this investigation is based on cross - sectional data from 275 independently living individuals who participated in the follow - up in 2008 of the longitudinal study on nutrition and health status of senior citizens of giessen ( gisela study ) , germany ( 50.6north ) .
investigations took place in the institute of nutritional science in giessen from july to october .
the ethical committee of the faculty of medicine at the justus - liebig - university , giessen , approved the research protocol .
exclusion criteria for the present study were any of the following conditions : incomplete data ( n=23 ) on dietary assessment and biochemical parameters , including serum 25-hydroxyvitamin d3 [ 25(oh)d3 ] and parathyroid hormone ; chronic renal disease ( n=5 ) ; and lifetime history of cancer of the gastrointestinal tract ( stomach , small intestine , colon ; n=11 ) .
fasting blood samples were collected , and serum aliquots were stored at 70c until further analysis .
serum 25(oh)d3 and parathyroid hormone were measured by an electrochemiluminescence immunoassay ( roche diagnostics gmbh , mannheim , germany ) .
participants completed a self - administered questionnaire on socioeconomic and lifestyle characteristics , such as age , sex , monthly household net income , smoking status , physical activity , and disease history .
bmi was defined as weight ( kg ) divided by height squared ( m ) .
percentage total body fat ( % tbf ) was determined by a single - frequency ( 50 khz ) bioelectrical impedance analyser ( akern - rjl bia 101/s ; data input , frankfurt , germany ) , according to manufacturer 's instructions and the predictive formula of roubenoff et al .
nutritional intake was determined using a 3-day estimated dietary record , which was developed and validated for the gisela study ( 20 ) .
validity was evaluated by nitrogen excretion in the 24-h urine in relation to protein intake , and by comparing energy intake and resting metabolic rate assessed by indirect calorimetry according to goldberg et al .
for every food item , both typical household measures ( e.g. slice , cup and spoon ) and the appropriate weights were given .
the participants were instructed to record their entire food intake on three consecutive days directly after consumption , starting on a sunday .
food , energy , and nutrient intakes were calculated using the german food code and nutrient data base ( federal institute for health protection of consumers and veterinary medicine , berlin , germany ) ( 22 ) version ii.3 . for the present analysis
, we created nine food groups to measure the contribution of particular food categories to vitamin d intake : fish / fish products ( e.g. fish , canned fish , seafood ) ; eggs ; fats / oils ( e.g. butter , lard , margarine , oil ) ; bread / bakery products ( e.g. bread , toast , cake , biscuits ) ; milk / dairy products ( e.g. milk , cheese , yoghurt , curd , cream ) ; potatoes / fruits/ vegetables and related products ; nutriments ( e.g. pasta , rice , cereals , corn flakes ) ; meat / meat products ( e.g. meat , innards , sausages , cold cuts , ham ) ; and the category others inclusive of , for example , sauces , sweets , snacks , and beverages .
the contribution of vitamin d by eggs and fats via processed foods was captured by the foods to which these components have been added during processing or , in the case of fats , of which they are an inherent component . in addition , subjects were asked to rank their usual fish , egg , and milk consumption frequencies on a scale from never to daily intake .
continuous data are expressed as mean and standard deviation ( sd ) and median and 5th to 95th percentile , when appropriate .
chi - square test or fisher 's exact test was used to assess differences in proportions .
we performed stratified analyses by sex ( females vs. males ) , median age ( < 76 vs. 76 years ) , median vitamin d status ( 63 vs. > 63
nmol / l ) , median bmi ( 26.8 vs. > 26.8 kg / m ) , and household net income ( < 1,500 vs. 1,500  /month ) to examine whether vitamin d intake and the contributing food groups differed between the respective groups .
spearman correlation was applied to evaluate correlations between vitamin d intake and sex , age , bmi , % tbf , pal , smoking behaviour ( never smokers vs. current and ex - smokers ) , household net income ( < 1,500 vs. 1,500  /month ) , nutritional parameters , and 25(oh)d3 . those variables that showed a significant association with vitamin d intake were entered in the multiple backward regression model with the logarithmically transformed ( log ) vitamin d intake as dependent variable .
statistical analyses were conducted with spss 21.0 for windows ( ibm , chicago , usa ) .
this investigation is based on cross - sectional data from 275 independently living individuals who participated in the follow - up in 2008 of the longitudinal study on nutrition and health status of senior citizens of giessen ( gisela study ) , germany ( 50.6north ) .
