Abstract
Purpose
Many researchers have reported that vitamin D can affect brain development as well as brain function. The prevalence of vitamin D deficiency in the Saudi population is 81% and it is more among women than among men. Though many studies have been done to find out the factors influencing the academic performance of Health sciences students, there is not adequate evidence regarding the influence of vitamin D level on academic performance. Therefore, this study aims to find out the association if any, between the vitamin D level and academic performance of health sciences students.
Design/methodology/approach
After obtaining the ethical committee approval, the data was collected from 86 female medical students, 70 female applied medical sciences students and 57 nursing students of Northern Border University. The detailed questionnaire contained the aim of the study, demographic characteristics and academic performance predictors such as self-efficacy, academic motivation, academic engagement and social engagement. The vitamin D levels were measured by an enzyme-linked immunosorbent assay (ELISA) machine (BioTek) which is available in the local hospital. The multiple linear regression analysis was used to find out the association between vitamin D levels and academic performance.
Findings
This study showed that vitamin D level had a significant association with the overall performance of the students as well as their self-efficacy.
Research limitations/implications
Since there is a lot of stress among health sciences students due to subject overload and inadequacy of time, the health aspects are often overlooked. This study emphasizes the importance of early screening of vitamin D levels and early intervention in those with low vitamin D levels for better academic performance.
Social implications
There is very little awareness of the impact of vitamin D deficiency on academic motivation, academic engagement, social engagement and self-efficacy among medical and health sciences students. This study can increase awareness.
Originality/value
There are very few studies done to find out the association between Vitamin D level and academic performance. This study is unique as it has highlighted the association between vitamin D level and grade point average (GPA) and also the association between vitamin D level and academic predictors such as self-efficacy, academic motivation, academic engagement and social engagement.
Keywords
Citation
AlZahrani, W.I. and Oommen, A. (2023), "Role of vitamin D in the academic performance of health sciences students in Saudi Arabia", Arab Gulf Journal of Scientific Research, Vol. 41 No. 1, pp. 40-47. https://doi.org/10.1108/AGJSR-04-2022-0028
Publisher
:Emerald Publishing Limited
Copyright © 2022, Wala Ibrahim AlZahrani and Anitha Oommen
License
Published in Arab Gulf Journal of Scientific Research. Published by Emerald Publishing Limited. This article is published under the Creative Commons Attribution (CC BY 4.0) licence. Anyone may reproduce, distribute, translate and create derivative works of this article (for both commercial and non-commercial purposes), subject to full attribution to the original publication and authors. The full terms of this licence may be seen at http://creativecommons.org/licences/by/4.0/legalcode
Introduction
Improvement in academic performance is considered to be one of the main goals of education (Al Shawwa et al., 2015). There are several studies done to find out the factors influencing the academic performance of university students. But there is a paucity of literature regarding the influence of vitamin D on the academic performance of university students (Burrows, Whatnall, Patterson, & Hutchesson, 2017). The role of vitamin D in improving cognitive function has been a subject of debate. Some studies have pointed out that higher vitamin D level is associated with increased cognitive function (Llewellyn, Langa, & Lang, 2009; Llewellyn et al., 2010; Buell et al., 2009, 2010; Annweiler et al., 2010; Lee et al., 2009). On the other hand, another group of researchers in their prospective study found no association between vitamin D levels and cognitive function in elderly men (Slinin et al., 2010). Due to the high prevalence of vitamin D deficiency especially among female university students in Saudi Arabia (Sulaiman, Abukanna, Alenezy, & Balla, 2017; Hasanato et al., 2015), it is important to find out whether vitamin D level has any influence on the academic performance of the female students. This study was, therefore, undertaken among female health sciences students to evaluate the influence of vitamin D level on academic performance.
Materials and methods
After obtaining the approval of the ethical committee, the study was done at Northern Border University. The data was collected from January 2022 to March 2022. The subjects of our study were the female students of colleges of medicine, applied medical sciences and nursing. The students with comorbidities like diabetes, hypertension and renal diseases were excluded from the study. In total, 213 students volunteered to participate in our study of which 86 students were from medicine, 70 students from applied medical sciences and 57 students were from nursing. A detailed questionnaire which had the aim of the study mentioned was used to collect the data. The first part of the questionnaire included the details such as the college in which they were studying and year of study and grade point average (GPA). The vitamin D level was measured using an enzyme-linked immunosorbent assay (ELISA) machine (BioTek) and vitamin D 25-OH ELISA Assay Kit from Calbiotech Incorporation which is available in the local hospital. The vitamin D levels were studied in three groups students with <12, 12–20 and >20 ng/ml, as earlier studies have shown that most of the female students have low levels of vitamin D in Saudi Arabia (Al-Elq, 2012).
