Dear Raid M. Al-Salih ,

Much research has mentioned the correlation between folic acid and vit. D.

Here are some examples.

Aslan, M. G., Findik, H., Okutucu, M., Aydin, E., Oruç, Y., Arpa, M., & Uzun, F. (2021). Serum 25-hydroxy vitamin D, vitamin B12, and folic acid levels in progressive and nonprogressive keratoconus. Cornea, 40(3), 334-341.

Esnafoğlu, E., & Yaman, E. (2017). Vitamin B12, folic acid, homocysteine and vitamin D levels in children and adolescents with obsessive compulsive disorder. Psychiatry research, 254, 232-237.

Konuksever, D., & Karakaya, S. P. Y. (2022). Evaluation of correlation between vitamin D with vitamin B12 and folate in children. Nutrition, 99, 111683.

Morse, N. L. (2012). Benefits of docosahexaenoic acid, folic acid, vitamin D and iodine on foetal and infant brain development and function following maternal supplementation during pregnancy and lactation. Nutrients, 4(7), 799-840.

Munger, K. L., Zhang, S., O’reilly, E., Hernan, M., Olek, M., Willett, W., & Ascherio, A. (2004). Vitamin D intake and incidence of multiple sclerosis. Neurology, 62(1), 60-65.

Rogenhofer, N., Mischitz, D., Mann, C., Gluderer, J., von Schönfeldt, V., Jeschke, U., & Thaler, C. J. (2019). Correlation of vitamin D3 (Calcitriol) serum concentrations with vitamin B12 and folic acid in women undergoing in vitro fertilisation/intracytoplasmatic sperm injection. Gynecologic and obstetric investigation, 84(2), 128-135.

I hope this can help your research.

Dear Raid M. Al-Salih

many studies supported this correlation. I think this correlation might be mediated by hyperhomocysteinemia, oxidative stress, and also other factors associated with "folate-trap" and also "vitamin d hydroxylases". Here are some articles:

Kuroda K, Horikawa T, Gekka Y, Moriyama A, Nakao K, Juen H, Takamizawa S, Ojiro Y, Nakagawa K, Sugiyama R. Effects of periconceptional multivitamin supplementation on folate and homocysteine levels depending on genetic variants of methyltetrahydrofolate reductase in infertile Japanese Women. Nutrients. 2021 Apr 20;13(4):1381.

Amer M, Qayyum R. The relationship between 25-hydroxyvitamin D and homocysteine in asymptomatic adults. The Journal of Clinical Endocrinology & Metabolism. 2014 Feb 1;99(2):633-8.

Bahulikar A, Tickoo V, Phalgune D. Association of Non-HDL Cholesterol, Homocysteine and Vitamin D in Acute Coronary Syndrome. The Journal of the Association of Physicians of India. 2018 Aug 1;66(8):22-5.

Verdoia M, Nardin M, Gioscia R, Saghir Afifeh AM, Viglione F, Negro F, Marcolongo M, De Luca G, Novara Atherosclerosis Study Group (NAS). Association between vitamin D deficiency and serum Homocysteine levels and its relationship with coronary artery disease. Journal of thrombosis and thrombolysis. 2021 Aug 1:1-9.

Raid M. Al-Salih Mojtaba Daneshvar Chou-Yi Hsu I just published this article about B12 vitamin and Folates.

Article Can supplementing vitamin B12 improve mental health outcomes...

Do let me know your thoughts