Introduction: Vitamin D deficiency is pan-endemic and is even common in our country despite ample sun exposure. Various factors like dietary factors, religious and social factors may be responsible. Very few studies have been carried out to look into vitamin D status of females in our country.
Objective: We carried out this study to see the vitamin D levels in females of different age groups of urban population.
Methodology: This retrospective cross-sectional study was carried out at Islamabad Diagnostic Centre, Islamabad from 1st March 2013 to 30th June 2013. Females of all age groups coming for the first time for evaluation of vitamin D status were included in the study. Vitamin D levels of >30 IU were taken as sufficient, 20–30 IU as insufficient and those less than 20 IU were labelled as deficient levels. Results were entered into SPSS version 17 for analysis.
Results: Total number of females included in the study period was 2657. Age range of these cases was between 13–95 years. In all cases, mean vitamin D level was 15.38 ± 13.025 SD. Among all cases, 73% of females were deficient in vitamin D (vitamin D <20 IU), 13% had insufficient levels (20–30 IU), and only 14% had desirable vitamin D levels (>30 IU). Vitamin D levels were relatively lower in younger females as compared to the older ones.
Conclusion: Vitamin D levels were significantly low in females of urban population. Only 14% of females had desirable vitamin D levels. Larger studies taking into account causes and effects of vitamin D deficiency, including bone mineral density, need to be conducted in our set-up.
Key words: Cholecalciferol, Vitamin D deficiency, urban population, females
The major source of vitamin D for most humans is exposure to sunlight. Vitamin D is metabolized in the liver to 25(OH)D and then in the kidneys to 1,25(OH)₂D. 1,25(OH)₂D produced by the kidneys enters the circulation to its major target tissues, the intestine and bone, where it interacts with its vitamin D receptor and enhances intestinal calcium absorption. Apart from these organs, many other tissues in the body, including macrophages, brain, colon, prostate, breast, and others, have the enzymes to locally produce 1,25(OH)₂D. The local production of 1,25(OH)₂D in non-calcium regulating tissues such as the colon, prostate, and breast has been reported to regulate many genes, which helps to control cell growth and cellular differentiation and may be responsible for decreasing the risk of the cells being transformed into a malignant state.
Vitamin D deficiency is now recognized as a pandemic. The major cause of vitamin D deficiency is the lack of sun exposure. Very few foods naturally contain vitamin D. Vitamin D deficiency causes rickets in children and will precipitate and exacerbate osteopenia, osteoporosis, and fractures in adults. Muscle weakness has also been associated with vitamin D deficiency. Vitamin D receptors are also present in skeletal muscles, and vitamin D deficiency has been associated with proximal muscle weakness, increase in body sway, and an increased risk of falling. Vitamin D deficiency in adults can also cause a skeletal mineralization defect. The unmineralized osteoid provides little structural support for the periosteal covering. As a result, patients often complain of isolated or generalized bone discomfort along with aches and pains in their joints and muscles. Vitamin D deficiency has also been associated with increased risk of common cancers, autoimmune diseases, hypertension, and infectious diseases.
The major source of vitamin D for humans is exposure to sunlight. Anything that diminishes the transmission of solar UV radiation to the earth’s surface or anything that interferes with the penetration of UVB (ultraviolet B radiation) into the skin will affect the cutaneous synthesis of vitamin D₃. Melanin is extremely efficient in absorbing UVB radiation and thus increased skin pigmentation markedly reduces vitamin D₃ synthesis. Similarly, sunscreens absorb UV radiation and, when topically applied, decrease the synthesis of vitamin D₃ in the skin. The practice of purdah, whereby all skin is covered and prevented from being exposed to sunlight, is one of the high-risk factors for vitamin D deficiency and explains why in the sunniest areas of the world vitamin D deficiency is very common. Aging is associated with decreased concentrations of 7-dehydrocholesterol, the precursor of vitamin D₃ in the skin. Because vitamin D is fat soluble, it is readily taken up by fat cells. Obesity is associated with vitamin D deficiency, and it is believed to be due to the sequestration of vitamin D by the large body fat pool. Medications including anti-seizure medications and glucocorticoids and fat malabsorption are also common causes of deficiency. Numerous epidemiological studies have assessed the prevalence of low serum 25(OH)D concentrations and have indicated that vitamin D inadequacy is a common problem worldwide, particularly among females. Various factors, including physiological changes with age, race, body mass index (BMI), sun exposure, latitude, and dietary vitamin D intake, are considered responsible.
