improper nutritional knowledge is one of the most important causes of nutritional problems , which can affect practice and cause more complications . it has been recommended that food choices and dietary behaviors can be impressed by knowledge about diet ( 1 ) . to effectively improve healthy eating , it is necessary to understand the nutritional attitudes and beliefs of the general community ( 2 ) . age , education level , gender and marital status can influence nutritional knowledge , attitude and practice ( kap ) ( 3 ) . the association of socioeconomic status ( ses ) with nutrition knowledge and beliefs has been confirmed ( 4 ) . many studies have found that nutrient intakes and dietary patterns of people in low ses groups threaten the general health and raise the risk of nutritional disease ( 5,6 ) . people in low ses group , due to lack of access to health care , improper living conditions , less knowledge and greater psychological stress , may be at a higher risk of poorer health conditions more than others ( 7 - 10 ) . with respect to the association of ses index with health behaviors ( 11 ) and undesirable health consequences , it is of prime importance to evaluate the effect of ses index on health - related behaviors . 
 
 in this study , the association between nutritional kap with ses was assessed among the iranians in urban and rural regions of 31 provinces of iran . the study population consisted of 14,136 iranian households who lived in urban and rural regions of 31 provinces , selected by multi - stage cluster sampling . non - iranian households were not included in the survey , and the households who were absent for tree times at the time of the interview were also excluded . the method of study has been published in a previous survey ( 12 ) . mothers or any over 15-year old member of the households , who were in charge of cooking for the entire family , were considered as statistical units of the study . a structured questionnaire and interview with a qualified person in families nutritional knowledge questions inquired about main food groups , causes of consuming food , role of main food groups , sources of protein intake , and role of dietary fiber as well as nutritional attitude toward health - related behaviors and food choices . to assess the practice of the households , the household members were asked about the frequencies of different consumed foods . ses was an index that included household assets ( house ownership , number of rooms in the house , having such equipment as tv , cell phone , car , freezer , washing machine , dish washing machine , phone , microwave , access to internet ) , occupation and education level of the heads of the families and the respondents and number of family members . data were analyzed using the stata version 11.0 ( stata corp , college station , tex . ) ( survey analysis ) . data were analyzed using the stata version 11.0 ( stata corp , college station , tex . ) ( survey analysis ) . the percentage of nutritional knowledge was significantly higher in families with good ses and it linearly increased with family ses . most people consumed food to prevent disease and be healthy ( 54.7% , 95% ci : 53.5 , 56.0 ) . more than half percent of households were aware of grain , meat and legumes , and dairy group ( 60.5% , 69.7% , and 52.5% , respectively ) . the percentage of knowledge about identification of fruit , vegetable and fat groups was less than half percent . about 73.1% of the households ( 95% ci : 71.9 , 74.3 ) were familiar with the role of dairy group ( growing and strengthen teeth and bones ) , although less than 10% of them were aware of the role of fruit groups in providing dietary fiber ( 8.6% , 95% ci : 7.1 , 9.2 ) . the percent of participants knowledge about legumes and soy , another source of protein , was 45.5% ( 95% ci : 44.2 , 46.8 ) and 40.1% ( 95% ci : 38.8 , 41.5 ) , respectively . only 10.1% of the participants were familiar with the concept of dietary fiber ; among them , the most percentage of knowledge belonged to bowel movement . 
 
 * ( % ( 95% ci ) ) , p<0.05 , ses ; socioeconomic status 
 
 the percentage of attitude is shown in table 2 . more than 97% of the participants had a favorable attitude towards the importance of nutrition and diet in health . respectively , 90.3% , and 70.4% of the participants had a favorable attitude toward importance of nutritional requirements of children rather than adults and the necessity of equal food intake in both genders when there is few food . the percentage of a favorable attitude of the family with good , moderate and weak ses about preferring fruit consumption than bread at time of hunger was 39.8% , 50.8% and 58.5% , respectively . the percentage of participants who disagreed with consuming steam cooked rice was significantly higher in families with weak ses . about 80.5% of the participants had a favorable attitude toward preferring consumption of tuna fish and the lowest percentage was related to weak ses families . households with good ses had a more favorable attitude about the necessity of daily consumption of vegetables or salad and the need for milk consumption in any age besides childhood period ( 95.3% , and 93.1% , respectively ) . the families with weak ses had the highest favorable attitude about preferring whole meal bread on other kinds of breads . the percentage of favorable attitude toward drinking water in the middle of eating food and the necessity of keeping body fitness in girls at puberty was 66.5% and 56.1% , respectively . when the participants were asked about the difference between nutrition fact of meat and mushrooms , only 25.4% agreed . * ( % ( 95% ci ) ) , p < 0.05 , ses ; socioeconomic status 
 
 table 3 demonstrates the practice of households based on ses . most households consumed fruit , vegetable , milk , yoghurt , cheese and sugar daily . consumption of foods such as rice , red meat , butter , cream , egg , legumes , dough , chicken and poultry was weekly in most participants . the other items such as viscera , tuna , nuts and synthetic juice were rarely or never consumed . families with good ses significantly consumed more fruit , vegetable , dairy group , red meat , chicken and poultry , fish and egg , while sugar consumption was significantly higher in families with weak ses . 
 
