The effect of inclusion of cabbage and potatoes in the maize and beans composite meal on the bioavailability of iron and zinc by in-vitro method

The extent of bioavailability of iron and zinc from meals is of great health concern since these micronutrients play key role in mental performance and immune response in human beings. In this study the bioavailability of iron and zinc from maize and bean composite was investigated and found to at 13% for iron and 27.7% for zinc. The inclusion of cabbage enhanced the bioavailability of both to 98.8% and 83.9% respectively to the extent that the differences in the concentrations of iron and zinc in the non-digested and digested samples were not significant (iron, p=0.12 : Zinc, p=0.263). There was a significant difference between concentration of iron and Zinc in the basic mixture when non-digested and digested were compared with p= 0.004 for iron and 0.012 for zinc respectively. In the samples where cabbage was included, there were no significant differences in the concentrations of iron and zinc between the non-digested and digested (iron, p=0.12, zinc, p=0.263) an indication of high bioavailability. The inclusion of potatoes reduced the bioavailability of iron and zinc to 76.86 % and 38.9% respectively. This is due to matrix effect where the potato introduces stronger physico-chemical interactions. The composite with maize, beans, cabbage and potatoes have a bioavailability of 76.2%, p= 0.249 for iron and 71.76%, p = 0.405 for zinc). This is an indication that cabbage has a higher enhancing effect than the potatoes. The generally high bioavailability of iron and zinc from a composite of beans and maize can be due to the interaction between the metal ions and tridentate amino acids in the beans where the chelate formed enhances their bioavailability. This interaction increases mucosal membrane permeability and lipo-solubility of the metal ions. The recommendation is that dietitians should educate people on best combination of foods that will enhance the bioavailability of not only iron and zinc but all micronutrients since they are of health importance to pregnant and lactating mothers, young children, adolescents and the elderly. Other alternatives include double fortification of salt with iron and zinc and bio-fortification.