L-Cystine plus L-theanine, study-specific combination

What it acts on

1. The cystine-theanine mixture reduced diarrhea in the mouse chemotherapy model.

   L-Cystine plus L-theanine, study-specific combination → Chemotherapy-associated diarrhea source_derived_draftungraded
   Experimental context and source evidence

   evidence_span

   {"source_cache": "artifacts/theanine-research/34922485.abstract.txt", "locator": "Primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "5828410d2c083fec47a3c7e1907b801a2dc616dbbb7e5ed36e59d503bceeb282", "start_char": 0, "end_char": 1703, "text_sha256": "5828410d2c083fec47a3c7e1907b801a2dc616dbbb7e5ed36e59d503bceeb282"}

   experimental_model

   Chemotherapy-associated intestinal injury experiment

   exposure

   Cystine plus theanine during 5-fluorouracil exposure

   limitations

   Combination product, not isolated theanine. Preservation of antitumor activity in the tested model does not establish compatibility with every human chemotherapy regimen.

   nutrient_topic

   L-Theanine research collection; topical membership is not evidence of a direct dietary effect. · L-Theanine

   organism

   Mice

   plain_language

   This result belongs to the tested two-ingredient mixture and its chemotherapy context.

   primary_references

   [theanine-p34922485] Oral administration of cystine and theanine attenuates 5-fluorouracil-induced intestinal mucositis and diarrhea by suppressing both glutathione level decrease and ROS production in the small intestine of mucositis mouse model. (2021). https://pubmed.ncbi.nlm.nih.gov/34922485/ DOI: 10.1186/s12885-021-09057-z

   tissue_or_cell_type

   Intestinal redox balance and crypt injury

   L-Theanine: metabolism, neural signaling, nutrient connections and human outcomes (2026-09-17) · lines 783–794

   AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Chemotherapy-associated intestinal injury experiment · source_derived_draft · unverified_draft

   ### theanine-ct-diarrhea The cystine-theanine mixture reduced diarrhea in the mouse chemotherapy model. Condition category: normal nutrient_topic: L-Theanine research collection; topical membership is not evidence of a direct dietary effect. plain_language: This result belongs to the tested two-ingredient mixture and its chemotherapy context. organism: Mice tissue_or_cell_type: Intestinal redox balance and crypt injury experimental_model: Chemotherapy-associated intestinal injury experiment limitations: Combination product, not isolated theanine. Preservation of antitumor activity in the tested model does not establish compatibility with every human chemotherapy regimen. exposure: Cystine plus theanine during 5-fluorouracil exposure evidence_span: {"source_cache": "artifacts/theanine-research/34922485.abstract.txt", "locator": "Primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "5828410d2c083fec47a3c7e1907b801a2dc616dbbb7e5ed36e59d503bceeb282", "start_char": 0, "end_char": 1703, "text_sha256": "5828410d2c083fec47a3c7e1907b801a2dc616dbbb7e5ed36e59d503bceeb282"} [theanine-p34922485] Oral administration of cystine and theanine attenuates 5-fluorouracil-induced intestinal mucositis and diarrhea by suppressing both glutathione level decrease and ROS production in the small intestine of mucositis mouse model. (2021). https://pubmed.ncbi.nlm.nih.gov/34922485/ DOI: 10.1186/s12885-021-09057-z

   Complete structured claim and evidence

2. The mixture reduced lung influenza virus titer at the reported postinfection time point in aged mice.

   L-Cystine plus L-theanine, study-specific combination → Lung influenza-virus titer source_derived_draftungraded
   Experimental context and source evidence

   evidence_span

   {"source_cache": "artifacts/theanine-research/19940390.abstract.txt", "locator": "Primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "1fddde12da03a7fd75a7415e00207f4ac2c34c9215ab504ea1b3735e36db3a26", "start_char": 0, "end_char": 1786, "text_sha256": "1fddde12da03a7fd75a7415e00207f4ac2c34c9215ab504ea1b3735e36db3a26"}

   experimental_model

   Aged-animal influenza challenge and immunization

   exposure

   Oral cystine plus theanine before influenza challenge

   limitations

   Animal combination study; enzyme-subunit identity is not inferred from the generic gamma-glutamylcysteine synthetase wording. No proof theanine alone prevents human influenza.

   nutrient_topic

   L-Theanine research collection; topical membership is not evidence of a direct dietary effect. · L-Theanine

   organism

   Aged mice

   plain_language

   A viral-load endpoint in aged mice remains distinct from a human clinical prevention claim.

