|Year : 2021 | Volume
| Issue : 4 | Page : 391-400
Vitamin D deficiency and diseases: A review from Pakistan
Yasir Mahmood1, Nazish Waris2, Asher Fawwad3, Abdul Basit4
1 Department of Research, Baqai Institute of Diabetology and Endocrinology, Baqai Medical University, Karachi, Pakistan
2 Clinical Biochemistry and Psychopharmacology Research Unit, Department of Biochemistry, University of Karachi, Karachi, Pakistan
3 Biochemistry Department, Baqai Medical University, Karachi, Pakistan; Baqai Institute of Diabetology and Endocrinology, Baqai Medical University, Karachi, Pakistan
4 Baqai Institute of Diabetology and Endocrinology, Baqai Medical University, Karachi, Pakistan
|Date of Submission||19-Mar-2021|
|Date of Decision||17-May-2021|
|Date of Acceptance||24-May-2021|
|Date of Web Publication||12-Jan-2022|
Prof. Asher Fawwad
Biochemistry Department, Baqai Medical University, Karachi.
Source of Support: None, Conflict of Interest: None
Objective: Vitamin D deficiency is claimed to be associated with many diseases in the world population. Many studies reported that vitamin D deficiency is quite prevalent in Pakistan. The aim of this review is to describe the current status of vitamin D deficiency in healthy individuals and in different disease conditions in this country. Materials and Methods: Search engines such as “Google Scholar,” “Medline,” and “PubMed” were used by applying key words such as vitamin D deficiency and different disease conditions in the Pakistani population. In this study, people with vitamin D levels less than 30 ng/mL were reported as being vitamin D deficient. Results: A total of 82 studies were included: Among these, 12 studies showed vitamin levels less than 30 ng/mL in healthy individuals (male and female) and 70 studies in different disease conditions. It was found that about 64.6% of healthy subjects had vitamin D levels less than 30 ng/ml. Moreover, 70 studies showed vitamin D deficiency in some diseases, such as musculoskeletal, bone, and periodontal problems, nursing mothers and children, tuberculosis (TB), diabetes, cardiovascular problems, and some type of cancers. Conclusion: The current status of vitamin D deficiency in the healthy population and in several diseases and conditions is thoroughly discussed in this review. This review could be helpful in understanding the status of vitamin D and the different aspects of vitamin D research in this population.
Keywords: Diseases, Pakistan, Pakistani population, vitamin D, vitamin D deficiency
|How to cite this article:|
Mahmood Y, Waris N, Fawwad A, Basit A. Vitamin D deficiency and diseases: A review from Pakistan. J Diabetol 2021;12:391-400
How did you gather the information you considered in your review?
The information present in this review article is gathered from online data sources such as “Google Scholar,” Medline, and PubMed.
What is the “take-home” message for the clinician?
Vitamin D deficiency is quite prevalent in the Pakistani population and it could cause different diseases. Therefore, it is worthwhile to consider the vitamin D levels in the management of such disease conditions that are described in this article.
| Introduction|| |
Vitamin D is an essential micronutrient that is important for the well-being of a living individual. Sunlight plays an important role in its production in the body. It acts as a pleiotropic hormone, and its deficiency in children manifests as improper bone growth called rickets. Previously, vitamin D was considered to only affect bone metabolism and calcium absorption, but subsequent studies found its vital role in many other physiological functions in the body. It has been found that almost all cell types have vitamin D receptors (VDR) and all vital organs and tissues of the body benefit from vitamin D. In recent decades, much attention has shifted toward understanding its role in different modalities such as diabetes mellitus, cardiovascular diseases, infections in particular TB, and certain autoimmune disorders such as psoriasis and multiple sclerosis. Certain cancers such as prostate, breast, and colon are also correlated with its deficiency.,
Since Pakistan is a developing country, and most of its population resides in the villages, its geographical location (30.3753° N, 69.3451° E) makes it a land of sunlight throughout the year. Because of their cultural norms, people wear dresses that cover the whole body. Malnourishment in the villages and imbalanced nutrition in urban settings are the common problems in this population. Due to unawareness and traditions, people cannot get proper sunlight, leading to vitamin D deficiency and making it prevalent all over the country.,
This review would be useful in understanding the recent status of vitamin D deficiency in healthy subjects and in various disorders, in the Pakistani population.
| Methods|| |
The search engines such as “Google Scholar,” “Medline,” and “PubMed” were used by applying some search key terms: “Vitamin D Pakistan,” “Vitamin D diseases Pakistan,” “Vitamin D deficiency Pakistan,” “Vitamin D tuberculosis Pakistan,” “Vitamin D Children Pakistan,” “Vitamin D rickets Pakistan,” “Vitamin D Women Pakistan,” “Vitamin D Cancer Pakistan,” and “Vitamin D receptor SNPs Pakistan.”
