Cancer and its treatment attack nutrition from every side: appetite, taste, the mouth, the gut and metabolism itself. The dietitian rarely controls the disease, but can often control whether a patient arrives at the next cycle, surgery or scan stronger or weaker. The evidence base is better than many people assume, and most of it fits on one page.
- Screen everyone, then confirm and grade malnutrition with GLIM: one phenotypic plus one aetiologic criterion.
- ESPEN 2021 targets: energy generally 25 to 30 kcal/kg/day, protein above 1 g/kg/day and, if possible, up to 1.5 g/kg/day.
- Taste change is common but highly variable between regimens. Manage it with flavour strategy, not just more seasoning.
- Severe mucositis with intake under 50% for more than 7 days is a red flag for urgent escalation.
Screen early, then diagnose with GLIM
Do not wait for a referral. Screen at diagnosis with a validated tool such as PG-SGA or NRS-2002, and repeat it during treatment, because risk climbs once treatment starts. A positive screen is not a diagnosis. The GLIM criteria confirm malnutrition when a patient meets at least one phenotypic criterion (unintentional weight loss, low BMI or reduced muscle mass) and at least one aetiologic criterion (reduced food intake or assimilation, or disease burden and inflammation). Weight loss of 5 to 10% within six months is moderate; more than 10% within six months is severe.
GLIM was published in 2019. In 2025 a 43-member working group reviewed five years of validation work and kept the weight-loss, BMI and intake criteria unchanged, so the 2019 cut-offs remain the ones to use (Jensen et al., 2025).
Energy and protein: what ESPEN actually says
The ESPEN practical guideline on clinical nutrition in cancer (Muscaritoli et al., 2021) assumes that total energy expenditure, if not measured, is similar to healthy adults and generally 25 to 30 kcal/kg/day. For protein, it recommends intake above 1 g/kg/day and, if possible, up to 1.5 g/kg/day. Those numbers are widely misquoted as higher. Use them as a starting point, then adjust against weight trajectory, intake and function. Spread protein across the day, and pair nutrition with resistance exercise wherever the patient can manage it.
For a patient who has eaten very little for a long time, the energy target is a destination, not a starting rate. Assess refeeding risk before escalating, start low, and step up under monitoring.
Taste changes: common, variable, manageable
A 2025 systematic review and meta-analysis pooled the prevalence of chemotherapy-induced taste alterations at about 70% across 30 studies (Zhang et al., 2025). The spread was enormous, though, with individual studies reporting anywhere from 21% to 100%. The fair message is that taste change is common, not that it is predictable for a given regimen. Typical patterns are a metallic taste (particularly with platinum agents), blunted sweet and salt so food tastes bland, and aversion to red meat.
- Metallic taste: plastic cutlery, tart or sour flavours to mask it, mint or ginger between meals.
- Bland taste: herbs, spices, marinades and umami foods such as mushrooms or parmesan, plus contrasting temperatures in one meal.
- Meat aversion: swap in eggs, dairy, legumes, fish, poultry or tofu so protein does not fall with it.
- Before meals: brush teeth or rinse to reset the mouth.
Taste usually begins to recover within weeks of finishing chemotherapy. After head and neck radiotherapy it can take many months and is occasionally permanent, so set expectations honestly.
Mucositis: two interventions worth knowing
In head and neck radiotherapy, oral mucositis is close to expected rather than merely a risk. The MASCC/ISOO guideline (Elad et al., 2020) contains two recommendations close enough to dietetics to quote at the multidisciplinary team meeting. First, oral cryotherapy: ice chips held in the mouth for 30 minutes, starting just before the infusion, is recommended to prevent mucositis with bolus 5-fluorouracil and with high-dose melphalan before stem cell transplant. It is cheap and often missed, but cold is contraindicated with oxaliplatin. Second, glutamine depends on route and population: oral glutamine is suggested in head and neck chemoradiotherapy, while parenteral glutamine is recommended against in stem cell transplant. It is not a blanket yes or no.
Appetite and early fullness
When appetite has gone, eat by the clock rather than by hunger: small, energy-dense, protein-rich meals or snacks every 2 to 3 hours, fortified foods, and liquid nutrition between meals rather than with them. Consider oral nutritional supplements when intake stays below about 75% of requirements. Framing food as part of treatment, taken in small regular doses, often helps patients who feel guilty about not finishing meals.
Antiemetic and appetite-stimulant prescribing, oncology treatment decisions and nutrition support routes are decided with the oncology team. The dietitian assesses, sets targets, manages nutrition impact symptoms and escalates early. This page is educational, not prescribing guidance.
Tying it together
Screen early, diagnose properly with GLIM, set ESPEN-based targets, and work symptom by symptom so the patient can keep eating through treatment. When oral intake fails, escalate quickly rather than waiting for weight loss to make the decision for you.
Sources
- Muscaritoli M, et al. ESPEN practical guideline: Clinical nutrition in cancer. Clin Nutr. 2021;40(5):2898-2913.
- Cederholm T, et al. GLIM criteria for the diagnosis of malnutrition: a consensus report from the global clinical nutrition community. Clin Nutr. 2019;38(1):1-9.
- Jensen GL, et al. GLIM consensus approach to diagnosis of malnutrition: a 5-year update. JPEN J Parenter Enteral Nutr. 2025;49(4):414-427.
- Elad S, et al. MASCC/ISOO clinical practice guidelines for the management of mucositis secondary to cancer therapy. Cancer. 2020;126(19):4423-4431.
- Zhang B, et al. Prevalence and risk factors of chemotherapy-induced taste alterations among cancer patients: a systematic review and meta-analysis. Eur J Oncol Nurs. 2025;74:102735.