India, authentic studies on the normal values of Vit

India, though a sunshine country, it isreported that prevalence of Vit D (D3) deficiency is not only significant to theextent of 85-90% but is also widespread. Vit D is also known as Cholecalciferol.Unfortunately, we are unable to find authentic studies on the normal values ofVit D3 in Indian population.  The studiesthat are available have a small sample size and only longitudinal studies arecarried out.

  There is no cross sectionalstudies of normal Vit D3 levels in Indian population with sufficient samplesize, to make it statistically significant.Unfortunately, the definition of normalvalues for Vit D varies rather widely. In India, most of the laboratories report Vit D levels as deficient,insufficient, sufficient and toxic.   Accordingly, serum levels of 25(OH) D lessthan 10ng/mL is considered deficient, between 11 to 30 as insufficient, between30 ng/mL to 100 ng/ml sufficient and above100 ng/mL as toxic.  However, these arewestern values, and its relevance to Indian population is not determined.  Again the significance of values deficientand insufficient is also not determined. There is no unanimity amongst experts about normal levels of Vit D as limitsby IOM (Institute of Medicine) and those given by U S Endocrine society arequite different as mentioned in table:4.

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It is perhaps necessary to note thatbefore starting therapy for severe Vit D deficiency, it is necessary to evaluatethe status with respect to Calcium, Phosphorus and PTH levels.Measurementsof Vit D levels:The assays of Vit D3 are performed by 4methods: (a) High Performance Liquid Chromatography (HPLC), (b) tandem massspectrometry; (c) Radio immunoassays using monoclonal antibodies; (d)chemiluminescent protein binging assay. Most of the laboratories in India use this chemiluminescent proteinbinging assay method.Sourcesof Vit D:Most important source of Vit D isSunlight, especially exposure of the skin to UVB radiation of the sunlight, andless than 10-15% from dietary sources. The sunlight is composed of EMR of varying wavelengths ranging from longlambda (IR) to short UVB radiation. The sunlight that reaches the earth has 90%UVA radiation where as only 7-10% is UVB radiation. It is UVB radiation thatproduces Vit D in skin. The production of Vit D in the skin is affected by timeof the day, year, latitude, altitude and prevailing weather conditions where welive.

Because of the direct sunlight (angle at which the sunlight hits theground—angle of incidence) is high compared to what it is in western countries(-differences in latitudes at which our country and western countries are). HenceUVB rays hit more directly, our country enjoys more UVB advantage over westerncountries. The disadvantage of UVB light is possible development of skin cancerbut in dark skinned people the risk of this and melanoma is very little.  Remember that children have greater capacityto produce Vit D compared to old people and hence require less exposure. Excessiveexposure to UVB does not lead to toxicity of Vit D.  People have tendency to use sun creams toprotect skin. Sun creams filter out UVB rays which leads to inadequateavailability of UVB rays for Vit D production through skin.

This brings thevital question, given all favourable conditions, why Vit D deficiency andinsufficiency is so common in our country. Or has it to do with poor Calciumintake in diet or some PTH abnormalities? Or has to do with Vit D receptors?Literature ReviewCupisti, et al. (2015)discussed in the paper about which factors were associated with vitamin Ddeficiency. They have considered a group of 405 patients who have chronickidney disease with stage 2 to stage 4 living in Italy. They observed that66.4% patients had deficiency and 16.5% patients had insufficiency of vitaminD.

Univariate analysis showed that vitamin D was negatively related toage, parathyroid hormone (PTH), protein, and Charlson index, while positivelyrelated to hemoglo­bin level. Multiple regression analysis showed that allfactors were associated except age and PTH. No relation was found between renalfunction and vitamin D deficiency.100 consecutive patients out of 405 patientswere given 1000 IU supplements of vitamin D once a week for 12 months. Oralvitamin D supplements reduced PTH serum level. So as a regular practice in CKDpatients, vitamin D supplements were recommended. Tokmak, et al. (2008) conducted studybetween May 2004 to June 2006 on 64 hemodialysis patients (26 females and 38males) of a German outpatient centre.

It was observed that majority of hemodialysispatients have vitamin D deficiency.  Thestudy was divided in to two phases: replenishment and maintenance. During thereplenishment phase, patients were given 20000 IU of cholecalciferol, in a formof capsule, once a week for 9 months (till feb, 2005). From these 64 patients,59 reached to maintenance phase.

These 59 patients were randomized in treatedgroup (30 patients) and untreated group(29 patients). 20000 IU of cholecalciferolonce a month for next 15 months (March 2005 to May 2006) was given to thepatients of treated group. Finally analysis was done on 23 patients of treatedgroup and 19 patients of untreated group. 57% of the patients achievedrecommended levels. However additional study is required to decide ideal dosageof vitamin D to achieve and maintain vitamin D levels in the majority ofpatients.

    DataCollection and Data description: We have collected data from differentlaboratories and doctors from Ahmedabad, Surat and Vadodara. But followingpoints should be kept in mind while making any general statement. Ø  Majorityof the data are due to the suggested blood test following some health problems.Very few observations are from free check up camp. Ø  Formany cases observations were given as > some value, in those cases for thesake of analysis we have taken next integer value as the observed value,therefore instead of mean we suggest to observe median as the measure and hencefor inference nonparametric techniques areused.

Ø  Inthe Ahemdabad data neither sex nor the age are specified therefore we tried toidentify the sex from the names. So there chances ofmistake to identify the sex as some names may be common for both male andfemale. Whereas in data from Surat and Vadodara, sex of child is notmentioned, so it is not possible to merge the data for even sex wise study orwe have to drop the data of child from Surat and Vadodara if we want to includeAhemdabad data. But again in Ahemdabad data age is not mentioned so we do notknow actually how many of them are children. Inthis situation, to have a logical comparison, we have used Ahmedabad data onlyfor aggregate analysis and not for sex wise and age wise analysis. Ø  Forall the categories (sex wise as well as age wise) common limits are used.

Ø   Number of data is displayed in the followingtable: 1. From these data, we have prepared 3 age categories and three sexcategories. Then using different limits of D3 level in blood by (1) regularlimits used by the laboratories in India (2) suggested by IOM and  (3) Suggested by U S Endocrine society, wehave compared the respective descriptive & inferential statistics andfindings