investigations took place in the institute of nutritional science in giessen from july to october .
the ethical committee of the faculty of medicine at the justus - liebig - university , giessen , approved the research protocol .
exclusion criteria for the present study were any of the following conditions : incomplete data ( n=23 ) on dietary assessment and biochemical parameters , including serum 25-hydroxyvitamin d3 [ 25(oh)d3 ] and parathyroid hormone ; chronic renal disease ( n=5 ) ; and lifetime history of cancer of the gastrointestinal tract ( stomach , small intestine , colon ; n=11 ) .
fasting blood samples were collected , and serum aliquots were stored at 70c until further analysis .
serum 25(oh)d3 and parathyroid hormone were measured by an electrochemiluminescence immunoassay ( roche diagnostics gmbh , mannheim , germany ) .
participants completed a self - administered questionnaire on socioeconomic and lifestyle characteristics , such as age , sex , monthly household net income , smoking status , physical activity , and disease history .
bmi was defined as weight ( kg ) divided by height squared ( m ) .
percentage total body fat ( % tbf ) was determined by a single - frequency ( 50 khz ) bioelectrical impedance analyser ( akern - rjl bia 101/s ; data input , frankfurt , germany ) , according to manufacturer 's instructions and the predictive formula of roubenoff et al .
nutritional intake was determined using a 3-day estimated dietary record , which was developed and validated for the gisela study ( 20 ) .
validity was evaluated by nitrogen excretion in the 24-h urine in relation to protein intake , and by comparing energy intake and resting metabolic rate assessed by indirect calorimetry according to goldberg et al .
for every food item , both typical household measures ( e.g. slice , cup and spoon ) and the appropriate weights were given .
the participants were instructed to record their entire food intake on three consecutive days directly after consumption , starting on a sunday .
food , energy , and nutrient intakes were calculated using the german food code and nutrient data base ( federal institute for health protection of consumers and veterinary medicine , berlin , germany ) ( 22 ) version ii.3 . for the present analysis
, we created nine food groups to measure the contribution of particular food categories to vitamin d intake : fish / fish products ( e.g. fish , canned fish , seafood ) ; eggs ; fats / oils ( e.g. butter , lard , margarine , oil ) ; bread / bakery products ( e.g. bread , toast , cake , biscuits ) ; milk / dairy products ( e.g. milk , cheese , yoghurt , curd , cream ) ; potatoes / fruits/ vegetables and related products ; nutriments ( e.g. pasta , rice , cereals , corn flakes ) ; meat / meat products ( e.g. meat , innards , sausages , cold cuts , ham ) ; and the category others inclusive of , for example , sauces , sweets , snacks , and beverages .
the contribution of vitamin d by eggs and fats via processed foods was captured by the foods to which these components have been added during processing or , in the case of fats , of which they are an inherent component . in addition , subjects were asked to rank their usual fish , egg , and milk consumption frequencies on a scale from never to daily intake .
continuous data are expressed as mean and standard deviation ( sd ) and median and 5th to 95th percentile , when appropriate .
chi - square test or fisher 's exact test was used to assess differences in proportions .
we performed stratified analyses by sex ( females vs. males ) , median age ( < 76 vs. 76 years ) , median vitamin d status ( 63 vs. > 63
nmol / l ) , median bmi ( 26.8 vs. > 26.8 kg / m ) , and household net income ( < 1,500 vs. 1,500  /month ) to examine whether vitamin d intake and the contributing food groups differed between the respective groups .
spearman correlation was applied to evaluate correlations between vitamin d intake and sex , age , bmi , % tbf , pal , smoking behaviour ( never smokers vs. current and ex - smokers ) , household net income ( < 1,500 vs. 1,500  /month ) , nutritional parameters , and 25(oh)d3 . those variables that showed a significant association with vitamin d intake were entered in the multiple backward regression model with the logarithmically transformed ( log ) vitamin d intake as dependent variable .
statistical analyses were conducted with spss 21.0 for windows ( ibm , chicago , usa ) .
however , 25(oh)d3 levels < 50 nmol / l were noticed in 21.3% of the subjects , while 21.3% had 25(oh)d3 levels 75
both sexes failed to meet the recommended daily intake of 20 g vitamin d ( 9 ) ; only one woman and two men ingested 20 g / day .
