Nutrition in diarrhoea
What weight loss is acceptable, what is concerning, and which deficiencies to consider
Why nutrition matters
Diarrhoea affects fluid balance, calorie intake, and absorption. This matters particularly in chronic diarrhoea.
Weight loss: acceptable vs concerning
Short-term weight loss
During acute diarrhoea, mild weight loss often reflects fluid loss and usually reverses with rehydration.
Concerning weight loss
Medical review is required for unintentional weight loss >5% of body weight, ongoing loss despite eating, or associated anaemia/night symptoms.
Common nutritional deficiencies
Fat-soluble vitamins
- Vitamin A — vision changes, dry skin
- Vitamin D — bone pain, fractures, weakness
- Vitamin E — neuropathy (rare)
- Vitamin K — bruising/bleeding
Water-soluble vitamins
- Vitamin B12 — anaemia, neuropathy, cognitive change
- Folate — anaemia
Minerals and electrolytes
- Iron — iron deficiency anaemia
- Magnesium — weakness, cramps, arrhythmia
- Zinc — impaired immunity
Eating during diarrhoea
- Continue eating if appetite allows
- Small frequent meals often better tolerated
- Avoid unnecessary elimination diets
Supplements
Supplement documented deficiencies; avoid blind high-dose use; monitor response.
Key takeaway: Weight loss and deficiencies are signals. Finding and treating the cause matters more than supplements alone.