the discovery that the majority of body tissues and cells harbor vitamin d receptors and that several possess the enzymatic equipment to convert the primary form in circulation into the active form , has provided new insights into the function of this steroid hormone . there is great interest in the role that vitamin d can play in many chronic diseases , including common cancers , autoimmune , infectious , and cardiovascular.13 the sources of vitamin d are primarily the cutaneous production and food intake . in brazil , the dietary source is scant , since foodstuffs such as fatty fish are not available in tropical and subtropical climates . there are no official recommendations in brazil on the fortification of foods with vitamin d.4 elderly populations present certain particularities . with aging , solar exposure is generally limited in view of the changes in lifestyle , such as clothing and activities outside the home . . however , more important is the lower cutaneous production of vitamin d with aging , due to the atrophic skin alterations with greater availability of the precursor 7-dehydrocholesterol . among other factors , the production of 1,25-dihydroxyvitamin d3 diminishes as a result of the decrease in kidney function with aging.57 several cutoffs related to the blood levels of 25-hydroxyvitamin d ( 25(oh)d ) have been proposed to define deficiency / insufficiency in asymptomatic individuals . this is partially due to the variability of the concentration of vitamin d according to geographic location and the different methodologies employed in the various studies.8,9 in northeast brazil , bandeira et al found significant differences in the bone mineral density and in the serum levels of parathyroid hormone , with 25(oh)d values below 25 ng / ml in postmenopausal women.10 ensrud et al , in a large american cohort , demonstrated that 25(oh)d levels below 20 ng / ml were associated with significant hip bone loss in older men , when compared with higher levels , but this loss was not found in younger.11 other studies have demonstrated that levels above 32 ng / ml are necessary for an adequate intestinal absorption of calcium.12,13 although the literature reveals a high prevalence of vitamin d deficiency in the elderly , as far as we are aware , no consistent population studies in the tropics have evaluated its prevalence in elderly men and its relation to sun exposure and skin phototypes . this was an analytical cross - sectional study , which involved 234 men aged over 60 years of age , randomly recruited from a basic care unit in the fifth health district ( 5th hd ) of the city of recife in the state of pernambuco , during the brazilian summer months , from october 2010 to january 2011 . the patients eligible for the study were free - living individuals ( people who are not living in an aged care institution ) , able to walk unaided and who had not used drugs such as corticosteroids for prolonged periods ( doses 2.5 mg of prednisone or equivalent for over 3 months ) , anticonvulsants , or lithium for 1 year . subjects with metabolic bone diseases and active neoplasms , except neoplasms of the skin such as basal cell and spino - cellular cancer , were excluded . the study protocol was approved by the ethics in research committee of the agamenon magalhes hospital . demographic and economic data , medications , calcium intake , and vitamin supplements were evaluated by means of a questionnaire . exposure to the sun was calculated using the sun index ( si ; fraction of the area of the body surface exposed multiplied by the number of hours of sun exposure per week).14 skin phototypes were classified into six types , according to fitzpatrick s classification ( type i being the lightest and type vi the darkest).15 daily calcium intake was defined by asking patients to advise their calcium intake from food and supplements and classified as follows : low = intake below two portions ( 250 ml ) per day of milk and/or dairy products and without calcium supplements ( < 600 mg / day ) ; intermediate = intake of two or more portions without calcium supplementation ( 6001,000 mg / day ) ; and high = daily calcium supplementation and the consumption of milk and/or dairy products ( > 1,000 mg / day).16 when the individual did not have a calcium intake from diary but used supplements , calcium intake was classified according to the calculation of the amount of calcium contained in the supplement . in brazil , the recommended intake of calcium is 1,000 mg daily . the questionnaire also asked whether the patient was using vitamin supplements containing vitamin d. serum 25(oh)d levels were measured by electrochemiluminescent competitive immunoassay using a diasorin liaison analyzer ( turin , italy ) , with the inter- and intra - assay coefficients of variations of 8%15% and 8%13% , respectively and a minimum limit of detection of 2 ng / ml.17 measurement of 25(oh)d by immunoassay is considered the method of choice for reasons of convenience , speed , turnaround , and cost.17 for the description of the prevalence rates , the percentages and respective 95% confidence intervals were recorded using the binomial method . pearson s chi - square test and student s t - test with equal or unequal variances were used for percentage and mean comparisons . the model was performed with step - wise