The one-year study, performed by researchers from Shanghai Jiao-tong University in China, found that a daily dose of 20 milligrams of lutein was associated with significant increases in contrast and glare sensitivity.
“Although the results of this study do not support a direct link between oral supplementation and changes in visual acuity, the present findings provide convincing evidence that supplementation with lutein can significantly improve visual performance and vision-related quality of life when ambient illumination is low,” they wrote in the journal Nutrition .
The carotenoids lutein and zeaxanthin are vital for eye health, with both being found in high levels in the macula, a yellow spot of about five millimeters diameter on the retina.
These compounds are the only carotenoids capable of filtering the harmful blue light than can damage cells in the eye, the rods and the cones. Cones are used for vision in well-lit conditions (photopic vision), whereas the eye switches over to the rods for seeing under very low level light (scotopic vision). At many-night time levels (mesopic vision), we use a combination of rods and cones.
A thin macular pigment can allow the blue light through and destroy the cells. Maintaining high levels of both carotenoids, and therefore the macular pigment, is a valid approach to maintaining eye health and reducing the risk of diseases, like age-related macular degeneration (AMD).
The Chinese researchers explained that, although it already know that lutein can affect visual performance, “we still have much to learn about its effect in occupational populations, like drivers”.
They recruited 120 normal people who spent an average of 10 hours per day driving during the two years before the study started. The participants were randomized to receive either the lutein supplement or placebo for one year. The researchers measured visual acuity, serum lutein concentrations, macular pigment optical density (MPOD), and visual performance at regular intervals during the study.
The lutein content of the supplement was certified by the State Food and Drug Administration of China.
Results showed that there was the lutein group trended towards improved visual acuity, but this did not reach significant differences.
On the other hand, both serum lutein levels and central MPOD increased significantly in the lutein group, while no such changes were recorded in the placebo group.
In addition, the researchers observed “significant increases in contrast and glare sensitivity, especially in the mesopic condition”.
“The increase in contrast and glare sensitivity is statistically significant, especially in the mesopic condition, which suggests that supplementation with lutein may benefit driving at night and other spatial discrimination tasks carried out under low illumination,” they conluded.
Published online ahead of print, doi: 10.1016/j.nut.2012.10.017
“Lutein supplementation improves visual performance in Chinese drivers: 1-year randomized, double-blind, placebo-controlled study”
Authors: Y. Yao, Q-h. Qiu, X-W. Wu, Z-y. Cai, S. Xu, X-q. Liang