Methodologies for assessing the household food availability in the context of food (in)security: a systematic review Metodologias de avaliação da disponibilidade de alimentos

Resumo O objetivo deste artigo é identificar métodos empregados para a avaliação da disponibilidade de alimentos no âmbito domiciliar em estudos sobre segurança alimentar e nutricional e discutir seus aspectos metodológicos. Revisão sistemática elaborada segundo o método PRISMA. Realizou-se busca nas bases de dados PubMed, SciELO e Lilacs, tendo sido incluídos estudos que empregaram métodos de avaliação da disponibilidade de alimentos no domicílio. Ao final, 19 artigos compuseram a revisão. A disponibilidade de alimentos foi avaliada predominantemente para um período de sete dias e a partir de única medição dos dados. Outras variáveis também foram observadas nos estudos, como dados sociodemográficos e de despesas com os alimentos. Dentre as limitações para a avaliação da disponibilidade domiciliar de alimentos, destaca-se a dificuldade de mensuração da distribuição de alimentos entre os membros da família e a falta de informação sobre a variabilidade desta disponibilidade. Tal avaliação pode ser melhorada através da investigação de pontos fortes e fracos dos instrumentos para maior detalhamento e precisão das informações. Recomenda-se o desenvolvimento e a validação de instrumentos específicos capazes de mensurar efetivamente a disponibilidade de alimentos em nível domiciliar. Palavraschave Segurança alimentar e nutricional, Revisão sistemática, Alimentos e bebidas Abstract This article aims to identify the methods used to assess household food availability in studies on food and nutritional security and to discuss its methodological aspects. Systematic review elaborated according to the PRISMA method. We searched at PubMed; Scielo and Lilacs databases, and studies that used methods of assessing the availability of food at home were included. In the end, 19 papers composed the review. Food availability was predominantly assessed for a seven days period and from a single data measurement. Other variables were also observed in the studies, such as socio-demographic data and expenditure on food. Among the limitations to assess the food availability at home, we can highlight the difficulty in measuring the food distribution among family members and the lack of information on the variability of this availability. Such assessment can be improved by investigating the strengths and weaknesses of the instruments for greater detail and accuracy of the information. We recommend the development and validation of specific instruments capable of effectively measure the food availability at the household level.

introduction According to the Food and Agriculture Organization of the United Nations (FAO) recommendations, regular access to sufficient, safe and nutritious food information is required to ensure food security, in order to meet individual nutritional preferences and needs for a healthy and active life 1 .
Therefore, food insecurity occurs when there is limited or uncertain availability and/or ability to have nutritionally adequate and safe food 2 . Availability and access to healthy food are required for promoting individual health and nutrition 3 , and are achieved when enough food is available to all individuals, whether from the production for self-consumption, shopping or donations 4 . However, food may be available, but not accessible to the population, due to socioeconomic limitations or other factors such as food monopoly, leading to Food and Nutritional Insecurity 5 .
The household environment has a great implication on the food intake 6 , such that the food found in the pantries are indicators of the family's actual food consumption 7 . Different methods for measuring household food availability have been developed and applied in the last years, but frequency of observations, types of food and data collection procedures vary from one method to another 8 , and the data availability can be collected from direct observation at home, considered the "gold standard", or through self-reporting, according to instruments proposed for this purpose, by telephone or mail 9 .
Nonetheless, only with adequate measurement tools will it be possible to better understand the causes of food insecurity, identify the most vulnerable populations, determine effective mechanisms to solve the problem and assess the impact of possible interventions 2 .
Therefore, assessing the food availability at household is essential to assess food insecurity 10 . For that reason, this literature review proposes to identify, the methods used to assess the household food availability in studies on food and nutritional security and to discuss its methodological aspects.