selection of variables , maintaining in the model the variables with a significance of up to 15.0% ( p < 0.15 ) . the following independent variables were studied : age , annual income , grouped skin phototypes ( group 1 : skin types i  iii ; group 2 : skin types iv  vi ) , calcium intake , and body mass index ( bmi ) . spss software ( v 15.0 ; ibm corp , armonk , ny , usa ) was used for the statistical calculations . this was an analytical cross - sectional study , which involved 234 men aged over 60 years of age , randomly recruited from a basic care unit in the fifth health district ( 5th hd ) of the city of recife in the state of pernambuco , during the brazilian summer months , from october 2010 to january 2011 . the patients eligible for the study were free - living individuals ( people who are not living in an aged care institution ) , able to walk unaided and who had not used drugs such as corticosteroids for prolonged periods ( doses 2.5 mg of prednisone or equivalent for over 3 months ) , anticonvulsants , or lithium for 1 year . subjects with metabolic bone diseases and active neoplasms , except neoplasms of the skin such as basal cell and spino - cellular cancer , were excluded . the study protocol was approved by the ethics in research committee of the agamenon magalhes hospital . demographic and economic data , medications , calcium intake , and vitamin supplements were evaluated by means of a questionnaire . exposure to the sun was calculated using the sun index ( si ; fraction of the area of the body surface exposed multiplied by the number of hours of sun exposure per week).14 skin phototypes were classified into six types , according to fitzpatrick s classification ( type i being the lightest and type vi the darkest).15 daily calcium intake was defined by asking patients to advise their calcium intake from food and supplements and classified as follows : low = intake below two portions ( 250 ml ) per day of milk and/or dairy products and without calcium supplements ( < 600 mg / day ) ; intermediate = intake of two or more portions without calcium supplementation ( 6001,000 mg / day ) ; and high = daily calcium supplementation and the consumption of milk and/or dairy products ( > 1,000 mg / day).16 when the individual did not have a calcium intake from diary but used supplements , calcium intake was classified according to the calculation of the amount of calcium contained in the supplement . in brazil , the recommended intake of calcium is 1,000 mg daily . the questionnaire also asked whether the patient was using vitamin supplements containing vitamin d. serum 25(oh)d levels were measured by electrochemiluminescent competitive immunoassay using a diasorin liaison analyzer ( turin , italy ) , with the inter- and intra - assay coefficients of variations of 8%15% and 8%13% , respectively and a minimum limit of detection of 2 ng / ml.17 measurement of 25(oh)d by immunoassay is considered the method of choice for reasons of convenience , speed , turnaround , and cost.17 for the description of the prevalence rates , the percentages and respective 95% confidence intervals were recorded using the binomial method . pearson s chi - square test and student s t - test with equal or unequal variances were used for percentage and mean comparisons . the model was performed with step - wise selection of variables , maintaining in the model the variables with a significance of up to 15.0% ( p < 0.15 ) . the following independent variables were studied : age , annual income , grouped skin phototypes ( group 1 : skin types i  iii ; group 2 : skin types iv  vi ) , calcium intake , and body mass index ( bmi ) . spss software ( v 15.0 ; ibm corp , armonk , ny , usa ) was used for the statistical calculations . the clinico - epidemiological characteristics of the elderly patients studied are shown in table 1 . the mean age was 69.4  6.5 years ( mean  standard deviation [ sd ] ) and the majority ( 66.7% ) had dark skin ( type iv , v , or vi of fitzpatrick s classification ) . when comparing prevalence according to skin type ( dark vs light ) for each serum 25(oh)d cutoff ( < 20 , < 25 , and < 30 ng / ml ) , we found no significant difference ( p = 0.46 ) . using cutoffs for serum 25(oh)d levels below 20 and 30 ng / ml , the prevalence of vitamin d deficiency was 31.5% and 66.7% , respectively ( figure 1 ) . mean serum 25(oh)d was 27.86  13.52 ng / ml ( mean  sd ) . after stratification according to age group ( 6069 , 7079 , and 80 years ) , no difference in the prevalence of vitamin d deficiency was found between them . there was a significant difference ( p = 0.006 ) between si means in the groups with serum 25(oh)d levels below and above 20 ng / ml ( 4.46  3.69 vs 6.01  5.54 ) . however , for the cutoffs of 25 ng / ml ( 5.07  4.31 vs 5.95  5.69 ) and 30 ng / ml ( 5.22  4.43 vs 6.12  6.14 ) , no significant difference was found . considering si values divided into quartiles ( qs ) , the lowest quartile ( q1 ) was 1.96 and the highest ( q4 ) was 7.86 . nonetheless , there was no statistical difference ( p = 0.113 ) in serum 25(oh)d levels between q1 ( 23.98  14.66 ) and q4 ( 29.88  13.78 ) , nor in the prevalence of hypovitaminosis d for the 20 , 25 , and 30 ng / ml cutoffs ( figure 2 ) . a low calcium intake was observed in 72% of the subjects and an annual family income