   primary_references

   [theanine-p19940390] Combined administration of (L)-cystine and (L)-theanine enhances immune functions and protects against influenza virus infection in aged mice. (2010). https://pubmed.ncbi.nlm.nih.gov/19940390/ DOI: 10.1292/jvms.09-0067

   tissue_or_cell_type

   Spleen and lung

   L-Theanine: metabolism, neural signaling, nutrient connections and human outcomes (2026-09-17) · lines 809–820

   AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Aged-animal influenza challenge and immunization · source_derived_draft · unverified_draft

   ### theanine-ct-influenza-titer The mixture reduced lung influenza virus titer at the reported postinfection time point in aged mice. Condition category: normal nutrient_topic: L-Theanine research collection; topical membership is not evidence of a direct dietary effect. plain_language: A viral-load endpoint in aged mice remains distinct from a human clinical prevention claim. organism: Aged mice tissue_or_cell_type: Spleen and lung experimental_model: Aged-animal influenza challenge and immunization limitations: Animal combination study; enzyme-subunit identity is not inferred from the generic gamma-glutamylcysteine synthetase wording. No proof theanine alone prevents human influenza. exposure: Oral cystine plus theanine before influenza challenge evidence_span: {"source_cache": "artifacts/theanine-research/19940390.abstract.txt", "locator": "Primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "1fddde12da03a7fd75a7415e00207f4ac2c34c9215ab504ea1b3735e36db3a26", "start_char": 0, "end_char": 1786, "text_sha256": "1fddde12da03a7fd75a7415e00207f4ac2c34c9215ab504ea1b3735e36db3a26"} [theanine-p19940390] Combined administration of (L)-cystine and (L)-theanine enhances immune functions and protects against influenza virus infection in aged mice. (2010). https://pubmed.ncbi.nlm.nih.gov/19940390/ DOI: 10.1292/jvms.09-0067

   Complete structured claim and evidence

3. The cystine-theanine mixture restored the intestinal GSH/GSSG ratio during 5-fluorouracil exposure.

   L-Cystine plus L-theanine, study-specific combination → Small-intestinal mucosal GSH/GSSG ratio source_derived_draftungraded
   Experimental context and source evidence

   evidence_span

   {"source_cache": "artifacts/theanine-research/34922485.abstract.txt", "locator": "Primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "5828410d2c083fec47a3c7e1907b801a2dc616dbbb7e5ed36e59d503bceeb282", "start_char": 0, "end_char": 1703, "text_sha256": "5828410d2c083fec47a3c7e1907b801a2dc616dbbb7e5ed36e59d503bceeb282"}

   experimental_model

   Chemotherapy-associated intestinal injury experiment

   exposure

   Cystine plus theanine during 5-fluorouracil exposure

   limitations

   Combination product, not isolated theanine. Preservation of antitumor activity in the tested model does not establish compatibility with every human chemotherapy regimen.

   nutrient_topic

   L-Theanine research collection; topical membership is not evidence of a direct dietary effect. · L-Theanine

   organism

   Mice

   plain_language

   This result belongs to the tested two-ingredient mixture and its chemotherapy context.

   primary_references

   [theanine-p34922485] Oral administration of cystine and theanine attenuates 5-fluorouracil-induced intestinal mucositis and diarrhea by suppressing both glutathione level decrease and ROS production in the small intestine of mucositis mouse model. (2021). https://pubmed.ncbi.nlm.nih.gov/34922485/ DOI: 10.1186/s12885-021-09057-z

   tissue_or_cell_type

   Intestinal redox balance and crypt injury

   L-Theanine: metabolism, neural signaling, nutrient connections and human outcomes (2026-09-17) · lines 757–768

   AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Chemotherapy-associated intestinal injury experiment · source_derived_draft · unverified_draft

