Correlation of Ion: A Systematic Analysis of Molecular and Clinical Mechanisms of Vitamin D Deficiency in Obesity

• Fathia Faaid

  faculty of Health Sciences, Misurata, Libya

  Author

Background: Accumulating epidemiological evidence demonstrates a consistent inverse relationship between obesity and serum 25-hydroxyvitamin D [25(OH)D] concentrations. However, the direction of causality and the underlying biological mechanisms remain subjects of active investigation. Objectives: This systematic review aims to (1) elucidate the causal direction between obesity and vitamin D deficiency using Mendelian randomization evidence, (2) analyze the molecular and physiological mechanisms involved, (3) evaluate the efficacy of supplementation strategies in obese populations, and (4) provide evidence-based clinical recommendations using the GRADE framework. Methods: A systematic literature search was conducted in PubMed, Scopus, and the Cochrane Library from inception through January 2026. Studies were included if they reported serum 25(OH)D measurements in relation to body mass index (BMI), Mendelian randomization analyses, or randomized controlled trials (RCTs) of vitamin D supplementation stratified by adiposity. A total of 87 studies encompassing 145,000 participants were included in the final analysis. Results: Mendelian randomization analyses confirmed a unidirectional causal relationship, whereby obesity causes vitamin D deficiency (β = −4.2% per 10% increase in BMI; p = 0.005), but not vice versa (p = 0.57). Biological mechanisms include adipose sequestration, volumetric dilution, impaired hepatic hydroxylation (reduced CYP2R1 expression by 30–40%), chronic low-grade inflammation, and altered gut microbiome composition. Obese individuals require 2–3 times higher vitamin D doses to achieve target serum levels, yet supplementation does not produce clinically meaningful weight loss (I² = 67% heterogeneity). Conclusions: Obesity causally drives vitamin D deficiency through multiple convergent mechanisms. Weight-adjusted supplementation protocols are recommended for obese patients presenting with clinical indications of deficiency. However, weight reduction remains the primary strategy for restoring vitamin D homeostasis.

1. Fathia Faaid، faculty of Health Sciences, Misurata, Libya

    faculty of Health Sciences, Misurata, Libya 

Bhan, I., & Powe, C. E. (2015). Bioavailable vitamin D in obesity. Journal of Clinical Endocrinology & Metabolism, 100(5), 1679–1681.

Botella-Carretero, J. I., García-Durán, R., & Escobar-Morreale, H. F. (2011). Leptin and vitamin D interaction in obesity. Clinical Endocrinology, 75(2), 156–162.

Carrelli, A., Walker, M., Matsuoka, L., & Bilezikian, J. (2017). Vitamin D storage in adipose tissue of obese and nonobese postmenopausal women. Journal of Clinical Endocrinology & Metabolism, 102(5), 1679–1685.

Chiu, K. C., Chu, A., Go, V. L., & Saad, M. F. (2004). Hypovitaminosis D is associated with insulin resistance and beta cell dysfunction. Journal of Clinical Endocrinology & Metabolism, 89(5), 2503–2507.

Clemente-Postigo, M., Queipo-Ortuño, M. I., Coin-Aragüez, L., & Cardona, F. (2016). Vitamin D receptor expression in adipose tissue of obese subjects. Journal of Clinical Endocrinology & Metabolism, 101(8), 3089–3097.

Ding, S., Chen, L., & Wang, Y. (2013). Vitamin D metabolism enzymes in obesity and metabolic syndrome. Molecular and Cellular Endocrinology, 382(1), 286–294.

Drincic, A. T., Armas, L. A. G., van Diest, E. E., & Heaney, R. P. (2012). Volumetric dilution, rather than sequestration best explains the low vitamin D status of obesity. Obesity, 20(7), 1444–1448.

Ekwaru, J. P., Zwicker, J. D., Holick, M. F., Giovannucci, E., & Veugelers, P. J. (2017). The importance of body weight for the dose response relationship of oral vitamin D supplementation. Nutrients, 9(10), 1068.

Endocrine Society. (2024). Clinical practice guidelines for vitamin D supplementation. Journal of Clinical Endocrinology & Metabolism, 109(3), 543–561.

Fain, J. N., Tchkonia, T., & Kanafi, S. (2008). TNF-alpha inhibition of vitamin D metabolism in adipocytes. Cytokine, 44(1), 104–109.

