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

Likely Effective

  • Esophageal cancer—likely to protect against esophageal cancer B1
  • Stroke—likely to reduce number of strokes I1-I5

May Be Effective

Unlikely to Be Effective

  • Cognitive disorders—unlikely to prevent cognitive decline A1-A9
  • Major adverse cardiovascular events—unlikely to result in fewer events D1
  • Osteoporosis fractures—unlikely to help prevent fracture E1

Not Enough Data to Assess

Editorial process and description of evidence categories can be found at EBSCO NAT Editorial Process.

Editorial process and description of evidence categories can be found at EBSCO NAT Editorial Process.

Safety Notes

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.


REFA Cognitive Disorders

REFA1 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.

REFA2 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.

REFA3 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.

REFA4 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.

REFA5 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.

REFA6 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.

REFA7 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.

REFA8 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.

REFA9 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.

REFB Esophageal Cancer

REFB1 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.

REFC High blood pressure

REFC1 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.

REFD Major Adverse Cardiovascular Events

REFD1 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.

REFE Osteoporosis Fractures

REFE1 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.

REFF Parkinson disease

REFF1 Shen L. Associations between B Vitamins and Parkinson’s Disease. Nutrients. 2015;7(9):197-208.

REFG Perinatal Depression

REFG1 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).


REFH1 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.

REFI Stroke

REFI1 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.

REFI2 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.

REFI3 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.

REFI4 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.

Revision Information

  • Reviewer: EBSCO NAT Review Board Eric Hurwitz, DC
  • Review Date: 07/2019
  • Update Date: 09/09/2019