Vitamin D deficiency continues to be an unrecognized epidemic in many populations around the world.[15
] It has been reported in healthy children, young adults, middle-aged adults, and the elderly, and is common among both males and females.[16
] Moreover, it is common even in the populations of the sunniest countries. In this study, we found vitamin D deficiency to be highly prevalent in healthy Saudi medical students in the preclerkship years of a medical school in the Eastern Province of Saudi Arabia. In fact, none of the students evaluated had normal levels of vitamin D, defined as 25OHD > 75 nmol/l,[5
] and the majority of male and female students at the start and at the end of the preclerkship period had 25OHD levels consistent with the definition of vitamin D deficiency. A similar high prevalence of low vitamin D was reported recently among patients from Eastern Province of Saudi Arabia.[12
] Also Ardawi et al
] reported an approximately 80% prevalence of hypovitaminosis D in 1172 Saudi women from the western region of Saudi Arabia, while Sadat-Ali et al
] found a 28% and 37% prevalence of hypovitaminosis in male patients aged 25–35 years and ≥50 years, respectively. The above reported variation in prevalence can be partially explained by the difference in the populations studied, the time of the year when the blood samples were collected and, possibly, the different laboratory methodologies used.[18
] This study was conducted during the month of November using the chemiluminescence immunoassay methodology. This may have contributed to the high prevalence of low vitamin D.
Recently, González-Padilla et al
] reported a high prevalence of hypovitaminosis D in medical students from Spain, and Multani et al
] found that 87.5% of resident doctors from India had low vitamin D levels. However, in a study that was conducted in a hospital in the Boston area of USA, only 36% of the healthy students, residents, and physicians aged 18–29 years were found to be vitamin D deficient.[7
] The markedly higher prevalence of low vitamin D in medical students in Saudi Arabia and Spain and the resident doctors from India as compared to individuals from the Boston area of USA , in spite of the abundance of sunlight found in the former areas may be related to the difference in dietary habits and food fortification[21
] in addition to racial and genetic factors. The results of this study, which showed that 100% of young educated students in the medical field have low vitamin D, raise a great concern about the future skeletal health of these young students. The 25OHD concentration was found recently to be an independent determinant of peak bone mass.[22
] Importantly, Lips et al
] and Heaney[24
] concluded that adequate vitamin D levels can prevent osteoporosis-related hip fractures.
In general, hypovitaminosis D has been reported in the literature as being more prevalent in women.[25
] Several factors were postulated for the low vitamin D level in females, including dietary habits, exposure to the sun, pregnancy and lactation. There is also controversy regarding the contribution of the wearing of a veil to lower vitamin D levels in Muslim women.[27
] Our female students had significantly lower consumption of dairy products. Also almost all of our female medical students were veiled. However, the lower 25OHD levels in the femle students included in this study may not be explained by the difference in sunlight exposure since there was no statistical significant difference between male and female students with regard to exposure to sunlight. The lower vitamin D levels in female students involved in this study also cannot be explained by difference in BMI since they had significantly lower BMI than the male students. Obesity is considered as one of the risk factors for low vitamin D levels; this low level of vitamin D in obese patients p ossibly resulting from the sequestrating effect of a high quantity of subcutaneous fat on circulating vitamin D.[29
] As expected, owing to lower vitamin D levels, females were found to have significantly lower serum calcium and higher mean PTH levels, possibly as part of an early secondary hyperparathyroidism leading to significantly lower serum phosphorus.[32
] The lower level of alkaline phosphatase in females is possibly related to the use of oral contraceptive pills.[33
After spending more than 3 years in college , fourth-year medical students were consuming less dairy products and seafood than the first-year students, and their low vitamin D levels persisted. The lower serum calcium and the higher PTH levels compared to first year students is another indicator of the poor dietary habits of this group of medical students. Al-Gelban[34
] found that students of a Saudi Teachers’ Training College had unhealthy lifestyles and dietary habits, while Nisar et al
] reported unhealthy lifestyles and dietary habits in students of a private medical university in Karachi.
The present study is one of the few studies carried out to evaluate the status of vitamin D in the medical community. The limitations of our study are that, being cross-sectional rather than longitudinal, comparisons between first-year and fourth-year students became suboptimal. Also, the use of the chemiluminescence immunoassay is not the gold standard method for the measurement of 25OHD levels. Besides, information on the consumption of dairy products and seafood, and exposure to sunlight was collected by means of a data collection sheet rather than a validated questionnaire.