> For the complete documentation index, see [llms.txt](https://myhealingcommunity.gitbook.io/myhealingcommunity-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://myhealingcommunity.gitbook.io/myhealingcommunity-docs/breast-cancer/er-positive-her2-negative/endocrine-therapy-resistance-and-dormancy/diet-and-gut-health-may-shape-immunotherapy-response.md). # Diet and Gut Health May Shape Immunotherapy Response What the Fidelle M, Paragios N, Zitvogel L, et al. Nature Medicine 2026 research suggests about histidine, gut health, T-cell metabolism, and checkpoint-inhibitor outcomes. Patient and practitioner facing research support summary of:\ **Fidelle M, Paragios N, Zitvogel L, et al. *****Nature Medicine***** 2026,**\ [**Metabolic determinants of cancer immunotherapy outcomes identified by plasma profiling.**](https://www.nature.com/articles/s41591-026-04481-9) ### Contents * [What did this study look at?](#what-did-this-study-look-at) * [The big finding: histidine looks helpful](#the-big-finding-histidine-looks-helpful) * [What about histidine in food?](#what-about-histidine-in-food) * [What is my histidine status and how do I track it?](#what-is-my-histidine-status-and-how-do-i-track-it) * [The gut microbiome: the “histidine filter”](#the-gut-microbiome-the-histidine-filter) * [Histidine and side effects](#histidine-and-side-effects) * [Histidine tested in mice](#histidine-tested-in-mice) * [Important cautions](#important-cautions) * [What patients should not do for now](#what-patients-should-not-do-for-now) * [Histidine food sources](#histidine-food-sources) * [A reasonable, cautious stance](#a-reasonable-cautious-stance) * [Practitioner-oriented research summary](#practitioner-oriented-research-summary) ### What did this study look at? Researchers studied blood and gut chemistry in more than 1,700 people with cancer treated with immune checkpoint inhibitors, including drugs such as nivolumab, pembrolizumab, atezolizumab, and ipilimumab. They measured 154 small molecules, called metabolites, in 4,336 blood plasma samples. They also looked at gut bacteria and stool metabolites. They wanted to understand: **Are there metabolic signals in the blood and gut that tell us who is more likely to benefit from immunotherapy?** ### The big finding: histidine looks helpful Histidine is an essential amino acid found in protein-rich foods, including meat, fish, eggs, dairy, and some plant proteins. In this study: * People with higher histidine in their blood at baseline tended to: * Have longer time before their cancer progressed. * Live longer overall in several independent patient groups. * In responders to immunotherapy, histidine levels often increased over time. * In non-responders, histidine levels stayed flat or decreased. * In separate cohorts of smokers with cardiovascular disease, higher histidine in the blood was linked to lower risk of developing or dying from tobacco-related cancers, including lung cancer. In simple terms, more histidine in the right context was a good sign for both cancer treatment and future cancer risk. ### What about histidine in food? In one lung cancer cohort, BIOBANK IO, people completed detailed food questionnaires. * Patients who ate more histidine per calorie, at least 1.25 g histidine per 1,000 kcal per day, mostly from meat, fish, and eggs eaten 3 to 4 times a week, had better progression-free survival on immunotherapy. * Surprisingly, in that specific group, blood histidine did not directly match up with progression-free survival. This hints that diet, gut microbes, and tissue metabolism interact in complex ways. So food sources of histidine may help, but it is not simply **eat more meat → higher blood histidine → guaranteed better outcome**. ### What is my histidine status and how do I track it? At present, routine stool tests marketed for ‘gut health’ do not usually quantify histidine or imidazole propionate directly. The research signal in this paper comes from advanced mass‑spectrometry metabolomics on stool, which is largely confined to research settings. Blood histidine, in contrast, can be measured on standard amino‑acid panels, but it does not tell us by itself whether the microbiome is diverting histidine into