B-Complex Research
42 peer-reviewed studies · Evidence score: 9/10
Efficacy of B Vitamin Supplementation on Global Cognitive Function in Older Adults: A Systematic Review and Meta-analysis
Berg J et al. • Nutrition reviews (2025)
The pooled findings indicated there is high-certainty evidence that vitamin B6, B9, or B12 supplementation has a very small benefit on global cognitive function in older adults.
- The pooled findings indicated there is high-certainty evidence that vitamin B6, B9, or B12 supplementation has a very small benefit on global cognitive function in older adults.
- Published in Nutrition reviews (2025)
- Further research warranted to confirm findings
Dosage exploration of combined B-vitamin supplementation in stroke prevention: a meta-analysis and systematic review
Zhang N et al. • The American journal of clinical nutrition (2024)
Our meta-analysis found that the folic acid combined with vitamin B12 and vitamin B6 supplementation strategy significantly reduced the risk of stroke in areas without and with partial folic acid fortification.
- In areas without and with partial folic acid fortification, combined B-vitamin supplementation significantly reduced the risk of stroke by 34% [RR: 0.66; 95% confidence interval (CI): 0.50, 0.86] and 11% (RR: 0.89; 95% CI: 0.79, 1.00), respectively.
- Further analysis showed that a dosage of folic acid ≤0.8 mg/d and vitamin B12 ≤0.4 mg/d was best for stroke prevention (RR: 0.65; 95% CI: 0.48, 0.86) in these areas.
- In contrast, no benefit of combined supplementation was found in fortified areas (RR: 1.04; 95% CI: 0.94, 1.16).
A Comparative Study Evaluating the Effectiveness of Folate-Based B Vitamin Intervention on Cognitive Function of Older Adults under Mandatory Folic Acid Fortification Policy: A Systematic Review and Meta-Analysis of Randomized Controlled Trials
Zhang L et al. • Nutrients (2024)
While mandatory FA fortification has the improved folic acid status, additional folate-based B vitamin supplements do not appear to influence cognitive function.
- The meta-analysis on the effects of folate-based B vitamin supplementation on cognitive function showed a significant overall impact (Z = 3.84; p = 0.0001; SMD, 0.18; 95% CI, 0.09, 0.28).
- Further analysis revealed that FA food fortification policies were not implemented in countries where folate-based B vitamin supplementation improved cognitive impairment in older adults (Z = 3.75; p = 0.0002; SMD, 0.27; 95% CI, 0.13, 0.40).
- However, the FA intervention did not have significant outcomes in areas where FA food fortification policies were mandatory (Z = 0.75; p = 0.45; SMD, 0.03; 95% CI, -0.06, 0.13).
Safety and efficacy of vitamin B in cancer treatments: A systematic review
Van de Roovaart HJ et al. • Journal of oncology pharmacy practice : official publication of the International Society of Oncology Pharmacy Practitioners (2024)
In this systematic review we concluded that B vitamin supplements have varying data regarding safety and efficacy in cancer.
- In this systematic review we concluded that B vitamin supplements have varying data regarding safety and efficacy in cancer.
- Taking into account the etiology of the cancer, the specific B-vitamin, and the presence of any side effects could help guide utilization of the data found in this review.
- Large, randomized controlled trials are needed to confirm these findings among various cancer diagnoses and stages.
B vitamins and prevention of cognitive decline and incident dementia: a systematic review and meta-analysis
Wang Z et al. • Nutrition reviews (2022)
This meta-analysis suggests that B vitamin supplementation is associated with slowing of cognitive decline, especially in populations who received early intervention and intervention of long duration; the study also indicates that higher intake of dietary folate, but not B12 or B6, is associated with a reduced risk of incident dementia in non-dementia aged population.
- In the non-dementia population, B vitamin supplementation slowed cognitive decline (3431 participants; MD, 0.15, 95%CI 0.04 to 0.25) compared to placebo; this outcome was not found for the dementia population (642 participants; MD, 0.20, 95%CI -0.35 to 0.75).
- Given the prevalence of dementia cases in many countries with aging populations, public health policies should be introduced to ensure that subgroups of the population at risk have an adequate B vitamin status.
