NUTRITIONAL CHARACTERISATION OF SELECTED YAM VARIETIES AND CONTRIBUTION OF YAM TO NUTRIENT INTAKE IN EKITI STATE, NIGERIA

Abstract

Excessive consumption of staples plays a contributory role in the global upsurge of the prevalence of diet related chronic diseases. Yam is a multi-species and multi-variety staple food with pivotal role in ensuring food security in Nigeria. Intra and inter species diversity of foods are being promoted as part of means to tackle malnutrition. Ekiti State is one of the highest producers and consumers of yam, without well documented information on varieties commonly consumed and their dietary diversity. This study was conducted to assess the available and commonly consumed yam varieties, inter-varietal nutritional differences, evaluate dietary diversity and contribution of yam to nutrient intake in Ekiti State. Proximate, mineral and phytochemical analyses were carried out on 12 purposively selected yam varieties using standard methods. Cross-sectional study of 450 adults selected from six Local Government Areas (LGA) in Ekiti State was done using a four-stage sampling method. Interviewer-administered questionnaire was used to collect data on sociodemographic characteristics, commonly-consumed yam varieties, yam consumption pattern, and dietary intake. Dietary intake was assessed with multi-pass 24-hour dietary recall to calculate the Individual Dietary Diversity Score (IDDS), energy and nutrients intake. The IDDS was derived from nine (9) food groups and categorised into low (1-3), medium (4-6) and high (7-9). Contribution of yam to total energy and nutrient intake was determined using standard procedure. Data were analysed using descriptive statistics, Chi square test and ANOVA at α0.05. Nutritional composition per 100g of yam varieties was significantly different for moisture (50.1-69.8)g, carbohydrate (27.3-46.1)g, protein (1.8-3.0)g, ash (0.5-1.3)g, and metabolisable energy (119-194) kcal. Saponin, alkaloids, phenols, phytate and tannin content ranged from 19.38-33.19%, 1.11-4.29%, 6.11-10.11 GEmg/100g, 1.26-1.93%, and 0.06-3.00%, respectively. Twenty five yam varieties were identified in the state and the seven most commonly-consumed varieties were Gambari (29.2%), Olo (15.1%), Aro (7.8%), Ileusu (3.1%), Dagidagi (2.4%), Gbakumo (2.2%) and Odo (2.2%). Respondents’ age was 34.1±12.2 years, and 56.0% were females. About 61% of the respondents consumed yam or its products daily, including pounded yam (65.5%) and boiled yam (24.0%). Preference for yam varieties was largely determined by season/availability (53.3%) andvii organoleptic properties (30.6%). Mean IDDS was 3.6±0.9, 57.6% fell within medium and 42.0% had low IDDS. Daily energy, protein, carbohydrate, iron and magnesium intake were 1985.4±615.3 kcal, 55.1±27.3g, 422.5±117.3g, 15.3±5.8mg, and 251.9±86.0mg, respectively. Yam and its products contributed an average of 31.7%, 5.4%, 27.3% and 31.9% of total energy, protein, iron and magnesium intake, respectively. The choice of the most preferred yam varieties was significantly associated with LGA, age, educational qualification, occupation and household monthly income. Only marital status was significantly associated with IDDS. Yam varieties had disparate macro- and micronutrient contents, and largely contributed to energy, carbohydrate and magnesium intake. The diet of respondents was not diverse enough, hence the need to address dietary diversity in order to improve nutrient intake adequacy in Ekiti State.