vitamin d intakes < 5 g / day and < 10 g / day were observed in 57.4 and 90.2% of the study population , respectively .
sex differences were not found in any of these analyses ( p>0.05 ) . of the subjects who made statements on their usual consumption frequencies of fish ( n=226 ) , eggs ( n=229 ) , and milk ( n=212 ) ,
2.2% ( n=5 ) , 0.9% ( n=2 ) , and 24.1% ( n=51 ) were non - consumers of fish , eggs , and milk ; 75.2% ( n=170 ) , 76.4% ( n=175 ) , and 26.4% ( n=56 ) reported to eat seldom or several times per month fish , eggs , and milk ; whereas 22.6% ( n=51 ) , 22.7% ( n=52 ) , and 49.5% ( n=105 ) stated that they consume fish , eggs , and milk several times per week or daily , respectively .
whitney u test , chi - square test , and fisher 's exact test for analysing sex differences ; missing data were present on total body fat ( n=5 ) , physical activity level ( n=26 ) , smoking behaviour ( n=2 ) , and monthly household net income ( n=41 ) . 

table 2 presents the median values and the 5th and 95th percentiles of the daily intake levels of the nine food groups , the corresponding absolute vitamin d intake by these food groups , and the relative contributions of the food groups to the daily vitamin d intake . for some of the food groups ( eggs , potatoes / fruits / vegetables , nutriments , meat / meat products , and others ) , median values for their contribution to vitamin d intake amounted to zero
this is due to the very low amount of vitamin d in these food groups and/or the fact that within the 3 days of dietary record , more than half of the subjects consumed no such foods ( as in the case of eggs , for example ) .
median and mean percentage contributions of food groups to the daily vitamin d intake differed considerably , indicating non - normally distributed data .
when expressed as mean values , contributions to the daily vitamin d intake amounted to approximately 40% for fish / fish products followed by eggs ( 15% ) , fats / oils ( 13% ) , bread / bakery products ( 12% ) , and milk / dairy products ( 12% ) .
the other food groups altogether added to less than 10% to the mean daily vitamin d intake .
daily intake levels of food groups and corresponding vitamin d intake ( n=235 ) stratifying our analysis by age ( < 76 vs. 76 years ) , vitamin d status tended to be higher in younger subjects compared to older subjects ( median : 65.2 vs. 61.2
nmol / l ; p=0.053 ) , whereas dietary vitamin d intake was significantly higher in older participants ( median : 2.4 vs. 4.1 g / day ; p=0.049 ) .
apart from a tendency towards a higher contribution of fish to the vitamin d intake in older participants ( 35 vs. 44% ; p=0.102 ) , contributing food groups did not differ between age groups .
no substantial differences in vitamin d intake levels or in relative contributions of food groups were found after stratifying the cohort according to the median vitamin d status ( p>0.05 ) . however , a slightly higher contribution of meat / meat products to the dietary vitamin d intake in subjects with a vitamin d status 63 nmol / l compared to subjects who had a higher vitamin d status was noticed ( 2.05 vs. 2.02% ; p = 0.024 ) .
after stratifying the cohort into two groups based on the median bmi , vitamin d status of subjects with a bmi 26.8 kg / m was higher than in subjects with a bmi>26.8 kg / m ( median : 67.3 vs. 59.3
no significant differences in vitamin d intake or in contributions of food groups were found ( p>0.05 ) .
similar results were observed when the cohort was divided according to the sex - specific median % tbf ( p>0.05 ) .
subsequent to the separation of the study population with regard to the monthly household net income ( < 1,500 vs. 1,500  ) , vitamin d status was higher in the upper income group ( median : 59.4 vs. 65.6 nmol / l ; p=0.020 ) , while vitamin d intake was significantly lower ( median : 5.5 vs. 2.7 g / day ; p=0.007 ) . compared to subjects reporting an income 1,500  /month , subjects with an income < 1,500  /month showed higher mean fractional contributions to dietary vitamin d intake by  fish ( 49 vs. 36% ; p=0.028 ) and by  potatoes / fruits / vegetables ( 2.4 vs. 2.3% , p=0.044 ) , whereas the contributions of  fats / oils ( 9 vs. 16% , p=0.010 ) and , albeit not significant , of  milk / dairy products ( 9 vs. 13% , p=0.066 ) were lower .
