A nutrient best known for protecting eyesight may soon have a new role in cancer treatment. Researchers have discovered that zeaxanthin, a plant-derived carotenoid abundant in foods like spinach, kale, and orange peppers, enhances the tumour-fighting power of immune cells and strengthens the effects of cancer immunotherapies (Figure 1).
Figure 1: Graphical abstract.
The study reveals that zeaxanthin, traditionally recognised for maintaining eye health, also acts as an immune enhancer, improving how CD8⁺ T cells detect and kill cancer cells. These findings highlight an unexpected link between nutrition and immune regulation and suggest a simple, safe way to augment advanced cancer treatments.
CD8⁺ T cells, also known as cytotoxic T lymphocytes, are key effectors in the body’s anti-tumour defence. They recognize and eliminate abnormal cells through their T-cell receptors (TCRs), molecular structures that identify cancer-associated antigens.
The researchers screened a large library of blood nutrients to determine which compounds directly influenced immune cell activity. Zeaxanthin emerged as a potent enhancer of TCR stability and signalling. When CD8⁺ T cells were exposed to cancer cells in the presence of zeaxanthin, the TCR complexes formed more efficiently, resulting in stronger intracellular signalling, higher cytokine production, and improved tumour cell killing.
This nutrient-driven effect effectively boosted immune vigilance, allowing T cells to recognize and destroy cancer cells more effectively than before.
In mouse models, dietary zeaxanthin supplementation alone slowed tumour growth. When combined with immune checkpoint inhibitors, therapies that remove inhibitory “brakes” on T cells, zeaxanthin produced an even greater anti-tumour effect.
The team further tested human T cells engineered to target specific tumour antigens, such as those found in melanoma, multiple myeloma, and glioblastoma. Treatment with zeaxanthin markedly improved their cytotoxic performance, indicating that this natural compound could enhance both natural and engineered immune responses.
These findings suggest that zeaxanthin may serve as an adjunctive therapy to existing immunotherapies, enhancing efficacy while maintaining safety and accessibility.
Zeaxanthin is already marketed as a dietary supplement for eye health and is naturally present in many fruits and vegetables. Its long history of human use and strong safety profile make it an ideal candidate for clinical testing as an immune-boosting dietary component.
By linking a common nutrient to enhanced immune activity, this work opens new avenues for developing cost-effective, widely accessible strategies to improve cancer treatment outcomes. Zeaxanthin’s dual benefits for vision and immunity may make it one of the most versatile natural compounds in modern medicine, a bridge between nutrition, metabolism, and immunotherapy.
Journal article: Zhang, F.Q., et al. 2025. Zeaxanthin augments CD8 effector T cell function and immunotherapy efficacy. Cell Reports Medicine.
Summary by Stefan Botha
