diabetes mellitus ( dm ) is a popular lifelong metabolic disease , and probably will remain the most frequent cause of death in the following decades .
diabetes as a concerned epidemic problem is increasing all over the world.[210 ] statistical estimations show that the number of diabetic individuals will be 65% of the world population ( 380 millions ) by 2025 .
the prevalence of dm is as much as nearly 5% of the world population and it has doubled during the recent 20 years .
it is the fifth cause of death in the usa and one of the four causes of non - communicable disorders in different age groups .
data show that almost 1520% of population in different areas may have either dm or impaired glucose tolerance ( igt ) in 2025 .
lifestyle modification could reduce the risk of diabetes by 3067% , and surprisingly , this reduction maintains even after removing the lifestyle modifications .
these modifications consist of physical activity and changes in dietary habits , which are 27% more useful than taking various medications .
most of the assessments revealed that broad preventive population - based strategies are critical to challenge the pandemic of dm .
dm is a multi - factorial disorder in which both genetic and environmental factors have major roles .
besides urbanization and technology development , the rapid nutritional and lifestyle transition faced by us doubles the burden of diseases .
poor quality of diet and nutritional habits have potential effects on the obesity - based chronic diseases.[22023 ] diet has a major role in preventing and managing hyperglycemia and dm .
previous focus of nutrition science was on the amount and distribution of nutrients and food components .
however , this approach has been replaced by a focus on a combination of nutrients and considering foods and food components together .
different unknown components and various interactions of food components provide the idea of focusing on dietary patterns instead of food components or nutrients .
dietary pattern approach helps in assessing the entire diet , which is also more understandable compared to just focusing on nutrient- or food - based approach to make recommendation for population . dietary pattern as a new focus in nutritional epidemiology is a suitable approach that covers biological native interactions of nutrient components in different food groups in relation with various disorders .
dietary pattern reflects an individual 's food consumption and its change during the life span , so it provides comprehensive information about dietary habits and identifies more effective recommendations to manage different chronic diseases .
the complex interactions are shown in numerous dietary patterns such as  mediterranean ,  dietary approaches to stop hypertension ( dash ) ,  prudent ,   western ,   traditional ,  and  healthy  dietary patterns .
therefore , we aimed to assess the relationship between different dietary pattern and the prevalence of type 2 dm and also assess the effect of different eating habits on managing type 2 dm in this review paper .
we reviewed all the study designs ( prospective cohort study , clinical trials , cross - sectional studies ) and focused on the available sources between 1992 and 2011 , including journals , electronic books , seminars , and symposium contexts .
the search focused on databases published in cochrane central register of controlled trials databases , pubmed , iran medex , and magiran using the keywords : diabetes mellitus , insulin resistance , metabolic syndrome , and dietary pattern .
we also studied food , insulin resistance ( ir ) , fasting blood glucose ( fbg ) , and homeostasis model assessment of insulin resistance ( homa - ir ) as the basic related features of dm and metabolic syndrome .
the relevance of surveys was found with a hierarchical approach on the basis of titles , abstracts , and full text of articles .
our search was limited to english materials we excluded letters , and studies focusing on single nutrients and food items , children , adolescents , and animal studies .
the information had been summarized based on fixed protocol : lead author , country , year of publication , sample size , sex and age of subjects , assay method , follow - up duration , outcome measure , race / ethnic , dietary pattern , effect size measurements [ odds ratio ( or)/relative risk ] , and confounding factors adjustments . in the initial search , we found more than 569 articles in pubmed on dm and dietary pattern , 23,296 entries on dm and diet , 344 articles on dietary pattern and ir , 10,359 entries on diet and ir , and 12,879 articles on dm and food .
after scanning the articles , 46,709 of the extracted studies were excluded on the basis of the title , abstract , and their major purposes which were limited to the single nutrients and food items .
this food habit emphasizes on good source of monoun - saturated fatty acids ( mufa ) from olive oil , accompanied with intake of vegetables , nuts , seeds , fruits , and whole grains , and reduction in the consumption of red meat and unhealthy fats .
high content of fiber , magnesium , polyphenol , and antioxidants makes this diet as a useful approach to control hyperglycemia and weight maintenance .
the results of a large spanish cohort study among 13,380 men and women showed that adherence to the mediterranean diet could decrease the risk of type 2 dm by 83% .
this inverse association between mediterranean dietary pattern and the prevalence of type 2 dm was observed in various multiethnic studies .
several epidemiological studies explained lower odds of having dm and inverse relation between glucose level,[3537 ] insulin,[3139 ] and homa - ir ( as one of the basic features of metabolic syndrome and type 2 dm)[3133364042 ] following adherence to the mediterranean dietary pattern even after controlling different confounding agents.[4348 ] higher adherence to the mediterranean dietary pattern score in normoglycemic persons decreased fasting glucose , insulin , and ir .
