Kale is often promoted for eye health due to its high content of the carotenoids lutein and zeaxanthin. These compounds are well-documented in scientific literature for their role in supporting the eyes, particularly in filtering harmful high-energy blue wavelengths of light and protecting and maintaining healthy cells in the eyes. Multiple clinical and epidemiological studies have shown that higher dietary intake of lutein and zeaxanthin is associated with a reduced risk of age-related macular degeneration (AMD) and cataracts, two of the leading causes of vision loss worldwide.

Kale is one of the richest dietary sources of both lutein and zeaxanthin. According to the USDA, one cup of cooked kale contains more than 20 mg of lutein and zeaxanthin combined, a significant amount compared to many other vegetables. The Age-Related Eye Disease Study 2 (AREDS2), a large, randomized clinical trial sponsored by the National Eye Institute, found that supplementation with lutein and zeaxanthin could help slow the progression of AMD in individuals at high risk.

While kale alone cannot prevent or treat eye diseases, its nutritional profile makes it an evidence-based food for supporting long-term eye health. Thus, the use of kale to support the eyes body system is justified based on scientific validation.