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ORIGINAL ARTICLE
Year : 2017  |  Volume : 7  |  Issue : 1  |  Page : 12-17

Intergenerational Decline in Vitamin D Status: A Cross-Sectional Study Among Medical Students and Their Teachers


1 Department of Community Medicine, Dr DY Patil Medical College, Hospital and Research Centre, Dr DY Patil Vidyapeeth, Pune, Maharashtra, India
2 Department of Microbiology and HeadCCL, Dr DY Patil Medical College, Hospital and Research Centre, Dr DY Patil Vidyapeeth, Pune, Maharashtra, India

Date of Web Publication25-Jan-2017

Correspondence Address:
Amitav Banerjee
Department of Community Medicine, Dr DY Patil Medical College, Hospital and Research Centre, Dr DY Patil Vidyapeeth, Pune, Maharashtra - 411 018
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/2231-0738.199070

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   Abstract 

Background and objectives: The present study was done to study the vitamin D status among medical students and their teachers to ascertain the intergenerational difference of vitamin D status. Materials and Methods: A cross-sectional study of 88 participants comprising 48 medical students and 40 faculty members was done. Serum 25-hydroxyvitamin D [serum 25(OH)D] level was assessed as a marker for vitamin D levels. A level of serum 25(OH)D < 10 ng/mL was considered as deficiency, 10–29 ng/mL as deficient, and 30–100 ng/mL as sufficient. Statistical analysis: Epi Info 2007 was used for statistical analysis. Chi-square test, t-test, and Kruskal–Wallis test were applied as applicable to observe the significant differences among the groups. Results: In the overall study sample, 14.77% showed deficiency, 61.36% were having insufficiency, and only 23.86% were having sufficient vitamin D status. Medical students were four times more likely to be deficient compared to faculty. This difference was statistically highly significant (P = 0.003). Similarly, the mean serum 25(OH)D levels was 17.46 ng/mL among the medical students compared to the mean level of 37.07 ng/mL among faculty giving a large difference of almost 20 ng/mL. This difference was again statistically highly significant (P < 0.0003). Conclusion: Besides the overall high prevalence of vitamin D deficiency in the study sample, there was an intergenerational difference in the levels of vitamin D, indicating that the younger generation is more vitamin D deficient compared to the older generation.

Keywords: Intergenerational decline, medical faculty, medical students, vitamin D status


How to cite this article:
Looned K, Banerjee A, Landge JA, Pandit DP. Intergenerational Decline in Vitamin D Status: A Cross-Sectional Study Among Medical Students and Their Teachers . Int J Nutr Pharmacol Neurol Dis 2017;7:12-7

How to cite this URL:
Looned K, Banerjee A, Landge JA, Pandit DP. Intergenerational Decline in Vitamin D Status: A Cross-Sectional Study Among Medical Students and Their Teachers . Int J Nutr Pharmacol Neurol Dis [serial online] 2017 [cited 2017 Dec 14];7:12-7. Available from: http://www.ijnpnd.com/text.asp?2017/7/1/12/199070


   Introduction Top


Vitamin D, regarded as “sunshine vitamin,” is a fat-soluble vitamin. It resembles sterols in structure and functions like a hormone.[1] Received primarily from exposure to Ultraviolet B (UVB) light rays of sunlight, it has numerous health benefits. Nutritionally important forms in man are ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3), also referred to as pro-vitamins. The recommended daily intake of vitamin D for adults is 1500–2000 IU/day so as to maintain the blood level consistently above 30 ng/mL.[2]

Vitamin D deficiency has been recognized as an independent risk factor for total mortality in the general population.[3] Besides the well-known role of vitamin D in growing children and women for maintaining skeletal health, emerging studies indicate the likely role of vitamin D as prevention against a vast array of noncommunicable and chronic diseases such as cancer, heart disease, autoimmune diseases, Type 2 diabetes, and depression.[3]

Studies the world over indicate very high prevalence of vitamin D deficiency.[4],[5],[6] At the national level, vitamin D deficiency has been reported to be 70–100% in the general population.[7] The high prevalence of vitamin D deficiency both globally and nationally is a public health problem, as many disease conditions are being recognized to be directly or indirectly related to vitamin D status.