however , this reduction was not significant after multiple adjustments were made for diabetic patients and subjects with impaired fasting glucose ( ifg ) .
the aforementioned findings are observed in elderly group and high - risk persons with cardiovascular risk factors and in also those with history of myocardial infarction.[315052 ] another cohort study on 7751 subjects in different ethnics compared four dietary patterns : 1 .
 mediterranean - like diet  containing rice , pasta , vegetables , fruits , and wine ; 2 .
 healthy pattern  that includes whole bread , fruits , vegetables , low - fat dairies , and little alcohol ; 3 .
 sweet pattern  rich in white bread , processed meat , and high - fat dairy products ; and 4 .
 unhealthy eating pattern  high in white bread , processed meat , fries , and full - cream milk .
results showed that healthy diet is the best pattern in lowering the incidence of dm .
observed a lower or of diabetes among greek adults with high score of adherence to the mediterranean dietary pattern .
the comparison of the effects of  mediterranean hypocaloric  diet and  very - low - carbohydrate hypocaloric
 diet on fasting plasma glucose , serum insulin level , and insulin 2 h post - load concentration and homa - ir did not show a significant difference even after 8 weeks weight loss in obese women .
a longitudinal clinical trial for 54 months revealed that consuming a mediterranean diet could decrease homa - ir and serum glucose and serum insulin levels in persons with metabolic syndrome . as patients with metabolic syndrome are at high risk for developing type 2 diabetes , following the mediterranean diet can have a protective effect in this regard .
table 1 shows the different studies which evaluate the effects of  mediterranean  dietary pattern on type 2 dm .
characteristics of various studies that evaluated the effects of  mediterranean  dietary pattern on diabetes mellitus type 2 several studies have focused on the association between lower risk of type 2 dm and adherence to the  prudent pattern . 
prudent pattern is another dietary pattern which is characterized by higher consumption of whole grains , vegetables , fruits , poultry / sea foods , legumes , and coffee . in an american prospective cohort study among 42,504 men , higher adherence to
the prudent pattern reduced the risk of dm by 16% , however , after 12 years of follow - up .
western dietary pattern contains red and processed meat , butter , french fries , refined grains , deserts , potatoes , sweets , high - fat dairy , and soda .
the results were similar to the findings of the  atherosclerosis risk in communities ( aric )  study and al so , the observations of fung et al . in the nurses health study ( nhs ) following 12 years . in another study , the  conservative  and  prudent  patterns were compared . 
conservative  eating pattern , which contains butter , potatoes , and whole milk , has been correlated positively with the risk of diabetes by 50% while adherence to the 
two cross - sectional studies of villegas et al . defined usual dietary pattern of adults in three clusters , which correspond to  traditional ,   prudent ,  and  alcohol and convenience  diets .
 traditional  pattern had high percent of fat in total calorie intake ; predominantly fat intake was in the forms of saturated fatty acids ( sfa ) and mufa , in contrast to 
prudent  diet which was characterized as a pattern rich in polyunsaturated fatty acids ( pufa ) , high p / s ratio , fiber , and antioxidant vitamin sources . 
alcohol and convenience  diet included the highest intake of alcohol , protein , cholesterol , vitamin b - complex , iron , phosphorus , selenium , zinc , and the lowest amount of pufa and antioxidant vitamins .
analysis showed the lowest ir and hemoglobin a1c ( hba1c ) level in subjects adhering to the  prudent dietary pattern .  an iranian nested cross - sectional study among 425 subjects with igt ( 2535 years old ) showed the association between plasma glucose as one of the major features of metabolic syndrome and five eating patterns : 1 .  western  pattern ( rich in sweets , butter , soda , mayonnaise , sugar , cookies , tail of a lamb , hydrogenated fat , and eggs ) ; 2 . 
prudent  pattern ( contains fish , peas , honey , nuts , juice , dry fruits , vegetable oil , liver and organic meat , and coconuts ) ; 3 .
 vegetarian  pattern ( includes potatoes , legumes , fruits , rice , green leafy vegetables , and fruits ) ; 4 .
 high - fat dairy  pattern ( high in fatty dairies ) ; and 5 .  chicken and plant  pattern ( rich in chicken , fruits , green leafy vegetables , and mayonnaise ) . after controlling various confounding factors ,
vegetarian  diet can reduce blood glucose level significantly . different studies that assessed the effects of  prudent  and  western  patterns among type 2 dm are shown in table 2 . characteristics of various studies that evaluated the effects of  prudent  and  western  dietary patterns on diabetes mellitus type 2 food items of similar dietary patterns are different , based on geographic and ethnic characters .
 traditional  pattern is characterized by higher consumption of refined grains , potato , tea , whole grains , hydrogenated fats , legumes , and casserole , or it can be defined as a pattern rich in high - fat sandwich spreads , red meat , potatoes , butter and lard , low - fat fish , sandwich meat , and sauces .