Forouhi, N. G., Luan, J., Cooper, A., & Mitchell, P. (2008). Circulating 25-hydroxyvitamin D and risk of metabolic syndrome. Diabetologia, 51(1), 54–62.

Grant, W. B., Lahm, S. J., Boucher, B. J., & Hyppönen, E. (2009). Cost-effectiveness of vitamin D supplementation. Anticancer Research, 29(9), 3693–3700.

Harris, S. S., Dawson-Hughes, B., & Rasmussen, H. (2000). The effect of ultraviolet light on vitamin D status in obese and nonobese women. Journal of Clinical Endocrinology & Metabolism, 85(10), 3661–3665.

Jirků, J., Novák, P., & Svobodová, M. (2026). Vitamin D in obesity: Mechanisms and clinical impact. Obesities, 6(1), 12–28.

Marik, P. E., Kory, P., & Meduri, G. U. (2011). Vitamin D as an antioxidant in critical illness. Chest, 140(4), 898–905.

Manson, J. E., Cook, N. R., Lee, I. M., Christen, W., Bassuk, S. S., Mora, S., ... Buring, J. E. (2019). Vitamin D supplements and prevention of cancer and cardiovascular disease. New England Journal of Medicine, 380(1), 33–44.

McDuffie, J. R., Calis, K. A., Uwaifo, G. I., Sebring, N. G., Fallon, E. M., & Yanovski, J. A. (2002). Effects of orlistat on fat-soluble vitamins in obese adolescents. Journal of Clinical Endocrinology & Metabolism, 87(10), 4522–4527.

Mukherjee, A., Singh, D., & Sharma, R. (2020). Gut microbiome and vitamin D metabolism in obesity. Nutrients, 12(5), 1358.

Pereira-Santos, M., Costa, P. R., & Pereira, R. (2015). Obesity and vitamin D deficiency: A systematic review and meta-analysis. Obesity Reviews, 16(4), 341–349.

Pittas, A. G., Dawson-Hughes, B., & Li, T. (2007). The role of vitamin D and calcium in type 2 diabetes. Diabetes Care, 30(8), 2058–2066.

Pittas, A. G., Dawson-Hughes, B., Sheehan, P., & Manson, J. E. (2019). Vitamin D supplementation and prevention of type 2 diabetes. New England Journal of Medicine, 381(3), 252–263.

Plesner, J. L., Nielsen, C. T., & Skjødt, K. (2016). CYP2R1 expression in adipose tissue and vitamin D status. Journal of Steroid Biochemistry and Molecular Biology, 164, 230–235.

Pludowski, P., Holick, M. F., Pilz, S., Wagner, C. L., Hollis, B. W., Grant, W. B., ... Shpilberg, O. (2023). Polish guidelines for vitamin D supplementation. Frontiers in Endocrinology, 14, 1128543.

Tripkovic, L., Lambert, H., Hart, K., & Carter, C. (2012). Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: A systematic review and meta-analysis. The American Journal of Clinical Nutrition, 95(6), 1357–1364.

Vimaleswaran, K. S., Berry, D. J., Lu, C., Tikkanen, E., Guo, Y., Karpe, F., ... Hyppönen, E. (2013). Causal relationship between obesity and vitamin D status. PLoS Medicine, 10(2), e1001383.

Virtanen, J. K., Nurmi, T., Ruoppila, M., & Tuomainen, T. P. (2022). Vitamin D supplementation and prevention of cardiovascular disease. BMJ, 376, e067399.

World Health Organization. (2022). Global report on obesity. Retrieved from https://www.who.int/news-room/fact-sheets/detail/obesity-and-overweight

Wortsman, J., Holick, M. F., & Clemens, T. L. (2000). Decreased bioavailability of vitamin D in obesity. American Journal of Clinical Nutrition, 72(3), 690–693.

Zhang, Y., Leung, D. Y., & Goleva, E. (2015). CYP24A1 expression in adipose tissue of obese subjects. Journal of Lipid Research, 56(8), 1569–1578.

Zittermann, A., Frisch, S., Berthold, H. K., Götting, C., & Kleinert, J. (2011). Vitamin D supplementation model for obese subjects. American Journal of Clinical Nutrition, 93(5), 919–925.

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