of us$4,200 in 64.5% . there were no statistical differences between the groups with a low calcium intake and those with an intermediate and high intake at the three cutoffs for 25(oh)d , nor were there between the groups with an annual income of < us$4,200 and of > us$4,200 . a low level of education , defined as illiteracy or incomplete primary school education , was observed in 82.8% and only seven subjects ( 2.5% ) were using vitamin supplements . table 2 presents the results of the multivariate linear regression analysis to determinate the independent factors associated with vitamin d deficiency . the numerical variables included in the initial model were age , si , and bmi . the dichotomous variables were income bracket , grouped skin phototype , vitamin d supplement use , calcium supplement use , and calcium intake . the variables remaining in the model were solar index , calcium intake , and bmi . in this study of elderly men living in the tropics , vitamin d deficiency was found to be very common . approximately one - third of participants presented with levels < 20 ng / ml , and the majority  that is , two - thirds  presented with levels < 30 ng / ml . similar results were found in the osteoporotic fractures in men study ( mros ) . in that study , 26% and 72% of the elderly men presented with levels < 20 and < 30 ng / ml , respectively . despite the similarity in results , we had expected that the prevalence of deficiency would be much lower in our region , given that the individuals studied live in an area with abundant sunlight and the blood collection was performed in the sunniest months of the summer . since the mros study did not use si as a clinical parameter , we could not compare this variable in the two studies . a fact that might account for the high prevalence in this region despite the high si is the increased prevalence of individuals considered to have dark skin according to fitzpatrick s classification15 as well as a high bmi . the mros study , after bivariate analysis , demonstrated that black people are independently associated with a high prevalence of vitamin d deficiency , with a 2.4-fold greater risk of deficiency than white people . melhus et al , in a cohort study carried out in sweden with elderly men , demonstrated that the prevalence of vitamin d deficiency , despite limited sun exposure in the winter and high latitude ( 60n ) , was rare for the 16 ng / ml cutoff.18 the mean serum 25(oh)d level was 27.5 ng / ml , which is similar to that of our patients ( 27.9 ng / ml ) . these data show that sun exposure in itself is not the preponderant factor in the prevention of 25(oh)d deficiency . in relation to sun exposure , it may be observed that in the population with greatest si ( q4 ) , when compared with the least exposed group ( q1 ) , no significant differences in mean serum 25(oh)d levels for the three cutoffs studied were observed , which suggests that the sun has little effect in preventing vitamin d deficiency in this population . in addition , the mean serum 25(oh)d in q4 was 29.8 ng / ml , demonstrating that , despite maximum sun exposure , mean 25(oh)d levels remained below 30 ng / ml . binkley et al19 demonstrated a prevalence of 25(oh)d deficiency of 51% , using the 30 ng / ml cutoff , in a population of young surfers ( mean age 24 years ) in hawaii ( 20n ) with a mean si of 11.1  0.7 . similarly , low serum 25(oh)d levels were observed in workers with a mean si 11.514 and in two of 18 puerto rican farmers with a weekly sun exposure of 3270 hours.20 in our study , the prevalence of dark - skinned patients ( types iv , v , and vi ) was 66.9% . when comparing prevalence according to skin type ( dark vs light ) for each serum 25(oh ) d cutoff , we found no significant difference ( p = 0.46 ) . harris et al found a significant difference between black and white people with regard to the prevalence of low 25(oh)d concentration.16 while 28% of elderly white men presented levels below the 20 ng / ml cutoff , the corresponding figure for elderly black men was 73.1% ( p < 0.001).15 these data are in agreement with loomis observation that black people produce less vitamin d than white people at normal levels of sun exposure.21 the majority of the individuals in our study ( 45.7% ) had a skin color classified as intermediate ( type iii and iv ) . the number of individuals classified in the extremes for skin color was very low ( four whites and 33 blacks ) , making comparative analysis misleading . in our study , 72% had a low calcium intake and only 2.5% ( n = 7 ) used vitamin supplements . it should be emphasized that the number of food items enriched with vitamin d is low in brazil . these numbers differ considerably from those of north america , where 24% of black and 44% of white elderly men and women studied were on vitamin d supplements.22 in this regard , forrest and stuhldreher demonstrated a high prevalence of vitamin d deficiency among a group of americans , particularly in those who were black , obese , and illiterate and in those with a low milk intake ( p < 0.05).23 as this study was not a population - based study , the results can not be translated to the general population . we found a high prevalence of vitamin d deficiency in elderly men living in the tropics , despite their high exposure to the sun in the summer months .