healthy diet usually contains higher intake of whole meal bread , fruit and vegetables , and polyunsaturated margarine , besides lower consumption of red meat , sweet foods , and wine and beer , or food rich in fruits , vegetables , tomato , poultry , legumes , tea , fruit juices , and whole grains .
pattern rich in red meat , processed meat , french fries , high - fat dairy products , refined grains , and sweets and desserts , or sweets , butter , soda , mayonnaise , sugar , cookies , tail of a lamb , hydrogenated fat , and eggs , and refined grains , red meat , butter , processed meat , high - fat dairy , sweets and desserts , pizza , potato , eggs , hydrogenated fats , and soft drinks is called as a 
western  dietary pattern . in a cross - sectional study of 486 iranian women between 40 and 60 years of age ,
 healthy  pattern defined by frequent consumption of fruits , green leafy and cruciferous vegetables , tomatoes , legumes , tea , and poultry ; 2 .
ready - to - use food items as the main footsteps of modernization or so - called as  western  dietary pattern ; and 3 . 
iranian traditional  pattern consists of whole and refined grains , potatoes , legumes , tea , hydrogenated fats , and broth .
the highest or of ir and syndrome x was observed in people with the adherence to the highest quintile of  western  diet .
this result is similar to the result of fung et al . who observed a positive association between  western  pattern adherence and insulin level .
pattern can reduce risk of ir by 45% , while adherence to the  western  dietary pattern increases this risk to 15% .
mcnaughton et al . in an australian cohort study ( whitehall ii ) observed higher incidence of type 2 diabetes and higher value of homa - ir by adherence to the highest quartile of a diet rich in soft drinks , sugar - sweetened beverages , burgers and sausages , snacks , and white bread , and low intake of fiber food sources , by 2.95 times .
a multiethnic hawaiian survey revealed that higher ors for type 2 dm were associated with  animal  foods ,  local ethnic  dishes , and 
 animal  and  local ethnic  dishes included high intake of cabbage , rice , shell fish , corned beef plus  hawaiian and filipino  dishes .
modern  dietary pattern had a lower postprandial plasma glucose , after adjusting the confounding factors in the analysis in brief more consumptions of vegetables , vegetable oil / vinegar dressing , fruits , cereals , rice , pasta , and poultry against 
traditional  diet ( contains red meat , high - fat meat sandwich , butter and lard , potatoes , low - fat fishes , and sauces ) .
this study showed that eating pattern can affect 2 h plasma glucose independent of subject 's tolerance .
analysis of dietary intake among 1508 samoan and american samoan subjects derived two major diets as  neo - traditional pattern  and  modern pattern .
  neo - traditional pattern  is rich in local dishes such as coconut products , lobster , starchy vegetables , crab , and low consumptions of soda and chips , while  modern dietary pattern  contains processed and ready - to - use foods like cake , butter , eggs , and chips . in contrast with  neo - traditional  pattern ,  modern  pattern represented lower serum glucose concentration and metabolic syndrome in samoan men and women .
the effects of  healthy ,   western ,  and  traditional  dietary patterns among type 2 dm were evaluated in various studies whose characters are reflected in table 3 .
characteristics of various studies that evaluated the effects of  healthy  and  western  and  traditional  dietary patterns on diabetes mellitus type 2 besides the first known effect of dash on blood pressure control,[7177 ] the other useful potent roles of its main components , such as low - fat dairies and fiber - based foods , were observed on lipid profile and features of metabolic syndrome .
dash can also reduce the coronary heart disease . in recent years , several surveys assessed dash effects on blood glucose and incidence of type 2 dm . in the insulin resistance atherosclerosis study ( iras ) of 862 subjects from three different ethnics ( hispanic , non - hispanic white and black ) ,  dash  diet lowered the risk of diabetes incidence by as much as 36% in whites against black and hispanic participants .
the effect of  dash  diet on fbg was shown in two randomized clinical trial studies . in one study ,
these diets consisted of  weight reducing  diet ,  dash  diet , and  control  diet . the  weight reducing 
diet is defined as a diet with lower calorie contents and more  consumption of healthy food items 
( such as vegetables , fruits , and low - fat dairies ) subjects in the  control group  followed their usual eating habits .
the other cross - over randomized clinical trial ( rct ) assessed the effects of  dash  diet on hba1c and fasting blood sugar ( fbs ) levels in diabetic patients .
reduction in fbg and hba1c following adherence to the dash diet showed that dash eating pattern is a useful strategy in controlling blood glucose among type 2 diabetic patients .
characteristics of various studies that evaluated the effects of  dash  dietary pattern on diabetes mellitus type 2 in panagiotakos study , a positive correlation between red meat intake and homeostasis model assessment of insulin . resistance and insulin secretory capacity ( homa - ir , homa - b ) , insulin , and blood glucose levels
however , there was no significant relationship between healthy food groups such as vegetables , legumes , and fruits consumption and glycemic control after controlling for potential confounders .
