Relationships between agrobiodiversity, dietary diversity and nutritional status in Tanzania

Background: Agrobiodiversity is important for biodiversity conservation and sustainable agriculture. Increasing agrobiodiversity may also improve dietary diversity and nutritional status in low income countries but research is lacking in this area. To fill this knowledge gap, this study explores relationships between agrobiodiversity, dietary diversity and nutritional status in Tanzania. The research investigates 1) the relationships between agrobiodiversity, dietary diversity and nutritional status in children in two villages in rural Tanzania and 2) the relationships between land cover, dietary diversity and nutrition in under five year olds in a nationally representative sample in Tanzania.
Methods: A cross-sectional survey was conducted in 122 randomly selected households in Minyenye village, Singida district and Mbwei village, Lushoto district. Female heads of households were interviewed to collect quantitative and qualitative data on demographics, livelihoods, complementary feeding and household food sources. Dietary diversity was calculated from 24 hour dietary recalls which were collected for the respondent and their oldest child under five. Agrobiodiversity data were systematically collected using the point intercept method. All plants, both intentional crops and other plants, growing on the household’s farms at the time of data collection were measured and Shannon Biodiversity Indices were calculated. In addition to these indices, the food sources section of the questionnaire was used to calculate household crop and animal diversity scores. Heights and weights were measured in all family members and MUAC was collected for all children under 15 years old. Relationships between these factors were explored using regression analyses. At the national level relationships between land cover, from GlobCover 2009, and dietary diversity and nutrition, from the 2010 Tanzanian Demographic and Health Survey (DHS), were investigated using spatial and regression analyses.
Results: No significant associations were seen between dietary diversity and nutritional status in either village and dietary diversity was negatively associated with height for age z-scores in the DHS analyses. No significant associations were seen between agrobiodiversity and dietary diversity. Agricultural, but not forest, land cover was associated with dietary diversity. Associations between both agrobiodiversity and land cover and child nutritional status are complex. In Minyenye, agrobiodiversity was positively associated with children’s height for age while in Mbwei these were negatively associated with children’s body mass index (BMI) z-scores. More agricultural and forest land cover was associated with higher weight for height, however more agricultural land cover was associated with lower height for age. Positive associations were seen between eating and rearing animals and dietary diversity but negative or no associations were seen with nutritional status. Selling crops was positively associated with dietary diversity but showed mixed associations with nutritional status at the local village scale.
Conclusion: Study results provide a word of caution for those attempting to increase agrobiodiversity to improve diet and nutritional status. The effectiveness of agricultural interventions aimed at improving nutrition through improvements in agrobiodiversity can only be evaluated in light of the multiple determinants of nutritional status. The current study’s results illustrate the complexity of the pathway from food production through consumption to nutrient utilization in low income countries.