Other than the GPA, the academic performance part of the questionnaire had four main components which are non-cognitive predictors of academic performance, namely, Self-Efficacy (SE), Academic Motivation (AM), Academic Engagement (AE) and Social Engagement (S. Eng.) (Feldman & Kubota, 2015; Olivier, Archambault, De Clercq, & Galand, 2019; Huang, 2011). Each of these components had items (questions) that they could answer in the form of a 1 to 5 Likert scale. The average response to all the questions formed a score for each component. The average of the scores of all four components was taken as the overall performance score. So, each participant had four components scores and one overall score that summarized her performance. IBM SPSS v26 software was used for statistical analysis. The demographic variables were analyzed using frequency distribution. The main variables, namely, the academic performance predictors, were summarized as mean and standard deviation (SD). Multiple linear regression analysis was used to find out the association between vitamin D level and academic performance. A p-value < 0.05 was considered statistically significant.
Results
The participants of this study were students from 3 colleges, namely, medicine (86), applied medical sciences (70) and nursing (57) who were in their 2nd to 5th year of study at the university. Overall, 291% of these students has their vitamin D level between 12 and 20 ng/ml, 23.9% had <12 ng/ml and 46.94% had >20 ng/ml. The descriptive statistics of the participants are shown in Table 1. Their median GPA was from 4 to 4.4. Their average SE score was 3.36. Average score of the response of each item under SE was similar except for the first item, namely, “can you manage your time well,” which had a lower average score (3.04). The average of AM score was 3.48. For two items, namely, “perform better” and “taking up challenges to reach goals” the average score was high (4.11 and 3.93, respectively). The average AE score was 3.04. But the item, “reading up topics before attending class” had a lower score (2.77). The average of S. Eng. score was 3.32. But the item, “how is your relationship with fellow students” had a high score (3.77) and “It’s normal thing to ask others for help” had a low average score of 3.06 (Table 2).
When the data was analyzed using multiple linear regression (Table 3), there was a significant association between vitamin D level and overall academic performance (p-value = 0.017) and also between vitamin D level and self-efficacy (p-value = 0.003). If the sample size was larger, small deviations from significance as in the case of AM and AE could have been cured. The medical students had a high overall academic performance when compared to the applied medical sciences students. When the GPA was analysed separately to find out its association with vitamin D level, in the 2nd-year and 3rd-year students, vitamin D levels had a significant association with GPA (p-values were 0.001 and 0.043, respectively) – Table 4.
Discussion
Several important roles including brain health, maintenance of bone health and prevention of fatigue and stress have been attributed to vitamin D by researchers (Holick, 2009; Anjum, Jaffery, Fayyaz, Samoo, & Anjum, 2018; Nowak et al., 2016; Quraishi & CamargoCA, 2012; Kusmiyati, Suryani, Heravati, & Firdausi, 2020). Studies done in the USA and UK have revealed that unhealthy dietary habits add to the health risk of university students (El Ansari et al., 2011; Lowry et al., 2000). Studies done on school children to find out the effect of dietary habits on school performance showed that there is a strong association between eating a healthy breakfast (containing milk and fruits), regularity of meals and school performance. The researchers were of the opinion that the beneficial effect they found may be partially due to the skipping of fast food or any unhealthy food which they would otherwise consume during the day (Kim et al., 2016; Mahoney, Taylor, Kanarek, & Samuel, 2005; Widenhorn-Muller, Hille, Klenk, & Weiland, 2008). A systematic review to examine the beneficial effect of breakfast on the academic performance of children and adolescents concluded that most of the studies were targeted at the memory and attention of students rather than cognitive tasks like problem-solving skills (Hoyland, Dye, & Lawton, 2009). Although these studies examine the role of a healthy diet in the performance of school students and university students, there are relatively few studies specifically examining the role of vitamin D level on academic performance.