Methods
It is a systematic review of the literature, arranged according to the Preferred Reporting Items for Systematic Reviews and Meta Analyzes (PRIS-MA) Guide 11 based on food safety studies that used methods of assessing the food availability at home. The PICO strategy (Problem, Intervention, Comparasion, Outcomes) was employed for the construction of the guiding question of the research which was: "What are the methods employed for the assessment of the availability of household foods in studies in the context of food and nutritional security?" The literature review was done independently, in September 2018, from the selection of studies published in PubMed; SciELO and Lilacs databases, using the same search criteria for all bases. The following combinations were used to search the articles: "food availability" OR "food available" AND "food security" and "food availability" OR "food available" AND "food insecurity", including articles published in English and Spanish, without limitation regarding the period of publication, in order to contemplate the scientific production until the moment of the research. For the manuscripts that did not provide sufficient information from their title and abstract, we proceeded to full reading, where we extracted information about the population and the type of study, the methods and limitations. Subsequently, we searched the gray literature, employing the same terms described, in databases that index this type of literature (http://www.dominiopublico.gov.br and http: //www.periodicos.capes.gov.br). The references of the eligible studies were analyzed to find other publications of interest.
The quality of the studies was not analyzed, since the review does not intend to assess the results, and only, identifies the methods proposed by them. The original articles, as well as dissertations and theses that used methods of assessing the availability of food at home were included in the review. Review studies, experimental studies with animals or plants, and studies assessing the availability of food outside home were excluded.
In order to verify the methods of assessing the availability of food at home, we elaborated an instrument that could synthesize the main data extracted from each study in a descriptive way (Chart 1), containing the following components: author, year and local of publication, study design, sample size, method and period of assessing food availability.

Results
The Figure 1 shows the flowchart of the studies selection to compose the research. The search re-chart 1. Summary of the methodological aspects of the studies that assessed food availability at the household level (n = 19). Self-administered questionnaire answered by the householdresidents, and when necessary, by the interviewer, to assess the availability, quantity, origin and expenditure of food and beverages.

Author
Seven days it continues sulted in 139 papers. The titles and abstracts of the papers were read to identify those that met the inclusion criteria to assess eligibility. In total, 129 papers were excluded, of which 30 were repeated papers, 11 were clinical studies, with food or animal, 21 were review or report papers, 40 took a broad approach to food security, but without assessing the availability or assess it outside the home. After reading the full text manuscripts assessed for eligibility, we verified that 27 studies were conducted in households, but did not address the food availability. With this, there were 10 eligible papers. Subsequently, the research in the gray literature resulted in the inclusion of 02 documents. Ultimately, a reverse search was performed based on the references of the selected papers, and with that 07 studies were included. Thus, 19 studies met the established selection criteria and composed this review.
In relation to the assessment of household Food and Nutrition Security, of the selected papers, one made use of the Latin American and Caribbean Food Security Scale (ELCSA) 12 , two used the Household Food Security Survey (HFSS) 19,28 , four used the HFSS reduced version [15][16][17][18] , one used the Community Childhood Hunger Identification Project (CCHIP) 13 , and one used the Radimer/Cornell food insecurity items 21 . All are validated psychometric scales that indicate whether adults or children in the same family experience food shortages or deprivation and modify food intake due to financial resource limitations 12,13,16 .
Other studies did not directly assess household food security from psychometric scales 7,13,[15][16][17][18][19]21,28 , whereas, one used family expenditure on food as a proxy for income, considering it a measure of intra-familiar food security 14 , e two assessed the situation of food insecurity in households using the concept of "household food energy availability" according to the method proposed by FAO 22,23 . Since food availability varies according to socioeconomic conditions, family composition, household location, and may compromise Food and Nutritional Security 26 , the other studies were included for assessing these aspects, such as the availability of fruits and vegetables at homes with children 7 , or food availability in households with children in rural areas 26 , the food availability of families receiving a supplementary nutritional assistance program 20,24 and household availability of food according to socioeconomic and demographic factors 25,27,29 .

