By Professor Gene Bruno, MS, MHS, RH(AHG)
Huntington College of Health Sciences
The carotenoid antioxidants lutein (L) and zeaxanthin (Z) are best known for the role they play in healthy visual development and functioning, including the ability to efficiently absorb blue light.1 By absorbing blue light, T&Z limit the amount that reaches the critical visual structures of the eye, thereby providing some protection from resulting oxidative damage2—which may additionally offer some degree of neuroprotection. This is important since decreased oxidative stress has been proposed as a mechanism for neuroprotection. A lesser known benefit of L&Z is their role in cognitive function, underscored by the fact that L&Z represent 72 percent of total carotenoids in the infant brain and 41 percent in adult brains.3,4
This cognitive role of L&Z was examined in a recently published study from the Journal of the International Neuropsychological Society.5 The hypothesis, that lower L&Z concentrations would be associated with neurobiological inefficiency during cognitive performance, was tested in 43 community-dwelling older adults (mean age=72 years; 58 percent female). L&Z concentrations were determined through serum samples, and through retinal levels that are measured using noninvasive flicker photometry.
Functional MRI technology (fMRI) was used to gauge the brain activity of participants while they attempted to recall word pairings they were taught earlier. The researchers then analyzed brain activity while the participants were in the machine. The results were that that those individuals with higher levels of L&Z didn’t require as much brain activity to complete the task, while those with lower levels of these carotenoids required higher levels of brain activity.
Basically, here’s the entire story in a nutshell. A certain amount of deterioration naturally occurs in the brain as people age. However, the brain tends to compensate for this a few ways. One such way is increasing brain activity to get a job done. This way, the brain can maintain the same level of cognitive performance. In the L&Z study, those with higher levels of these carotenoids did not require more brain activity to get the job done because they were more “neurally efficient.”
Not surprisingly, another 2014 study from the journal Age and Ageing,6 found that older adults with higher levels of L&Z (measured as optical pigment density), had significantly better global cognition, verbal learning and fluency, recall, processing speed and perceptual speed than those with lower levels.
Research suggests that 10 mg of lutein and 2 mg of zeaxanthin daily will yield positive benefits—although additional benefits may occur using 20 mg and 4 mg, respectively.7
1 Halliwell B, Gutteridge JMC. Free Radicals in Biology and Medicine. Third ed. New York, NY: Oxford University Press; 1999.
2 Krinsky NI, Landrum JT, Bone RA. Biologic mechanisms of the protective role of lutein and zeaxanthin in the eye. Annu Rev Nutr. 2003;23:171-201.
3 Vishwanathan R, Kuchan MJ, Johnson EJ. Lutein is the predominant carotenoid in the infant brain. Poster #1.23. 16th International Symposium on Carotenoids. Acta Biologica Cracoviensia series Botanica.2011;53(suppl.1):29.
4 Johnson EJ et al., Brain levels of lutein and zeaxanthin are related to cognitive function in centenarians (Abstract) FASEB J. 2011;25:975.
5 Lindbergh CA, Mewborn CM, Hammond BR, Renzi-Hammond LM, Curran-Celentano JM, Miller LS.
6 Relationship of Lutein and Zeaxanthin Levels to Neurocognitive Functioning: An fMRI Study of Older Adults. J Int Neuropsychol Soc. 2016 Oct 25:1-12. [Epub ahead of print]
7 Vishwanathan R, Iannaccone A, Scott TM, Kritchevsky SB, Jennings BJ, Carboni G, Forma G, Satterfield S, Harris T, Johnson KC, Schalch W, Renzi LM, Rosano C, Johnson EJ. Macular pigment optical density is related to cognitive function in older people. Age Ageing. 2014 Mar;43(2):271-5.
Gene Bruno, MS, MHS, the dean of academics for Huntington College of Health Sciences, is a nutritionist, herbalist, writer and educator. For more than 30 years he has educated and trained natural product retailers and health care professionals, has researched and formulated natural products for dozens of dietary supplement companies, and has written articles on nutrition, herbal medicine, nutraceuticals and integrative health issues for trade, consumer magazines and peer-reviewed publications.
He can be reached at firstname.lastname@example.org.