dietary vitamin d intake was associated with age , % tbf , intake of energy , fat and alcohol , frequency of fish intake , and household net income , but did not correlate with sex , bmi , smoking , pal , use of vitamin d supplements , and consumption frequencies of eggs and milk .
except for a positive correlation with alcohol intake ( r 
 s=0.152 ; p=0.020 ) , 25(oh)d3 levels did not correlate with dietary parameters ( p>0.05 ) .
spearman correlations between vitamin d intake and relevant parametersa 
 
 r 
 s = spearman correlation coefficient .
missing data were present on total body fat ( n=5 ) ; consumption frequencies of fish ( n=9 ) , eggs ( n=6 ) , and milk ( n=23 ) ; physical activity level ( n=26 ) ; smoking behaviour ( n=2 ) ; and monthly household net income ( n=41 ) .
frequencies were dichotomised in never to several times per month ( coded as 0 ) versus several times per week to daily ( coded as 1 ) . multiple regression analysis ( n=185 ) was performed with log vitamin d intake as the dependent variable and age , % tbf , intake of energy , fat and alcohol , frequency of fish intake , and household net income as independent variables . thereby , fat intake ( =0.283 ; p<0.0001 ) and frequency of fish consumption ( =0.235 ; p=0.001 ) were identified as positive determinants of dietary vitamin d intake , whereas alcohol intake ( =0.122 ; p=0.082 ) , net income ( =0.174 ; p=0.013 ) , and % tbf ( =0.174 ; p=0.014 ) negatively affected vitamin d intake .
this regression model explained 19.6% of the variance in dietary vitamin d intake in elderly subjects .
the exclusion of two people with very high dietary vitamin d intake levels ( 26 and 37 g / day ) provided approximately equivalent results .
however , 25(oh)d3 levels < 50 nmol / l were noticed in 21.3% of the subjects , while 21.3% had 25(oh)d3 levels 75
both sexes failed to meet the recommended daily intake of 20 g vitamin d ( 9 ) ; only one woman and two men ingested 20 g / day .
vitamin d intakes < 5 g / day and < 10 g / day were observed in 57.4 and 90.2% of the study population , respectively .
sex differences were not found in any of these analyses ( p>0.05 ) . of the subjects who made statements on their usual consumption frequencies of fish ( n=226 ) , eggs ( n=229 ) , and milk ( n=212 ) ,
2.2% ( n=5 ) , 0.9% ( n=2 ) , and 24.1% ( n=51 ) were non - consumers of fish , eggs , and milk ; 75.2% ( n=170 ) , 76.4% ( n=175 ) , and 26.4% ( n=56 ) reported to eat seldom or several times per month fish , eggs , and milk ; whereas 22.6% ( n=51 ) , 22.7% ( n=52 ) , and 49.5% ( n=105 ) stated that they consume fish , eggs , and milk several times per week or daily , respectively .
whitney u test , chi - square test , and fisher 's exact test for analysing sex differences ; missing data were present on total body fat ( n=5 ) , physical activity level ( n=26 ) , smoking behaviour ( n=2 ) , and monthly household net income ( n=41 ) .

 table 2 presents the median values and the 5th and 95th percentiles of the daily intake levels of the nine food groups , the corresponding absolute vitamin d intake by these food groups , and the relative contributions of the food groups to the daily vitamin d intake . for some of the food groups ( eggs , potatoes / fruits / vegetables , nutriments , meat / meat products , and others ) , median values for their contribution to vitamin d intake amounted to zero
this is due to the very low amount of vitamin d in these food groups and/or the fact that within the 3 days of dietary record , more than half of the subjects consumed no such foods ( as in the case of eggs , for example ) .
median and mean percentage contributions of food groups to the daily vitamin d intake differed considerably , indicating non - normally distributed data . when expressed as mean values , contributions to
the daily vitamin d intake amounted to approximately 40% for fish / fish products followed by eggs ( 15% ) , fats / oils ( 13% ) , bread / bakery products ( 12% ) , and milk / dairy products ( 12% ) .
the other food groups altogether added to less than 10% to the mean daily vitamin d intake .
stratifying our analysis by age ( < 76 vs. 76 years ) , vitamin d status tended to be higher in younger subjects compared to older subjects ( median : 65.2 vs. 61.2
nmol / l ; p=0.053 ) , whereas dietary vitamin d intake was significantly higher in older participants ( median : 2.4 vs. 4.1 g / day ; p=0.049 ) .