reverse association between dm incidence and dietary pattern rich in  meat and milk  was observed in another study .
white rice was the dominant food item in all three diets . but noodle and dumpling in  korean  pattern and processed meat products in  meat and alcohol  eating habit showed significantly different effect on fbg .
 meat and alcohol  dietary pattern increased the risk of high blood glucose by 33% .
furthermore , data from the puerto rican elder inhabitants with rice and bean rich diet were studied in a longitudinal investigation among 1167 subjects .
analysis of their eating habits extracted three main patterns :  meat and french fries ,   traditional pattern 
( rice , beans , and oils ) ,  sweets , sugary beverages , and dairy desserts .  after controlling the confounders , just 
a cross - sectional study among 984 iranian women revealed that the clusters of diet containing  fish , vegetables , legumes , cereals , and fruits ,  and diet rich in  dairy products and eggs  could decrease fbs . however , diet rich in  red or white meat , meat products , and potatoes ,   pasta  and  sweet  patterns had unfavorable effects .
a reverse association of habitual diet with hyperglycemia and hyperinsulinemia was also observed in a nested cross - sectional survey of six dietary patterns among sweden adults .
data showed lower hyperinsulinemia in women with higher milk - fat  based food habits against taking white bread items , in common .
he et al . derived four dietary patterns after analysis of semi - quantitative food frequency questionnaire among 20,210 chinese adults : 
( high vegetables and low animal food style in the southeast area ) ,  new affluence  ( rich in animals and soy products which is used by well - to - do individuals ) , and  yellow earth  [ high carbohydrate ( cho ) and low fruits , vegetables , and animal dishes , which is common in the northwest area ] . comparing  green water consumer ,  the prevalence of igt in
 yellow earth  and  new affluence  escalated to ratios of 1.22 and 2.05 , in sequence .
risk of dm in caucasian , japanese , american , and native hawaiian participants in a 14-year follow - up survey showed a significant difference according to sex , and their three dietary designs included :  fat and meat ,   vegetables ,  and  fruit and milk  dietary patterns .
the hazard ratios for type 2 diabetes among women / men who adhered to the fifth quartiles of mentioned diets were 1.22/1.40 , 1.02/0.86 , and 0.85/0.92 , respectively .
these ratios were significant in all ethnics , except for  native hawaiian  subjects .
another multiethnic population - based cohort study among 6814 white , black , hispanic , and chinese subjects , which was conducted during 5 years , revealed two patterns which were defined as : 1 .
beans , tomatoes , refined grains , high - fat dairy , red meat and 2 .
whole grain , fruit , nuts / seeds , green leafy vegetables , low - fat dairy , and low - risk food patterns as the common dietary habits .
adherence to the first diet was accompanied with 18% higher risk ratio , while the others reduced the risk by 15% .
dietary pattern had decreased diabetes incidence by almost 22% , in contrast to  meat , fruit , and vegetable rich pattern  which increased the relative risk to 1.05 .
all the mentioned studies in this review paper had used factor analysis and cluster analysis .
these analyses detect dietary patterns from the existing data with no any prior assumption of disease . besides these posteriori methods , another method for evaluating the overall diet
is based on our previous knowledge about the effects of dietary components on health and disease . which is a prior method .
this method is based on scoring different components of a diet according to the scientific evidence regarding diet 
high  diet quality index  which is defined based on dietary variety , and high intake of whole grain , lean protein , low - fat dairy , and high - fiber food items was associated with or of type 2 dm by 0.38 in men and or for pre - diabetes by 0.66 in women .
alternative healthy eating index ( ahei ) is defined based on its association with various disorders , which consists of nine chief components of diet quality such as intake of vegetables , nuts , fruits , soybean , the white - to - red meat ratio , trans fatty acids , polyunsaturated to saturated fatty acids ratio ( p / s ratio ) , alcohol drinking , and taking multivitamin , and it is a suitable substitute for hei . in a prospective study , fung et al .
data show that high index can lower the incidence of type 2 diabetes by 36% during 18 years .
the cluster analysis on dietary intake of 1052 italians derived five main components which included : 
( low in fat but rich in mufa and cho ) ,  animal products  ( high in animal protein , sfa , and cholesterol ) ,  starch  ( rich in vegetable protein and starch ) ,  vegetal / fat(high in olive oil and seeds ) , and  vitamin / fiber(rich in fruits and vegetables ) .
observed the lowest igt prevalence by adherence to  starch  pattern , in contrast to  animal  food pattern . in the four dietary patterns derived from population - based cohort study , a negative association between commonly consumed fiber - based foods and white meat in  diet 1  and
diet rich in cake , vegetable , and cheese pattern named as  diet 2  with igt was seen .
there was also a 28% reduction in diabetes incidence following adherence to the diet containing fiber - based foods and white meat .
sex difference in relation to dietary pattern and features of metabolic syndrome was reflected significantly in malmo diet and cancer study of swedish adults .