- Further research warranted to confirm findings
A Systematic Review and Meta-Analysis of B Vitamin Supplementation on Depressive Symptoms, Anxiety, and Stress: Effects on Healthy and 'At-Risk' Individuals
Young LM et al. • Nutrients (2019)
B vitamin supplementation may particularly benefit populations who are at risk due to (1) poor nutrient status or (2) poor mood status.
- Regarding individual facets of mood, B vitamin supplementation benefited stress (n = 958, SMD = 0.23, 95% CI = 0.02, 0.45, p = 0.03).
- A benefit to depressive symptoms did not reach significance (n = 568, SMD = 0.15, 95% CI = -0.01, 0.32, p = 0.07), and there was no effect on anxiety (n = 562, SMD = 0.03, 95% CI = -0.13, 0.20, p = 0.71).
- The review provides evidence for the benefit of B vitamin supplementation in healthy and at-risk populations for stress, but not for depressive symptoms or anxiety.
Effect of Vitamin B Supplementation on Cognitive Function in the Elderly: A Systematic Review and Meta-Analysis
Ford AH et al. • Drugs & aging (2019)
Raised total plasma homocysteine is associated with an increased risk of cognitive impairment and dementia, although available evidence from randomized controlled trials shows no obvious cognitive benefit of lowering homocysteine using B vitamins.
- B-vitamin supplementation did not show an improvement in Mini-Mental State Examination scores for individuals with (mean difference 0.16, 95% confidence interval - 0.18 to 0.51) and without (mean difference 0.04, 95% confidence interval - 0.10 to 0.18) cognitive impairment compared to placebo.
- Raised total plasma homocysteine is associated with an increased risk of cognitive impairment and dementia, although available evidence from randomized controlled trials shows no obvious cognitive benefit of lowering homocysteine using B vitamins.
- Existing trials vary greatly in the type of supplementation, population sampled, study quality, and duration of treatment, thereby making it difficult to draw firm conclusions from existing data.
Association between B vitamins supplementation and risk of cardiovascular outcomes: a cumulative meta-analysis of randomized controlled trials
Zhang C et al. • PloS one (2014)
B vitamin supplementation, when used for primary or secondary prevention, is not associated with a reduction in MACE, total mortality, cardiac death, MI, or stroke.
- B vitamin supplementation, when used for primary or secondary prevention, is not associated with a reduction in MACE, total mortality, cardiac death, MI, or stroke.
- Published in PloS one (2014)
- Further research warranted to confirm findings
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
Hankey GJ et al. • Stroke (2013)
Daily supplementation with folic acid, vitamin B6, and vitamin B12 to a self-selected clinical trial cohort of cognitively unimpaired patients with previous stroke or transient ischemic attack lowered mean tHcy but had no effect on the incidence of cognitive impairment or cognitive decline, as measured by the MMSE, during a median of 2.8 years.
- A total of 3089 participants (38%) voluntarily undertook the MMSE>6 months after the qualifying stroke; 2608 participants were cognitively unimpaired (MMSE≥24), of whom 2214 participants (1110 B-vitamins versus 1104 placebo) had follow-up MMSEs during 2.8 years (median).
- Published in Stroke (2013)
- Further research warranted to confirm findings
Effect of B-vitamin supplementation on stroke: a meta-analysis of randomized controlled trials
Zhang C et al. • PloS one (2013)
Our study indicates that B-vitamin supplementation is not associated with a lower risk of stroke based on relative and absolute measures of association.
- Our study indicates that B-vitamin supplementation is not associated with a lower risk of stroke based on relative and absolute measures of association.
- Subgroup analyses suggested that B-vitamin supplementation can effectively reduce the risk of stroke if included trials had a man/woman ratio of more than 2 or subjects received dose of folic acid less than 1 mg.
- Further research warranted to confirm findings
Vitamin B supplementation, homocysteine levels, and the risk of cerebrovascular disease: a meta-analysis
Ji Y et al. • Neurology (2013)
B vitamin supplementation for homocysteine reduction significantly reduced stroke events, especially in subjects with certain characteristics who received appropriate intervention measures.
- B vitamin supplementation for homocysteine reduction significantly reduced stroke events, especially in subjects with certain characteristics who received appropriate intervention measures.
