Data from the Irish Longitudinal Study on Ageing, published in the Journal of Gerontology, Series A, indicated that the xanthophyll carotenoids lutein and zeaxanthin were independently associated with better scores for a range of cognitive measure.
In addition, the researchers also found evidence that higher zeaxanthin levels were associated with better processing speed. However, no such associations were observed for lutein.
"To our knowledge, this is the first study to investigate plasma lutein and zeaxanthin in relation to cognition, with between-domain comparisons, in a large population-based sample of older adults," wrote the authors. "The results are in concordance with smaller studies of the association between plasma/serum and brain xanthophyll carotenoids and cognition."
Lutein and brain health
The link between lutein and eye health was first reported in 1994 by Dr Johanna Seddon and her co-workers at Harvard University, who found a link between the intake of carotenoid-rich food, particularly dark green leafy vegetables like spinach, and a significant reduction in age-related macular degeneration (AMD) (JAMA, Vol. 272, pp. 1413-1420).
Numerous studies with data from primates, children, middle-aged people, and the elderly now support the importance of lutein in brain health.
Indeed, recent findings from pediatric brain tissue studies have shown that about 60% of the total carotenoids in the pediatric brain tissue is lutein, and yet NHANES data show that lutein is only about 12% of the carotenoids in the diets, so there is a preference for lutein in the brain (Vishwanathan et al. J Pediatr Gastroenterol Nutr. 2014).
Much of the research has been led by Elizabeth Johnson, PhD, Scientist I in the Antioxidants Laboratory in the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, Dr Billy Hammond’s group at the University of Georgia, and Prof John Nolan and Prof Stephen Beatty from the Macular Pigment Research Group at the Waterford Institute of Technology in Ireland.
The new paper was authored by scientists from Queens University Belfast, The Irish Longitudinal Study on Ageing, and scientists from the Macular Pigment Research Group at the Waterford Institute of Technology.
Prof John Nolan, co-author on the paper, told NutraIngredients-USA: "This work is very important as it adds to recent findings that show a link between the macular carotenoids and cognitive function. In this study, we confirm that plasma lutein and zeaxanthin were independently associated with better composite scores across the domains of global cognition, memory, and executive function.
"The uniqueness of this study relates to its very large representative sample of the older population. The next question is to assess the impact of enriching these nutrients in different populations (e.g. the healthy population and patients with mild cognitive impairment). We have already finished a gold standard clinical trial in healthy individuals and we expect to publish that study in 2017."
Study details
The researchers analyzed data from 4,076 community-dwelling Irish adults aged 50 or older. The results showed that the carotenoids were associated with “better composite scores across the domains of global cognition, memory, and executive function”. Interestingly, only zeaxanthin was found to be associated with better processing speed.
"Although it is premature to draw inferences from these results as to the absolute or relative importance of the carotenoids for cognitive function, there is a good biological basis for hypothesizing that these compounds may be neuroprotective, owing to their antioxidant and putative anti-inflammatory cell signaling properties," wrote the researchers.
"Longitudinal investigations in similarly large population cohorts are needed to establish the prognostic significance of this relationship," they concluded.
Source: The Journals of Gerontology, Series A: Biological Sciences and Medical Sciences
Published online ahead of print, doi: 10.1093/gerona/glw330
“Plasma Lutein and Zeaxanthin Are Associated With Better Cognitive Function Across Multiple Domains in a Large Population-Based Sample of Older Adults: Findings from The Irish Longitudinal Study on Aging”
Authors: J. Feeney et al.