33 older men and women received a supplement that contained 10 milligrams (mg) lutein plus 2 mg of the lutein isomer zeaxanthin, while 14 participants in the same age range received a placebo daily for one year. Retinal levels of lutein and zeaxanthin were measured as macular pigment optical density before and after the treatment period. Magnetic resonance imaging (MRI) of the brain was also conducted at these time points.

Among participants who had greater increases in macular pigment optical density in response to supplementation there was less decline in total and prefrontal gray matter brain volume than among participants who did not respond as well to the supplements.

“Exploratory analyses suggested that there was a small group of individuals who reaped greater benefit from lutein and zeaxanthin supplementation and who showed less decline in global and prefrontal gray matter volume than individuals who did not appear to benefit from the intervention,” writes Catherine M. Mewborn and colleagues. “To that end, future studies could explore factors which may impact the efficacy of lutein and zeaxanthin supplementation, such as vascular health, co-supplementation with other nutrients, and other factors known to interact with nutrient bioavailability and absorption. Replication of this study in a larger and more diverse sample may also determine whether there are some individuals who could benefit even more from lutein and zeaxanthin supplementation, such as individuals who are more cognitively impaired or have had less access to nutritious diets across their lifetime.”

These studies provide further support for supplementing with lutein and zeaxanthin. While these carotenoids are better known for their protective effects in the eyes, there is a growing awareness of their benefit to the brain, where they exist as 66% to 77% of total carotenoids.