Review: Meta-analysis of the association between production diversity, diets, and nutrition in smallholder farm households

Undernutrition and low dietary diversity remain big problems in many developing countries. A large proportion of the people affected are smallholder farmers. Hence, it is often assumed that further diversifying small-farm production would be a good strategy to improve nutrition, but the evidence is mixed. We systematically review studies that have analyzed associations between production diversity, dietary diversity, and nutrition in smallholder households and provide a meta-analysis of estimated effects. We identified 45 original studies reporting results from 26 countries and using various indicators of diets and nutrition. While in the majority of these studies positive results are highlighted, less than 20% of the studies report consistently positive and significant associations between production diversity and dietary diversity and/or nutrition. Around 60% report positive associations only for certain subsamples or indicators, the rest found no significant associations at all. The average marginal effect of production diversity on dietary diversity is positive but small. The mean effect of 0.062 implies that farms would have to produce 16 additional crop or livestock species to increase dietary diversity by one food group. The mean effect is somewhat larger in Sub-Saharan Africa than in other regions, but even in Africa farms would have to produce around 9 additional species to increase dietary diversity by one food group. While results may look differently under very specific conditions, there is little evidence to support the assumption that increasing farm production diversity is a highly effective strategy to improve smallholder diets and nutrition in most or all situations.