Nutrition and Supplementation During Cancer Treatment

General Guidelines

• The American Cancer Society advises caution with high-dose supplements during cancer treatment, and open dialogue between patients and healthcare providers is essential regarding dietary supplementation to ensure no contraindication with prescribed cancer therapy 1
• The European Society for Clinical Nutrition and Metabolism (ESPEN) and other guideline societies provide recommendations for the use of glutamine and glutathione in various clinical settings, with varying levels of evidence and agreement 2, 3, 4, 5, 6

Recommendations for Glutamine Supplementation

• The European Society for Clinical Nutrition and Metabolism (ESPEN) recommends against administering high-dose parenteral glutamine in critically ill patients with acute kidney injury or chronic kidney disease (Grade A recommendation with 100% agreement) and against parenteral glutamine-dipeptide in unstable and complex ICU patients, particularly those with liver and renal failure (Grade A recommendation) 2, 3
• The Surviving Sepsis Campaign guidelines recommend against the use of glutamine to treat sepsis and septic shock (strong recommendation, moderate quality of evidence) 4
• Glutamine supplementation may help with chemotherapy-induced mucosal inflammation, vomiting, diarrhea, and cytopenia, but evidence is mixed and more research is needed 5, 6
• A systematic review and meta-analysis found that glutamine supplementation may decrease mucositis severity/duration, reduce clinical infections, and reduce graft versus host disease, but may increase malignancy relapse rate (relative risk 2.91) 5

Recommendations for Glutathione Supplementation

• The Cystic Fibrosis Foundation guidelines conclude that evidence is insufficient to recommend for or against the chronic use of inhaled glutathione to improve lung function, quality of life, or reduce exacerbations 7
• Glutathione supplementation has been shown to reduce neurotoxicity rates in patients receiving cisplatin and oxaliplatin, but more recent studies have found no significant advantage for glutathione in preventing paclitaxel neurotoxicity 8
• The American College of Clinical Nutrition states that glutathione supplementation is not recommended as a necessary nutritional medication for the general population, due to insufficient evidence supporting its routine use 9
• Ensuring adequate protein nutrition is crucial for maintaining glutathione homeostasis, as suggested by clinical guidelines 9

Safety and Efficacy of Supplementation

• The ESPEN guidelines (2017, 2021) and the most recent clinical nutrition guidelines (2025) explicitly state that there are insufficient consistent clinical data to recommend glutamine or glutathione supplementation during conventional cytotoxic or targeted therapy, or to improve clinical outcome in patients undergoing high-dose chemotherapy and hematopoietic stem cell transplantation 5, 6
• Long-term safety data for glutathione supplementation is lacking, and intravenous glutathione administration has inadequate safety data, particularly for chronic use 5, 6
• Experimental therapies like IV glutathione or NAD should be reserved for clinical trials or when conventional approaches have failed, according to the Clinical Nutrition guideline society 6

Approach to Supplementation

• Clinical response should be monitored with follow-up testing as part of a comprehensive approach to addressing metabolic abnormalities 6
• No clear recommendations are available for glutathione formulations, but dietary approaches, such as consuming foods rich in GSH precursors (sulfur-containing amino acids), are recommended as an alternative to direct GSH supplementation 10, 6