risk of hyperglycemia accompanying dietary pattern rich in meat and dairies increased by 64% among men , while it was not significantly associated with hyperglycemia among women however , heidemann revealed that those in the highest quartiles of diet rich in fruits and poor in meat , beer , and soft drink had lower incidence of type 2 dm by 0.27 . in framingham offspring study ,  fruits , reduced fat dairy , and whole grains ,   refined grains and sweets ,   beer  and  soda  diets were extracted .
data revealed that adherence to  soda  pattern is accompanied by higher fasting insulin level . a pattern high in fruits , vegetables , whole grains , and reduced fat dairy protects against insulin resistance compared to sweet food pattern and soda pattern which are associated with insulin resistance .
table 5 shows the different surveys that assess the effects of various dietary patterns among type 2 dm patients .
characteristics of various studies that evaluated the effects of different dietary patterns on diabetes mellitus type 2
this food habit emphasizes on good source of monoun - saturated fatty acids ( mufa ) from olive oil , accompanied with intake of vegetables , nuts , seeds , fruits , and whole grains , and reduction in the consumption of red meat and unhealthy fats .
high content of fiber , magnesium , polyphenol , and antioxidants makes this diet as a useful approach to control hyperglycemia and weight maintenance .
the results of a large spanish cohort study among 13,380 men and women showed that adherence to the mediterranean diet could decrease the risk of type 2 dm by 83% .
this inverse association between mediterranean dietary pattern and the prevalence of type 2 dm was observed in various multiethnic studies .
several epidemiological studies explained lower odds of having dm and inverse relation between glucose level,[3537 ] insulin,[3139 ] and homa - ir ( as one of the basic features of metabolic syndrome and type 2 dm)[3133364042 ] following adherence to the mediterranean dietary pattern even after controlling different confounding agents.[4348 ] higher adherence to the mediterranean dietary pattern score in normoglycemic persons decreased fasting glucose , insulin , and ir .
however , this reduction was not significant after multiple adjustments were made for diabetic patients and subjects with impaired fasting glucose ( ifg ) .
the aforementioned findings are observed in elderly group and high - risk persons with cardiovascular risk factors and in also those with history of myocardial infarction.[315052 ] another cohort study on 7751 subjects in different ethnics compared four dietary patterns : 1 .
 mediterranean - like diet  containing rice , pasta , vegetables , fruits , and wine ; 2 .
 healthy pattern  that includes whole bread , fruits , vegetables , low - fat dairies , and little alcohol ; 3 .
 sweet pattern  rich in white bread , processed meat , and high - fat dairy products ; and 4 .
 unhealthy eating pattern  high in white bread , processed meat , fries , and full - cream milk .
results showed that healthy diet is the best pattern in lowering the incidence of dm .
observed a lower or of diabetes among greek adults with high score of adherence to the mediterranean dietary pattern .
the comparison of the effects of  mediterranean hypocaloric  diet and  very - low - carbohydrate hypocaloric
 diet on fasting plasma glucose , serum insulin level , and insulin 2 h post - load concentration and homa - ir did not show a significant difference even after 8 weeks weight loss in obese women .
a longitudinal clinical trial for 54 months revealed that consuming a mediterranean diet could decrease homa - ir and serum glucose and serum insulin levels in persons with metabolic syndrome . as patients with metabolic syndrome are at high risk for developing type 2 diabetes , following the mediterranean diet can have a protective effect in this regard .
table 1 shows the different studies which evaluate the effects of  mediterranean  dietary pattern on type 2 dm .
characteristics of various studies that evaluated the effects of  mediterranean  dietary pattern on diabetes mellitus type 2
several studies have focused on the association between lower risk of type 2 dm and adherence to the  prudent pattern . 
prudent pattern is another dietary pattern which is characterized by higher consumption of whole grains , vegetables , fruits , poultry / sea foods , legumes , and coffee . in an american prospective cohort study among 42,504 men , higher adherence to
the prudent pattern reduced the risk of dm by 16% , however , after 12 years of follow - up .
western dietary pattern contains red and processed meat , butter , french fries , refined grains , deserts , potatoes , sweets , high - fat dairy , and soda .
the results were similar to the findings of the  atherosclerosis risk in communities ( aric )  study and al so , the observations of fung et al . in the nurses health study ( nhs ) following 12 years . in another study ,
 conservative  eating pattern , which contains butter , potatoes , and whole milk , has been correlated positively with the risk of diabetes by 50% while adherence to the 
two cross - sectional studies of villegas et al . defined usual dietary pattern of adults in three clusters , which correspond to  traditional ,   prudent ,  and  alcohol and convenience  diets . 
traditional  pattern had high percent of fat in total calorie intake ; predominantly fat intake was in the forms of saturated fatty acids ( sfa ) and mufa , in contrast to 
prudent  diet which was characterized as a pattern rich in polyunsaturated fatty acids ( pufa ) , high p / s ratio , fiber , and antioxidant vitamin sources . 