Inclusion and exclusion criteria
All relevant studies found by the search terms mentioned earlier have been included. However, studies involving Pakistani expatriates outside the country were excluded from the study.
Levels of vitamin D
In this study, people with vitamin D levels less than 30 ng/mL were reported as being vitamin D deficient and those with vitamin D levels 30 ng/mL and higher were reported as being normal.
Status of vitamin D deficiency in healthy individuals
The results of a small-scale survey of randomly selected asymptomatic subjects (n = 300) of Karachi showed that 84.3% of subjects had vitamin D levels less than 30 ng/mL. Female subjects (62.3%) were found to be more vitamin D deficient than male subjects (55.2%). Another study of 858 subjects (351 males and 507 females) who belonged to a low-income suburban community in Karachi showed that 89.9% of subjects had vitamin D levels less than 30 ng/mL. Female subjects were again found to have more vitamin D deficiency than male subjects.
A study conducted on 500 subjects (29% males and 71% females) from the capital Islamabad showed that only 11% of subjects had normal vitamin D levels (30 ng/mL).
An interesting study regarding awareness about sun exposure and the importance of vitamin D was conducted among the undergraduate medical students of different varsities. It was revealed that the participants were well aware of the importance of vitamin D but most of them intentionally evaded sun exposure, and only 8% of the participants were aware of minimal exposure to sunlight to prepare vitamin D levels. As vitamin D levels were not measured in this study, it was difficult to correlate symptoms such as body pain with vitamin D deficiency.
Another study conducted to analyze vitamin D levels in students at a medical college in Peshawar showed that 95.19% of subjects were vitamin D deficient. A similar study on 191 randomly selected medical students (86.43% females and 13.57% males) in Karachi showed that 96.4% of students had low vitamin D levels (<30 ng/mL).
In Lahore, a comprehensive study carried out in healthy subjects (50 males and 38 females) indicated that 98.86% of subjects have a vitamin D level below 30 ng/mL. It was further revealed that subjects such as females, fair-skinned individuals, indoor job holders, and people with high socioeconomic status living a sedentary lifestyle were deficient in vitamin D.
Another small-scale study conducted in 244 (79% females and 21% males) healthy adults revealed deficient vitamin D levels (<30 ng/mL) in 76.2% of the subjects with a significant correlation to the area of skin exposed to sunlight. Likewise, an observational study to assess the prevalence of vitamin D deficiency in healthy male subjects (n = 180) in Hyderabad, Sindh demonstrated that 88.8% of the subjects had vitamin D deficiency (<30 ng/mL).
A large-scale study was conducted in Karachi to evaluate the impact of socioeconomic conditions, diverse residencies, and vitamin D levels in different localities of the metropolis. A total of 4,788 subjects were randomly selected. The results showed that 74% of the subjects were deficient in vitamin D (<30 ng/mL). The post hoc analyses revealed that subjects belonging to densely populated areas with lower socioeconomic status had significantly lower levels of vitamin D than those of middle-income and less populated areas. Another Karachi-based study of 305 premenopausal women from various locations showed that 90.1% of subjects were deficient in vitamin D (<30 ng/mL) due to low sunlight exposure.
A large retrospective analysis of data (audit) of 60,937 samples (30.7% male and 69.3% female) from across the country found that 61.1% of subjects had an average log vitamin D value of 1.14 ng/mL (13.8 ng/mL). Samples received from Khyber Pakhtunkhwa had the lowest levels of vitamin D (11 ng/mL), and samples from Azad Kashmir had the highest levels of vitamin D (17.1 ng/mL). The overall results showed a prevalence of vitamin D deficiency in the country regardless of location and gender differences. Also, another similar study identified that 15.3% of 4,830 participants had normal vitamin D levels.
| Vitamin D Deficiency in Different Disease Conditions|| |
Musculoskeletal, bone, and periodontal health
Vitamin D deficiency is directly associated with certain bone and musculoskeletal problems, such as musculoskeletal pain, rickets, osteopenia, osteomalacia, osteoporosis, and osteoarthritis, and vitamin D supplementation alleviates the pain., Musculoskeletal pain was a notable feature in a study of 400 participants (43.5% males and 55.5% females) aged between 18 and 80 years in a less developed city Swat due to inadequate levels of vitamin D (<30 ng/mL) in the body. Similar results were obtained from a cross-sectional observational study conducted in Rahim Yar Khan, Punjab province. Among 400 patients with musculoskeletal pain, 47% had low vitamin D levels (<30 ng/mL). In another study of fibromyalgia and nonspecific musculoskeletal pain conducted in Karachi, lower levels of vitamin D were reported in the affected female subjects. Similarly, out of 100 subjects with signs of fatigue, 92 subjects were found to be vitamin D deficient.
