Probiotics are live microorganisms that, when consumed in adequate amounts, confer a health benefit. Common genera include Lactobacillus, Bifidobacterium, and Saccharomyces. They are found in fermented foods — curd, yoghurt, kefir, kanji, idli, dosa, kimchi — and as supplements.
Prebiotics are non-digestible food components — mainly certain fibres — that selectively feed beneficial gut bacteria. Sources include onion, garlic, leek, banana, oats, asparagus, and inulin-rich vegetables.
The evidence for probiotics is strain-specific and condition-specific. The strongest clinical evidence is for IBS (modest symptom reduction), antibiotic-associated diarrhoea (prevention), and C. difficile infection prevention. Claims about immunity, mental health, and weight are currently exploratory.
Probiotic foods as part of a varied diet are a sensible, low-risk approach. High-dose probiotic supplements in immunocompromised individuals carry rare but real safety concerns — discuss with your clinician.