Comparative performance of pearl millet-and sorghum-based diets vs. wheat-and rice-based diets for trace metal bioavailability

Pearl miller and sorghum offer a cheap source of energy compared to wheat and rice and are widely consumed by rural communities in many parts of the world. Due to the low consumption of vegetables and animal foods, millets also are the major suppliers of micronutrients especially for low-income groups. It is of prime importance to study how millets perform in terms of bioavailable contents of trace metals. Investigations were carried out using weanling mice which offer a model for the initial testing of bioavailability of trace metals before human trials. Four isocaloric diets differing only in the type of cereal, i.e pearl millet, sorghum, wheat and rice, were prepared representing habitual dietary patterns observed by National Nutrition Monitoring Bureau (NNMB) of India. Mice were allocated randomly to 4 groups of 8 mice each, and housed individually in metal free metabolic cages. A fifth group of 8 mice fed a balanced synthetic diet served as control. All the groups were fed ad libitum. The absorption of zinc and iron averaged for 3 periods of 5 days each was significantly higher for the wheat and pearl millet group than for the other 2 experimental groups (p<0.05), as were also the levels of liver zinc and iron. The weight gain was also highest (6.9 +/- 1.2 g) in the pearl millet group as compared to sorghum (1.58 +/- 0.59 g), wheat (1.66 +/- 1.27 g) and rice (-0.72 +/- 0.62 g) groups. The levels of liver copper were comparable in all the 5 groups. These results further confirm our earlier in vitro results indicating the superiority of pearl millet but not sorghum in bioavailability of zinc and iron.