In optometry, we’ve seen discussions about lutein and zeaxanthin make their way from the lab room to the exam room as we’ve become more aware of their role in preventive eye care. We may start to see this same transition happening in other areas of health care, as more research emerges about how xanthophylls contribute to systemic health and a number of common chronic conditions.

In part 1 of this three-part series ( “Add Color to Your Diet,” May 2012), we explained how xanthophylls protect the retina and enhance visual function. In the second installment ( “Beyond the Eye,” July 2012), we reviewed their protective role in skin damage and various types of cancer. In this third and final segment, we look at the relationship between xanthophylls and chronic conditions of the mind and body—including heart disease, metabolic syndrome, diabetes and cognitive impairment.

Heart Disease
A growing body of experimental evidence and observational studies suggest that lutein and zeaxanthin may play a role preventing coronary heart disease and stroke. The Los Angeles Atherosclerosis Study found lutein to be highly effective in reducing oxidation of low-density lipoproteins (LDL) and inhibiting the inflammatory response of monocytes to LDL trapped in the artery wall.¹

With in vitro experiments of human LDL, lutein and zeaxanthin have been shown to act as scavengers of peroxynitrite radicals. It has also been demonstrated that high plasma levels of lutein were associated with decreased risk of heart attack.²

Metabolic Syndrome and Diabetes
Using a cross-sectional survey to investigate the presumed association, Australian researchers found that serum carotenoids—including lutein and zeaxanthin—are inversely associated with type 2 diabetes and impaired glucose metabolism.³

Another survey revealed that the odds ratio for metabolic syndrome in the highest tertile of serum zeaxanthin/lutein was significantly lower than in the lowest tertile in Japanese women.⁴

In a U.K. study, subjects with type 2 diabetes had reduced macular pigment optical density (MPOD) compared to those in a group of control subjects. The authors suggest that the reduced macular pigment levels may result from increased oxidative stress in the diabetic macula.⁵

A more recent study reported that type 2 diabetes patients, with or without retinopathy, had reduced MPOD when compared with that in non-diabetic patients. In addition, researchers observed a significant inverse correlation between MPOD and HbA1C levels.⁶ This growing evidence suggest that dietary changes or supplementation with lutein and zeaxanthin could benefit diabetic patients.

Brain and Cognitive Impairment
Over the past decade, there’s been increasing interest in the relationship between xanthophylls and cognitive function. At last year’s International Symposium on Carotenoids, preliminary research demonstrated for the first time that lutein is the predominant carotenoid present in key areas of the infant brain, including areas that regulate overall brain function, cognition, vision, hearing and speech.⁷

In addition to these findings, there’s been a growing body of evidence supporting the role of these carotenoids in adult and elderly brains. In measuring the major carotenoids in the brain, researchers found that xanthophylls accounted for 66% to 77% of total carotenoids in all brain regions examined.⁸

Similar to the foveal center, the ratio of zeaxanthin to lutein was high and these two xanthophylls were significantly correlated. The frontal cortex—generally vulnerable in Alzheimer’s disease—had higher concentrations of all the compounds studied than the occipital cortex, which is generally unaffected. Frontal lobes, but not occipital lobes, exhibited an age-related decline in retinol, total tocopherols, total xanthophylls and total carotenoids.⁸

In an exploratory trial of docosahexaenoic acid (DHA) and lutein supplementation, nearly 50 women between the ages of 60 and 80 were randomly assigned to placebo, DHA, lutein, or lutein and a DHA supplement.⁹ Following supplementation, verbal fluency scores improved significantly in the DHA, lutein and combined treatment groups. Memory scores and rate of learning improved significantly in the combined treatment group, who also displayed a trend toward more efficient learning. Measures of mental processing speed, accuracy and mood were not affected by supplementation. These exploratory findings suggest that DHA and lutein supplementation may offer cognitive benefit for older adults.⁹

Similarly, the EVA Study in France measured plasma carotenoid levels and cognitive performance in an elderly population. Their results showed that participants with the lowest cognitive functioning (25th percentile) had a higher probability of having low levels of specific plasma carotenoids, lycopene and zeaxanthin.¹⁰

Earlier this year, researchers studied the relationship between markers of lutein, zeaxanthin and omega-3 fatty acid status (via serum and MPOD) and cognitive function in a cohort of healthy older adults. Of all variables tested, MPOD was the largest and most consistent predictor of cognitive function. The analysis suggested that both serum xanthophylls and omega-3 fatty acids account for small but significant proportions of variance in cognitive function.¹¹

Although it is not possible to affirm if low levels of carotenoids precede or are the consequence of cognitive impairment, these results suggest that low carotenoid levels could play a role in cognitive impairment. The importance of these differences and the role(s) of these antioxidants in the brain remain to be determined.

As the scientific community continues to investigate and elucidate the role of xanthophylls in systemic health, staying up to date on the latest findings will help us, as eye care providers, be better advocates for our patients and our colleagues in other health care specialties.

Drs. Pelino and Pizzimenti have no proprietary interest in any instrument, food product, supplement or vitamin. Dr. Pizzimenti serves on the scientific advisory board for ZeaVision.

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