The major source of vitamin D is exposure to natural sunlight.[8] Therefore, the major reason for deficiency of vitamin D is lack of exposure to sunlight.[9],[10] The current practice of wearing sunscreens reduces vitamin D synthesis. A sunscreen with a sun protection factor of 30 reduces vitamin D synthesis in the skin by 95%.[11] People with dark skins have a natural sun protection requiring three to five time longer exposures to sun to synthesize the same amount of vitamin D as a person with white skin.[12] People who are obese are at greater risk of vitamin D deficiency, as there is an inverse relationship of serum vitamin D levels and body mass index.[13]

The consequences of vitamin D deficiency are both short-term and long-term. Vitamin D deficiency influences calcium, phosphorus, and bone metabolism. The deficiency adversely affects the absorption of calcium and phosphorus.[1] The consequent increase in the levels of parathyroid hormone results in osteoclastic activity, creating foci of bone weakness and a generalized fall in bone mineral density. In the long-term, this causes osteopenia and osteoporosis.[14]

Many studies have indicated an association between low vitamin D levels and cancer.[15] Many studies also indicate its role in prevention of heart and cardiovascular diseases. It has been suggested that the protective role is mediated via the renin–angiotensin hormone system, through anti-inflammatory mechanism.[16] Systolic blood pressure and pulse pressure have been shown to be inversely and significantly correlated with serum vitamin D levels.[17]

Onset of type 2 diabetes mellitus has been shown to be associated with low levels of vitamin D. Vitamin D and calcium supplementation checked rise in blood glucose among elderly subjects in a clinical trial.[18]

Some recent studies among medical professionals, medical students, and health care professionals have consistently revealed a high prevalence of vitamin D deficiency.[19],[20],[21],[22] This was perhaps expected considering the lifestyle changes in recent years. These studies were, however, mostly confined to the samples representing one particular generation of medical professionals. Few studies have been done to observe the difference in vitamin D levels across generations of medical professionals.

While medical students of the older generation used two wheelers and bicycles, the present generation of students travel in air-conditioned cars, cutting off any exposure to sunlight. Against the above background, the present cross-sectional study was undertaken. The aim was to estimate the vitamin D status among medical students and faculty of a tertiary care medical institution testing the hypotheses that changing lifestyles among medical students would affect their vitamin D levels adversely as compared to faculty.


   Materials and Methods Top


Ethics statement

Ethical approval for the study was obtained from the Institutional Ethics Committee. In addition, written informed consent was obtained from the study participants.

Study design

The study was a cross-sectional survey among medical students and medical faculty of a tertiary care teaching hospital.

Sample size calculation

Primer of Biostatistics software[23] was used for the sample size estimation.

Using this software, the following inputs were used for the sample size calculation:

  1. Type 1 or α error = 0.05
  2. Type 2 or β error = 0.20
  3. Power of study = 80%
  4. Effect size (difference of means of 25(OH)D to be detected in the two groups) = 10 ng
  5. Standard deviation (SD) = 15 ng


With the above inputs, the sample size estimated was 37 participants in each group. In our study, we included 48 students and 40 faculty members.

Sampling technique

A random sample of 48 undergraduate medical students of 7th semester was included. Similarly, a random sample of 40 medical teachers of the college was included.

Exclusion criteria

Individuals on steroids or immunosuppressant, immunocompromised individuals, and individuals on vitamin D supplements for 3 months prior to study onset were excluded from the study. Participants who were diabetics were also excluded, as most of them were on vitamin D supplements.

Assessment of vitamin D status

Serum 25-hydroxyvitamin D [serum 25(OH)D] levels were used for assessment of vitamin D status. The kit used for assessment of 25(OH)D levels was Quanti Vitamin D Microlisa manufactured by J Mitra & Co Private Limited, New Delhi, India. The kit works on the principle of enzyme immunoassay based on competitive Enzyme-linked immunosorbent assay (ELISA).

First, the samples were diluted with biotin labeled 25(OH)D conjugate and incubated in the wells of the microplate. During incubation, endogenous 25(OH)D of a sample competes with a 25(OH)D3 biotin conjugate for binding of the anti-vitamin D antibodies immobilized on the plate. During a second incubation, binding of 25(OH)D-biotin was detected by enzyme conjugate (peroxidase-labeled streptavidin). Washing was done after this. In the third incubation, color reaction was started by addition of substrate and stopped after a defined time. The color intensity is inversely proportion to the concentration of 25(OH)D in the sample.