alcohol and convenience  diet included the highest intake of alcohol , protein , cholesterol , vitamin b - complex , iron , phosphorus , selenium , zinc , and the lowest amount of pufa and antioxidant vitamins .
analysis showed the lowest ir and hemoglobin a1c ( hba1c ) level in subjects adhering to the  prudent dietary pattern .  an iranian nested cross - sectional study among 425 subjects with igt ( 2535 years old ) showed the association between plasma glucose as one of the major features of metabolic syndrome and five eating patterns : 1 .  western  pattern ( rich in sweets , butter , soda , mayonnaise , sugar , cookies , tail of a lamb , hydrogenated fat , and eggs ) ; 2 .
 prudent  pattern ( contains fish , peas , honey , nuts , juice , dry fruits , vegetable oil , liver and organic meat , and coconuts ) ; 3 .
 vegetarian  pattern ( includes potatoes , legumes , fruits , rice , green leafy vegetables , and fruits ) ; 4 .
 high - fat dairy  pattern ( high in fatty dairies ) ; and 5 .  chicken and plant  pattern ( rich in chicken , fruits , green leafy vegetables , and mayonnaise ) .
vegetarian  diet can reduce blood glucose level significantly . different studies that assessed the effects of  prudent  and  western  patterns among type 2 dm are shown in table 2
. characteristics of various studies that evaluated the effects of  prudent  and  western  dietary patterns on diabetes mellitus type 2
food items of similar dietary patterns are different , based on geographic and ethnic characters .
 traditional  pattern is characterized by higher consumption of refined grains , potato , tea , whole grains , hydrogenated fats , legumes , and casserole , or it can be defined as a pattern rich in high - fat sandwich spreads , red meat , potatoes , butter and lard , low - fat fish , sandwich meat , and sauces .
healthy diet usually contains higher intake of whole meal bread , fruit and vegetables , and polyunsaturated margarine , besides lower consumption of red meat , sweet foods , and wine and beer , or food rich in fruits , vegetables , tomato , poultry , legumes , tea , fruit juices , and whole grains .
pattern rich in red meat , processed meat , french fries , high - fat dairy products , refined grains , and sweets and desserts , or sweets , butter , soda , mayonnaise , sugar , cookies , tail of a lamb , hydrogenated fat , and eggs , and refined grains , red meat , butter , processed meat , high - fat dairy , sweets and desserts , pizza , potato , eggs , hydrogenated fats , and soft drinks is called as a 
western  dietary pattern . in a cross - sectional study of 486 iranian women between 40 and 60 years of age
 healthy  pattern defined by frequent consumption of fruits , green leafy and cruciferous vegetables , tomatoes , legumes , tea , and poultry ; 2 .
ready - to - use food items as the main footsteps of modernization or so - called as  western  dietary pattern ; and 3 . 
iranian traditional  pattern consists of whole and refined grains , potatoes , legumes , tea , hydrogenated fats , and broth .
the highest or of ir and syndrome x was observed in people with the adherence to the highest quintile of  western  diet .
this result is similar to the result of fung et al . who observed a positive association between  western  pattern adherence and insulin level .
pattern can reduce risk of ir by 45% , while adherence to the  western  dietary pattern increases this risk to 15% .
mcnaughton et al . in an australian cohort study ( whitehall ii ) observed higher incidence of type 2 diabetes and higher value of homa - ir by adherence to the highest quartile of a diet rich in soft drinks , sugar - sweetened beverages , burgers and sausages , snacks , and white bread , and low intake of fiber food sources , by 2.95 times .
a multiethnic hawaiian survey revealed that higher ors for type 2 dm were associated with  animal  foods ,  local ethnic  dishes , and 
 animal  and  local ethnic  dishes included high intake of cabbage , rice , shell fish , corned beef plus  hawaiian and filipino  dishes .
modern  dietary pattern had a lower postprandial plasma glucose , after adjusting the confounding factors in the analysis in brief more consumptions of vegetables , vegetable oil / vinegar dressing , fruits , cereals , rice , pasta , and poultry against 
traditional  diet ( contains red meat , high - fat meat sandwich , butter and lard , potatoes , low - fat fishes , and sauces ) .
this study showed that eating pattern can affect 2 h plasma glucose independent of subject 's tolerance .
analysis of dietary intake among 1508 samoan and american samoan subjects derived two major diets as  neo - traditional pattern  and  modern pattern .
  neo - traditional pattern  is rich in local dishes such as coconut products , lobster , starchy vegetables , crab , and low consumptions of soda and chips , while  modern dietary pattern  contains processed and ready - to - use foods like cake , butter , eggs , and chips .
in contrast with  neo - traditional  pattern ,  modern  pattern represented lower serum glucose concentration and metabolic syndrome in samoan men and women .
the effects of  healthy ,   western ,  and  traditional  dietary patterns among type 2 dm were evaluated in various studies whose characters are reflected in table 3 .
characteristics of various studies that evaluated the effects of  healthy  and  western  and  traditional  dietary patterns on diabetes mellitus type 2
besides the first known effect of dash on blood pressure control,[7177 ] the other useful potent roles of its main components , such as low - fat dairies and fiber - based foods , were observed on lipid profile and features of metabolic syndrome .
