Nutritional composition and mineral bioavailability of selected root and tuber crops in the Bicol Region, Philippines

Filipinos consume root and tuber crops as inexpensive sources of nourishment. However, the limited information on the nutritional and mineral bioavailability of root and tuber crops inhibits their optimal utilization in what could possibly address nutrient deficiencies among the populations. This study determined the proximate composition of cassava, sweet potato, taro, giant swamp taro, cocoyam, and purple yam through the Association of the Analytical Chemists (AOAC) standard method. The mineral bioavailability was determined in vitro by simulating digestion from the oral up to the intestinal phase. Mineral and trace metal contents were quantified using a Microwave Plasma Atomic Emission Spectrometer (MP-AES). The crops’ ash, protein, fat, and total dietary fiber contents ranged from 1.23-3.53%, 2.01-9.32%, 0.18-0.83%, and 4.23-19.3%, respectively. Taro (9.32%) and purple yam (6.71%) have the highest protein contents among the crops examined and can be considered as sources of protein based on the recommended nutrient intake (RENI) for Filipino adults. Except for cassava, most of the studied crops were high sources of total dietary fiber, with the giant swamp taro (48% RENI) as the highest. Total minerals such as K, Ca, Mg, Na, and considerable quantities of Zn, Mn, Fe, and Cu were detected. The mineral bioavailability varied for Zn (47.0-98.0%), Cu (37.5-86.8%), Mn (31.5-91.8%), Mg (31.9-90.2%), Ca (2.54-31.1%) and Fe (4.7-20.7%). Consumption of 100 g of the examined crops, except for giant swamp taro and cassava, can contribute to the daily Cu for adults aged 19-29. Taro contributes to the daily nutritional requirement for bioavailable Ca and Mg, while giant swamp taro contributes to Zn and Mn requirements. None of the examined crops contained sufficient bioavailable Fe to contribute to Filipinos’ daily requirements. The study can help address the limited information on the nutritional and mineral bioavailability of root and tuber crops, which hampers their utilization to address some nutrient deficiency among the Filipino population, and emphasizes the consumption of these crops to enhance dietary diversification, which can alleviate some nutrient deficiencies in the country.