   ### theanine-ct-redox The cystine-theanine mixture restored the intestinal GSH/GSSG ratio during 5-fluorouracil exposure. Condition category: normal nutrient_topic: L-Theanine research collection; topical membership is not evidence of a direct dietary effect. plain_language: This result belongs to the tested two-ingredient mixture and its chemotherapy context. organism: Mice tissue_or_cell_type: Intestinal redox balance and crypt injury experimental_model: Chemotherapy-associated intestinal injury experiment limitations: Combination product, not isolated theanine. Preservation of antitumor activity in the tested model does not establish compatibility with every human chemotherapy regimen. exposure: Cystine plus theanine during 5-fluorouracil exposure evidence_span: {"source_cache": "artifacts/theanine-research/34922485.abstract.txt", "locator": "Primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "5828410d2c083fec47a3c7e1907b801a2dc616dbbb7e5ed36e59d503bceeb282", "start_char": 0, "end_char": 1703, "text_sha256": "5828410d2c083fec47a3c7e1907b801a2dc616dbbb7e5ed36e59d503bceeb282"} [theanine-p34922485] Oral administration of cystine and theanine attenuates 5-fluorouracil-induced intestinal mucositis and diarrhea by suppressing both glutathione level decrease and ROS production in the small intestine of mucositis mouse model. (2021). https://pubmed.ncbi.nlm.nih.gov/34922485/ DOI: 10.1186/s12885-021-09057-z

   Complete structured claim and evidence

4. The cystine-theanine mixture reduced reactive oxygen species in intestinal crypts.

   L-Cystine plus L-theanine, study-specific combination → Intestinal crypt reactive oxygen species production source_derived_draftungraded
   Experimental context and source evidence

   evidence_span

   {"source_cache": "artifacts/theanine-research/34922485.abstract.txt", "locator": "Primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "5828410d2c083fec47a3c7e1907b801a2dc616dbbb7e5ed36e59d503bceeb282", "start_char": 0, "end_char": 1703, "text_sha256": "5828410d2c083fec47a3c7e1907b801a2dc616dbbb7e5ed36e59d503bceeb282"}

   experimental_model

   Chemotherapy-associated intestinal injury experiment

   exposure

   Cystine plus theanine during 5-fluorouracil exposure

   limitations

   Combination product, not isolated theanine. Preservation of antitumor activity in the tested model does not establish compatibility with every human chemotherapy regimen.

   nutrient_topic

   L-Theanine research collection; topical membership is not evidence of a direct dietary effect. · L-Theanine

   organism

   Mice

   plain_language

   This result belongs to the tested two-ingredient mixture and its chemotherapy context.

   primary_references

   [theanine-p34922485] Oral administration of cystine and theanine attenuates 5-fluorouracil-induced intestinal mucositis and diarrhea by suppressing both glutathione level decrease and ROS production in the small intestine of mucositis mouse model. (2021). https://pubmed.ncbi.nlm.nih.gov/34922485/ DOI: 10.1186/s12885-021-09057-z

   tissue_or_cell_type

   Intestinal redox balance and crypt injury

   L-Theanine: metabolism, neural signaling, nutrient connections and human outcomes (2026-09-17) · lines 770–781

   AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Chemotherapy-associated intestinal injury experiment · source_derived_draft · unverified_draft

   ### theanine-ct-ros The cystine-theanine mixture reduced reactive oxygen species in intestinal crypts. Condition category: normal nutrient_topic: L-Theanine research collection; topical membership is not evidence of a direct dietary effect. plain_language: This result belongs to the tested two-ingredient mixture and its chemotherapy context. organism: Mice tissue_or_cell_type: Intestinal redox balance and crypt injury experimental_model: Chemotherapy-associated intestinal injury experiment limitations: Combination product, not isolated theanine. Preservation of antitumor activity in the tested model does not establish compatibility with every human chemotherapy regimen. exposure: Cystine plus theanine during 5-fluorouracil exposure evidence_span: {"source_cache": "artifacts/theanine-research/34922485.abstract.txt", "locator": "Primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "5828410d2c083fec47a3c7e1907b801a2dc616dbbb7e5ed36e59d503bceeb282", "start_char": 0, "end_char": 1703, "text_sha256": "5828410d2c083fec47a3c7e1907b801a2dc616dbbb7e5ed36e59d503bceeb282"} [theanine-p34922485] Oral administration of cystine and theanine attenuates 5-fluorouracil-induced intestinal mucositis and diarrhea by suppressing both glutathione level decrease and ROS production in the small intestine of mucositis mouse model. (2021). https://pubmed.ncbi.nlm.nih.gov/34922485/ DOI: 10.1186/s12885-021-09057-z

   Complete structured claim and evidence

5. Cystine plus theanine increased splenic gamma-glutamylcysteine synthetase mRNA in aged mice.

   L-Cystine plus L-theanine, study-specific combination → Splenic glutathione-synthesis gene expression source_derived_draftungraded
   Experimental context and source evidence

   evidence_span

   {"source_cache": "artifacts/theanine-research/19940390.abstract.txt", "locator": "Primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "1fddde12da03a7fd75a7415e00207f4ac2c34c9215ab504ea1b3735e36db3a26", "start_char": 0, "end_char": 1786, "text_sha256": "1fddde12da03a7fd75a7415e00207f4ac2c34c9215ab504ea1b3735e36db3a26"}

   experimental_model

   Aged-animal influenza challenge and immunization

   exposure

   Oral cystine plus theanine before influenza challenge

   limitations

   Animal combination study; enzyme-subunit identity is not inferred from the generic gamma-glutamylcysteine synthetase wording. No proof theanine alone prevents human influenza.