The tendency of university students is to consume fast food during break hours as they do not have adequate time to enjoy regular meals and most of them are found to have vitamin D deficiency. In a study done in UAE, the researcher highlighted the fact that 44% of female college students from different Arab countries had vitamin D deficiency (Nimri, 2018). Some researchers who studied the vitamin D levels of young women between 25 and 30 years of age in Saudi Arabia, reported that vitamin D level of <20 ng/ml was found in 30% of women (Al-Turki, Sadat-Ali, Al-Elq, Al-Mulhim, & Al-Ali, 2008). Another study done among college students in Saudi Arabia found that 67.8% of female college students had vitamin D level <20 ng/ml (Alzaheb & Al-Amer, 2017). In our study, we found that 23.9% of female health sciences students had <12 ng/ml, whereas 53% of them had <20 ng/ml.
To find out the association between vitamin D level and academic performance, we used academic performance predictors such as self-efficacy, academic motivation, academic engagement and social engagement along with GPA (Brown, Lent, & Larkin, 1989; Dogan, 2015; Mai, Yusuf, & Saleh, 2015). Self-efficacy is defined as a personal belief in one’s own ability to manage things in life (Walker & Greene, 2009). Self-efficacy helps in facing challenges, forming strategies to overcome challenges and also solving problems (Bandura, 1994). Researchers have found a positive correlation between self-efficacy and academic performance (Yazici, Seyis, & Altun, 2011). In our study, we found a significant association between vitamin D level and self-efficacy. Researchers have put forward the theory that self-efficacy is a direct predictor of academic achievement (Schunk & Mullen, 2012). The significant association between vitamin D level and self-efficacy observed in our study stresses the importance of maintaining adequate levels of vitamin D for academic achievement.
Academic motivation and Academic engagement had some relationship with vitamin D level but there was no statistically significant association (p-value > 0.05). There are no studies found in the available literature to compare our results. However, a study done to find out the impact of vitamin D deficiency on depression among university students revealed that there is a significant relationship between low vitamin D level and prevalence of depression among university students (Tashtoush et al., 2018). Social engagement had no association with vitamin D level. The overall score of the predictors had a significant association with vitamin D level. This further strengthens the evidence that vitamin D level can influence academic performance.
The GPA had a significant association with vitamin D level only in 2nd- and 3rd-year students. As the students experience maximum stress during the initial years of study in medicine as well as allied health sciences, low vitamin D level can aggravate the stress affecting their academic performance adversely.
Conclusion
Our study highlights the importance of early screening of vitamin D level and early intervention for those with low vitamin D level along with adequate diet advice, to improve the academic performance of medical and health science students. Further studies with a larger number of students are needed to establish the role of vitamin D in academic performance.
Limitations of the study
The sample size was small as the students had to get the vitamin D test done and many students were reluctant to do it due to the fear of contracting COVID-19 infection when they visit the hospital laboratory.
Sample characteristics and demographics
| Variable | Categories | Frequency | % (N = 213) |
|---|---|---|---|
| College | Applied medical science | 70 | 32.9 |
| Medicine | 86 | 40.4 | |
| Nursing | 57 | 26.8 | |
| College year | 2 | 61 | 28.6 |
| 3 | 34 | 16.0 | |
| 4 | 57 | 26.8 | |
| 5 | 61 | 28.6 | |
| GPA | <2.5 | 3 | 1.4 |
| 2.5 + | 3 | 1.4 | |
| 3 + | 17 | 8.0 | |
| 3.5 + | 28 | 13.1 | |
| 4 + | 74 | 34.7 | |
| 4.5 + | 88 | 41.3 | |
| Vitamin D (ng/ml) (Mean = 20.3, SD = 10.8) | <12 | 51 | 23.9 |
| 12-20 | 62 | 29.1 | |
| >20 | 100 | 46.94 |
