Zeaxanthin supplement bottle. (Image created with AI (OpenAI, 2025))
In A Nutshell
- Zeaxanthin, found in corn, spinach, and eggs, boosted immune T cells in mouse cancer studies.
- Mice given zeaxanthin showed slower melanoma and colon tumor growth.
- The nutrient worked even better when paired with checkpoint immunotherapy.
- These results are early-stage and untested in humans; very high doses were used in mice.
CHICAGO — Scientists searching for nutrients that bolster the immune system have identified an unexpected candidate: zeaxanthin, a pigment found in corn, spinach, and egg yolks that is commonly marketed for eye health.
Researchers at the University of Chicago discovered that zeaxanthin enhanced the ability of CD8+ T cells to attack and destroy tumor cells in mice. When mice with melanoma tumors received daily oral doses of zeaxanthin, tumor growth slowed in mice compared to untreated animals. The compound also worked with checkpoint inhibitor drugs, a type of immunotherapy, to further suppress tumor growth.
The findings, published in Cell Reports Medicine, emerged from a systematic screen of hundreds of nutrients circulating in human blood. The research team co-cultured immune cells with tumor cells in the presence of various dietary compounds to identify which ones improved the immune system’s cancer-fighting capacity.
Structural Twins with Different Effects
Zeaxanthin and lutein are chemical cousins. Both belong to the carotenoid family, differ by just one double bond in their molecular structure, and concentrate in the human retina where they filter blue light. Both are sold as vision supplements, often combined in the same pill.
Yet only zeaxanthin enhanced immune function in the experiments.
When the scientists tested lutein alongside zeaxanthin, lutein failed to increase T cell activation or improve tumor control in mice. This specificity suggests that zeaxanthin’s effects depend on its precise molecular shape rather than general antioxidant properties shared by many carotenoids.
The research team tested several structurally similar compounds and found that only zeaxanthin and fucoxanthin, another carotenoid from seaweed, significantly boosted T cell activity. The symmetrical structure of zeaxanthin, with matching ring structures at both ends of its molecular chain, may be critical for its immune effects.
How Zeaxanthin Works
The researchers traced zeaxanthin’s effects to the surface of CD8+ T cells, a type of immune cell that kills cancer cells. On the surface of these cells sits a protein cluster called the T cell receptor, which acts as the cell’s antenna for detecting threats.
Using a specially designed version of zeaxanthin, the team found evidence that zeaxanthin attaches to parts of this receptor. Rather than simply sitting in cell membranes like other carotenoids, zeaxanthin appears to help assemble the receptor complex on the cell surface.
This triggers a cascade of activity inside the cell. Zeaxanthin treatment increased calcium release and turned on key proteins that activate immune cells. When the researchers blocked these internal signals with drugs, zeaxanthin’s effects disappeared.
Analysis of immune cells inside tumors revealed that zeaxanthin supplementation increased the number of cancer-killing T cells. These cells showed higher levels of activation and produced more inflammatory signals that help fight tumors.
Boosting Immunotherapy
The researchers tested whether zeaxanthin could enhance anti-PD-1 therapy, a widely used cancer treatment that removes the brakes on immune cells. Mice receiving both zeaxanthin and anti-PD-1 drugs showed better tumor control than those receiving either treatment alone in both melanoma and colon cancer models.
In laboratory experiments with human cells, zeaxanthin enhanced the tumor-killing ability of engineered immune cells designed to recognize specific cancer targets. These modified cells killed melanoma cells more effectively when treated with zeaxanthin.
These results hint at potential for zeaxanthin to complement immunotherapy, though this has not been tested in people. Current immunotherapies work well for some patients but fail in many others.
Dietary Sources and Dosing Questions
Zeaxanthin occurs naturally in many foods. Corn and corn products contain high concentrations, as do leafy greens including kale, spinach, and collard greens. Egg yolks provide another source.
Humans cannot make zeaxanthin and must get it from diet or supplements. Blood levels reflect recent intake.
In the mouse experiments, the dose was 500 milligrams of zeaxanthin per kilogram of body weight daily. This dose is far higher than typical human use and may not be achievable through diet or supplements. For context, most zeaxanthin supplements contain 2-10 milligrams per capsule.
The researchers detected increased zeaxanthin levels in both blood and the fluid surrounding tumors. Concentrations were higher in the tumor environment than in blood.
Whether typical dietary intake or standard supplement doses would produce similar effects in humans remains unknown.
What Comes Next
The research has several limitations. All experiments used mouse models, which don’t perfectly replicate human cancer. The study examined only two tumor types, melanoma and colon cancer.
While zeaxanthin had minimal effects on most other immune cell types, the researchers did observe some changes in helper immune cells and regulatory cells that can suppress immune responses. The mechanism by which the nutrient helps assemble the receptor needs further study. The experiments confirmed that zeaxanthin attaches to receptor parts, but the precise details remain unclear.
Human trials would be needed to determine whether zeaxanthin supplementation during immunotherapy improves outcomes for cancer patients. Zeaxanthin has long been used in eye health supplements without major safety issues, but interactions with cancer therapy remain untested.
