Vision Enhancement and Cognitive Development in Children

Additional Benefits of Macular Pigment Supplements?

The carotenoids lutein, zeaxanthin and meso-zeaxanthin preferentially accumulate in neural tissue including the macula where they form macular pigment (MP). In humans, lutein and zeaxanthin cannot be produced endogenously and are, therefore, acquired entirely from dietary sources (green leafy vegetables, yellow peppers, corn and eggs are some of the best sources of these carotenoids). MP exhibits blue light-filtering, antioxidant, anti-inflammatory and neuroprotective properties which are believed to benefit eye health and vision.

Interestingly, however, lutein and zeaxanthin are also found in several specific regions in the brain including the frontal, occipital and temporal cortices, hippocampus and cerebellum. Recent research exploring these carotenoids has moved beyond diseases such as AMD, to explore other neurodegenerative conditions of both the eye and the brain, including glaucoma and Alzheimer’s disease. This blog explores their potential at the opposite end of the age spectrum, examining their affinity for ocular and brain tissue in relation to possible influences on vision and cognitive development during infancy and childhood.

Optimal cognitive performance in different age groups has been shown to be associated with plasma, retinal and brain concentrations of lutein and zeaxanthin. Importantly, the available evidence suggests that the cognitive capacity of healthy people can be enhanced by supplementation with these carotenoids. Lutein and zeaxanthin accumulate in neural tissue even before birth, being passed to the foetus via the placenta during gestational development in the womb. They have been found in ocular tissue from 18 weeks of prenatal development, while in the brain they have also been found in preterm infants. Later, breast milk provides an excellent source of bioavailable carotenoids before children begin to consume solid food sources themselves (note: formula feed has much poorer lutein bioavailability than breastmilk).

"Vision is a key driver of development through observation and facilitating exploration of the environment."

The infant brain appears to be exquisitely sensitive to lutein, capable of accumulating circulating dietary lutein so effectively that it comprises the dominant carotenoid in brain tissue despite limited intake. Such selective concentration of lutein and the multitude of effects these carotenoids have on neural cell viability suggests that these compounds may play a key role in the early processes of neural and hence cognitive development in children. It has been shown, for example, that these carotenoids may influence visual recognition memory in infants, relational memory, executive processes and academic performance in older children. Such findings are consistent with the presence of lutein and zeaxanthin in visual and auditory areas of the brain, as well as in areas associated with executive function and memory.

How can Lutein and Zeaxanthin Influence Cognitive Development?

In the eye, MP acts as a pre-receptoral optical filter that serves to optimise and refine the visual signal to be delivered to the brain. Although normal vision is not a prerequisite for normal cognitive development, in sighted individuals, vision is a key driver of development through observation and facilitating exploration of the environment. Therefore, there is a possibility that MP could improve cognitive development in children simply by enhancing vision, the dominant sense in sighted individuals. Although it remains unclear how much suboptimal vision could affect an individual’s cognitive development long-term, this notion is worth exploring.

Beyond their visual attributes, lutein and zeaxanthin may support cognitive development in children by protecting and enhancing retinal and brain function through their antioxidant, anti-inflammatory and neuroprotective properties. Omega 3 fatty acids are widely accepted as important for cognition in children. These are neuroprotective yet vulnerable to oxidation both in the eye and brain but could be protected by the potent antioxidant action of lutein and zeaxanthin. Collectively, the varied benefits of lutein and zeaxanthin may exert a tangible impact on neural development as well as on the delay of age-related cognitive and visual decline.

How Good is our Diet?

Nutrition during the pre and early postnatal period may have a key role in the prevention of neurodegeneration later in life. The modern diet, however, is not particularly suited to high carotenoid intake. Instead, the increasing rate of childhood obesity across the globe is a consequence of high intake of processed, sugar-laden foods which replace healthier fruit and vegetables, leaving both adults and children deprived of essential micronutrients. There is currently no RDA for lutein or zeaxanthin intake, but we know that intake is poor and likely deteriorating globally. Rising obesity levels may also mean that they aren’t absorbed as efficiently into neural tissue, as carotenoids are competitively stored in adipose tissue before reaching the eye and brain.

While there is limited evidence to date in this emerging area of research, strategies for dietary interventions that combine omega-3 fatty acids with the antioxidant, anti-inflammatory and neuroprotective properties of lutein and zeaxanthin are worthy of investigation for child vision and cognitive development. These might include simple dietary guidelines for young children, expectant and nursing mothers.

Given the difficulty of encouraging a healthy intake of fruit and vegetables in children, macular carotenoid supplement use could be considered where appropriate, which may translate into visual and cognitive enhancements. This is particularly important during childhood which is a critical period for brain development and maturation of the central nervous system. The impact of the modern diet and obesity epidemic on visual and cognitive development are yet to fully emerge, but the risks are worth noting and the possible benefits of carotenoid supplementation explored. Macular pigment supplements are typically marketed and prescribed for those at risk of age-related eye disease such as AMD. It is now worth considering their use at the opposite end of the age spectrum, when vision is just developing.

Suggested further reading:

Loskutova E, Shah K, Flitcroft DI, Setti A, Butler JS, Nolan Y, Loughman J. Lutein and zeaxanthin: The possible contribution, mechanisms of action and implications of modern dietary intake for cognitive development in children. HRB Open Res. 2019 Apr 26;2:8. https://hrbopenresearch.org/articles/2-8
Johnson EJ. Role of lutein and zeaxanthin in visual and cognitive function throughout the lifespan. Nutr Rev. 2014;72(9):605–12. https://academic.oup.com/nutritionreviews/article/72/9/605/1860232

James Loughman is the Clinical Research Director for Ocuco Ltd.

An Optometrist with more than 20 years of clinical, academic, research and management experience, James recently joined Ocuco as Clinical Research Director. James is also presently the Director of the Centre for Eye Research Ireland, a research facility based in the Dublin Institute of Technology, the same university where he received his PhD in 1997; James oversees a portfolio of research including technology development and big data analytics projects alongside various clinical trials for the control of myopia, glaucoma and other blinding conditions.