   nutrient_topic

   L-Theanine research collection; topical membership is not evidence of a direct dietary effect. · L-Theanine

   organism

   Aged mice

   plain_language

   Precursor supplementation was linked to expression of glutathione-synthesis machinery, not proof of every downstream antioxidant benefit.

   primary_references

   [theanine-p19940390] Combined administration of (L)-cystine and (L)-theanine enhances immune functions and protects against influenza virus infection in aged mice. (2010). https://pubmed.ncbi.nlm.nih.gov/19940390/ DOI: 10.1292/jvms.09-0067

   tissue_or_cell_type

   Spleen and lung

   L-Theanine: metabolism, neural signaling, nutrient connections and human outcomes (2026-09-17) · lines 796–807

   AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Aged-animal influenza challenge and immunization · source_derived_draft · unverified_draft

   ### theanine-ct-splenic-expression Cystine plus theanine increased splenic gamma-glutamylcysteine synthetase mRNA in aged mice. Condition category: normal nutrient_topic: L-Theanine research collection; topical membership is not evidence of a direct dietary effect. plain_language: Precursor supplementation was linked to expression of glutathione-synthesis machinery, not proof of every downstream antioxidant benefit. organism: Aged mice tissue_or_cell_type: Spleen and lung experimental_model: Aged-animal influenza challenge and immunization limitations: Animal combination study; enzyme-subunit identity is not inferred from the generic gamma-glutamylcysteine synthetase wording. No proof theanine alone prevents human influenza. exposure: Oral cystine plus theanine before influenza challenge evidence_span: {"source_cache": "artifacts/theanine-research/19940390.abstract.txt", "locator": "Primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "1fddde12da03a7fd75a7415e00207f4ac2c34c9215ab504ea1b3735e36db3a26", "start_char": 0, "end_char": 1786, "text_sha256": "1fddde12da03a7fd75a7415e00207f4ac2c34c9215ab504ea1b3735e36db3a26"} [theanine-p19940390] Combined administration of (L)-cystine and (L)-theanine enhances immune functions and protects against influenza virus infection in aged mice. (2010). https://pubmed.ncbi.nlm.nih.gov/19940390/ DOI: 10.1292/jvms.09-0067

   Complete structured claim and evidence

6. Overall influenza antibody titers and seroconversion did not differ significantly between mixture and placebo groups.

   L-Cystine plus L-theanine, study-specific combination → Influenza vaccine seroconversion source_derived_draftungraded
   Experimental context and source evidence

   evidence_span

   {"source_cache": "artifacts/theanine-research/19149835.abstract.txt", "locator": "Primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "a45aa5961c392e87f67d397ff9637dc5d65457d06397de0aaa5712c4daf00cf8", "start_char": 0, "end_char": 1659, "text_sha256": "a45aa5961c392e87f67d397ff9637dc5d65457d06397de0aaa5712c4daf00cf8"}

   experimental_model

   Randomized placebo-controlled vaccine response study

   exposure

   32 participants cystine-theanine; 33 placebo; 14 days supplementation

   limitations

   Overall negative result; subgroup observations require confirmation and do not establish universal benefit in low-protein states.

   nutrient_topic

   L-Theanine research collection; topical membership is not evidence of a direct dietary effect. · L-Theanine

   organism

   65 elderly humans

   plain_language

   The main population result was negative.

   primary_references

   [theanine-p19149835] Co-administration of l-cystine and l-theanine enhances efficacy of influenza vaccination in elderly persons: nutritional status-dependent immunogenicity. (2008). https://pubmed.ncbi.nlm.nih.gov/19149835/ DOI: 10.1111/j.1447-0594.2008.00483.x

   tissue_or_cell_type

   Influenza hemagglutination-inhibition and seroconversion

   L-Theanine: metabolism, neural signaling, nutrient connections and human outcomes (2026-09-17) · lines 822–833

   AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Randomized placebo-controlled vaccine response study · source_derived_draft · unverified_draft

