B vitamins include a number of different vitamins. They include thiamin, riboflavin, niacin, pantothenic acid, biotin, vitamin B6, folic acid, and vitamin B12. B vitamin supplements may include all or some of these types. B vitamins are thought to improve brain function and blood flow. They are often recommended for pregnant women. B vitamins can be taken as pills or as a powder.
There are no advised doses for B vitamins.
What Research Shows
May Be Effective
Unlikely to Be Effective
Editorial process and description of evidence categories can be found at EBSCO NAT Editorial Process.
It is likely safe to take B vitamins in small doses for a short time. Not enough studies have been done to say whether they are safe to use for a long period.
Talk to your doctor about any supplements or therapy you would like to use. Some can interfere with treatment or make conditions worse.
A. Cognitive Disorders
A1. Wald DS, Kasturiratne A, et al. Effect of folic acid, with or without other B vitamins, on cognitive decline: meta-analysis of randomized trials. Am J Med. 2010;123(6):522-427.
A2. Dangour AD, Whitehouse PJ, et al. B-vitamins and fatty acids in the prevention and treatment of Alzheimer's disease and dementia: a systematic review. J Alzheimers Dis. 2010;22(1):205-224.
A3. Clarke R, Bennett D, et al. Effects of homocysteine lowering with B vitamins on cognitive aging: meta-analysis of 11 trials with cognitive data on 22,000 individuals. Am J Clin Nutr. 2014;100(2):657-666.
A4. Cao L, Tan L, et al. Dietary Patterns and Risk of Dementia: a Systematic Review and Meta-Analysis of Cohort Studies. Mol Neurobiol. 2016 Nov;53(9):6144-6154.
A5. Muñoz Fernández SS, Ivanauskas T, et al. Nutritional Strategies in the Management of Alzheimer Disease: Systematic Review with Network Meta-Analysis. J Am Med Dir Assoc. 2017 Oct 1;18(10):897.e13-897.e30.
A6. Butler M, Nelson VA, et al. Over-the-Counter Supplement Interventions to Prevent Cognitive Decline, Mild Cognitive Impairment, and Clinical Alzheimer-Type Dementia: A Systematic Review. Ann Intern Med. 2018 Jan 2;168(1):52-62.
A7. D'Cunha NM, Georgousopoulou EN, et al. Effect of long-term nutraceutical and dietary supplement use on cognition in the elderly: a 10-year systematic review of randomised controlled trials. Br J Nutr. 2018 Feb;119(3):280-298.
A8. McCleery J, Abraham RP, et al. Vitamin and mineral supplementation for preventing dementia or delaying cognitive decline in people with mild cognitive impairment. Cochrane Database Syst Rev. 2018 Nov 1;11:CD011905.
A9. Rutjes AW, Denton DA, et al. Vitamin and mineral supplementation for maintaining cognitive function in cognitively healthy people in mid and late life. Cochrane Database Syst Rev. 2018 Dec 17;12:CD011906.
B. Esophageal Cancer
B1. Qiang Y, Li Q, et al. Intake of Dietary One-Carbon Metabolism-Related B Vitamins and the Risk of Esophageal Cancer: A Dose-Response Meta-Analysis. Nutrients. 2018 Jun 27;10(7). pii: E835.
C. High blood pressure
C1. Menzel D, Haller H, et al. L-Arginine and B vitamins improve endothelial function in subjects with mild to moderate blood pressure elevation. Eur J Nutr. 2018;57(2):557-568.
D. Major Adverse Cardiovascular Events
D1. Zhang C, Wang ZY, et al. Association between B vitamins supplementation and risk of cardiovascular outcomes: a cumulative meta-analysis of randomized controlled trials. PLoS One. 2014 Sep 19;9(9):e107060.
E. Osteoporosis Fractures
E1. Ruan J, Gong X, et al. Effect of B vitamin (folate, B6, and B12) supplementation on osteoporotic fracture and bone turnover markers: a meta-analysis. Med Sci Monit. 2015 Mar 24;21:875-881.
F. Parkinson disease
F1. Shen L. Associations between B Vitamins and Parkinson’s Disease. Nutrients. 2015;7(9):197-208.
G. Perinatal Depression
G1. Sparling TM, Henschke N, et al. The role of diet and nutritional supplementation in perinatal depression: a systematic review. Matern Child Nutr. 2017 Jan;13(1).
H1. Firth J, Stubbs B, et al. The effects of vitamin and mineral supplementation on symptoms of schizophrenia: a systematic review and meta-analysis. Psychol Med. 2017 Jul;47(9):1515-1527.
I1. Hankey GJ, Ford AH, et al. Effect of B vitamins and lowering homocysteine on cognitive impairment in patients with previous stroke or transient ischemic attack: a prespecified secondary analysis of a randomized, placebo-controlled trial and meta-analysis. Stroke. 2013 Aug;44(8):2232-2239.
I2. Zhang C, Chi FL, et al. Effect of B-vitamin supplementation on stroke: a meta-analysis of randomized controlled trials. PLoS One. 2013 Nov 25;8(11):e81577.
I3. Dong H, Pi F, et al. Efficacy of Supplementation with B Vitamins for Stroke Prevention: A Network Meta-Analysis of Randomized Controlled Trials. PLoS One. 2015;10(9):e0137533.
I4. Park JH, Saposnik G, et al. Effect of B-Vitamins on stroke risk among individuals with vascular disease who are not on antiplatelets: A meta-analysis. Int J Stroke. 2016;11(2):206-211. I5. Spence JD, Yi Q, et al. B vitamins in stroke prevention: time to reconsider. Lancet Neurol. 2017 Sep;16(9):750-760.
Last reviewed July 2019 by EBSCO NAT Review Board Eric Hurwitz, DC Last Updated: 9/9/2019