Health effects, sources, utilization and safety of tannins: a critical review

Tannins are complex, astringent and water soluble phenolic compounds known to reduce the bioavailability of nutrients in gut. Furthermore, tannins pose some health consequences viz. antinutritional effect, reduced digestibility, mutagenic and carcinogenic effects and inducer, hepatotoxic activity and co-promoters of several diseases. However, recent studies have explored and confirmed numerous health benefits like anti-oxidant, anti-cancerous, anti-allergic, anti-inflammatory, anti-helminthic and anti-microbial activities). Owing to their astringency, the food applications are very limited; whereas, they have wide applications in pharmaceutical industries. The present review has been aimed to highlight the classification, sources, occurrence, health effects, industrial applications and the safe limits of consumption of tannins.