apart from a tendency towards a higher contribution of fish to the vitamin d intake in older participants ( 35 vs. 44% ; p=0.102 ) , contributing food groups did not differ between age groups .
no substantial differences in vitamin d intake levels or in relative contributions of food groups were found after stratifying the cohort according to the median vitamin d status ( p>0.05 ) . however , a slightly higher contribution of meat / meat products to the dietary vitamin d intake in subjects with a vitamin d status 63 nmol / l compared to subjects who had a higher vitamin d status was noticed ( 2.05 vs. 2.02% ; p = 0.024 ) .
after stratifying the cohort into two groups based on the median bmi , vitamin d status of subjects with a bmi 26.8 kg / m was higher than in subjects with a bmi>26.8 kg / m ( median : 67.3 vs. 59.3
no significant differences in vitamin d intake or in contributions of food groups were found ( p>0.05 ) .
similar results were observed when the cohort was divided according to the sex - specific median % tbf ( p>0.05 ) .
subsequent to the separation of the study population with regard to the monthly household net income ( < 1,500 vs. 1,500  ) , vitamin d status was higher in the upper income group ( median : 59.4 vs. 65.6 nmol / l ; p=0.020 ) , while vitamin d intake was significantly lower ( median : 5.5 vs. 2.7 g / day ; p=0.007 ) . compared to subjects reporting an income 1,500  /month , subjects with an income < 1,500  /month showed higher mean fractional contributions to dietary vitamin d intake by
 fish ( 49 vs. 36% ; p=0.028 ) and by  potatoes / fruits / vegetables ( 2.4 vs. 2.3% , p=0.044 ) , whereas the contributions of  fats / oils ( 9 vs. 16% , p=0.010 ) and , albeit not significant , of  milk / dairy products ( 9 vs. 13% , p=0.066 ) were lower .
dietary vitamin d intake was associated with age , % tbf , intake of energy , fat and alcohol , frequency of fish intake , and household net income , but did not correlate with sex , bmi , smoking , pal , use of vitamin d supplements , and consumption frequencies of eggs and milk .
except for a positive correlation with alcohol intake ( r 
 s=0.152 ; p=0.020 ) , 25(oh)d3 levels did not correlate with dietary parameters ( p>0.05 ) .
spearman correlations between vitamin d intake and relevant parametersa 
 
 r 
 s = spearman correlation coefficient .
missing data were present on total body fat ( n=5 ) ; consumption frequencies of fish ( n=9 ) , eggs ( n=6 ) , and milk ( n=23 ) ; physical activity level ( n=26 ) ; smoking behaviour ( n=2 ) ; and monthly household net income ( n=41 ) .
frequencies were dichotomised in never to several times per month ( coded as 0 ) versus several times per week to daily ( coded as 1 ) . multiple regression analysis ( n=185 ) was performed with log vitamin d intake as the dependent variable and age , % tbf , intake of energy , fat and alcohol , frequency of fish intake , and household net income as independent variables .
thereby , fat intake ( =0.283 ; p<0.0001 ) and frequency of fish consumption ( =0.235 ; p=0.001 ) were identified as positive determinants of dietary vitamin d intake , whereas alcohol intake ( =0.122 ; p=0.082 ) , net income ( =0.174 ; p=0.013 ) , and % tbf ( =0.174 ; p=0.014 ) negatively affected vitamin d intake .
this regression model explained 19.6% of the variance in dietary vitamin d intake in elderly subjects .
the exclusion of two people with very high dietary vitamin d intake levels ( 26 and 37 g / day ) provided approximately equivalent results .
this cross - sectional study demonstrates that independently living elderly subjects can generally obtain 25(oh)d3 concentrations 50
the facts that this study was conducted in summer and gisela subjects spent on average 2 h daily outdoors are probably the main reasons for this observation ( 23 ) .
a sun exposure of 515 min / day of hands , face , and arms from 10 am to 3 pm in summer is considered as sufficient to provide 1,000 iu of vitamin d ( 24 ) .
contrary to the present investigation , several studies found a significant association between vitamin d intake and serum 25(oh)d levels ( 1 , 4 , 25 , 26 ) , but predominantly these studies did not focus on vitamin d status of elderly subjects during summer .
in addition , studies were frequently carried out in countries , such as the united states and canada , where food fortification is more common than in germany .
a vitamin d intake of 34 g / day as noticed in the present study is apparently too low to influence 25(oh)d3 levels of the elderly in summer , when uvb exposure is the main contributor ( 8 , 23 ) .