Academic performance Likert scale response
| Components | Item | Mean | SD |
|---|---|---|---|
| Self-efficacy (SE) | Can you manage your time well | 3.04 | 1.28 |
| Can you participate well in group discussions | 3.32 | 1.31 | |
| Do you have a good understanding of subjects | 3.46 | 1.23 | |
| Are you confident in talking to the faculty members | 3.50 | 1.32 | |
| Do you perform well in exams | 3.48 | 1.31 | |
| SE Score | 3.36 | 1.10 | |
| Academic motivation (AM) | Do you have clear academic goals | 3.55 | 1.33 |
| Do you want to perform better | 4.11 | 1.30 | |
| Are you willing to take up challenges to reach your goals | 3.93 | 1.31 | |
| I am far from failing | 2.72 | 1.45 | |
| I know when to be serious and when to have fun | 3.08 | 1.33 | |
| AM Score | 3.48 | 0.66 | |
| Academic engagement (AE) | I like to do academic presentations | 3.00 | 1.39 |
| I like to do academic research projects with others | 3.06 | 1.32 | |
| I like to discuss lectures with faculty members | 3.14 | 1.34 | |
| I read up topics before I attend the class | 2.77 | 1.42 | |
| I like to get a feedback from my faculty members | 3.23 | 1.44 | |
| AE Score | 3.04 | 1.17 | |
| Social Engagement (S. Eng.) | How is your relationship with fellow students | 3.77 | 1.37 |
| Do you enjoy studying with others | 3.26 | 1.42 | |
| It 1s a normal thing to ask others for help | 3.06 | 1.32 | |
| Are you cool against criticism | 3.17 | 1.39 | |
| Are you active in community services | 3.22 | 1.35 | |
| Do you like to participate in any academic-related activity | 3.24 | 1.40 | |
| Do you have a good relationship with the faculty | 3.50 | 1.40 | |
| S. Eng. Score | 3.32 | 0.74 | |
| Overall Performance Score | 3.30 | 0.74 | |
Vitamin D versus academic components
| Academic component | Effect p-value | Parameter | Parameter p-value |
|---|---|---|---|
| Self-efficacy | 0.003 | MED | 0.037 |
| AMS + NUR | 0.799 | ||
| Year 2 | 0.652 | ||
| Year 3 | 0.191 | ||
| Year 4 | 0.185 | ||
| Year 5 | 0.692 | ||
| Academic motivation | 0.091 | MED | 0.142 |
| AMS + NUR | 0.873 | ||
| Year 2 | 0.056 | ||
| Year 3 | 0.028 | ||
| Year 4 | 0.563 | ||
| Year 5 | 0.389 | ||
| Academic engagement | 0.086 | MED | 0.011 |
| AMS + NUR | 0.967 | ||
| Year 2 | 0.923 | ||
| Year 3 | 0.475 | ||
| Year 4 | 0.520 | ||
| Year 5 | 0.743 | ||
| Social engagement | 0.397 | MED | 0.012 |
| AMS + NUR | 0.478 | ||
| Year 2 | 0.406 | ||
| Year 3 | 0.640 | ||
| Year 4 | 0.388 | ||
| Year 5 | 0.396 | ||
| Overall performance | 0.017 | MED | 0.007 |
| AMS + NUR | 0.790 | ||
| Year 2 | 0.685 | ||
| Year 3 | 0.297 | ||
| Year 4 | 0.531 | ||
| Year 5 | 0.975 |
Note(s): (MED-Medicine, AMS-Applied Medical Sciences, NUR- Nursing)
Vitamin D versus GPA
| Effect | Effect p-value | Parameters | Parameter p-value (robust) |
|---|---|---|---|
| College | 0.393 | AMS &NUR: 0.140 | 0.217 |
| MED: 0.087 | 0.333 | ||
| College year | 0.000 | Year 2: 0.582 | 0.001 |
| Year 3: 0.376 | 0.043 | ||
| Year 4: 0.292 | 0.118 | ||
| Year 5: 0.207 | 0.289 | ||
| Vitamin D level | 0.145 | 0.005 | 0.134 |
References
Al Shawwa, L., Abulaban, A., Abulaban, A., Merdad, A., Baghlaf, S., Algethami, A., … & Balkhoyor, A. (2015). Factors potentially influencing academic performance among medical students. Advances in Medical Education and Practice, 6, 65–75.
Al-Elq, A. H. (2012). The status of Vitamin D in medical students in the preclerkship years of a Saudi medical school. Journal of Family & Community Medicine, 19(2), 100–104.
Al-Turki, H. A., Sadat-Ali, M., Al-Elq, A. H., Al-Mulhim, F. A., & Al-Ali, A. K. (2008). 25-Hydoxyvitamin D levels among healthy Saudi Arabian women. Saudi Medical Journal, 12, 1765–1768.
Alzaheb, R. A., & Al-Amer, O. (2017). Prevalence and predictors of hypovitaminosis D among female university students in Tabuk, Saudi Arabia. Clinical medicine insights: Women’s health. available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5428152/ (accessed 20 April 2022).
Anjum, I., Jaffery, S. S., Fayyaz, M., Samoo, Z., & Anjum, S. (2018). The role of vitamin D in brain health: A mini literature review. Cureus, 10(7). available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6132681/ (accessed 20 April 2022).
