The study looked at how the levels of important nutrients in kale leaves change as they grow. They found that the highest amounts of lutein, β-carotene, and chlorophyll were present in leaves that were 1-3 weeks old. Mature kale leaves had more nutrients compared to young or "baby" leaves, with the lowest levels found in older, senescent leaves. Harvesting kale when it is fully developed results in the highest nutrient content. This suggests that growing kale to full maturity can increase its nutritional value for consumers.