( 25 ) who found a significant association between vitamin d intake and vitamin d status in 507 free - living subjects aged 6584 years in all seasons except for summer .
( 27 ) with 3,113 postmenopausal women , the association between dietary vitamin d and 25(oh)d was significant only in winter and spring .
obviously , vitamin d intake becomes negligible in case of sufficient sun exposure , but it may gain in importance in wintertime , particularly for elderly obese subjects as a higher % tbf has been linked to lower 25(oh)d3 levels ( 23 ) .
our results indicate that subjects with higher % tbf consume less vitamin d than lean subjects even after taking energy intake and frequency of fish consumption into account .
this may further enhance the impairment of the vitamin d status in case of an insufficient sun exposure . in our study ,
fish and fish products were by far the major sources of dietary vitamin d independent of sex , age , vitamin d status , bmi , and net income .
in addition , fats / oils , eggs , bread / bakery products , and milk / dairy products contributed to vitamin d intake .
although innards contain high amounts of vitamin d ( 6 ) , such foods are not commonly consumed by the general population . in the present study ,
a representative study of german subjects aged 1480 years provided comparable results by also stressing the importance of regular fish intake as a main source of vitamin d followed by fat spreads , eggs , and dairy products ( 13 ) , but 25(oh)d concentrations were not investigated .
although regular intake of fish was associated with a higher vitamin d intake in our study , fish intake did not affect vitamin d status .
it should be stressed that fish intake of the gisela participants was only slightly below the current german food - based dietary guideline which recommends a weekly intake of at least 150  g of fish ( 28 ) , but still vitamin d intake was low .
this may be due to a higher consumption of lean fish , which contains lower quantities of vitamin d than fatty fish ( 29 ) .
compared to other european countries , fish intake in germany is rather low ( 30 ) . however , even in populations with higher fish consumption , frequency of fish intake is not associated with 25(oh)d levels in the elderly ( 31 ) . in general , the amount of vitamin d in fish varies widely , and often differs from the vitamin d content that is listed in current food composition tables ( 32 ) .
for example , it has been shown that wild - caught salmon contains nearly five times more vitamin d than farmed salmon ( 33 ) .
regular consumption of fatty fish such as herring and salmon is required to get high amounts of dietary vitamin d. as pointed out by sirot et al .
( 29 ) , recommendations on fish consumption should refer to species and not only differentiate between lean and fatty fish to take into account differences in contents of nutrients and contaminants .
current german food - based dietary guidelines recommend a higher consumption of lean rather than fatty fish and give no explicit statement on fish species ( 28 ) . whether a re - evaluation of the current guidelines could result in an increased vitamin d intake has to be evaluated .
contaminants in seafood and aspects of sustainability of fisheries may argue against an increase in fish consumption .
main vitamin d providing food groups differ among countries . in the united states and canada , milk , meat , and fish are the leading food sources of vitamin d ( 7 , 15 ) , while in the united kingdom , these are fish , meat , cereals , and fat spreads ( 34 ) . in japan ,
fish intake is by far the main contributor followed by eggs and mushrooms ( 35 ) .
differences in assessment methods , dietary habits , and food fortification policies may account for these divergent results ( 7 , 36 ) . in germany , only a few foods are allowed to be fortified with vitamin d including margarine , edible oil , and some diet and dairy products ( 37 ) . enhanced food fortification with vitamin d and supplement use
whether these recommendations are appropriate for all people independent of their individual risk for vitamin d deficiency is up for discussion .
vitamin d supplements are considered as a simple , effective , and low - cost intervention ( 38 ) .
however , elderly subjects often take many different drugs , so that an additional supplement may not be an appropriate public health strategy regarding compliance and potential interactions . likewise
, an expansion of food fortification polices should undergo a well - considered risk  benefit assessment .
there are indications that food enrichment can not ensure adequate vitamin d intake levels for the elderly without putting children at risk ( 3 ) .
furthermore , lactose malabsorption / intolerance is frequently observed in the elderly ( 39 ) and thus milk as a food providing vitamin d seems unsuitable for the elderly population .