Vitamin D deficiency with poor bone health was observed in premenopausal women. It was found that out of 174 subjects, 96.9% of subjects showed vitamin D deficiency whereas 36.8% had a high bone turnover. A similar study was conducted on 143 postmenopausal women in rural communities to assess bone mineral density by quantitative ultrasound index (QUI) and their dietary habits. The results showed that 42% of the women had osteopenia and 29% had osteoporosis. Low dietary calcium and vitamin D intake was established from the study.
Another study assessed dietary calcium, vitamin D, and bone turnover in 305 female subjects in three towns of Karachi city. It was found that 90.5% of subjects were vitamin D deficient and among them, 42.6% had secondary hyperparathyroidism. Moreover, 76.7% female subjects had low calcium levels whereas 23.3% had a normal bone turnover.
A survey conducted in Karachi showed that only 34% (out of 252) of female subjects were conscious of osteopenia and osteoporosis, whereas 77% of subjects had back, leg, and joint pain.
A multicenter cross-sectional study on 291 subjects (39.5% males and 60.5% females) from three big cities (Karachi, Lahore, and Islamabad) showed that 84% of subjects had vitamin D deficiency (30 ng/mL). A significant difference in Vitamin D levels was found based on age and skin color. A total of 147 (48%) subjects had low BMD, of whom 98 (66.6%) people had osteopenia and among them, 80 (81.6%) subjects had low vitamin D levels. A nonsignificant relationship was found between vitamin D, low bone mineral density, serum calcium, and phosphorus levels.
There is a strong association between vitamin D and periodontal health worldwide. A study conducted in pregnant (n = 36) and nonpregnant women (n = 35) showed that pregnant women were more vitamin D deficient than nonpregnant women; however, no association was found between vitamin D deficiency and periodontal diseases. Randomized clinical trials of 85 females at 12 weeks of gestation revealed that the subjects’ weekly status and birth weight could not improve after 4,000 doses of EE vitamin D per day.
The association between vitamin D levels and aforementioned disease conditions was not described based on an adequately adjusted model; therefore, it could not be inferred that only vitamin D deficiency is the cause of the conditions just cited.
Nursing mothers and children
Vitamin D deficiency is also associated with complications such as poor fetal growth, rickets, and neonatal eczema. The status of vitamin D was usually assessed in parturient and gravidae in a tertiary care hospital in Karachi. Maternal and fetal vitamin D levels were estimated from blood and cord blood, respectively. It was found that 89% of the subjects were vitamin D deficient (<30 ng/mL), whereas the vitamin D levels were found to be inversely correlated with maternal blood pressure.
Vitamin D deficiency was also found in nursing mothers (85.1%) of Southern Punjab. According to the study, most of the mothers used to live in open houses with the greatest exposure to the sunlight (168.81 minutes/day). Despite the ample sun exposure, vitamin D deficiency could be due to women`s clothing style, which is very common in society.
Vitamin D deficiency was also found in healthy infants between 9 and 12 months of age in Rawalpindi. The radiological studies of wrists showed 53.8% of infants with rickets and suboptimal levels of vitamin D (<30 ng/mL), possibly due to vitamin D deficiency, low sun exposure, clothing styles, cultural norms of staying indoors, or less physical activity of their mothers during pregnancy.
Another study showed that 99.5% of women and 97.3% of neonates in Karachi, whereas 89% of women and 85% of neonates in rural areas of Jehlum were found to be vitamin D deficient. Similarly, another study revealed maternal vitamin D deficiency (<30 ng/mL) during early pregnancy in 44% of subjects (total number of subjects = 301) visiting a tertiary care hospital in Karachi. A similar study reported 77% vitamin D deficiency from neonates to children (15 years of age).
Nutritional rickets was observed in 74% of children admitted to a health care center in Karachi with symptoms of severe pneumonia. The rickets was common (79.8%) in the age group between 2 and 12 months. Vitamin D status was not measured in this study, but it can be inferred that the children will be severely vitamin D deficient.