 * ( % ( 95% ci ) ) , p<0.05 , ses ; socioeconomic status the aim of this study was to assess the association between nutritional kap with ses among iranian households . the best knowledge in all items was seen in families with good ses index and it linearly increased with family ses . households with weak ses had the best favorable attitude toward the difference between mushroom and meat nutrition fact , preferring whole meal bread on other kinds of breads and preferring fruit consumption than bread at time of hunger . the consumption of food items such as red meat , chicken and poultry , fish , egg , dairy group , fruit , vegetable and nuts was significantly higher in households with good ses index while the other items including rice , tuna , legumes and sugar were consumed the most in weak families . these findings are supported by other surveys that have shown that more intake of fruit and vegetable are related to more diet costs , and diet rich in fat and sugar is contributed to lower costs ( 13,14 ) . findings from a survey on 4,356 us adults suggested that better ses index independently promotes the possibility of adequate fruits and vegetables intake and overall diet quality . they also reported that nutritional knowledge and belief can affect the positive association between ses and diet quality indicators(4 ) . as it is confirmed in other studies , the socio - demographic variation in intake can be associated with nutritional knowledge as a partial mediator in improving diet . the result of this study also revealed that healthy eating was significantly associated with knowledge and possibility of meeting current recommendations for fruit , vegetable and fat intake ( 15 ) . the association of ses and dietary knowledge or income and diet is supported by other studies ( 16 - 19 ) . another way that ses can influence diet is related to food purchasing differences . a study on australians in 2000 showed that food purchasing differences due to household income is related to diet via food - cost concern ( 20 ) . food purchase decisions due to a person s attitude toward food price can influence diet quality . based on this survey , people who care about food price were more likely to live in low - income , food - insecure households , they had low education , were tenants and did not own homes , and were service workers . they were more susceptible to diseases such as overweight , high blood pressure , heart disease and diabetes than the others ( 21 ) . our results showed higher consumption of food items such as sugar , tuna and lower consumption of nuts and protein sources such as meat , fish , egg and dairy product in families with weak ses , which can be associated with an increased rate of some diseases . thus , implementing measures to guide people in the line of healthier nutrition is necessary and it can help decrease the rate of diet - related diseases , especially in low ses households . with respect to the increasing nutritional disease and the important role of dietary behaviors , increasing nutritional kap may be a way to change life style and health related behaviors , but it is not enough . therefore , targeted policies should be coupled with efforts to promote diet and nutritional kap for those people with unfavorable socio - economic status . some cost - effective strategies should be presented for the low - income groups in the society to neutralize the negative effect of income on food purchasing patterns and health related life style .
background : improper nutritional knowledge is one of the most important causes of nutritional problems , 
 which can affect practice and cause more complications . the aim of this study was to assess the association between 
 nutritional knowledge , attitude and practice ( kap ) of iranian households with socioeconomic status 
 ( ses ) . 
 methods : the study population was 14,136 households ( 57 clusters of 8 individuals in each province ) who 
 lived in urban and rural regions of 31 provinces of iran . 
 the sample size of the study was selected using multistage 
 cluster sampling technique . a structured questionnaire and interview with the qualified person in each 
 family 
 was used to collect data . 
 the questionnaire included demographic , ses and nutritional kap questions . 
 using principle component analysis , some variables including household assets , occupation and education level 
 of the heads of the families and respondents and the number of family members were used to construct family 
 ses . 
 the ses was categorized as good , moderate and weak . 
 pearson s chi - square test was used to analyze categorical 
 variables . 
 results : the percentage of knowledge about growing up , acquiring energy and being healthy as reasons for 
 eating food was 24.1% , 44.8% and 54.7% , respectively . 
 only 69.7% , 60.5% and 52.5% of the participants had 
 knowledge of identification of meat and legumes , grain and dairy group , respectively . 
 more than 97% of the 
 participants had a favorable attitude toward importance of nutrition in health . 
 the nutritional knowledge linearly 
 increased with increasing ses . 
 families with good ses significantly consumed more fruit , vegetable , dairy 
 group , red meat , chicken and poultry , fish and egg while sugar consumption was significantly higher in families 
 with weak ses ( p<0.05 ) . 
 conclusion : ses can influence the rate of nutritional kap . some policies should be considered to increase nutritional kap especially in lower ses group in the society .