Annweiler, C., Schott, A. M., Allali, G., Bridenbaugh, S. A., Kressig, R. W., Allain, P., … & Beauchet, O. (2010). Association of vitamin D deficiency with cognitive impairment in older women: Cross-sectional study. Neurology, 74(1), 27–32.
Bandura, A. (1994). Self-efficacy. Encyclopaedia of human behaviour (Vol. 4, pp. 71–81). New York: Academic Press.
Brown, S. D., Lent, R. W., & Larkin, K. C. (1989). Self-efficacy as a moderator of scholastic aptitude-academic performance relationships. Journal of Vocational Behaviour, 35, 64–75.
Buell, J. S., Scott, T. M., Dawson-Hughes, B., Dallal, G. E., Rosenberg, I. H., Folstein, M. F., & Tucker, K. L. (2009). Vitamin D is associated with cognitive function in elders receiving home health services. Journals of Gerontology. Series A, Biological Sciences and Medical Sciences, 64(8), 888–895.
Buell, J. S., Dawson-Hughes, B., Scott, T. M., Weiner, D. E., Dallal, G. E., Qui, W. Q., … & Tucker, K. L. (2010). 25-Hydroxyvitamin D, dementia, and cerebrovascular pathology in elders receiving home services. Neurology, 74(1), 18–26.
Burrows, T. L., Whatnall, M. C., Patterson, A. J., & Hutchesson, M. J. (2017). Associations between dietary intake and academic achievement in college students: A systematic review. Healthcare (Basel), 5(4), 60.
Dogan, U. (2015). Student engagement, academic self-efficacy, and academic motivation as predictors of academic performance. Anthropologist, 20(3), 553–561.
El Ansari, W., Stock, C., John, J., Deeny, P., Phillips, C., Snelgrove, S., … & Mabhala, A. (2011). Health promoting behaviours and lifestyle characteristics of students at seven universities in the UK. Central European Journal of Public Health, 19(4), 197–204.
Feldman, B. D., & Kubota, M. (2015). Hope, self-efficacy, optimism, and academic achievement: Distinguishing constructs and levels of specificity in predicting college grade-point average. Learning and Individual Difference, 37, 210–216. available from: https://doi.org/10.1016/j.lindif.2014.11.022 (accessed 20 April 2022).
Hasanato, R., Al-Mahboob, A., Al-Mutairi, A., Al-Faraydi, J., Al-Amari, K., Al-Jurayyad, R., & Mohamed, S. (2015). High prevalence of vitamin D deficiency in healthy female medical students in Central Saudi Arabia: Impact of nutritional and environmental factors. Acta Endocrinologica, 11(2), 257–261.
Holick, M. F. (2009). Vitamin D status: Measurement, interpretation, and clinical application. Annals of Epidemiology, 19(2), 73–78.
Hoyland, A., Dye, L., & Lawton, C. L. (2009). A systematic review of the effect of breakfast on the cognitive performance of children and adolescents. Nutrition Research Reviews, 22, 220–243.
Huang, S. (2011). Predicting students’ academic performance in college using a new non- cognitive measure: An instrument design and a structural equation exploration of some non-cognitive attributes and academic performance (Dissertation Graduate Program in Education). The Ohio State University, Predicting Students’ Academic Performance in College Using. available from: https://www.semanticscholar.org (accessed 20 April 2022).
Kim, S. Y., Sim, S., Park, B., Kong, I. G., Kim, J. H., & Choi, H. G. (2016). Dietary habits are associated with school performance in adolescents. Medicine (Baltimore), 95(12). available from: https://pubmed.ncbi.nlm.nih.gov/27015180/ (accessed 20 April 2022).
Kusmiyati, Y., Suryani, E., Heravati, L., & Firdausi, A. (2020). Kesmas: Jurnal Kesehatan Masyarakat Nasional (National Public Health Journal), 15(3), 128–133.
Lee, D. M., Tajar, A., Ulubaev, A., Pendleton, N., O’Neill, T. W., O’Connor, D. B., … & Wu, F. C. (2009). Association between 25-hydroxyvitamin D levels and cognitive performance in middle-aged and older European men. Journal of Neurology, Neurosurgery, and Psychiatry, 80(7), 722–729.
