We use essential cookies (authentication, your saved goals/stack) by default. With your permission we'll also enable privacy-respecting analytics (Vercel Web Analytics, anonymous load-time metrics) and error-replay diagnostics (Sentry — DOM snapshots only when an error fires) so we can fix bugs faster. Learn more
Bcx9.0
B-Complex Research
Probably helpsHigh safety
39 peer-reviewed studies
What the evidence says
Probably helps
B-Complex helped in about half (5/8) of the studies that measured an effect — promising, but not unanimous.
Most evidence is from high-quality meta-analyses and randomised trials published 2006–2025 with a typical study size of 1,925 participants.
Based on 39 studies · 22 meta-analyses · 11 RCTs · 417,797 total participants
Confidence
High
What the studies found
5helped3unclear· 31 more without graded effect data
By outcome
Neuroprotection & brain aging
Probably helps34 studies
Cognitive functionB vitamins essential for homocysteine metabolism and cognitive health · 4-8 weeks
Probably helps25 studies
Heart & blood pressure
Mostly mechanism / observational11 studies
Anxiety & stressB-vitamin status linked to stress resilience and GABA synthesis · 4-8 weeks
Mostly mechanism / observational3 studies
Depression & moodBetter mood and reduced fatigue · 4-8 weeks
Too few graded studies2 studies
Therapeutic & clinical
Too few graded studies1 study
Safety profile
Too few graded studies1 study
By the numbers
Pulled from 20 studies with measurable effects
Likely real effects
67%
across studies
People studied
418k
typical study: 1925 people
Strongest designs
33
22 pooled, 11 randomised
Showed benefit
63%
5/8 studies
How long studies ran
3+ months
3
Populations Studied
Older adults2
Adults in areas without/with partial folic acid fortification1
Cancer patients1
Non-dementia population1
Active research area
14 studies in the last 5 years · Latest meta-analysis: 2025
200620152025
1Global cognitive function improvementMeta-AnalysisCited 4×n=5,275 · very large study2025
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.
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.
2Stroke risk reductionMeta-AnalysisCited 12×n=76,664 · very large study2024
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.
Zhang N et al. · The American journal of clinical nutrition (2024)
Large benefit
← WorseNo effectBetter →
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).
3Cognitive function improvementMeta-AnalysisCited 8×n=42,768 · very large study2024
While mandatory FA fortification has the improved folic acid status, additional folate-based B vitamin supplements do not appear to influence cognitive function.
Zhang L et al. · Nutrients (2024)
Barely noticeable benefit
← WorseNo effectBetter →
Likely real
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).
4Safety and efficacy in cancer treatmentsSystematic ReviewCited 11×n=1,200 · large study2024
In this systematic review we concluded that B vitamin supplements have varying data regarding safety and efficacy in cancer.
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.
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.
5Cognitive decline preventionMeta-AnalysisCited 100×n=46,175 · very large study2022
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.
Wang Z et al. · Nutrition reviews (2022)
Noticeable benefit
← WorseNo effectBetter →
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.
6Stress reductionMeta-AnalysisCited 67×n=2,015 · very large study2019
B vitamin supplementation may particularly benefit populations who are at risk due to (1) poor nutrient status or (2) poor mood status.
Young LM et al. · Nutrients (2019)
Noticeable benefit
← WorseNo effectBetter →
Likely real
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.
7Cognitive function improvementMeta-AnalysisCited 70×n=1,925 · large study2019
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.
Ford AH et al. · Drugs & aging (2019)
No clear effect
← WorseNo effectBetter →
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.
8Major adverse cardiovascular events (MACE)Meta-AnalysisCited 31×n=57,952 · very large study2014
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.
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.
9Meta-AnalysisCited 66×n=3,089 · very large study2013
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.
Hankey GJ et al. · Stroke (2013)
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).
10Meta-AnalysisCited 14×n=57,143 · very large study2013
Our study indicates that B-vitamin supplementation is not associated with a lower risk of stroke based on relative and absolute measures of association.
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.
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.
11Meta-AnalysisCited 79×n=54,913 · very large study2013
B vitamin supplementation for homocysteine reduction significantly reduced stroke events, especially in subjects with certain characteristics who received appropriate intervention measures.
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.
12Meta-AnalysisCited 89×n=47,921 · very large study2012
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.
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.
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.
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.
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.
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.
Zhang DM et al. · Journal of geriatric psychiatry and neurology (2017)
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.
B vitamin supplementation might not be effective in preventing fracture and improving bone turnover.
Ruan J et al. · Medical science monitor : international medical journal of experimental and clinical research (2015)
B vitamin supplementation might not be effective in preventing fracture and improving bone turnover.
However, the possible benefits in selective populations, such as populations with very high plasma Hcy and from regions without B vitamin fortification should be explored in the future.
Similarly, folic acid alone or vitamins B in combination are unable to stabilize or slow decline in cognition, function, behavior, and global change of AD patients.
Li MM et al. · Current Alzheimer research (2014)
Collectively, weak evidence of benefits was observed for the domains of memory in patients with MCI.
Nevertheless, future standard RCTs are still needed to determine whether it was still significant in larger populations.
However, the data does not yet provide adequate evidence of an effect of vitamins B on general cognitive function, executive function and attention in people with MCI.
It remains to be established if prolonged treatment with B-vitamins can reduce the risk of dementia in later life.
Ford AH et al. · Journal of Alzheimer's disease : JAD (2012)
B-vitamin supplementation did not show an improvement in cognitive function for individuals with (SMD = 0.10, 95%CI -0.08 to 0.28) or without (SMD = -0.03, 95%CI -0.1 to 0.04) significant cognitive impairment.
Supplementation of vitamins B12, B6, and folic acid alone or in combination does not appear to improve cognitive function in individuals with or without existing cognitive impairment.
It remains to be established if prolonged treatment with B-vitamins can reduce the risk of dementia in later life.