Subclinical rickets was also observed in several areas of Pakistan. A study of 189 children aged 11 to 16 years showed a 27% prevalence of subclinical rickets in the Hazara district of KPK. Similarly, in Kaghan Valley, 26 students were evaluated for subclinical rickets and all were found to be positive for the condition as well as vitamin D deficient with high alkaline phosphatase levels.
An interventional study was conducted to evaluate the effect of vitamin D in two oral doses of 200,000 IU in malnourished children in the 6- to 58-month age range. Compared with the control group, the results of this interventional clinical trial showed significant improvement in the development of these children.
Vitamin D deficiency has been observed in the onset of diabetes (type 1 and 2) in the world population. The active form of vitamin D (calcitriol) after binding with its receptor (VDR) plays an important role in insulin secretion and insulin sensitivity in the targeted cells. Observational studies in the Pakistani population have shown vitamin D deficiency in type 2 diabetes mellitus (T2DM)., A case-control study conducted at a hospital in Gujranwala of Punjab province showed that vitamin D levels were significantly lower in people with diabetes than in the control group but both groups were vitamin D deficient. A Karachi-based study showed a negative association between vitamin D and blood glucose levels in patients with T2DM. Similarly, another study showed that 62% of the patients with T2DM had elevated HbA1c levels, poor glycemic control, and vitamin D deficiency. A study conducted by our team found that vitamin D levels were negatively correlated with random blood sugar and HbA1c levels in the patients with diabetes. However, vitamin D levels were not significantly different between good and poor glycemic control subjects. Elevated levels of HbA1c, which represent poor glycemic control, are a common pattern in T2DM. A positive association of vitamin D deficiency with poor glycemic control is found in another study in the Pakistani population.
A randomized clinical trial was conducted at a tertiary care hospital in Lahore, Punjab to evaluate the effectiveness of vitamin D administration in the improvement of glycemic control in T2DM. Patients were divided into two groups. One group was administered only metformin 500 mg after dinner, whereas the second group was administered 200,000 IU of vitamin D along with 500 mg metformin after dinner for six months. The result showed an improvement in vitamin D levels in the group administered vitamin D and metformin, but HbA1c levels were not found to be significantly different after six months between the two groups.
Vitamin D deficiency was also studied in patients with T2DM with dyslipidemia. A study evaluating the effects of statin use with vitamin D levels showed no significant association with dyslipidemia. However, a significant negative association was found between total cholesterol and vitamin D levels, indicating that vitamin D levels had a significant effect on hypercholesterolemia in patients with T2DM.
Microvascular complications of diabetes, such as retinopathy, neuropathy, and nephropathy, have been associated with vitamin D deficiency in the world population. Meta-analysis showed that vitamin D deficiency was associated with the onset of diabetic neuropathy in both Caucasian and Asian populations. Microvascular complications of diabetic retinopathy have been found to be associated with vitamin D deficiency in patients with T2DM of Peshawar, KPK.
VDR and their metabolizing enzymes are present throughout the cardiovascular system. The VDR knockout mice exhibited severe impairments in the cardiovascular system, including cardiac hypertrophy. Many observational studies and results of meta-analyses have shown that vitamin D deficiency is associated with cardiovascular disorders.,,,, A few studies have been conducted on the relationship between vitamin D deficiency and cardiovascular events in the Pakistani population. A study of patients with first acute myocardial infarction (AMI) showed an association between vitamin D deficiency and a genetic variant in the vitamin D binding protein (VDBP). However, another study assessing the effects of vitamin D, calcium deficiency, and hypertension showed a weak correlation of these two factors with mean systolic and diastolic blood pressures.
Vitamin D deficiency has been studied for its relevance to cardiometabolic syndrome, and it has been found to be significantly associated with hypertension in the Pakistani population. High levels of parathyroid hormone (PTH) could be responsible for the development of hypertension., An ongoing study on the Pakistani population showed a significant relationship between PTH levels and mutations in the calcium-sensing gene (R990G) in subjects with vitamin D deficiency. However, blood pressure was not monitored in this study.
Many epidemiological studies have shown that certain cancers have a higher prevalence in geographical locations, where there is less exposure to the sun throughout the year. Vitamin D levels of 50 ng/mL and 30 ng/mL were associated with a 60% and 33% lower risk of colorectal cancer, respectively, and a vitamin D level of more than 50 ng/mL was found to have preventive effects. Other studies also showed that UVB exposure and vitamin D are associated with a lower risk of cancer and higher survival from cancer.
