Could corn become the latest in eye protection?

Carrot is the vegetable most often said to be good for the eyes. But corn could also help boost eye health one day, thanks to its natural store of antioxidants and importance as an animal feed.

That’s the conclusion of a new study, in which researchers bred corn to contain high amounts of the potent eye-protecting antioxidants, lutein and zeaxanthin, and then examined whether eggs carried more of these beneficial carotenoids when laying hens were fed the new corn diets.

A pile of yellow corn and high-carotenoid corn

In a paper published online today (Feb. 6)  in Crop Science, the study’s leader Elizabeth Lee reports that a high-carotenoid corn diet did in fact yield eggs containing more lutein and zeaxanthin, although the effect was greater when hens were fed a competing source of lutein from marigold petals.

Still, says Lee, a professor at University of Guelph in Guelph, Ontario, this proof-of-concept study suggests high-carotenoid corn could offer another means to produce eggs enriched in health-promoting antioxidants. High-lutein eggs, for example, are already available to North American consumers to prevent age-related macular degeneration, a progressive eye disease that is the leading cause of blindness in older adults.

The macula of those suffering from the disease is depleted in lutein and zeaxanthin, which is why doctors often advise patients to eat foods rich in these antioxidants, such as leafy, dark green vegetables. However, it’s also known that the human body absorbs more lutein and zeaxanthin from food in the presence of oil. And this makes egg yolks—which owe their characteristic yellow color to carotenoids—an ideal choice for getting more antioxidants into the diet, Lee says.

Hens are typically fed marigold petals from Latin America to generate high-lutein eggs. But because corn is one of the only vegetables (besides leafy greens) that contains large amounts of lutein and zeaxanthin, Lee and her collaborators wondered if it could substitute for marigold, especially since corn grain is already widely fed to chickens.

To investigate this potential, Lee’s team built on previous efforts to develop and characterize high-lutein and high-zeaxanthin corn varieties. Using conventional breeding techniques, the researchers first crossed plants from the exotic, Argentine Orange Flint race of maize with conventional North American corn. They then selected from among the offspring those plants whose kernels were most orange in color.

After generating these new corn lines—which have higher lutein and zeaxanthin levels than any previously documented—the scientists fed grain from one high-lutein line and one high in zeaxanthin to laying hens. Next, they measured the carotenoid levels in the egg yolks and compared them to the levels in yolks from two control diets: a standard diet of number 2, yellow corn and one supplemented with a lutein extract from marigold petals.

The two high-carotenoid corn diets consistently resulted in egg yolks that were higher in lutein and zeaxanthin than the number 2, yellow corn diet. And while the levels were lower than in eggs from chickens fed marigold extract, the study suggests that boosting the levels further in corn should be relatively straightforward, the scientists say.

More importantly, the findings demonstrate how plants can be bred to produce “functional foods”—foods that offer health benefits beyond ordinary nutrition. Breeding crops for this purpose is a relatively new endeavor for crop scientists, but one that has great “potential for delivering enhanced nutritional properties to improve human health,” Lee says.

The study was funded by the Natural Sciences and Engineering Research Council of Canada; the Ontario Ministry of Agriculture, Food and Rural Affairs; Egg Farmers of Canada; Grain Farmers of Ontario; Canadian Foundation for Innovation; and Ontario Innovative Trust.

View the paper's abstract: