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Calcium (Ca) is one of the essential macro-mineral to be taken in adequate quantities for maintaining healthy body functions. It contributes about 1.9% of an adult’s body weight with various benefits viz. reducing the risk of cancer, cardiovascular diseases and diabetes and is very significant in preventing diseases like Osteoporosis and Osteopenia. The RDI of Calcium as mentioned by FAO varies for every human-growth stage as 500mg/day (1-3 years) till1000-1200 mg/day (65 years) depending on the body’s requirement. Though its need for intake is high, their source availability seems to be low for low-income groups. Milk is a common source of Calcium but about 65% of World’s population is lactose intolerant. Calcium supplements are also costly and seems to have side effects. Thus, the idea of consuming the staple crops providing adequate calcium required are highly recommended. This article deals with a research conducted on harnessing calcium in one such traditional and well-adapted crop, the finger millet (known as ragi), through bio-fortification process. It is chosen since it has the highest calcium content of all the cereals 344 mg/100g which is again 3 times higher than that of milk. It is termed as ‘super-cereal’ as it is gluten-free, low fat, non-allergic and easily digestible. It requires low soil fertility and are stress-resilient along with excellent storage qualities.
The bio-fortification involves two process: bio-accessibility and bioavailability. The former explains measuring of the nutrient fraction available for absorption after its release from food matrix in the gastrointestinal tract, while the latter involves exertion of positive health effect by the ingested, digested and absorbed nutrient reaching the systematic circulation. The calcium bioavailability in ragi was found to be 36.6% soluble and 28% dialyzable which is higher than that of rice, sorghum and maize. However, the bio-fortification was challenged by several factors like intrinsic grain properties and extrinsic post-harvest changes. Considering the intrinsic factors, the ragi has high levels of resistant starch and dietary fibres which improves calcium absorption, meanwhile the anti-nutritional factors like phytates andoxalates which exhibits negative correlation with calcium bioavailability are present in higher levels in ragi than other cereals. Yet, these factors have nutraceutical value and protective effects and cannot be disregarded completely. So, many simple processing techniques have been researched on not affecting the actual grain performance through bio-fortification. Among many methods, decortication (the removal of seed coat) proved to be improving bio-accessibility by 37.5% while decreasing the inhibitory contents followed by other methods like malting and sprouting which also improves bio-accessibility to a considerable extent. The research on extrinsic factors like age and gender proved to be accelerating the bio-fortification idea since irrespective of the socio-demographic profile, the calcium retention proved to be highest on a ragi-inclusive diet of all ages.
However, the major challenges comes at the genetic engineering perspectives. Inadequate accuracy in choosing the right genetic variation for calcium content over wide agro-ecological varieties prevails hugely. The development of many genetic resources like mapping markers and breeding lines for specific nutritional traits are under research. The unavailability of sufficient markers and genome sequence information in finger millet has limited the breeding efforts for nutritional improvement. The homeostasis of calcium in ragi is not completely understood due to insufficient information on protein profiling. Besides, the role of soil interaction, morphological traits and hormones on homeostasis remains unknown. But, all these factors are being driven away by the development of a novel technique, Next-Generation Sequencing (NGS), a highly multiplexed genetic technique which explores the depth and breadth of genetic diversity across germplasm sets bringing forward a huge wealth of genetic information. This will eventually lead to a new horizon for finger millet Calcium bio-fortification. With the implementation of such high-throughput approaches, it will be much easier to investigate the genetic architecture of this trait through comparative mapping in various cereals. Also, rather than arbitrarily increasing grain calcium content, we should target improvement in efficiency to mobilize, acquire, transport and store calcium in more bioavailable forms in the edible portions. On health perspectives, we should focus demonstrating ragi’s bio-efficacy in order to monitor any potential negative trade-offs and unintended effects. Even after successful calcium bio-fortification of finger millet, its introduction and success as a functional food still entails knowledge of adequate food processing strategies and consumer preferences. Therefore, a multi-disciplinary research approach, incorporating nutrition, agriculture and market research, is needed to ensure the impact of high calcium bio-fortified finger millet. Overall, the finger millet bio-fortification will improve the quality of life for both the rural-subsided farmers as well as the consumers.
For Reference: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5526919/