The following criteria as specified by the manufacturers of the kit were taken as vitamin D status:

  1. Deficiency: Below 10 ng/mL
  2. Insufficiency: 10–29 ng/mL
  3. Sufficiency: 30–100 ng/mL
  4. Toxicity: >100 ng/mL


Data management and statistical analysis

The World Health Organization/Centers for Disease Control and Prevention software for epidemiology, Epi Info (Version 3.5.2, December 17, 2010), was used for data entry and statistical analysis.

Descriptive statistics: Quantitative data such as serum levels of 25(OH)D were summarized with mean and SD. Categorical data such as vitamin D status (deficient, insufficient, and sufficient) were summarized with percentages with 95% confidence interval.

Inferential statistics: Chi-square test was used for ascertaining significant difference of vitamin D status among the groups. Two-sample t-test exploring significant difference in the mean serum 25(OH)D levels between the groups was used when the variances were equal, and the distribution was normal. When the variances were unequal as elicited by Bartlett’s test, nonparametric statistics were used for tests of significance.

Questionnaire regarding diet and exposure to sun

During the planning stage, a questionnaire regarding diet and exposure to sun was developed. However, during pilot testing, it was found to have poor validity due to recall bias and identical responses, and this part of the data collection was abandoned.


   Results Top


Description of the study sample

A total of 48 students and 40 faculty members participated in the study, as shown in [Table 1]. The mean age of the students was 20.83, while the mean age of medical faculty was 40.07 years. There were 36 males and 52 females [Table 2].
Table 1: Distribution of the study sample by category

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Table 2: Distribution of participants according to gender

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Vitamin D status in the study sample

[Table 3] shows the vitamin D status in the study sample. Majority of the participants, 61.36% (54/88), were having insufficient serum 25(OH)D levels. Only 23.86% (21/88) had adequate vitamin D status while 14.77% (13/88) were deficient.
Table 3: Vitamin D status in the study population

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Comparison of status of vitamin D levels students with faculty

[Table 4] compares the vitamin D status between medical students and faculty. The findings were interesting and unexpected. A larger proportion of medical students were deficient (22.92%) compared to medical teachers (5%). Similarly, only 8.33% of students were having vitamin D sufficiency as compared to 42.50% of the faculty. These differences were statistically significant (χ2 = 16.35, df = 2, P = 0.003).
Table 4: Showing who is more deficient, student or faculty?

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Gender-wise comparison of vitamin D status

[Table 5] answers the question regarding which gender is more deficient in vitamin D status. Though the proportion of deficient females was slightly at 15.38% compared to males 13.89%, this small difference was statistically not significant (χ2 = 0.51, df = 2, P = 0.77).
Table 5: Gender-wise distribution of vitamin D status

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Comparison of vitamin D status serum marker between student and faculty

The comparison of the means of the two groups is shown in [Table 6]. As with the vitamin D status, students fared poorly in the mean levels of serum 25(OH)D compared to faculty. The mean level of students was 17.46 ng/mL compared to the much higher mean level of faculty, which was 37.07 ng/mL, a very large difference of 20 ng/mL. Besides being a large difference, this was also statistically highly significant (Kruskal–Wallis H = 21.01, df = 1, P < 0.001). Note: Nonparametric test was employed, as the Bartlett’s test for inequality of population variances was positive.
Table 6: Means [25(OH)D levels] ng/mL in students and faculty

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Comparison of vitamin D status serum marker between the genders

The comparison of the means of the two genders is shown in [Table 7]. Though males showed marginally higher mean levels of serum 25(OH)D of 29.05 ng/mL compared to females who had mean level of 24.52, this difference was statistically not significant (t = 0.97, df = 86, P < 0.33).
Table 7: Means [25(OH)D levels] comparison of male and female participants

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   Discussion Top


The present study also reiterates the state of vitamin D deficiency found among health care professionals by earlier studies.[19‐22] What the present study adds to these earlier studies which were confined to a single generation is the comparison of vitamin D status among two generations, that is, among medical students and their teachers. The mean serum marker for vitamin D was much lower among students compared to their teachers. This mean difference of 20 ng is a matter of concern for the health of the younger generation. Youth needs to build up strong bones and skeleton to last into old age. In addition, the recent concerns regarding association of low vitamin D levels with a number of chronic diseases such as cancer,[24] cardiovascular diseases,[25] diabetes,[26] metabolic syndrome and obesity,[27],[28] Parkinson’s disease,[29] depression,[28] cognitive ability in old age,[30] fractures,[31] multiple sclerosis,[32] macular degeneration,[33] to name a few, do not bode well for the future. Increasing trends of these diseases will pose a public health burden of great magnitude if the trend of low vitamin D status continues in coming generations.

