Eating for eagle eyes: Colorful fruits and vegetables could improve visual range, study finds

09 Jun 2023 --- Adding more dark leafy greens and yellow or orange vegetables to athletes’ diets may help improve how well they see a target at a distance. According to US-based researchers, brightly colored foods are high in lutein and zeaxanthin – plant compounds that help to improve eye health and functional vision.

The carotenoids lutein and zeaxanthin can be found in eggs and various colorful fruits and vegetables like leafy greens – for example, spinach and kale – carrots, red bell peppers, pumpkin, broccoli, kiwis and peas. 

When consumed, these compounds are accumulated as yellow pigments in the eye’s blue-light absorbing filter, called the macular pigment. 

“We have data from modeling and empirical studies showing that higher macular pigment in your retina will improve your ability to see over distance. The application for athletes is clear,” says lead author Jack Harth from the University of Georgia, US. 

“Much of the research into macular lutein and zeaxanthin has focused on health benefits, but from a functional perspective, higher concentrations of these plant pigments improve many aspects of visual and cognitive ability.” 

Optimally, athletes would consume over 6 mg of lutein and zeaxanthin daily from leafy greens and colorful fruits.Optimally, athletes would consume over 6 mg of lutein and zeaxanthin daily through their diet. For example, one cup of raw kale contains around 11 mg of lutein, while one cup of spinach contains about 8 mg of lutein. 

Blue haze limits visual range 
According to the review, blue light is one of the reasons why objects are more challenging to see the further away they are. 

“From a center fielder’s perspective, if that ball’s coming up in the air, it will be seen against a bright blue sky or a gray background if it’s a cloudy day. Either way, the target is obscured by atmospheric interference coming into that path of the light,” explains Harth.

Standard measures to reduce the impact of blue light among athletes include using black or blue-blocking sunglasses. Harth suggests eating more foods rich in lutein and zeaxanthin can improve the eye’s natural ability to handle blue light exposure. 

However, he cautions that people absorb lutein and zeaxanthin from food at different levels. It could take time before they see improvements, while there may be no improvements for some. 

Recent research has also identified that using high- and medium-fat cow’s and coconut milk in spinach smoothies may make it easier to digest lutein. 

Dietary habits 
The review, published in Exercise and Sport Sciences Reviews, suggests that athletes’ intake of carotenoid-rich foods is very low, as in most Americans. 

The authors refer to various studies that show a link between the intake of these carotenoids and the density of macular pigments. In addition to filtering blue light, research indicates it could support other health benefits, such as protection from skin damage and brain injury. 

Eating more foods rich in lutein and zeaxanthin could improve the eye’s natural ability to handle blue light exposure.“In a long series of studies, we have shown that increasing amounts of lutein and zeaxanthin in the retina and brain decrease glare disability and discomfort and improve chromatic contrast and visual-motor reaction time,” adds co-author Billy Hammond from the University of Georgia. 

“Supplementing these compounds facilitates executive functions like problem-solving and memory. All of these tasks are particularly important for athletes.” 

Leafy green consumption has been linked to various health benefits. A diet that prioritizes leafy vegetables and berries has been linked to a reduction in Alzheimer’s disease-related biomarkers.  

The current research expands on testing the visual range ability of pilots. 

“We’re at a point where we can say we’ve seen visual range differences in pilots that match the differences found in modeling, and now, we’ve also seen it in laboratory tests. A future goal would be to bring people outside and measure their ability to see contrast over distance through real blue haze and outdoor environments,” concludes Harth.

By Jolanda van Hal