Traditional vegetable preservation technologies practiced in Acholi subregion of Uganda improves mineral bioavailability but impacts negatively on the contribution of vegetables to household needs for micronutrients

The impact of traditional African preservation methods on the contribution of vegetables to household micronutrient needs (Recommended Dietary Allowance: RDA) has largely remained unquantified. Using Acholi subregion of Uganda as a case area, this study examined using the predominant vegetables consumed in fresh and preserved forms (cowpeas-Vigna unguicullata, okra/lady fingers-Abelmoschus esculentus, Malakwang-Hibscus cannabinus, and eggplants-Solanum melongena), the effect of major traditional vegetable preservation methods (sun drying, boiling and sun drying, and salting and sun drying) on the contents of micronutrients (vitamin A, iron, zinc, calcium, magnesium, and phosphorus), the levels of antinutritional factors (total polyphenols, oxalate, tannins, and phytate), bioavailability of iron and zinc, and the contribution of vegetables to the cumulative annual household RDA for micronutrients. Laboratory analysis showed that all the preservation methods, except the sun drying method reduced the contents of micronutrients by 20%-82% (p <= .05). The contents of antinutritional factors reduced by 1%-80% while in vitro bioavailability of iron and zinc increased by 21%-296% (p <= .05). Nutritional computation revealed that except for calcium, the preservation methods combined, reduced the contribution of the vegetables to cumulative annual RDA for other micronutrients by 28%-60%. These results demonstrate that improvements in bioavailability of essential nutrients (iron and zinc) by traditional preservation methods investigated are associated with significant loss of micronutrients which culminates in significant reduction in the contribution of cultivated vegetables to household RDA for micronutrients. Traditional African preservation methods should be optimized for nutrient retention.