, several surveys assessed dash effects on blood glucose and incidence of type 2 dm . in the insulin resistance atherosclerosis study ( iras ) of 862 subjects from three different ethnics ( hispanic , non - hispanic white and black ) ,  dash  diet lowered the risk of diabetes incidence by as much as 36% in whites against black and hispanic participants .
the effect of  dash  diet on fbg was shown in two randomized clinical trial studies . in one study ,
these diets consisted of  weight reducing  diet ,  dash  diet , and 
diet is defined as a diet with lower calorie contents and more  consumption of healthy food items 
( such as vegetables , fruits , and low - fat dairies ) subjects in the  control group  followed their usual eating habits .
the other cross - over randomized clinical trial ( rct ) assessed the effects of  dash  diet on hba1c and fasting blood sugar ( fbs ) levels in diabetic patients .
reduction in fbg and hba1c following adherence to the dash diet showed that dash eating pattern is a useful strategy in controlling blood glucose among type 2 diabetic patients .
characteristics of various studies that evaluated the effects of  dash  dietary pattern on diabetes mellitus type 2
in panagiotakos study , a positive correlation between red meat intake and homeostasis model assessment of insulin .
resistance and insulin secretory capacity ( homa - ir , homa - b ) , insulin , and blood glucose levels was observed among 2832 subjects without cardiovascular disorders .
however , there was no significant relationship between healthy food groups such as vegetables , legumes , and fruits consumption and glycemic control after controlling for potential confounders .
reverse association between dm incidence and dietary pattern rich in  meat and milk  was observed in another study .
noodle and dumpling in  korean  pattern and processed meat products in  meat and alcohol  eating habit showed significantly different effect on fbg . 
meat and alcohol  dietary pattern increased the risk of high blood glucose by 33% .
furthermore , data from the puerto rican elder inhabitants with rice and bean rich diet were studied in a longitudinal investigation among 1167 subjects .
analysis of their eating habits extracted three main patterns :  meat and french fries ,   traditional pattern 
( rice , beans , and oils ) ,  sweets , sugary beverages , and dairy desserts .
a cross - sectional study among 984 iranian women revealed that the clusters of diet containing  fish , vegetables , legumes , cereals , and fruits ,  and diet rich in  dairy products and eggs  could decrease fbs .
however , diet rich in  red or white meat , meat products , and potatoes ,   pasta  and  sweet  patterns had unfavorable effects .
a reverse association of habitual diet with hyperglycemia and hyperinsulinemia was also observed in a nested cross - sectional survey of six dietary patterns among sweden adults .
data showed lower hyperinsulinemia in women with higher milk - fat  based food habits against taking white bread items , in common .
he et al . derived four dietary patterns after analysis of semi - quantitative food frequency questionnaire among 20,210 chinese adults : 
( high vegetables and low animal food style in the southeast area ) ,  new affluence  ( rich in animals and soy products which is used by well - to - do individuals ) , and  yellow earth  [ high carbohydrate ( cho ) and low fruits , vegetables , and animal dishes , which is common in the northwest area ] . comparing  green water consumer ,  the prevalence of igt in 
yellow earth  and  new affluence  escalated to ratios of 1.22 and 2.05 , in sequence .
risk of dm in caucasian , japanese , american , and native hawaiian participants in a 14-year follow - up survey showed a significant difference according to sex , and their three dietary designs included :  fat and meat ,   vegetables ,  and  fruit and milk  dietary patterns .
the hazard ratios for type 2 diabetes among women / men who adhered to the fifth quartiles of mentioned diets were 1.22/1.40 , 1.02/0.86 , and 0.85/0.92 , respectively .
these ratios were significant in all ethnics , except for  native hawaiian  subjects .
another multiethnic population - based cohort study among 6814 white , black , hispanic , and chinese subjects , which was conducted during 5 years , revealed two patterns which were defined as : 1 .
beans , tomatoes , refined grains , high - fat dairy , red meat and 2 . whole grain , fruit , nuts / seeds , green leafy vegetables , low - fat dairy , and low - risk food patterns as the common dietary habits .
adherence to the first diet was accompanied with 18% higher risk ratio , while the others reduced the risk by 15% .
dietary pattern had decreased diabetes incidence by almost 22% , in contrast to  meat , fruit , and vegetable rich pattern  which increased the relative risk to 1.05 .
all the mentioned studies in this review paper had used factor analysis and cluster analysis .
these analyses detect dietary patterns from the existing data with no any prior assumption of disease . besides these posteriori methods , another method for evaluating the overall diet
is based on our previous knowledge about the effects of dietary components on health and disease . which is a prior method .
