Although the United Nations has enshrined the right to food in the Universal Declaration of Human Rights, household food security is dependent on two main factors: the availability of food, which may be grown, raised, bought, traded or gathered from the wild and the physical and economic access to sufficient amounts of food to meet all nutritional needs at all times.
Undernutrition is a global public health problem that is estimated to be the underlying cause of about 35% of all deaths during early childhood.
The Cost of the Diet method and software could be used to inform programme design and behaviour change communication in the fields of nutrition, food security, livelihoods and social protection as well as to influence policies and advocacy debates on the financial cost of meeting energy and nutrient specifications. When the cost is expressed as a percentage of income, the affordability of the diet can be estimated.
The output summarises for each diet the costs, quantity and proportion of energy and nutrient specifications provided by all the foods selected for a given individual or household by day, week, season and year. Most parameters in the software can be modified by users to examine the potential impact of a wide range of theoretical interventions.
These data are presented to a linear programming solver within the software which selects the least expensive combination of local foods for four standard diets that meet specifications for: energy only energy and macronutrients energy, macronutrients and micronutrients and energy, macronutrients and micronutrients but with constraints on the amounts per meal that are consistent with typical dietary habits. Data are collected during a market survey to calculate the average cost of foods per 100 g while focus group discussions are used to assess local dietary habits and preferences. The software contains five databases: the energy and nutrient content of foods the energy and nutrient specifications of individuals predefined groups of individuals in typical households the portion sizes of foods and currency conversion factors. This paper describes the principles of the method the mathematics underlying the linear programming the parameters and assumptions on which the calculations are based and then illustrates the output of the software using examples taken from assessments. The Cost of the Diet method and software was developed to apply linear programming to better understand the extent to which poverty may affect people’s ability to meet their nutritional specifications. When food is available, the main obstacle to access is usually economic: people may not be able to afford a nutritious diet, even if they know what foods to eat.