Current agricultural and food systems encourage research and development on major crops, neglecting regionally important minor crops. Small millets include a group of small-seeded cereal crops of the grass family Poaceae. This includes finger millet, foxtail millet, proso millet, barnyard millet, kodo millet, little millet, teff, fonio, job's tears, guinea millet, and browntop millet. Small millets are an excellent choice to supplement major staple foods for crop and dietary diversity because of their diverse adaptation on marginal lands, less water requirement, lesser susceptibility to stresses, and nutritional superiority compared to major cereal staples. Growing interest among consumers about healthy diets together with climate-resilient features of small millets underline the necessity of directing more research and development towards these crops. Except for finger millet and foxtail millet, and to some extent proso millet and teff, other small millets have received minimal research attention in terms of development of genetic and genomic resources and breeding for yield enhancement. Considerable breeding efforts were made in finger millet and foxtail millet in India and China, respectively, proso millet in the United States of America, and teff in Ethiopia. So far, five genomes, namely foxtail millet, finger millet, proso millet, teff, and Japanese barnyard millet, have been sequenced, and genome of foxtail millet is the smallest (423-510 Mb) while the largest one is finger millet (1.5 Gb). Recent advances in phenotyping and genomics technologies, together with available germplasm diversity, could be utilized in small millets improvement. This review provides a comprehensive insight into the importance of small millets, the global status of their germplasm, diversity, promising germplasm resources, and breeding approaches (conventional and genomic approaches) to accelerate climate-resilient and nutrient-dense small millets for sustainable agriculture, environment, and healthy food systems.

Background and objectivesMore than 2 billion people suffer with malnutrition arising from dietary protein and micronutrients deficiencies. To enhance the dietary nutrient quality, the current study used two largely grown varieties of finger millet, pearl millet, pigeonpea, and chickpea to evaluate the effect of millet–legume blends for their enhanced protein digestibility, amino acid profiles, and essential micronutrients.FindingsOur study revealed the presence of significant levels of proteins (6.3%–22.3%), essential amino acids, and micronutrients (Fe: 2.6–8.5 mg; Zn: 2–5.5 mg; Ca: 22‐450 mg in 100 g) in these varieties. When specific millets combined with legumes in 3:1 proportion, significantly enhanced nutritional value of food by providing a balanced amino acid with good protein digestibility, and high levels of iron (7.58 mg) and zinc (4.96 mg) with 100 g of pearl millet and calcium (400.57 mg) with 100 g of finger millet.ConclusionsPigeonpea and chickpea have a good level of proteins with essential amino acids except methionine and cysteine, whereas millet had balanced amino acid including methionine and cysteine (50% higher) and much higher levels of micronutrients (Fe, Zn and Ca). Therefore, specific millets and legumes combination complemented higher levels of micronutrients in addition to complete proteins to support comprehensive human nutrition.Significance and noveltyThis study opens prospects for selecting complementary nutrient‐dense varieties for household consumption. Industries can explore these product developments significantly to reduce malnutrition if consumed adequately, which is not possible with polished rice, refined wheat flour or maize even if it is combined with legumes.

The study assessed the potential for use of millets in mid-day school meal programs for better nutritional outcomes of children in a peri-urban region of Karnataka, India, where children conventionally consumed a fortified rice-based mid-day meal. For a three-month period, millet-based mid-day meals were fed to 1500 adolescent children at two schools, of which 136 were studied as the intervention group and were compared with 107 other children in two other schools that did not receive the intervention. The intervention design was equivalent to the parallel group, two-arm, superiority trial with a 1:1 allocation ratio. The end line allocation ratio was 1.27:1 due to attrition. It was found that there was statistically significant improvement in stunting (p = 0.000) and the body mass index (p = 0.003) in the intervention group and not in the control group (p = 0.351 and p = 0.511, respectively). The sensory evaluation revealed that all the millet-based menu items had high acceptability, with the highest scores for the following three items: finger millet idli, a steam cooked fermented savory cake; little and pearl millet bisi belle bath, a millet-lentil hot meal; and upma, a pearl and little millet-vegetable meal. These results suggest significant potential for millets to replace or supplement rice in school feeding programs for improved nutritional outcomes of children.