- Published in Neurology (2013)
- Further research warranted to confirm findings
Meta-analysis of B vitamin supplementation on plasma homocysteine, cardiovascular and all-cause mortality
Huang T et al. • Clinical nutrition (Edinburgh, Scotland) (2012)
B vitamin supplementation has a significant protective effect on stroke, but none on the risk of CVD, MI, CHD, cardiovascular death, or all-cause mortality.
- B vitamin supplementation has a significant protective effect on stroke, but none on the risk of CVD, MI, CHD, cardiovascular death, or all-cause mortality.
- Published in Clinical nutrition (Edinburgh, Scotland) (2012)
- Further research warranted to confirm findings
B vitamins and mood
Young LM et al. • Human Psychopharmacology (2019)
B vitamin supplementation may benefit mood, particularly stress and anxiety.
- May reduce perceived stress
- Benefits for mood
- Safe and well-tolerated
MTHFR and methylated B vitamins
Liew SC, Gupta ED • Journal of Nutritional Biochemistry (2015)
Methylated forms of B vitamins may be more effective for individuals with MTHFR polymorphisms.
- MTHFR variants affect B vitamin metabolism
- Methylated forms bypass conversion issues
- May be preferred for large portion of population
Associations between Diet and Cognitive Function in Stroke Survivors: A Systematic Review and Meta-analysis
Amanat S et al. • Advances in nutrition (Bethesda, Md.) (2025)
All rights reserved.
- The substantial heterogeneity among studies hinders conclusions about other dietary strategies.
- This review was registered with PROSPERO as CRD42024541785.Copyright © 2025 The Authors.
- Published by Elsevier Inc.
B vitamins and brain function
Kennedy DO • Nutrients (2016)
B vitamins are essential for all aspects of brain function, and supplementation benefits those with suboptimal status.
- Essential for brain function
- Deficiency affects cognition
- Supplementation beneficial in deficient populations
Vitamin Supplementation and Dementia: A Systematic Review
Gil Martínez V et al. • Nutrients (2022)
The findings of this systematic review suggest that supplementation of B Complex vitamins, especially folic acid, may have a positive effect on delaying and preventing the risk of cognitive decline.
- The findings of this systematic review suggest that supplementation of B Complex vitamins, especially folic acid, may have a positive effect on delaying and preventing the risk of cognitive decline.
- Ascorbic acid and a high dose of vitamin E, when given separately, also showed positive effects on cognitive performance, but there is not sufficient evidence to support their use.
- The results of vitamin D supplementation trials are not conclusive in assessing the potential benefits that vitamin D might have on cognition.
Nutritional interventions and cognitive-related outcomes in patients with late-life cognitive disorders: A systematic review
Solfrizzi V et al. • Neuroscience and biobehavioral reviews (2018)
All rights reserved.
- Antioxidant-rich foods (nuts, grapes, cherries) and fatty acid supplementation, mainly n-3 polyunsaturated fatty acids (PUFA), improved specific cognitive domains and cognitive-related outcomes in MCI, mild-to-moderate dementia, and AD.
- All rights reserved.
- Further research warranted to confirm findings
Deficiency of B vitamins in women of childbearing age, pregnant, and lactating women in Brazil: a systematic review
de Macedo TSG et al. • Systematic reviews (2025)
There is a clear need for more robust studies across all Brazilian regions to improve understanding of vitamin deficiency rates and to support effective nutritional interventions.
- B12 deficiency prevalence varied widely, reaching up to 29.4%.
- Folate deficiencies were generally low, with only one study reporting a rate as high as 37%.
- There is a clear need for more robust studies across all Brazilian regions to improve understanding of vitamin deficiency rates and to support effective nutritional interventions.
Efficacy of Vitamin B Supplementation on Cognition in Elderly Patients With Cognitive-Related Diseases
Zhang DM et al. • Journal of geriatric psychiatry and neurology (2017)
However, it did not translate into cognitive improvement, indicating that the existing data on vitamin B-induced improvement in cognition by lowering homocysteine levels are conflicting.
- The results reveal that the intervention group achieved significantly greater reduction in homocysteine levels than the control (pooled difference in means = -3.625, 95% confidence interval [CI] = -5.642 to -1.608, P < .001).
- However, no significant difference in MMSE (pooled difference in means = 0.027, 95% CI = -0.518 to 0.573, P = 0.921) was observed between the groups.
- Taken together, vitamin B supplementation was effective in reducing serum homocysteine levels.