   ### theanine-vaccine-overall-null Overall influenza antibody titers and seroconversion did not differ significantly between mixture and placebo groups. Condition category: normal nutrient_topic: L-Theanine research collection; topical membership is not evidence of a direct dietary effect. plain_language: The main population result was negative. organism: 65 elderly humans tissue_or_cell_type: Influenza hemagglutination-inhibition and seroconversion experimental_model: Randomized placebo-controlled vaccine response study limitations: Overall negative result; subgroup observations require confirmation and do not establish universal benefit in low-protein states. exposure: 32 participants cystine-theanine; 33 placebo; 14 days supplementation evidence_span: {"source_cache": "artifacts/theanine-research/19149835.abstract.txt", "locator": "Primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "a45aa5961c392e87f67d397ff9637dc5d65457d06397de0aaa5712c4daf00cf8", "start_char": 0, "end_char": 1659, "text_sha256": "a45aa5961c392e87f67d397ff9637dc5d65457d06397de0aaa5712c4daf00cf8"} [theanine-p19149835] Co-administration of l-cystine and l-theanine enhances efficacy of influenza vaccination in elderly persons: nutritional status-dependent immunogenicity. (2008). https://pubmed.ncbi.nlm.nih.gov/19149835/ DOI: 10.1111/j.1447-0594.2008.00483.x

   Complete structured claim and evidence

7. Higher H1N1 seroconversion was reported in low-total-protein and low-hemoglobin subgroups receiving the mixture.

   L-Cystine plus L-theanine, study-specific combination → Influenza vaccine seroconversion source_derived_draftungraded
   Experimental context and source evidence

   evidence_span

   {"source_cache": "artifacts/theanine-research/19149835.abstract.txt", "locator": "Primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "a45aa5961c392e87f67d397ff9637dc5d65457d06397de0aaa5712c4daf00cf8", "start_char": 0, "end_char": 1659, "text_sha256": "a45aa5961c392e87f67d397ff9637dc5d65457d06397de0aaa5712c4daf00cf8"}

   experimental_model

   Randomized placebo-controlled vaccine response study

   exposure

   32 participants cystine-theanine; 33 placebo; 14 days supplementation

   limitations

   Overall negative result; subgroup observations require confirmation and do not establish universal benefit in low-protein states.

   nutrient_topic

   L-Theanine research collection; topical membership is not evidence of a direct dietary effect. · L-Theanine

   organism

   65 elderly humans

   plain_language

   A subgroup signal can guide another study; it does not overturn the overall null result.

   primary_references

   [theanine-p19149835] Co-administration of l-cystine and l-theanine enhances efficacy of influenza vaccination in elderly persons: nutritional status-dependent immunogenicity. (2008). https://pubmed.ncbi.nlm.nih.gov/19149835/ DOI: 10.1111/j.1447-0594.2008.00483.x

   tissue_or_cell_type

   Exploratory low-total-protein or low-hemoglobin subgroups

   L-Theanine: metabolism, neural signaling, nutrient connections and human outcomes (2026-09-17) · lines 835–846

   AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Randomized placebo-controlled vaccine response study · source_derived_draft · unverified_draft

   ### theanine-vaccine-subgroup Higher H1N1 seroconversion was reported in low-total-protein and low-hemoglobin subgroups receiving the mixture. Condition category: normal nutrient_topic: L-Theanine research collection; topical membership is not evidence of a direct dietary effect. plain_language: A subgroup signal can guide another study; it does not overturn the overall null result. organism: 65 elderly humans tissue_or_cell_type: Exploratory low-total-protein or low-hemoglobin subgroups experimental_model: Randomized placebo-controlled vaccine response study limitations: Overall negative result; subgroup observations require confirmation and do not establish universal benefit in low-protein states. exposure: 32 participants cystine-theanine; 33 placebo; 14 days supplementation evidence_span: {"source_cache": "artifacts/theanine-research/19149835.abstract.txt", "locator": "Primary indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "a45aa5961c392e87f67d397ff9637dc5d65457d06397de0aaa5712c4daf00cf8", "start_char": 0, "end_char": 1659, "text_sha256": "a45aa5961c392e87f67d397ff9637dc5d65457d06397de0aaa5712c4daf00cf8"} [theanine-p19149835] Co-administration of l-cystine and l-theanine enhances efficacy of influenza vaccination in elderly persons: nutritional status-dependent immunogenicity. (2008). https://pubmed.ncbi.nlm.nih.gov/19149835/ DOI: 10.1111/j.1447-0594.2008.00483.x

   Complete structured claim and evidence