When one considers the socioeconomic background of the medical students in the present study, a lot of conventional thinking about nutritional disorders is challenged. All the students come from affluent backgrounds. So poverty cannot be blamed for the state of vitamin D malnutrition, as is the usual practice for under-nutrition. The affluent young today spend more time indoors compared to earlier generations. Commuting is by cars rather than by two wheelers. All these lead to very limited exposure to natural sunlight.

The strength of the present study is the hard outcome measure, that is, serum 25(OH)D levels measured by standard kits in a laboratory of a tertiary care teaching hospital. The limitation was that we faced difficulty while trying to record dietary intake, and daily duration of exposure to sunlight by interview method with help of a designed questionnaire. As we were not getting any meaningful response due to recall bias, lack of interest by the participants, and subjectivity of the respondents, we abandoned this part of the data collection. Further studies with more time and resources can try to explore the association of diet and exposure to sunlight with vitamin D status, though some earlier studies have found only modest impact of exposure to sunlight on vitamin D status due to a number of confounding factors such as skin pigmentation and use of sunscreen.[34],[35],[36] With more resources, studies on bone density and vitamin D levels can also be further explored.

What are the remedial measures available? A three-pronged attack on vitamin D deficiency consisting of supplementation, food fortification, and educational program has been suggested.[7] This is based on the findings of earlier studies and also supported by the present study that vitamin D deficiency in Indians is highly prevalent. Therefore, there is a need to have national level programs to make available affordable and accessible vitamin D supplements and vitamin D fortified foods for the general population.

Now, the question is: Does supplementation work in the long run? Studies have been addressing this issue. In a study done by Goswami et al., 22 healthy Indians with low levels of serum 25(OH)D were supplemented with oral D3 60,000 IU/week and calcium 1 g/day for 8 weeks. After 8 weeks, the serum marker levels increased from baseline levels; however, after one year, all the subjects were deficient once again.[37] This indicates that supplementation has to be continual which may be difficult to monitor in the general population.

A more pragmatic approach in the general population may be fortification of foods with vitamin D. Most Indians are vegetarians. Fortification of popular foods, which is consumed by Indians in all parts of the country, is a practical remedial measure of vitamin D deficiency. Fortification of food also has lesser risk of toxicity.[7]

A couple of studies on impact of food fortification have been reported. In a randomized controlled trial, toddlers from socioeconomically deprived section of society were given fortified laddoos, which increased serum calcium and vitamin D levels and also the bone mineral content.[38] In another trial, 776 subjects of both genders were given fortified milk, which caused significant improvement in the vitamin D status.[39] These studies, while indicating that fortification works, need to be validated by large-scale population studies.

Lastly, what about the educational programs to tackle the burden of widespread vitamin D deficiency? The education program should cover all stakeholders including doctors (the present study reinforces the maxim, “physician − heal thyself”), economists, social scientists, lay public, education experts, and the policy makers responsible for government policy. Sufficient investment in resources is needed for education of all concerned in tackling the problem of vitamin D deficiency.


   Conclusion Top


Like earlier studies, the present study also reinforces the fact that vitamin D status is poor in the population. What is pertinent is the fact that the study sample consisted of medical students and doctors who are the affluent section of any society, and high proportion of insufficiency in this select population is a cause for concern. However, this should not surprise us, as earlier studies among health care professionals have also reported high prevalence of vitamin D deficiency. What this study has added compared to earlier studies among medical professionals is the intergenerational comparison of vitamin D levels among two generations. The difference in the serum markers for vitamin D status among these two groups was large and statistically highly significant. This is a gloomy picture, as low levels of vitamin D have been reported to have both short-term and long-term adverse effects on health. Besides, musculoskeletal health and low levels of vitamin D status have been shown to be associated with a large number of chronic diseases such as diabetes, metabolic syndrome, autoimmune disorders, cardiovascular diseases, depression, cognitive impairment, and Parkinson’s disease.

If this trend of low vitamin D levels continues through generations, we will have a large burden of chronic diseases as a major public health problem in future.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
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    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]



 

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