The research does show that certain dietary nutrients can directly boost anti-tumor immunity, opening possibilities for using supplements alongside conventional cancer treatment.
Disclaimer: This article is for general informational purposes only. It summarizes findings from animal studies and should not be taken as medical advice. Zeaxanthin’s effects in humans with cancer have not been tested. Always consult a healthcare professional before making changes to diet or supplements.
Paper Summary
Methodology
Researchers assembled a library of commercially available nutrients found in human blood, including dietary supplements, lipids, peptides, and metabolites. They performed a co-culture screen where mouse Pmel-1 CD8+ T cells stimulated with anti-CD3/CD28 antibodies were cultured with B16F10 melanoma cells in the presence of each compound. Cell death was measured using a luciferase assay. Hits from the screen were validated in additional co-culture experiments and tested in mouse tumor models using C57BL/6 mice bearing subcutaneous B16F10 or MC38 tumors. Mice received daily oral gavage of zeaxanthin or vehicle control, and tumor growth was monitored. The study employed flow cytometry to analyze tumor-infiltrating immune cells, RNA sequencing to assess gene expression changes, and KAS-seq to measure transcriptional dynamics. A photo-affinity labeling probe was synthesized to identify zeaxanthin binding partners through click chemistry and mass spectrometry. Phospho-antibody arrays tracked activation of signaling pathways in treated T cells.
Results
Zeaxanthin treatment enhanced CD8+ T cell cytotoxicity against tumor cells in co-culture assays, while lutein showed no effect. Oral zeaxanthin supplementation reduced tumor growth in mice bearing B16F10 melanoma or MC38 colon tumors. Depletion of CD8+ T cells abolished this effect, confirming their requirement. Flow cytometry revealed increased CD8+ T cell infiltration into tumors with elevated expression of activation markers (CD69, ICOS) and cytokines (TNF-α, IFN-γ, IL-2). Zeaxanthin increased CD4+ Th1 cells and decreased regulatory T cells in tumors but did not affect other immune populations. The compound promoted T cell receptor complex formation on the cell surface within minutes of stimulation. Photo-affinity labeling demonstrated direct binding to TCR components including TCRα, TCRβ, and CD3ζ. Phospho-antibody arrays showed activation of proximal TCR signaling molecules (ZAP-70, Lck, PLCγ) and downstream pathways involving calcium signaling and NF-κB. Inhibitors of Lck, PLCγ, calcineurin, NFAT, or NF-κB blocked zeaxanthin’s enhancement of T cell function. RNA-seq identified enrichment of TCR signaling and interferon-stimulated genes. Zeaxanthin combined synergistically with anti-PD-1 checkpoint inhibitors to suppress tumor growth. The compound also enhanced cytotoxicity of human TCR-engineered T cells against melanoma targets.
Limitations
The study was conducted entirely in mouse models and cell culture systems, which may not accurately reflect human physiology or cancer biology. Only two tumor types were tested (melanoma and colon cancer), limiting generalizability to other malignancies. The zeaxanthin dose used in mice (500 mg/kg body weight) substantially exceeds typical human dietary intake or supplement doses, raising questions about clinical feasibility. While zeaxanthin bound to the TCR complex, the precise structural basis for its effects compared to the inactive isomer lutein was not fully resolved at the molecular level. The study did not examine potential toxicity or side effects of high-dose zeaxanthin administration. Effects were primarily limited to CD8+ T cells, and impacts on the broader immune system remain incompletely characterized. The duration of supplementation was relatively short, and long-term effects were not assessed. Human validation studies have not been conducted.
Funding and Disclosures
This work was supported by NIH grants CA140515, CA174786, and CA276568 (J.C.), HG006827 (C.H.), and Predoctoral T32 5T32CA009594 (F.Q.Z.), the Ludwig Center at the University of Chicago (C.H.), a Sigal Fellowship in Immuno-oncology (H.F.), and the Harborview Foundation Gift Fund (C.H. and J.C.). C.H. is an Investigator of the Howard Hughes Medical Institute. J.C. has patents pending on zeaxanthin. C.H. has financial interests in several biotechnology companies including serving as a scientific founder and equity holder of Aferna Bio, Inc. and Ellis Bio Inc.
Publication Details
Zhang, F.Q., Li, J., Zhang, R., Tu, J., Xie, Z., Tsuji, T., Shah, H., Ross, M.O., Lyu, R., Matsuzaki, J., Tabor, A., Xue, K., Choudhry, F., Yin, C., Youshanlouei, H.R., Shah, S., Drazer, M.W., He, Y.-Y., Bissonnette, B.M., Li, Y., Mao, H., Huang, J., Dong, L., Su, R., He, C., Odunsi, K., Chen, J., & Fan, H. (2025). “Zeaxanthin augments CD8+ effector T cell function and immunotherapy efficacy,” Cell Reports Medicine, September 16, 2025. DOI: 10.1016/j.xcrm.2025.102324