ImP. ### The gut microbiome: the “histidine filter” Your gut bacteria can transform histidine into different metabolites. This study showed: * In a healthy, eubiotic microbiome, fecal histidine levels correlated with a previously defined favourable microbiota score linked to better immunotherapy outcomes. * In dysbiosis, meaning an unbalanced gut microbiome, bacteria more often converted histidine into imidazole propionate, or ImP, and other products. * Higher ImP, and higher ImP/histidine ratios in stool and blood, were associated with worse progression-free survival. * In high-risk smokers in PREVALUNG, blood histidine was higher in people with eubiotic microbiome signatures. * Blood histidine was inversely associated with inflammatory markers such as IL-6 and IL-1 receptor family proteins. This means histidine may be helpful only if the gut microbiome can handle it well, rather than turning it into harmful by-products. ### Histidine and side effects Immune checkpoint therapy can cause immune-related side effects, for example colitis. In this paper: * Blood histidine was not linked to severe toxicities, grade ≥3. * In several melanoma cohorts, higher histidine in stool, and other essential amino acids, was associated with lower odds of severe immune-related adverse events, including colitis. So gut histidine may relate not just to efficacy, but also to toxicity risk with immunotherapy. ### Histidine tested in mice To test whether histidine is just a marker or can actually help, they treated tumour-bearing mice: * Mice with fibrosarcoma or melanoma received oral histidine along with PD-1 or PD-1/CTLA-4 antibodies. * Histidine: * Accelerated tumour rejection and improved survival when combined with immunotherapy. * Increased fitness of CD8 T cells by enhancing their mitochondrial fatty-acid oxidation, their energy production system. * Helped T cells resist exhaustion in in-vitro models of repeated stimulation. This suggests histidine can directly support immune cells, at least in animal models. ### Important cautions * This study does not prove that taking histidine supplements will help every patient. * It shows strong associations and some animal evidence, but human trials are still needed. * Histidine can be broken down into histamine and ImP. * In some contexts, these may promote inflammation or tumour growth, especially in dysbiosis. * People differ widely in diet, microbiome, kidney function, and tumour type. * What is helpful for one person could be neutral or harmful for another. ### What patients should not do for now * Do not start high-dose histidine supplements on your own based on this study. * We do not yet know the safe and effective dose ranges in cancer patients on immunotherapy, especially with gut dysbiosis. * Do not radically change diet, for example with very high meat intake, without discussing it with your oncology and nutrition teams. * Diet changes can affect weight, metabolic health, and the microbiome in unpredictable ways. ### Histidine food sources
CategoryFoodApprox. histidine (mg/100 g)Notes
Animal – meatPork chop~1,300Typical cut, cooked. One of the highest common sources.
Animal – meatBeef round or lean beef~1,200Includes many lean beef cuts.
Animal – meatLamb~1,100Roast or chop.
Animal – poultryChicken breast~1,000Skinless, cooked.
Animal – poultryTurkey breast~930Skinless, cooked.
Animal – fishCod~1,800Very high. Also carries higher histamine risk if not fresh.
Animal – fishSalmon~800Atlantic or Chinook, cooked.
Animal – fishTuna~880Canned in water or fresh, cooked.
Animal – dairy/eggsParmesan cheese~1,600Hard aged cheeses are dense sources.
Animal – dairy/eggsGouda or firm cheeses~1,000Values vary by cheese type.
Animal – dairy/eggsWhole egg~300One large egg is about 50 g.
Plant – legumesSoybeans, edamame, cooked~450–1,100Very rich source. Numbers vary with preparation.
Plant – legumesLentils, cooked~250–350Similar across lentil varieties.
Plant – legumesChickpeas, cooked~240–260Includes canned, drained.
Plant – legumesKidney, black, or pinto beans, cooked~230–250Most common beans fall in this range.
Plant – nuts and seedsHemp seeds~970Very high density per 100 g.
Plant – nuts and seedsPumpkin seeds~780Raw, shelled.
