The results of this study show that distributions including an RUSF for children 6 to 23 months and a family protective ration had a modest but positive effect on prevention of wasting and anthropometric status. Importantly, deaths were halved for those who received the supplements compared to those who did not.
To our knowledge, this is the first study to document the benefits of distribution programs with RUSF in terms of mortality in this context. A previous randomized controlled trial conducted in the same two districts showed a marked effect on wasting and a moderate effect on stunting. However, a larger amount (500 kcal/d vs. 250 kcal/d) of a similar, but different, product (ready to use therapeutic food, Plumpy’nut®) was used. Although results suggested lower mortality, too few deaths were recorded to reach significance 
RUSFs are formulated to supply all of the essential nutrients; both those required to maintain body function and for normal growth 
. A deficiency of one or several of the functional nutrients impairs physiological or immunological function without any effect on anthropometric indices. Benefits in terms of mortality, combined with a very modest effect upon weight and MUAC may potentially have been due to the correction of functional deficiencies, not causally associated with anthropometric deficits, but resulting in functional changes increasing mortality risk 
. It is noteworthy that many of the deaths were in children that were neither moderately or severely malnourished anthropometrically, and it appeared that this group of not-wasted children benefited most from the RUSF distribution in terms of mortality avoidance. This was unexpected and would indicate that even modest amounts of those nutrients whose deficiency is not associated particularly with wasting could be implicated in the reduction in mortality. This would have major implications for targeting in such situations, and perhaps for the composition of the RUSF supplied.
There are several important limitations to these results which require discussion. First, the selection of the villages to study was taken at random and fairly represents the population at large although children themselves were not randomized to receive the distributions, but were either registered or failed to be registered at the time of the initial mass-registration and subsequently observed. It is unclear why some children were not registered initially; possibly caretakers were absent at the time of registration, the benefits of the program were not adequately explained or advertised, or they felt their child did not need the RUSF on offer. As a result, differences between the intervention group and comparison group could account for the observed reduction in mortality. However, in addition to accounting for differences in the statistical analyses, baseline anthropometry of children was not significantly different between groups. The intervention group had a slightly lower, but not statistically different, mean weight-for-length, came from larger families and were younger. These are recognized risk factors for mortality; thus, the children receiving the distributions were likely to have been at higher risk of death than the comparison group. It is important to note that the population was under very severe stress with mortality rates when expressed in conventional emergency terms of 1.6/10,000/d for the intervention group and 2.7/10,000/d for the comparison group. As children identified as severely malnourished were admitted to therapeutic programs, in the absence of the distribution program mortality may have been higher. In addition, mortality in the comparison group may be underestimated; five children in the intervention group and 35 in the comparison group were lost to follow-up. If all, or a proportion, of these children were lost to follow-up because of death, the strength of the reduction in mortality with the distribution would increase. Overall, there were fewer deaths among children in the intervention group irrespective of the number of distributions received.
Second, there may be unexplained differences between the intervention and comparison group. One possible hypothesis arising from these results is that families receiving the distributions have children already showing signs of deterioration, as evidenced by the presence of known risk factors at baseline. Families with children who are in better health at the time of registration may chose not to participate highlighting the potential weakness of programs with closed enrollment. Although all families with children with heights equivalent to children aged 6 to 23 months were eligible for the distributions and nutritional programs if admission criteria were met, further research and improvements in terms of program awareness, acceptability and accessibility are needed. Furthermore, it is clearly an error to apply closed registration strategies in regions with a high background mortality and undernutrition. Operationally feasible strategies allowing for open registration for distributions should be developed in order to maximize coverage.
Third, it is possible that the severity of the situation was the reason for the extensive sharing of supplement within the family and this in turn led to the modest differences in wasting found, despite observed differences in mortality which has not been adequately documented elsewhere to our knowledge 
. Nevertheless, even small changes in MUAC or weight may be of clinical significance for those who are already in the lower tail of the distribution of nutritional status 
. Increased energy intake has previously been associated with increased weight gain 
, and the energy provided by RUSF is within the range (200 to 300 kcal/day, assuming average breast milk intake and sharing within the family) that older infants require from complementary foods 
. Previous evaluations of RUSF supplementation have been consistent in demonstrating improved weight gain in a variety of study populations and against a range of comparator products, including micronutrient fortified flours 
and porridge 
Fourth, over the four month follow-up, we did not observe an effect upon stunting. Review of complementary feeding interventions suggests that the effect of RUSF on linear growth has been inconsistent, with significant improvements achieved only in some settings 
and the acceleration of length gain may only occur after supplementation has been given for several months 
Fifth, it was not possible to differentiate the effect of the RUSF from the family protection rations, nor was it the aim of this study. However, the distribution of protective rations was inconsistent and almost non-existent during the fourth distribution. This coupled with the known inadequacies of nutrient composition of the family ration to meet the needs of young children contribute to the limited evidence for including an RUSF in distributions. Finally, potential errors in the child’s age at recruitment or measurement errors for the anthropometric variables, despite continual training of field teams, may have reduced or increased the statistical power to detect significant effects.
It is important to highlight that the cornerstone of all medical interventions is the early and appropriate treatment of children at risk of death, irrespective of the cause. Although formal verbal autopsies were not conducted in this study, parents reported the cause of death of their child to be malaria or fever in almost all instances. Children in our cohort benefitted from a comprehensive pediatric care package and were referred for nutritional treatment if they met the inclusion criteria for nutritional programs operating in the two districts. Participation in distribution programs provided advantages beyond that of the rations received and may have led families to seek prompt medical treatment for other conditions. However, it is important to emphasize that all families, whether they received or did not receive the distributions were screened between each distribution and referred for free and comprehensive medical care and rescue facilities; the mortality rate in the villages that were not included in this cohort study could thus have been substantially higher.
In conclusion, the results of this study show that the RUSF distribution with a protection ration for the families had a positive effect on wasting and anthropometric status of children who received the distribution in comparison to those who did not. Importantly, deaths were halved for recipients compared to non-recipients. These results suggest that with similar access to health services, distributions can have a positive impact on child survival. Contextual factors will continue to be important in determining the dose, duration, period and modalities of such preventive intervention based on RUSF. Dietary supplementation with foods specifically formulated for vulnerable populations have become a component of government-run social safety net programs 
. In settings of endemic malnutrition and high child mortality, the health impacts of RUSF documented through humanitarian projects may help inform decision making for longer term programming.