Several studies have been conducted in the Pakistani population to explore the link between vitamin D deficiency and the incidence of certain cancers. Breast cancer is a common type of cancer among women in this country., Studies in different parts of the country have shown a negative association between vitamin D levels and breast cancer incidence. In one of the studies, 42 subjects with newly diagnosed breast cancer were found to be vitamin D deficient. In Lahore, 300 newly diagnosed premenopausal and postmenopausal women belonging to different parts of the Punjab province showed a positive association between vitamin D deficiency and the tumor size in breast cancer. However, in this study, tumor grade and stage were not associated with vitamin D levels. Another study that recognizes the onset of breast cancer in women with the relevance of dietary habits, dress style, and sun exposure showed that vitamin D deficiency was more common in patients with breast cancer.
A study evaluating the effect of vitamin D supplements on breast cancer risk found that the odds of breast cancer were more significant in the subjects who did not take vitamin D supplements. A cross-sectional study to evaluate body mass index (BMI), bone markers, and vitamin D status in patients with newly diagnosed breast cancer showed low levels of vitamin D in the subjects. Another study conducted in Multan, South Punjab, also showed that 90% of patients with breast cancer had vitamin D deficiency.
Apart from breast cancer, vitamin D deficiency has also been studied in patients with leukemia. One study showed that vitamin D deficiency was prevalent in patients with B-chronic lymphoid leukemia. Another study showed that after remission-induction chemotherapy, vitamin D deficiency was increased as compared with subjects without chemotherapy.
The first treatment of skin TB was discovered by lamp arc radiation, and the inventor Niels Ryberg Finsen (1890–1904) received a Nobel Prize for this discovery. It is suggested that UV radiation from the lamp arc produces vitamin D in the body and facilitates the production of antimicrobial peptides such as cathelicidin to fight against infectious diseases, including TB.,, Many observational studies have shown that vitamin D deficiency is highly associated with TB in some populations, including the Pakistani population.,,
Some case-control studies have found severe vitamin D deficiency in patients with pulmonary and extrapulmonary TB.,,,,,,, A case-control study aimed at evaluating the amount of vitamin D, antimicrobial peptide cathelicidin, chemerin, and inflammatory marker TNF α in pulmonary TB; in healthy subjects, a significant association was found between vitamin D, cathelicidin, chemerin, and TNF α.
An interventional trial called the SUCCINIT study (Supplementary cholecalciferol in recovery from TB) was conducted in patients with pulmonary TB to evaluate the effectiveness of vitamin D supplements. A total of 259 patients with newly diagnosed TB were randomly divided into two groups (Vitamin D group n = 132 and placebo group n = 129). The vitamin D group was administered 600,000 IU of vitamin D on a weekly basis for two weeks along with standard medications, whereas the placebo group was administered normal saline along with standard medications. The results of the study showed improved clinical, radiological, and host defense outcomes in patients in the vitamin D group.
Another interventional trial was conducted to evaluate the adjuvant effects of vitamin D and anti-tuberculosis therapy (ATT), compared with ATT alone for 77 days. The results showed an improvement in some parameters, such as an increase in serum vitamin D, calcium, BMI, and hemoglobin, and a decrease in erythrocytes sedimentation rate (ESR), C-reactive proteins (CRP), total white blood count, and a 12-day earlier sputum conversion as compared with the placebo group.
A similar study also showed an early sputum conversion in smear-positive pulmonary TB on administration of vitamin D (100,000 IU) every 14th day for a three-month period. The results showed an improvement in the vitamin D levels and rate of sputum smear conversion in patients with pulmonary TB. CXCL10 is a chemoattractant factor that is found to be elevated in patients with TB. In 119 patients with TB in Karachi, vitamin D levels were negatively associated with CXCL10 levels.
Genetic variations in vitamin D synthesis genes and their metabolism are related to many diseases in the world.,,
VDR is a type of nuclear receptor that regulates the expression of many genes, after combining with its ligand calcitriol (an active form of vitamin D). The variations in the VDR gene have also been associated with several disease conditions in different populations.,,,
Many studies in the Pakistani population showed that certain diseases are associated with certain types of SNPs in the VDR gene. The Apa1 SNP present in the 3′ intronic region of VDR may affect the stability of the mRNA of VDR. Some SNPs in the VDR gene were found to be associated with type 1 diabetes mellitus (T1DM). Another study was conducted to probe a link between T1D and two SNPs of VDR (Fok1 and Apa1) in children. The results of this study showed that vitamin D deficiency was prevalent in the studied group, but no significant association was found between SNPs and T1D. This may be due to a very small sample size (44 cases and 44 controls).
