An Absorption Study in Young Women to Evaluate the Effect of Polyphenols on Iron Absorption From Ragi (Finger Millet) Using the Iron Isotopic Method

Finger Millet (Eleusine coracana), more commonly known as Ragi, is a type of a millet crop grown in India, including other countries especially in East Africa. Ragi has been perceived as a potential "super cereal" by the United States National Academies being one of the most nutritious among all major cereals. From the nutritional perspective, finger millet is considerably rich in minerals and its micronutrient density is higher than that of the world's major cereal grains: rice and wheat .

Millets (Ragi or finger millet and Jowar or sorghum) were consumed by 59% of rural and 28% of urban population in Karnataka. Ragi consumption was seen predominantly in south Karnataka with 27% of rural and 17% of urban population reporting consumption.

Ragi is the richest source of calcium among cereals with up to 10-fold higher calcium content than brown rice, wheat or maize and three times than that of milk. It is also rich in iron and fiber, making this crop more nutritive as compared to other most commonly used cereals. Finger millet is enriched in the essential amino acids like lysine and methionine which are important in human health and growth but remain absent from most other plant foods . In addition, it also contains useful amounts of the two polyunsaturated fatty acids- linoleic acid and α-linolenic acid , metabolized products of which facilitate normal development of the central nervous system. Despite the well-documented health benefits of finger millet, only a limited progress has been made in context to its nutraceutical applications as functional food. Although, it may have remained underutilized by the general population due to either unawareness or apprehension, its immense potential for enhancing the nutritional and therapeutic attributes by acting as functional food cannot be ignored.

Ragi also contains different antinutrients such as phytates and polyphenols, which have been known to have an inhibiting effect on the absorption of iron. On an average, white finger millet contains 0.04-0.09% polyphenols and brown varieties have 0.08-3.47% . It was found that found proto-catechuic acid (45.0 mg/100 g) is the major free phenolic acid in ragi. In another study of total phenolic compounds in finger millet, it was found to have 85% benzoic acid derivatives (gallic acid, protocatechuic acid, p-hydroxybenzoic acid, vanillic acid, syringic acid) while rest of the fraction were either cinnamic acid derivatives (ferulic acid, trans-cinnamic acid, p-coumaric acid, caffeic acid, sinapic acid) or flavonoids (quercetin, Proanthocyanidins like condensed tannins) . Among bound phenloic acids, ferulic and p-coumaric acid are the major fractions and account for 64-96 and 50-99% of total ferulic and p-coumaric acid content of finger millet grains, respectively.

The dark variety of ragi is the most widely consumed type. The white ragi is the lesser consumed type. However, the levels of polyphenols, which inhibit the absorption of iron, are ten times lower in the white ragi as compared to the dark ragi. Thus, it is important to evaluate the extent of inhibition of the polyphenols on the iron absorption. This information would be beneficial for policy making and promotion of cultivation of the type of ragi that could be most effective for the consumers