Zeaxanthin, a carotenoid found in green leafy vegetables and fruits, may improve cancer-fighting activity of immune cells, CD8+ T cells, according to a study published in Cell Reports Medicine. It enhances CD8+ T cells' activity, which rely on T-cell receptor (TCR) to destroy abnormal cells. It strengthens TCR complex on CD8+ T cells, boosting greater T-cell activation and tumor-killing capacity.