this method is based on scoring different components of a diet according to the scientific evidence regarding diet 
high  diet quality index  which is defined based on dietary variety , and high intake of whole grain , lean protein , low - fat dairy , and high - fiber food items was associated with or of type 2 dm by 0.38 in men and or for pre - diabetes by 0.66 in women .
alternative healthy eating index ( ahei ) is defined based on its association with various disorders , which consists of nine chief components of diet quality such as intake of vegetables , nuts , fruits , soybean , the white - to - red meat ratio , trans fatty acids , polyunsaturated to saturated fatty acids ratio ( p / s ratio ) , alcohol drinking , and taking multivitamin , and it is a suitable substitute for hei . in a prospective study , fung et al .
data show that high index can lower the incidence of type 2 diabetes by 36% during 18 years .
the cluster analysis on dietary intake of 1052 italians derived five main components which included : 
( low in fat but rich in mufa and cho ) ,  animal products  ( high in animal protein , sfa , and cholesterol ) ,  starch  ( rich in vegetable protein and starch ) ,  vegetal / fat(high in olive oil and seeds ) , and 
observed the lowest igt prevalence by adherence to  starch  pattern , in contrast to  animal  food pattern . in the four dietary patterns derived from population - based cohort study ,
diet 1  and diet rich in cake , vegetable , and cheese pattern named as  diet 2  with igt was seen .
there was also a 28% reduction in diabetes incidence following adherence to the diet containing fiber - based foods and white meat .
sex difference in relation to dietary pattern and features of metabolic syndrome was reflected significantly in malmo diet and cancer study of swedish adults .
risk of hyperglycemia accompanying dietary pattern rich in meat and dairies increased by 64% among men , while it was not significantly associated with hyperglycemia among women however , heidemann revealed that those in the highest quartiles of diet rich in fruits and poor in meat , beer , and soft drink had lower incidence of type 2 dm by 0.27 .
in framingham offspring study ,  fruits , reduced fat dairy , and whole grains ,   refined grains and sweets ,   beer  and  soda  diets were extracted .
pattern is accompanied by higher fasting insulin level . a pattern high in fruits , vegetables , whole grains , and reduced fat dairy protects against insulin resistance compared to sweet food pattern and soda pattern which are associated with insulin resistance .
table 5 shows the different surveys that assess the effects of various dietary patterns among type 2 dm patients .
characteristics of various studies that evaluated the effects of different dietary patterns on diabetes mellitus type 2
dietary intakes have important roles against insulin resistance , and in the prevention and management of hyperglycemia . epidemiological studies revealed that dietary patterns high in fiber - rich food items such as vegetables , fruits , whole grains , seeds and nuts , plus white meat sources like poultry and fish could have protective effects against the incidence of dm . however , dietary patterns rich in processed meat and red meat , refined cereals , and sfas are associated with higher risk of dm .
healthy patterns , mediterranean , and prudent dietary patterns also are protective dietary patterns against dm . however , adherence to western dietary pattern is associated with higher risk of diabetes .
these results are in line with iranian dietary pattern surveys which emphasize on adherence to healthy pattern to manage abnormal glucose homeostasis .
it is suggested to see the relationship of different dietary patterns and the incidence of type 2 diabetes in cohort studies among different populations in future studies .
 objective : to investigate the role of dietary patterns in prevention and management of type 2 diabetes mellitus.materials and methods : a systematic review of databases which were published in isi , cochrane central register of controlled trials databases , pubmed , iran medex , and magiran was performed . 
  diabetes  and  dietary pattern  were used as the keywords.results:a total of 58 studies which aimed to focus on diabetes mellitus , insulin resistance , metabolic syndrome , dietary pattern , and other related key words were reviewed . 
 more than 47,447 articles were found and 46,709 entries of the extracted studies were excluded on the basis of the title and abstracts . 
 the major dietary patterns were :  
 healthy  
 ,  western  ,  traditional  ,  prudent  ,  unhealthy  , 
  mediterranean  ,  modern  , and  dietary approach to stop hypertension  
 ( dash ) diets . 
 comparison of the effects of different diets revealed that dietary patterns containing fiber - rich foods have a protective role in managing diabetes mellitus .  
 healthy  ,  mediterranean  ,  prudent  , and  dash  
 dietary patterns were associated with lower risk of hyperglycemia.conclusions:the adherence to the mediterranean , prudent , or dash diets could control hyperglycemia . 
 the higher intake of vegetables , fruits , nuts , whole grains , and lower intake of red meat could reduce the risk of type 2 diabetes mellitus . 
INTRODUCTION
MATERIALS AND METHODS
RESULTS AND DISCUSSION
Mediterranean dietary pattern
Prudent and Western dietary pattern
Healthy, Western, and Traditional dietary patterns
DASH dietary pattern
Other dietary habits
CONCLUSION