Discussion
It was observed a predominance of only a single measurement of food availability [7][8][9]14,17,18,20,22,23,[26][27][28][29] . Some methods of assessing household food availability are sometimes impracticable due to their extension and the need for sufficient human and financial resources. Therefore, reduced instruments may be useful for this analysis 13,15 . On the other hand, a single application can generate biases and misinterpretations about household food availability, presenting an imprecise description of the food available for consumption 15,16 , furthermore, the use of instruments with a limited number of items does not reliably determine the quantity or quality of the food available 16,17 .
Food availability may be affected by a series of irregular events including family parties, acute illness, and times of family difficulty. Using several measures, it is possible to better observe the impact of these events, as well as intra-family variability 16 . Researches investigating, in greater detail, the food availability may improve the assessment of these aspects, which are susceptible to variations according to the family situation 16,17 .
This highlights the importance of multiple measures of food availability and the feasibility of more extensive assessments 16 . Which allows information obtainment on the weekly change in availability and the presence and quantity of specific foods, noting that the number of measures and the most appropriate period of time for application of the instruments depend on their purpose 15 .
Other authors focus their instruments on assessing the availability of certain types of food to achieve a specific objective, such as the household availability of fruit and vegetables 7,19 , or special situations, such as the availability of food for cancer prevention, cardiovascular diseases 30 , Human Immunodeficiency Virus (HIV) care 31 . However, due to data limitations, the measurement of a greater variety of foods seems to be more complete and with satisfactory validity 9 .
Regarding the relationship between food security and food availability, the availability, access, use of the food and the stability are recognized as the pillars of food security 32 and when one of these aspects is violated, it is characterized food and nutritional insecurity 33 . Besides being among the main determinants of the food system 34 , household availability is influenced by several factors, such as composition and family income, storage conditions and access to food commercialization establishments 16 , production for self consumption 22 , regional production and infrastructure of the food system such as stock and transportation 32 .
Unsatisfactory socioeconomic conditions such as low income 13,15,17,25,29 and low education of the head of the family 12,25 are also negatively related to food security and food availability. Insecure food households have less availability of most food 12,17,19,28,29 . In contrast, the food production for self-consumption positively influences the food availability at home 22,35 .
We also emphasize that four studies assessed secondary data on household food availability from food surveys of national representativity 12,14,24,25 . Surveys such as these that produce information at the national level, regarding household food availability enable the characterization of the temporal changes in the population's feeding, and contribute with information on the adequacy of the composition of families' feeding 25 , in addition to its use for nutritional surveillance, elaboration and assessment of public policies 14 .
We can highlight the importance of the use of validated methods for assessing the household food availability is highlighted. The development of several household measurement instruments does not include comprehensive validity tests, and validity is a fundamental criterion, since an instrument should be associated with the expected results of the study 13 .
A suggested method for assessing the validity of food availability instruments is the completion of the instrument by the research participants, and then their answers are compared with the questionnaire applied by the researcher (gold standard). The comparisons are assessed regarding the consistency of the results, using statistical method or through the analysis of sensitivity and specificity 30 .
Household food availability is associated with ingestion, habit and dietary patterns 19,30 , and, although important results of home-based surveys are observed, they have the limitation of not knowing the individual food consumption 22,24 , since they do not assess the dietary intake of each family member or characteristics such as weight, height and level of physical activity in order to determine the appropriate individual intake. Such information could point to a more accurate perspective of the Food and Nutrition Security situation 12,36 .
Other limitations observed in methods of assessing food availability are the short assessment period and the variety of foods covered in the instruments, since from a food and nutritional security perspective, feeding is adequate when offered in sufficient quantity and quality and permanently, thus, a less comprehensive assessment may be a bias in determining the food available and its variation at home over a longer period. Moreover, socioeconomic and cultural aspects, not always addressed in the studies, are determinants on food and nutritional security, therefore, besides food availability, assessing these factors becomes important for a better understanding of the conditions and consequences of feeding and food and nutritional (in)security of the population.
The use of only three databases is considered a limiting factor of this review, with this, possible eligible publications may not have been identified. Despite the gray literature survey, it was restricted to the bases indicated in the methodology. As the gray literature is difficult to systematize the search, it is possible that some study related to the theme of the review has not been contemplated. However, despite the limitations, we believe that it was possible to critically demonstrate and discuss the main methods employed in the assessment of food availability in the households in studies related to Food and Nutritional Security.

considerations and recommendations
It was observed that the majority of the studies opted for assessing the food availability from a single application of the instrument, containing as main information the quantity and quality of the food purchased in the households, almost always followed by the Food Security measurement.
Among the limitations to assess the household food availability, the difficulty of measuring the food distribution between family members is highlighted, as well as the lack of information on monthly, intra-and inter-personal variability of food availability. However, the availability assessment can be improved by investigating the strengths and weaknesses of the instruments for further detail and accuracy of the information.
As the household food availability is influenced by several factors, it is of extreme importance that these are also taken into account in the studies. The relevance of household food availability assessment is due both to its close relation with food security and to its determinant role in the family choices, habits and food consumption.
Whenever possible, we recommend the use of methods involving a wide variety of food and a longer time to assess availability, in order to better observe the variability and stability of food availability at home. The importance of the development and validation of specific instruments for the different populations capable of effectively measuring the availability of food at the household level is also emphasized. collaborations E Schott worked on the design, research, methodology and final writing; FAC Rezende worked on the design, methodology and final writing; SCC Franceschini worked on the design; methodology, final writing and on the approval of the version to be published; SE Priore and AQ Ribeiro worked on the final revision to be published.