In our country, despite a sunny climate, very low levels of vitamin D have been observed. Very few studies have been carried out to look into vitamin D status in our females. We carried out this study to see the vitamin D levels in females of different age groups of urban dwelling.
This retrospective cross-sectional study was carried out at Islamabad Diagnostic Centre, Islamabad from 1st March 2013 to 30th June 2013.
Females of all age groups coming for the first time for evaluation of vitamin D status were included in the study. Vitamin D estimation was done on Cobas E-411. Vitamin D levels of >30 IU were taken as sufficient, 20- 30 IU as insufficient and those less than 20 IU were labelled as deficient levels.
Results were entered into SPSS version 17 for statistical analysis. Females were divided into two groups; Group 1 included females between 15 and 45 years and Group 2 comprised females more than 45 years. Both groups were then further divided depending upon their vitamin D levels. Mean, median, and ranges were calculated for all groups. Comparison of both groups was done, and a p-value of less than 0.05 was taken as statistically significant.
The total number of females included in the study period was 2657. The age range of these cases was between 13–95 years. In all cases, the mean vitamin D level was 15.38 ± 13.025 SD. Among all cases, 73% of females were deficient in vitamin D (vitamin D <20 IU), 13% had insufficient levels (20–30 IU), and 14% of the females had desirable vitamin D levels (>30 IU). Between the two groups, vitamin D levels were relatively lower in Group 1 (mean = 14.54 IU) as compared to Group 2 (mean = 16.51 IU), but this difference was statistically insignificant with a p-value of 0.825. Decade-wise distribution showed a notable finding with continuously increasing levels of vitamin D with increasing age (Table 2). In all age groups, mean vitamin D levels were lower than 20 IU.
Table 1: Vitamin D Levels in Different Groups
| Group | n | Age Range (years) | Vitamin D Levels (IU) | Mean ± SD | <20 n (%) | 20–30 n (%) | >30 n (%) |
|---|---|---|---|---|---|---|---|
| All cases | 2657 | 13–95 | 1.05–79.20 | 15.38 ± 13.03 | 1942 (73%) | 344 (13%) | 371 (14%) |
| Group 1 | 1527 | 13–45 | 1.05–79.20 | 14.54 ± 13.69 | 1181 (77.4%) | 156 (10.2%) | 189 (12.4%) |
| Group 2 | 1130 | >45 | 1.28–58.54 | 16.52 ± 11.99 | 761 (67.4%) | 188 (16.6%) | 181 (16.0%) |
Vitamin D, also described as ‘the Sun Vitamin’, is a steroid with hormone-like activity. It regulates the functions of over 200 genes and is essential for growth and development of the body. Hypovitaminosis D is considered responsible for rickets, birth defects, osteoporosis, osteoarthritis, osteomalacia, and chronic bone and muscle pains. Recent research has associated vitamin D deficiency as a contributing factor in diseases such as heart disease, hypertension, neurological disorders, autoimmune disease, depression, and cancer. Vitamin D deficiency is now recognized as a pandemic. Poor diet, cultural practices of the region, and poverty are some of the important reasons for vitamin D deficiency. Numerous epidemiological studies have assessed the prevalence of low serum 25(OH)D concentrations and have indicated that vitamin D inadequacy is a common problem worldwide. Differences in the prevalence of vitamin D inadequacy have been related to a variety of factors, including physiological changes with age, race, body mass index (BMI), sun exposure, and dietary vitamin D intake.
