BLOG: Focus on nutritional health for the eyes, brain
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The human diet includes about 50 of the 700+ carotenoids that occur in nature, and just a few of these carotenoids are able to cross the blood-brain barrier to accumulate in neural tissue.
Lutein is the dietary carotenoid found in the highest concentration in the brain. And lutein, along with zeaxanthin and meso-zeaxanthin, also accumulates in the retina.
These macular xanthophylls, as they are known, are powerful antioxidants that are found in high concentrations in dark, leafy greens like spinach and kale, as well as from other brightly colored foods, like corn, eggs and avocado. Their presence in the brain is likely part of the body’s strategy to protect oxygen-hungry critical neural tissues from oxidative damage that promotes inflammation and, over time, contributes to neurodegenerative disease.
There is now a large body of research demonstrating the value of macular xanthophylls in visual and cognitive function (Stringham, Johnson et al.). Most Americans don’t eat enough of the foods containing lutein and zeaxanthin, and 15% to 20% of people lack the enzymes necessary to convert meso-zeaxanthin from lutein.
In 2019, my colleagues and I demonstrated for the first time that a daily supplement regimen containing these three nutrients could significantly decrease the inflammatory marker interleukin-1 in the blood and increase brain-derived neurotrophic factor (BDNF), a molecule linked to neuroplasticity (Stringham, Holmes, et al.). After just 6 months of supplementation, we saw improved parameters of cognitive performance, including processing speed, memory and attention, among the healthy young college students in the study.
Another study showed that pre-mortem cognition among centenarians in Georgia was directly related to the amount of lutein in their brains post-mortem (Mohn et al.). This finding hinted to those of us in the carotenoid/neural health research world that perhaps macular xanthophylls might have a protective effect against brain injury.
Oxidative stress is behind many of the negative outcomes of traumatic brain injury (TBI), and it was hypothesized that varying levels of macular xanthophylls might have something to do with the wide variation in TBI severity and recovery times. Of course, this is a difficult hypothesis to test in a controlled way in humans. Instead, a validated mouse model of concussion was used to test this idea (Gunal et al.).
Just as was seen in our college students who took a daily macular xanthophyll supplement, treating the “concussed” mice with all three macular carotenoids reduced pro-inflammatory cytokines and increased BDNF compared to placebo. More importantly, the mice had a dramatic reduction in the deleterious effects of TBI, including infarct size, brain edema, light and sound sensitivity, and vestibular dysfunction.
This is exciting because it is actionable. Many optometrists are already recommending that patients supplement or increase their dietary intake of lutein, zeaxanthin and meso-zeaxanthin for the macular benefits of these nutrients. This research suggests that macular xanthophyll supplementation may also support improved cognition and confer significant protection against brain injury and oxidative damage.
Optometrists should know that not all supplements are created equal. I recommend looking for supplements made using pharmaceutical-grade processing, with demonstrated bioavailability and third-party testing that proves the supplement contains what the label says it does.
As optometrists move into more comprehensive medical care, a focus on nutritional health can be a great way to support patients’ eyes — and their brains.
References:
- Gunal MY, et al. Neurotox Res. 2021;doi:10.1007/s12640-021-00385-3.
- Mohn E, et al. The relationship of lutein and DHA in age-related cognitive function. Presented at: Experimental Biology Conference; April 2013; Boston.
- Stringham NT, Holmes PV, et al. Physiol Behav. 2019;doi:10.1016/j.physbeh.2019.112650.
- Stringham JM, Johnson EJ, et al. Curr Dev Nutr. 2019;doi:10.1093/cdn/nzz066.
For more information:
James M. Stringham, PhD, is a neuroscientist with a lifelong interest in the effects of nutrition on the eye and brain. He has published more than 50 peer-reviewed articles and technical reports and delivered more than 300 lectures on the healthful benefits of lutein, zeaxanthin and meso-zeaxanthin. Stringham completed post-doctoral work at Harvard and the University of Georgia, served as a vision scientist for the Air Force Research Laboratory and taught at Duke University. He is currently the chief scientific officer at MacuHealth. He will be teaching a course on “New evidence for nutrition-based strategies to minimize effects of concussion/TBI” at the 2022 NORA conference. For more information and to register, visit https://noravisionrehab.org/about-nora/annual-conferences/2022-annual-conference.
Disclaimer: The views and opinions expressed in this blog are those of the authors and do not necessarily reflect the official policy or position of the Neuro-Optometric Rehabilitation Association unless otherwise noted. This blog is for informational purposes only and is not a substitute for the professional medical advice of a physician. NORA does not recommend or endorse any specific tests, physicians, products or procedures. For more on our website and online content, click here.
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