our results indicate that a high vitamin d intake level is apparently not required in free - living elderly subjects in summer when sun exposure is sufficient .
hence , a food fortification which is limited to winter months might be appropriate , but may be difficult to implement .
a special feature of our approach is that we investigated in a subgroup analysis whether vitamin d intake and vitamin d food sources differ by sex , age , vitamin d status , bmi , or income .
overall , considerable differences regarding the contribution of food groups to the dietary vitamin d intake were not found except for household income . in this context ,
fish / fish products contributed less to the vitamin d intake of subjects with a monthly household net income of 1,500  compared to subjects who reported a lower income , whereas in the upper income group , a higher percentage of dietary vitamin d was provided by the food category 
fats / oils. in contrast to some previous studies ( 15 , 16 ) , in which income was a positive predictor of vitamin d intake , household income was inversely associated with vitamin d intake in our subjects .
however , despite a lower intake level , serum 25(oh)d3 concentrations were higher in the upper income class , although the self - reported time spent outdoors and the proportion of supplement users did not differ between these two income groups ( p>0.05 ) .
these observations may be due to the fact that the overall vitamin d intake levels were too low to influence the vitamin d status significantly during the summer .
in addition , low income subjects had a significantly higher % tbf than subjects with higher income ( 42 vs. 38% , p=0.001 ) , which may have masked any potential effect of a somewhat higher vitamin d intake on the vitamin d status of the subjects with lower income , as it was shown that the % tbf is a negative predictor of 25(oh)d3 concentrations ( 23 ) . limitations of the present study are the cross - sectional design and the sample size .
although the gisela study is not based on a nationally representative sample , independently living elderly people represent the majority of older individuals in industrialised countries ( 4 ) . in general ,
dietary assessment tools have several limitations including the presence of under-/over - reporting and intra-/inter - subject variability of food intake ( 40 ) .
nutrient databases are frequently not up - to - date , not standardised , and fortified and convenience foods are under - represented ( 41 ) .
in addition , vitamin d intake levels by supplements were not assessed ; however , the number of supplement users was small .
concerning the association between net income and vitamin d intake , some subjects gave no statement on their net income , which may have biased the association .
elderly people living in private households do not reach the current recommended vitamin d intake level .
frequency of fish consumption and intake of fat are positive determinants of vitamin d intake , while % tbf and household net income are inversely associated with vitamin d intake .
there are no substantial differences in vitamin d food sources depending on sex , age , vitamin d status , and bmi .
income - dependent differences in habitual dietary vitamin d intake are not reflected by serum 25(oh)d3 concentrations in the independently living elderly during summertime . dietary advice and
if sun exposure and dietary vitamin d intake can not provide sufficient vitamin d concentrations , supplements may be advisable .
this investigation received no specific grant from any funding agency in the public , commercial , or not - for - profit sectors .
 backgroundelderly subjects are at risk of insufficient vitamin d status mainly because of diminished capacity for cutaneous vitamin d synthesis . in cases of insufficient endogenous production , 
 vitamin d status depends on vitamin d intake.objectivethe purpose of this study is to identify the main food sources of vitamin d in elderly subjects and to analyse whether contributing food sources differ by sex , age , vitamin d status , body mass index ( bmi ) , or household income . 
 in addition , we analysed the factors that influence dietary vitamin d intake in the elderly.design and subjectsthis is a cross - sectional study in 235 independently living german elderly aged 6696 years ( bmi=274 kg / m2 ) . 
 vitamin d intake was assessed by a 3-day estimated dietary record.resultsthe main sources of dietary vitamin d were fish / fish products followed by eggs , fats / oils , bread / bakery products , and milk / dairy products . 
 differences in contributing food groups by sex , age , vitamin d status , and bmi were not found . 
 fish contributed more to vitamin d intake in subjects with a household income of < 1,500  /month compared to subjects with higher income . in multiple regression analysis , fat intake and frequency of fish consumption were positive determinants of dietary vitamin d intake , whereas household income and percentage total body fat negatively affected vitamin d intake . 
 other parameters , including age , sex , physical activity , smoking , intake of energy , milk , eggs and alcohol , showed no significant association with vitamin d intake.conclusionlow habitual dietary vitamin d intake does not affect vitamin d status in summer , and fish is the major contributor to vitamin d intake independent of sex , age , vitamin d status , bmi , and the income of subjects . 