Table 2: Vitamin D Levels in Different Decades
| Age Range (Years) | Number of Cases | Vitamin D Levels Range (IU) | Mean ± SD (IU) |
|---|---|---|---|
| 13–25 | 294 | 3.00 – 70.00 | 13.63 ± 13.45 |
| 25–35 | 656 | 1.05 – 78.00 | 14.16 ± 13.29 |
| 35–45 | 577 | 1.20 – 79.20 | 15.43 ± 14.20 |
| 45–55 | 542 | 1.28 – 58.84 | 16.00 ± 11.87 |
| 55–65 | 382 | 1.30 – 55.99 | 16.20 ± 11.60 |
| 65–75 | 160 | 2.00 – 50.78 | 18.39 ± 12.92 |
| 75–85 | 40 | 2.80 – 50.23 | 18.39 ± 12.69 |
| 85–95 | 06 | 3.08 – 36.37 | 20.70 ± 13.73 |
Vitamin D deficiency is prevalent all over the world. Though our country receives abundant sunlight, vitamin D deficiency is endemic. There are multiple studies in different countries regarding the prevalence of vitamin D deficiency. These studies have shown a high prevalence of vitamin D deficiency in Asian countries. In our study, about 86% of females had low vitamin D levels, and younger females had relatively lower levels than the older females. Almost similar findings were noted in a study done in Tehran, where a high prevalence (81%) of vitamin D deficiency was observed, particularly among young and middle-aged females, which is comparable to our study. Prevalence of vitamin D deficiency has been identified in 70% and 97% of healthy asymptomatic people in two different studies done in Pakistan. Sunlight exposure promotes vitamin D synthesis, and one would expect this region to be free from vitamin D deficiency. Unfortunately, there is a high prevalence due to lack of proper diet, poor calcium intake, and social customs.
In another study on women with osteoporosis, 64% had serum levels <30 ng/ml. It was also noted that women who were taking vitamin D supplements had better vitamin D levels and showed improved bone mineral density. Seasonal variation in vitamin D levels has also been reported, with lower serum 25(OH)D levels observed in women during winter compared to those recruited during summer in some countries. In our study, 88% of women below 45 years (reproductive age group) had insufficient vitamin D levels.
There are multiple factors for vitamin D deficiency in our country. One of the reasons may be social and religious customs, as most of our women do not go outside and, even if they do, their bodies are covered. Moreover, our dietary habits are not favorable since seafood is not routinely consumed, our food is not fortified as in Western countries, and vitamin D supplements are not commonly taken by most females. There are relatively few foods that are natural sources of vitamin D and eaten regularly, such as oily fish and egg yolk. Dietary vitamin D supplements, in the form of fish liver oils, synthesized vitamin D, or vitamin D fortified foods, can make significant contributions. Vitamin D supplements have been found to increase bone mineral density and thus reduce the risk of fractures in females.
Similarly, dark pigmentation has been found to decrease skin synthesis of vitamin D because UV light cannot penetrate to the appropriate layer of the skin. Vitamin D deficiency is associated with secondary hyperparathyroidism with consequent ill effects on bone mineral density. Marwah et al. studied vitamin D deficiency and its effects on bone mineral density in Indian adolescents (10–18 years of age) and concluded that metabolic bone disorders secondary to vitamin D deficiency continue to be prevalent in the Indian subcontinent, especially among lower socioeconomic populations. Postmenopausal women are particularly prone to vitamin D deficiency, leading to an early onset of osteoporosis.
Different studies have found vitamin D deficiency to be more prevalent in winter than in summer, more common in women who spend little time outdoors, those who wear clothes covering most of the body, or frequently use sunscreen. This tendency to deficiency is found in most parts of the world. The mean serum concentration of 25(OH)D of 30 ng/ml is considered desirable for health, while a level of 20 ng/ml is considered the minimum acceptable. However, these values are insufficient, especially for pregnant females, sick adults, and older adults.
Vitamin D deficiency is highly prevalent, even in countries with abundant sunlight, as skin exposure to sunlight is limited by lifestyle and other factors. We found that only 14% of females had desirable levels of vitamin D, and these belonged to an urban dwelling population. As this deficiency may be associated with increasing incidence of aches and pains and an increased risk of fractures, particularly in postmenopausal females, it is suggested that these findings (as has been demonstrated in different studies) be highlighted and conveyed to the general public through awareness campaigns and media. Moreover, the government should implement a mandatory programme for vitamin D fortification of selected foodstuffs. Larger studies taking into account the causes and effects of vitamin D deficiency, including bone mineral density, should be conducted in our set-up.
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