Food Based Dietary Guidelines (FBDG), in order to be attainable, should take into account the cultural context of the population for which they are developed. They need to focus on foods that actually determine the intake of nutrients for which desirable changes have been identified. Inter-individual variability of nutrient intakes – a measure of the heterogeneity of intakes – is determined by the variability in the consumption of its food sources among the population. The foods that determine a high proportion of inter-individual variability in nutrient intake can be identified on the basis of data banks that describe food and nutrient intakes in the population. The experience accumulated to design Food Frequency Questionnaire through selection of key foods suggests that high quantitative contributors to a specific nutrient may not be important determinants of its intake. On the other hand, the Pearson correlation between the intake of each food source and the total nutrient intake allows quantification of the percentage of variability explained by each item and takes into account the possibility of correlations between different food sources. Once a key food is identified, several strategies are available to modify its intake in the population: through changes in the percentage of consumers/in the mean portion size/in the frequency of intake. The anticipated level of change can be predicted according to the strategy adopted.