Llewellyn, D. J., Langa, K. M., & Lang, I. A. (2009). Serum 25-hydroxyvitamin D concentration and cognitive impairment. Journal of Geriatric Psychiatry and Neurology, 22(3), 188–195.
Llewellyn, D. J., Lang, I. A., Langa, K. M., Terrera, G. M., Phillips, G. L., Cherubini, A., … & Melzer, D. (2010). Vitamin D and risk of cognitive decline in elderly persons. Archives of Internal Medicine, 170(13), 1135–1141.
Lowry, R., Galuska, D. A., Fulton, J. E., Wechsler, H., Kann, L., & Collins, J. L. (2000). Physical activity, food choice, and weight management goals and practices among US college students. American Journal of Preventive Medicine, 18(1), 18–27.
Mahoney, C. R., Taylor, H. A., Kanarek, R. B., & Samuel, P. (2005). Effect of breakfast composition on cognitive processes in elementary school children. Physiology and Behavior, 85, 635–645.
Mai, M. Y. M., Yusuf, M., & Saleh, M. (2015). Motivation and engagement as a predictor of students’ science achievement satisfaction of Malaysian of secondary school students. European Journal of Social Sciences. available from: https://revistia.com/files/articles/ejser_v2_i4_15/Mohammed.pdf (accessed 20 April 2022).
Nimri, L.F. (2018). Vitamin D status of female UAE college students and associated risk factors. Journal of Public Health, 40(3), e284–e290. available from: https://doi.org/10.1093/pubmed/fdy009 (accessed 20 April 2022).
Nowak, A., Boesch, L., Andres, E., Battegay, E., Hornemann, T., Schmid, C., … Krayenbuehl, P. A. (2016). Effect of vitamin D3 on self-perceived fatigue: A double-blind randomized placebo-controlled trial. Medicine, 95(52). available from: https://pubmed.ncbi.nlm.nih.gov/28033244/# (accessed 20 April 2022).
Olivier, E., Archambault, I., De Clercq, M., & Galand, B. (2019). Student self-efficacy, classroom engagement, and academic achievement: Comparing three theoretical frameworks. Journal of Youth and Adolescence, 48, 326–340. available from: https://doi.org/10.1007/s10964-018-0952-0 (accessed 20 April 2022).
Quraishi, S. A., Camargo, & CA Jr. (2012). Vitamin D in acute stress and critical illness. Current Opinion in Clinical Nutrition and Metabolic Care, 15(6), 625–634.
Schunk, D. H., & Mullen, C. A. (2012). Self-efficacy as an engaged learner. In Handbook of research on student engagement (Vol. 219–236). New York, NY: Springer.
Slinin, Y., Paudel, M., Taylor, B. C., Fink, H. A., Ishani, A., Canales, M. T., … & Ensrud, K. E. (2010). 25-Hydroxyvitamin D levels and cognitive performance and decline in elderly men. Neurology, 74(1), 33–41.
Sulaiman, A. H., Abukanna, A. M., Alenezy, A. A., & Balla, A. A. (2017). Prevalence of vitamin D deficiency among university female students in northern border region of kingdom of Saudi Arabia. Annals of Medical and Health Science Research, 7, 280–283.
Tashtoush, N., Anas, L., Taleb, R., Wajdi, R., Alanazi, K., Alshehri, N., … & Asdaq, S. (2018). Vitamin D deficiency and its impact on depression among al-maarefa university students, Riyadh, Saudi Arabia. Asian Journal of Pharmaceutics, 12, S916–S926.
Walker, C. O., & Greene, B. A. (2009). The relations between student motivational beliefs and cognitive engagement in high school. Journal of Educational Research, 102, 463–472.
Widenhorn-Muller, K., Hille, K., Klenk, J., & Weiland, U. (2008). Influence of having breakfast on cognitive performance and mood in 13- to 20-year-old high school students: Results of a crossover trial. Pediatrics, 122, 279–284.
Yazici, H., Seyis, S., & Altun, F. (2011). Emotional intelligence and self-efficacy beliefs as predictors of academic achievement among high school students. Procedia -Social and Behavioral Sciences, 15, 2319–2323.
Acknowledgements
The authors are grateful for the grant awarded by Northern Border University for the study entitled “Role of Vitamin D in the Academic Performance of Female Medical Students and Applied Medical Sciences Students in Saudi Arabia” with decision no (12/42/H). Our special thanks to the students of Northern Border University who participated in this study.
Conflict of Interest: There is no conflict of interest.