The prevalence of iron deficiency anemia is highest among low and middle-income countries. Millets, including sorghum, are a traditional staple in many of these countries and are known to be rich in iron. However, a wide variation in the iron composition of millets has been reported, which needs to be understood in consonance with its bioavailability and roles in reducing anemia. This systematic review and meta-analysis were carried out to analyze the scientific evidence on the bioavailability of iron in different types of millets, processing, and the impact of millet-based food on iron status and anemia. The results indicated that iron levels in the millets used to study iron bioavailability (both in vivo and in vitro) and efficacy varied with the type and variety from 2 mg/100 g to 8 mg/100 g. However, not all the efficacy studies indicated the iron levels in the millets. There were 30 research studies, including 22 human interventions and 8 in vitro studies, included in the meta-analysis which all discussed various outcomes such as hemoglobin level, serum ferritin level, and absorbed iron. The studies included finger millet, pearl millet, teff and sorghum, or a mixture of millets. The results of 19 studies conducted on anaemic individuals showed that there was a significant (p < 0.01) increase in hemoglobin levels by 13.2% following regular consumption (21 days to 4.5 years) of millets either as a meal or drink compared with regular diets where there was only 2.7% increase. Seven studies on adolescents showed increases in hemoglobin levels from 10.8 ± 1.4 (moderate anemia) to 12.2 ± 1.5 g/dl (normal). Two studies conducted on humans demonstrated that consumption of a pearl millet-based meal significantly increased the bioavailable iron (p < 0.01), with the percentage of bioavailability being 7.5 ± 1.6, and provided bioavailable iron of 1 ± 0.4 mg. Four studies conducted on humans showed significant increases in ferritin level (p < 0.05) up to 54.7%. Eight in-vitro studies showed that traditional processing methods such as fermentation and germination can improve bioavailable iron significantly (p < 0.01) by 3.4 and 2.2 times and contributed to 143 and 95% of the physiological requirement of women, respectively. Overall, this study showed that millets can reduce iron deficiency anemia.

Calcium deficiency during child growth leads to osteoporosis in later stages of life. Finger millet is one of the calcium dense foods, with three times the level of calcium than milk, and the only cereal that contains high calcium content which is consistent across different varieties (364 ± 58 mg/100 g). Thus, finger millet has potential for addressing calcium deficiency naturally. This study aimed to determine the retention and impact of finger millet calcium on bone turnover through a systematic review and meta-analysis. Three human studies were eligible for systematic review. Of these, only two were eligible for meta-analysis to assess the retention of calcium in children of 9 to 12 years. One study on bone turnover markers was not used in the meta-analysis as at least two studies are required to conduct meta-analysis. Due to the lack of complete data only four studies were eligible for meta-analysis to assess the in vitro bioavailability of calcium from unprocessed and a range of different types of processed finger millet. The result shows that there was significant retention (p < 0.05) of 23.4 ± 2.9% calcium from finger-millet-based diet which could help bone accretion during child growth if finger-millet-based diet is consumed. The bone turnover marker study shows that the resorption of calcium reduced by 28% and 47% among peri and post-menopausal women respectively after feeding the nutria mixed grain ball. However, there is no significant change in bone formation marker. Depending on the type of processing, calcium bioavailability either increased or decreased. One in vitro study showed that calcium bioavailability from finger millet was 28.6% when boiled, whereas three studies on processing show that certain processing can double the calcium bioavailability to 61.4%. Irrespective of the type of processing, finger millets contribute to high calcium retention and extremely high bioavailable calcium and could be useful for healthy growth and in dealing with complications related to calcium deficiency.