Adult Malnutrition
Overview
•Deficient nutrient intake, absorption, or utilisation relative to requirements → altered body composition and impaired physiological function
•~3 million affected in UK; ~1 in 3 adults admitted to hospital are malnourished or at risk on admission
•Most prevalent in: older adults (>65), chronic illness (cancer, GI disease), mental health conditions, community-dwellers
Aetiology
•Inadequate intake - anorexia, dysphagia, depression, poverty, social isolation
•Malabsorption - Coeliac disease, Crohn's, short bowel syndrome, pancreatic insufficiency, cholestatic liver disease
•Increased requirements - sepsis, cancer, burns, major surgery, hyperthyroidism, chronic inflammation
Presentation
•Unintentional weight loss - >5% in 3 months or >10% in 6 months is clinically significant
•Muscle wasting - temporal, thenar/hypothenar, interossei
•Peripheral oedema - low albumin reduces oncotic pressure (late, insensitive marker)
•Impaired wound healing, recurrent infections, fatigue, angular stomatitis/glossitis, skin/hair/nail changes
Management
NICE CG32: oral first, enteral second, parenteral only when gut cannot be used. Always address the underlying cause alongside nutritional support.
First-line
- 1Dietary modification - fortify food (butter, cheese, cream) + oral nutritional supplements (ONS) e.g. Fortisip, Ensure Plus (1.5-2.4 kcal/mL)
Second-line
- 1Enteral tube feeding - NG tube (short-term); PEG tube (>4 weeks); used when gut functional but patient cannot eat orally (e.g. post-stroke dysphagia, head and neck cancer)
Third-line
- 1Parenteral nutrition (PN) - IV via central venous catheter; reserved for non-functional gut (short bowel syndrome, high-output fistula, prolonged ileus); risks: line infection, thrombosis, liver dysfunction
Complications
Key complications
Impaired immunity - infection, sepsis
Poor wound healing - dehiscence, pressure ulcers
Sarcopenia - falls, functional decline
Respiratory failure - loss of diaphragm/intercostal mass
Cardiac dysfunction - myocardial atrophy, arrhythmias
Wernicke's encephalopathy (thiamine deficiency)
Osteomalacia (vitamin D deficiency)
Peripheral neuropathy (B12 deficiency)
Increased in-hospital mortality
Investigations - Screening (MUST)
MUST (Malnutrition Universal Screening Tool) - BAPEN recommended tool for adults in community and hospital settings. Identifies risk; does not diagnose malnutrition. NICE CG32 supports use at hospital admission and in care homes.
Component | Score 0 | Score 1 | Score 2 |
BMI (kg/m²) | >20 | 18.5-20 | <18.5 |
Unintentional weight loss (3-6 months) | <5% | 5-10% | >10% |
Acute disease effect | - | - | Acutely ill + no intake >5 days (add 2) |
•Score 0 - low risk: routine care
•Score 1 - medium risk: observe, document intake
•Score ≥2 - high risk: refer to dietitian, commence nutrition support
Investigations - Bloods
🥇 First-line
•FBC (anaemia, lymphopenia), U&E (baseline + refeeding risk), LFTs + albumin, bone profile (Ca, phosphate, Mg - critical before nutrition support), CRP, B12/folate/iron/vitamin D, TFTs
🥈 Second-line
•anti-tTG IgA (coeliac), faecal elastase (pancreatic insufficiency), upper/lower GI endoscopy (IBD, malignancy)
Refeeding Syndrome
Potentially life-threatening complication of rapidly reintroducing nutrition to severely malnourished or prolonged-fasting patients.
•Mechanism: carbohydrate reintroduction → insulin surge → intracellular shift of phosphate, potassium, and magnesium → hypophosphataemia → impaired ATP synthesis → cardiac arrhythmia, respiratory failure, seizures, death
•High-risk patients: BMI <16, unintentional weight loss >15%, little/no intake for >10 days, low baseline electrolytes; classically in anorexia nervosa, alcoholism, prolonged post-operative nil-by-mouth
•Prevention: check and correct phosphate, potassium, magnesium before and during refeeding; start feeding slowly (≤10 kcal/kg/day), build up over 4-7 days; prescribe thiamine (Pabrinex IV or oral thiamine) before and during refeeding to prevent Wernicke's encephalopathy