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).
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.