Plant – nuts and seedsWatermelon seeds~770Often eaten as a roasted snack.
Plant – nuts and seedsPeanuts~660Peanut butter is similar by weight.
Plant – nuts and seedsSunflower seeds~630Raw, shelled.
Plant – nuts and seedsAlmonds~540Raw.
Plant – nuts and seedsSesame seeds~520Hulled. Tahini is similar per 100 g.
Plant – grainsSpirulina, dried~1,000+Often listed as a plant super-source.
Plant – grainsQuinoa, dry~280–300Present, but less dense than legumes or nuts.
Plant – grainsWhole wheat, dry~250–300Includes whole-wheat flour.
Plant – veg/otherGarlic, raw~110Lower than legumes or nuts, but notable.
Plant – veg/otherShiitake mushrooms~55Per 100 g fresh.
Plant – veg/otherSpinach~60Leafy greens provide smaller amounts.
Plant – fruitDried banana~400High per 100 g dried. Much lower in fresh fruit.
Plant – fruitFresh banana~70–80Moderate, but not a top source.
Values are approximate and compiled from USDA FoodData Central-based sources. They are best used to compare foods, meaning what is relatively higher or lower in histidine, not to calculate exact gram-level dosing. ### A reasonable, cautious stance Based on this research, it is sensible to: * Recognise that metabolism and gut health matter for immunotherapy outcomes. * Ask your team whether participating in metabolomics or microbiome studies is possible in your setting. * Focus on balanced, protein-adequate nutrition and gut-friendly strategies, including fibre, diversity, and avoiding unnecessary antibiotics, rather than chasing single amino acids. * In dysbiosis, prioritise microbiome repair, including dietary fibre, diversity, and FMT where evidence supports it, before or alongside histidine. Clinical trials will be needed to test whether histidine-guided diet or supplementation can safely and reliably improve outcomes. ### Practitioner-oriented research summary
Expand to read the practitioner facing (more nitty gritty) summary from the same paper **Metabolic determinants of immunotherapy outcome: histidine, succinate, fatty acids and microbiome context** #### Study design and methods * Multi-cohort metabolomics-metagenomics analysis within the ONCOBIOME framework, plus external trials: 16 cohorts, 1,714 patients, 4,336 plasma samples, and 620 fecal samples. * Tumour types included NSCLC, colorectal cancer, renal cell carcinoma, bladder cancer, and melanoma. * Treatments included PD-1/PD-L1, CTLA-4, combinations with chemotherapy, TKIs, radiotherapy, and FMT. * Targeted mass-spectrometry metabolomics measured 154 plasma metabolites longitudinally at 2 to 5 time points over up to 27.8 months. * Machine-learning pipeline: * DynForest joint longitudinal-survival random forest model. * Variable importance, VIMP, driven ablation guided by minimum description length criteria. * Training on pooled IML1 (NCT04567446) and SABR (NCT02992912) cohorts. * Validation on PANDORE (NCT03212651). The final model retained 8 predictors: age, BMI, histidine, succinic acid, carnitine, docosatrienoic acid, hexadecanedioic acid, and creatinine. It achieved ROC AUC 0.88 at 12 months in training and 0.73 in validation. #### Core prognostic and predictive signals **Histidine** * Histidine was the dominant metabolic predictor of PFS across iterations, with consistently positive VIMP. * Cox and KM analyses across IML1+SABR, AtezoTRIBE, MIND-DC, PRIMM, and CheckMate-025 showed: * Higher baseline plasma histidine associated with prolonged PFS and or OS. * In CheckMate-025 in mRCC, higher histidine was enriched in the MSKCC favourable-risk group. * Baseline histidine was independently prognostic for PFS and OS. * Longitudinally, responders exhibited rising plasma histidine trajectories across several cohorts, including PROMIT, where chemotherapy-induced Δhistidine predicted subsequent PD-1 response. **High-risk smokers** * In FLEMENGHO, PREVALUNG, and ROBINSCA, meaning smokers with cardiovascular disease or high cardiovascular risk, higher histidine predicted: * Reduced incidence of