The correlation between SNPs in the VDR gene and vitamin D levels in healthy women in the Pakistani population was studied. Two SNPs (Fok1 and Taq1) were found to be significantly associated with vitamin D deficiency and insufficiency.
Vitamin D circulates in the body after binding with VDBP, a type of transporter protein. A case-control study showed a significant association of group-specific 1–2 (Gc 1–2) genotype and T2DM risk in subjects. Another study found a significant link between vitamin D deficiency and the IF-IF genotype of the VDBP gene with AMI in the Pakistani population. Breast cancer is common in Pakistani women. An analysis of 360,933 cases with breast cancer revealed that the incidence of breast cancer was higher among women of Asian origin than Caucasians. Meta-analyses of some studies undertaken to investigate the role of VDR gene variation and the onset of breast cancer showed a positive correlation between different world populations. Many studies in the Pakistani population have shown that the VDR gene variation is associated with breast cancer. A case-control study (103 cases and 161 controls) showed that the GG genotype of cdx-2 SNP may increase the risk of breast cancer in young females belonging to Southern Punjab. Tru9I SNP in the VDR gene studied in 228 patients and 503 controls found that this SNP may be associated with the risk of the disease. From the same study, it was found that the mutant Tru9I was significantly associated with grade IV carcinoma in the study group. The b allele of the Bsm1 polymorphism of the VDR gene showed a positive association with breast cancer. The study included 463 cases known as BRCA1/2 cases and 1,012 controls. The subgroup analysis of the study found a significant association between BRCA1/2 noncarriers and subjects with a family history of breast and/or ovarian cancer.
The overall results of many studies have shown that the variations in the VDR gene are not associated with certain disease conditions in the Pakistani population. A study conducted by our group showed that only the TT genotype of the TaqI polymorphism was significantly associated with T2DM in Karachi, Pakistan (Mahmood et al., unpublished data).
| Summary|| |
A total of 82 studies were included, in which 12 studies represented vitamin D levels in healthy individuals [Table 1] and 70 studies under different conditions [Table 2]. It was found that vitamin D deficiency is prevalent in all parts of the country and about 64.6% of healthy subjects had vitamin D levels less than 30 ng/mL. In addition, 70 studies have shown its deficiency in certain diseases such as musculoskeletal, bone, and periodontal problems, nursing mothers and children, TB, diabetes, cardiovascular problems, and some type of cancers. Thus, these related diseases can be improved by treating vitamin D deficiency.
|Table 1: Studies indicating vitamin D status in the healthy individuals of Pakistan|
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|Table 2: Vitamin D deficiency in different health conditions in Pakistani population|
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Pakistanis enjoy a nonvegetarian diet, which is a rich source of vitamin D. However, true vitamin D intake was not estimated to be due to the unawareness regarding the quantity of consuming diet and the unavailability of a food composition database for vitamin D used in Pakistan. Moreover, history of vitamin D food fortification and use of vitamin D supplements in Pakistan was also not found in the literature. Another main contributing factor for vitamin D deficiency is limited sun exposure due to the avoidance of sunlight and covering of the whole body except the face and hands while being outdoors. Women were found to be more vitamin D deficient than men due to cultural norms and clothing styles. Some previous studies in different parts of the world have also shown that cultural norms and dress styles were associated with vitamin D deficiency in women.,,
Limited studies have been conducted to see the association of genetic variations with certain diseases. The results of these studies do not establish a significant association with different diseases. This could be due to the small sample size with a limited scope of the study.
The vitamin D levels should be maintained at a normal range (30 ng/mL) by vitamin D supplementation or by optimal sun exposure. Sunlight should be preferred, because it is also beneficial for other physiological functions of the body.
Men, women, and children should be encouraged and facilitated to expose themselves to sunshine. A balanced diet containing dairy products fortified with vitamin D and seafoods should be recommended for childbearing and nursing mothers.
A national survey may be conducted to assess the present status of vitamin D in the population and the possible cause of vitamin D deficiency in the population.
Most of the studies did not use appropriate measures of analyses by using inadequately adjusted statistical models to associate vitamin D deficiency with the disease conditions along with different assay types that may affect the results of vitamin D levels.
The results of genetic studies are limited and cannot be inferred; therefore, further research with a large data set is needed to determine logical conclusions.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2]