Recent scientific studies have established a relationship between the consumption of phytochemicals such as carotenoids, polyphenols, isoprenoids, phytosterols, saponins, dietary fibers, polysaccharides, etc., with health benefits such as prevention of diabetes, obesity, cancer, cardiovascular diseases, etc. This has led to the popularization of phytochemicals. Nowadays, foods containing phytochemicals as a constituent (functional foods) and the concentrated form of phytochemicals (nutraceuticals) are used as a preventive measure or cure for many diseases. The health benefits of these phytochemicals depend on their purity and structural stability. The yield, purity, and structural stability of extracted phytochemicals depend on the matrix in which the phytochemical is present, the method of extraction, the solvent used, the temperature, and the time of extraction.

World is facing agrarian as well as nutritional challenges. Agricultural lands with irrigation facilities have been exploited to maximum, and hence we need to focus on dry lands to further increase grain production. Owing to low fertility, utilization of dry lands to produce sufficient quality grains is a big challenge. Millets as climate change compliant crops score highly over other grains like wheat and rice in terms of marginal growing conditions and high nutritional value. These nutri-cereals abode vitamins, minerals, essential fatty acids, phyto-chemicals and antioxidants that can help to eradicate the plethora of nutritional deficiency diseases. Millets cultivation can keep dry lands productive and ensure future food and nutritional security.

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.