tobacco-associated cancers. * Reduced risk of death from lung cancer. #### Other metabolites * Succinate was associated with treatment failure and shorter PFS in several cohorts. * It was considered a negative metabolic checkpoint, consistent with pro-inflammatory and oncometabolite literature. * Long-chain fatty acids, including docosatrienoic acid and hexadecanedioic acid: * Were included in the final machine-learning signature. * Higher levels were linked to reduced PFS in some analyses. * Creatinine and carnitine also contributed to the model, reflecting renal function and fatty-acid transport. #### Mechanistic insights: histidine and T cell metabolism **Human immunophenotyping** High circulating histidine correlated with: * Activated CD4 T cells, IL-2Rα/CD25. * TH1 markers, CXCR3, and TFH markers, CXCR5. * CCR6+ B cells, nonclassical monocytes, and increased double-positive T cells, which are hallmarks of TCR engagement. **Murine models: MCA205 fibrosarcoma and RET melanoma** * Histidine gavage, 0.1 or 1 g/kg, plus PD-1 or PD-1+CTLA-4: * Accelerated tumour rejection. * Improved OS versus ICI alone or isotype controls. * Histidine pre-treatment via drinking water: * Delayed tumour establishment. * Reduced aggressiveness, with a dose-dependent effect. * Pharmacokinetics: * Dose-independent increases in plasma and intratumoral histidine. * Modulation of intratumoral AMP, down, and tryptophan, up, suggesting shifts in adenosine and tryptophan immunometabolism. **T cell metabolism and function** * Seahorse analysis of naive CD8 T cells: * Histidine, 1 mM, under low-glucose, fatty-acid-oxidation-permissive conditions increased oxygen consumption rate, OCR. * The effect was CPT1a-dependent and blocked by etomoxir. * Histidine enhanced: * Expansion of pre-effector CD8 T cells, CD44−CD62L−, in tumour-draining lymph nodes and tumours. * Expression of LAG3 and differentiation into ICOS+4-1BB+ effector TILs. * Resistance to TCR-driven exhaustion in repetitive stimulation models. * Dendritic-cell antigen presentation in DC–B3Z cross-presentation assays. These data support histidine as a metabolic co-factor promoting fatty-acid-oxidation-dependent CD8 T cell fitness and antitumour function. #### Diet-microbiome-metabolite axis **BIOBANK IO (NSCLC)** * FFQ-derived histidine intake, normalised to calories: * Histidine ≥1.25 g/1,000 kcal/day was associated with prolonged PFS, HR 0.64, P=0.03. * Plasma histidine was not correlated with PFS or OS, suggesting decoupling of intake and circulating levels in this cohort. **PREVALUNG and TOPOSCORE** * In PREVALUNG FFQ, plasma histidine did not correlate with fish, meat, or egg intake, but: * It was significantly higher in microbiome SIG2/eubiosis versus SIG1/dysbiosis categories. * It inversely correlated with inflammatory cytokines IL-6, IL-1RL1, and IL-18R1, but not CRP. **Histidine conversion to ImP** * In melanoma cohorts with fecal metabolomics: * Fecal histidine positively correlated with favourable microbiota S-score. * Dysbiosis, S-score ≤0.5, accompanied higher plasma ImP. * Plasma and fecal ImP correlated. * Plasma ImP/fecal histidine ratio inversely correlated with S-score. * Ratios: * Fecal trans-urocanic acid to ImP associated with better outcomes, HR 0.34, P≈0.07. * Fecal ImP/histidine associated with worse outcomes, HR 2.2, P≈0.05. * Plasma trans-urocanic acid to histidine ratio negatively associated with PFS, HR 1.70, P≈0.05. Interpretation: in dysbiosis, histidine is preferentially shunted to ImP and possibly histamine, generating an immunosuppressive or pro-inflammatory milieu that blunts histidine’s beneficial effects. #### Toxicity, irAEs * Plasma histidine was not associated with grade ≥3 immunotoxicity in IML1 or IML1+AtezoTRIBE. * In four metastatic melanoma cohorts, MIMic, FMT-LUMINate, PROMIT, and MelAutim, n=142: * Higher stool histidine and other essential amino acids inversely correlated with severe irAEs, grade ≥3, including colitis. * Similar