Discussion

Over the decades it is clear that Vitamin D serves multiple functions. Its critical role in reducing the risk of cancer, multiple sclerosis and type 1 diabetes mellitus is being explored, over and above the established role in calcium absorption and metabolism for bone health. Maternal vitamin D is critical for the proper development of fetus and its tooth.

In our study, we wanted to analyze the Vitamin D levels in normal healthy office going people and know how many would be deficient, as they get minimum time for sun exposure.

India is a tropical country extending from large 8.4°N latitude to 37.6°N latitude. The larger part of the Indian population lives in areas where ample sunlight is received. Contrary to the belief, India is a Vitamin D deficient nation. In North India (27°N), 96% of neonates, 91% of healthy school girls, 78% of healthy hospital staff and 84% of pregnant women were found to have hypovitaminosis D. In South India (13°N), hypovitaminosis D is equally prevalent among different population groups [12,14,15].

In a study by Goswami R, et al. conducted on healthy subjects in Delhi who differed with respect to variables relevant to vitamin D and bone mineral metabolic status, such as direct sunlight exposure, season of measurement, skin pigmentation, etc [16]. The results show that the groups which had significantly lower exposure to sunlight and the group with depigmentation had significantly lower 25(OH)D concentrations. The groups which had lower sunlight exposure when restudied in summer had significantly higher 25(OH)D concentrations than in the winter, suggesting sunlight exposure playing very vital role in synthesis of Vitamin D.

In another study by Vu LH, et al. conducted in office workers of Australia, a subtropical climate zone, show the difference in serum levels of 25(OH)D concentrations in summer and winter [17]. The results reveal that in summer, 14% of participants were classed as “insufficient”, compared with 51% in winter. In this study, high 25(OH)D levels in summer were associated with time spent outdoors in nonpeak UV periods.

Inadequate synthesis in winter is seen as far south as Turkey and Israel [18].

Data from the European population shows that mean serum 25(OH)D levels of 20 to 30nmol/l (8 ng/mlto southern European centres to 40 to 50nmol/l in northern Europe among the elderly people [19]. This is relatively unusual as ultraviolet rays are more effective in the southern Europe than the northern Europe. Our study also shows similar results because though India is tropical country the vitamin D levels are lower in study subjects.

The results of our study are in concordance with the above mentioned studies. The Vitamin D levels were deficient in office going employees in south India. More than 90% of the individuals are either deficient or insufficient of Vitamin D. The vitamin D were measured in the last week of August, a month of rainy season. During this season the weather is cloudy and little UVB rays reaching the earth. The other possible risk factors could be less number of hours spent in sunlight and may be pollution playing its role as it prevents the UV B rays reaching the earth.

Although there is adequate sunshine in India high temperatures during daytime and sultry humid climate are deterrents to sun exposure [20].

The culture of clothing may also be one the reasons as Indians customarily wear cloths covering the entire body and exposing very little skin to UVB rays. Matsuoka LY, et al. study showed the significance of segmental body contributions to vitamin D3 production [21]. The study revealed that serum vitamin D3 levels were significantly higher in individuals exposing the trunk, legs and entire body to sunlight. In individuals exposing the head and neck or arms, the vitamin D3 level was higher than the basal level, but the difference was not significant. This may be one of the reasons for lower levels of vitamin D in our study subjects, as most of the office employees would be clothing covering the most of the body parts except for face and neck.

In previous study conducted in south India on Women of Reproductive (WR) and Postmenopausal (PMW) Age Groups have shown that in WR 25(OH)D deficiency, insufficiency and replete state was seen in 76%, 16.5% and 7.5% respectively and in the PMW 25(OH)D deficiency, insufficiency and replete states was seen in 70%, 23% and 7% respectively [22]. Our study also adds to the evidence that Women of Reproductive age group especially between 20 and 30 years of age are deficient in Vitamin D levels (67% were deficient of age group 20 and 40 years). Women in our study had higher prevalence of the deficiency (83% Vs 75%) when compared to men.

Vitamin D stores are depleted if the diet has high fiberin particular, phosphate and phytates, which is usually common in Indian food habit [23,24].

There is a possibility of role of genetics in the etiology of Vitamin D deficiency as Vitamin D levels have a significant hereditable component. The results from study by Awumey, EM et al. show that Asian Indians residing in the southern United States are at risk for developing vitamin D deficiency due to increased 25(OH)D-24- hydroxylase activity which degrades 25(OH)D to inactive metabolites [25]. This can be one of the possible reasons for vitamin D deficiency in our study as well.

Vitamin deficiency problem is not confined to India alone as it is widely prevalent in countries like China, Pakistan, Middle-East and Africa. The prevalence is less common in USA, Japan, northern Europe and Canada as they use the milk fortified with Vitamin D and Vitamin D supplements [18].

In northern Europe and Netherlands, the population have adequate levels of Vitamin D as there is high consumption of fatty fish and cod liver oil and have Vitamin D supplements [26].

Strategies to improve Vitamin D status [27,28]

National Institute for Health and Care Excellence (NICE) guidance classifies people who live or confined indoors for long period and South Asians as at risk group for developing Vitamin D deficiency. It has formulated certain guidelines for preventing Vitamin D deficiency among the population at risk. These include

Though food fortification might be one of the solutions for overcoming the problem of low vitamin D levels in general population, it has certain limitations. These could be, first the amount of vitamin D added to milk need to be adequate. Second, milk may not be consumed by all who are prone for deficient of Vitamin D. Third, only few products are fortified with vitamin D like yoghurt etc [29].

Strategies to improve food fortification may include fortifying new products such as calcium- and vitamin D-fortified orange juice, cheese and bread [30].

This is high time for public health policies to think of fortification of food with Vitamin D and about Vitamin D supplements. Dietary recommendation about Vitamin D and Calcium supplementation.