patterns have been reported in mRCC immune checkpoint inhibitor settings. This supports a protective role of fecal histidine, and related amino acids, in irAE risk modulation. #### Translational implications and caution **Potential applications** * Histidine as a prognostic and predictive biomarker: * Baseline plasma histidine and its trajectory could be integrated into risk stratification for ICI efficacy and long-term cancer risk in high-risk populations. * Histidine supplementation: * Oral histidine, 4–8 g/day, has historical safety data in non-oncology trials. * It might be explored as an adjunct to ICI, particularly in: * Older or metabolically frail patients with impaired one-carbon metabolism and mitochondrial capacity. * Stage III/IV cohorts receiving first-line ICI. * Intravenous histidine could theoretically bypass gut dysbiosis, which affects up to about 60% of advanced cancer patients at ICI initiation. * Integrated interventions: * Combining histidine-optimised diet, microbiome profiling, S-score/TOPOSCORE, fecal and plasma histidine–ImP monitoring, and microbiome modulation, including FMT, prebiotics, and probiotics, to support histidine-friendly ecosystems. **Key limitations and safety considerations** * This is an observational, multi-cohort study, with risk of residual confounding despite extensive multivariable modelling and external validation. * Metabolomics sample sizes were moderate. * High-dimensional data are prone to false positives, though the MDL/VIMP framework helps mitigate this. * Histidine metabolism is context-dependent: * In dysbiosis, histidine degradation to ImP and histamine may promote immunosuppression, metabolic dysfunction, or tumour progression. * Prior histidine and histamine literature includes instances of pro-tumoural or pro-angiogenic effects. * This underlines the need for dose and context control. * There are no human randomised controlled trials yet testing histidine supplementation in ICI recipients with metabolomic and microbiome endpoints. #### Suggested practitioner use-cases You might structure clinical-facing guidance as: **Section A – Biomarker layer** * Consider plasma histidine as an investigational biomarker of ICI response probability and long-term risk in research settings. * Track longitudinal histidine with PFS and OS in your own cohorts, ideally alongside succinate and key fatty acids. **Section B – Microbiome stratification** * Use microbiome signatures, for example S-score or TOPOSCORE, to classify patients into eubiosis versus dysbiosis before any histidine-focused intervention. * In dysbiosis, prioritise microbiome repair, including dietary fibre, diversity, and FMT where evidence supports it, before or alongside histidine. **Section C – Trial design ideas** * Randomised, microbiome-stratified studies of oral histidine, or intravenous histidine, plus standard ICI, with endpoints including: * PFS and OS. * T-cell metabolic phenotypes, including fatty-acid oxidation and OCR. * Plasma and fecal histidine, ImP, and urocanic acid. * irAE incidence, especially gastrointestinal toxicity. **Section D – Patient communication** * Emphasise the complexity and early-stage nature of this work. * Position histidine as a promising metabolic lever rather than a current standard of care.
*** {% hint style="warning" %} This information is for education only. It is not medical advice, diagnosis, or treatment. Please speak with a qualified clinician before making changes to care, medication, or supplement use. {% endhint %} {% hint style="info" %} © 2026 Abbey Mitchell. All rights reserved. Please share by URL rather than copying page text. {% endhint %} --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://myhealingcommunity.gitbook.io/myhealingcommunity-docs/breast-cancer/er-positive-her2-negative/endocrine-therapy-resistance-and-dormancy/diet-and-gut-health-may-shape-immunotherapy-response.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.