Vitamin B complex
Summary
Pooled trials found a small reduction in stress scores but no clear effect on depression or anxiety (grade C). High-dose folic acid, B6 and B12 lowered homocysteine without reducing the combined rate of cardiovascular death, heart attack and stroke, and in diabetic kidney disease they worsened kidney function. High-dose B6 has been linked to nerve damage.
Key facts
- Small benefit for stress (SMD 0.23, n = 958); depression and anxiety not significantly changed[1]
- Folic acid 2.5 mg + B6 50 mg + B12 1 mg for 5 years: no fewer cardiovascular events (RR 0.95, n = 5,522)[3]
- High-dose B vitamins sped GFR loss (−5.8 mL/min) and doubled vascular events in diabetic nephropathy[4]
- 90 Dutch reports of neuropathy linked to B6 supplements containing 1.4–100 mg per tablet[6]
- The stress meta-analysis was partly funded by Bayer Healthcare[1]
- 5 graded human outcomes on this page
- October 13, 2026
How it works
EstablishedB vitamins act as coenzymes in energy metabolism and one-carbon metabolism; folic acid, B6 and B12 together lower blood homocysteine, which is the rationale for heart and brain trials.[3][5]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
At a glance: strongest evidence per outcome
| Outcome | Grade | Effect | Strongest evidence | Rows |
|---|---|---|---|---|
| Mood | Grade C | Mixed | Meta-analysis of 16 trials · n = 2,015 · 2019 | 2 rows |
| Kidney | Grade C | Worsened | RCT · n = 238 · 2010 | 1 row |
| Brain | Grade C | Improved | RCT · n = 168 · 2010 | 1 row |
| Heart | No effect | No effect | RCT · n = 5,522 · 2006 | 1 row |
Every graded row
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| Stress, depressive symptoms and anxiety | Mixed | Grade C | Meta-analysis · n = 2,015 · 2019 Healthy and at-risk adults in 16 RCTs (12 meta-analysed) Form: Supplements with at least 3 B vitamins · Dose: Varied by trial · Duration: ≥4 weeks Stress improved (SMD 0.23, 95% CI 0.02–0.45; n = 958); depressive symptoms did not reach significance (SMD 0.15, P = 0.07) and anxiety was unchanged (SMD 0.03). | 31527485 (opens PubMed)Source [1] |
| Kidney function and vascular events in diabetic nephropathy | Worsened | Grade C | RCT · n = 238 · 2010 Adults with type 1 or 2 diabetes and diabetic nephropathy (Canada) Form: Folic acid + vitamin B6 + vitamin B12 · Dose: 2.5 mg folic acid, 25 mg B6, 1 mg B12 daily · Duration: Mean 31.9 months GFR fell 16.5 vs 10.7 mL/min/1.73 m² at 36 months (difference −5.8); heart attack, stroke, revascularisation and death were more common (HR 2.0, 95% CI 1.0–4.0). | 20424250 (opens PubMed)Source [4] |
| Rate of brain shrinkage in mild cognitive impairment | Improved | Grade C | RCT · n = 168 · 2010 Adults over 70 with mild cognitive impairment (UK; MRI subset) Form: Folic acid + vitamin B6 + vitamin B12 · Dose: 0.8 mg folic acid, 20 mg B6, 0.5 mg B12 daily · Duration: 24 months Whole-brain atrophy 0.76% per year vs 1.08% with placebo. | 20838622 (opens PubMed)Source [5] |
| Work-related strain and mood | Improved | Grade D | RCT · n = 60 · 2011 Employed adults with work stress (Australia) Form: High-dose vitamin B complex (two formulations) · Dose: Daily high-dose B complex · Duration: 90 days Lower personal strain and less confusion and depressed mood at 12 weeks after adjusting for personality and work demands; no changes in other mood or anxiety measures. | 21905094 (opens PubMed)Source [2] |
| Cardiovascular death, heart attack and stroke | No effect | No effect | RCT · n = 5,522 · 2006 Adults 55+ with vascular disease or diabetes Form: Folic acid + vitamin B6 + vitamin B12 · Dose: 2.5 mg folic acid, 50 mg B6, 1 mg B12 daily · Duration: Mean 5 years Homocysteine fell 2.4 µmol/L, but the composite of cardiovascular death, heart attack and stroke was unchanged (18.8% vs 19.8%; RR 0.95, 95% CI 0.84–1.07). Stroke alone was less frequent (RR 0.75) and hospitalisation for unstable angina more frequent (RR 1.24). | 16531613 (opens PubMed)Source [3] |
Forms
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| B-50 or B-100 style complexes | Varies[1] | Amounts vary widely by brand; compare the B6 content with the upper limits.[7] | The B6 content is the main concern: neuropathy reports involved products with 1.4–100 mg per tablet.[6] | Mood and stress trials |
| Folic acid, B6 and B12 combinations | Varies[3][5] | Lower homocysteine in trials.[3][5] | Higher doses worsened kidney outcomes in diabetic nephropathy.[4] | Heart, kidney and brain trials |
Studied doses
Doses studied in human trials ranged from combinations of 0.8 mg folic acid, 20 mg B6 and 0.5 mg B12 daily for 24 months to 2.5 mg folic acid, 50 mg B6 and 1 mg B12 daily for 5 years; mood trials used multi-B products for at least 4 weeks.[1][3][5]
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
Other supplements
- Other B6 sourcesCase reportStacking products raises total B6; Dutch neuropathy reports involved products with as little as 1.4 mg per tablet up to 100 mg.[6]
Who should be careful
- Diabetic kidney disease
- High-dose folic acid, B6 and B12 worsened GFR decline and increased vascular events in the DIVINe trial.[4]
- Tingling or numbness
- Peripheral neuropathy has been reported with B6-containing supplements; stop and check total B6 intake.[6]
- People expecting heart protection
- Lowering homocysteine with B vitamins did not reduce the combined rate of cardiovascular events in HOPE-2.[3]
- People taking several B6-containing products
- The US upper limit for vitamin B6 is 100 mg/day for adults; in 2023 EFSA set a much lower adult limit of 12 mg/day because of neuropathy concerns. Add up the B6 from every product you take.[7]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
Vitamin B6 and nerve damage
- Case series
- Of 90 reports to the Netherlands pharmacovigilance centre, causality assessment found it plausible that B6 supplements caused neuropathy symptoms; product amounts ranged from 1.4 to 100 mg per tablet.[6]
Frequently asked questions
Does vitamin B complex help with stress?
Pooled trials found a small improvement in stress scores, partly funded by a supplement maker; effects on depression and anxiety were not significant.[1]
Do B vitamins protect the heart?
Not overall. In 5,522 high-risk adults, folic acid, B6 and B12 lowered homocysteine but did not reduce the combined rate of cardiovascular death, heart attack and stroke; strokes alone were fewer, while hospital admissions for unstable angina rose.[3]
Can B complex be harmful?
High-dose B6 has been linked to nerve damage, and high-dose B vitamins worsened kidney function in people with diabetic nephropathy.[4][6]
Do B vitamins help memory?
One trial in mild cognitive impairment found slower brain shrinkage on MRI; this is an imaging marker, not proof of better memory.[5]
Sources
- [1]A Systematic Review and Meta-Analysis of B Vitamin Supplementation on Depressive Symptoms, Anxiety, and Stress: Effects on Healthy and 'At-Risk' Individuals.. Nutrients, 2019. meta-analysis
- [2]The effect of 90 day administration of a high dose vitamin B-complex on work stress.. Hum Psychopharmacol, 2011. RCT
- [3]Homocysteine lowering with folic acid and B vitamins in vascular disease.. N Engl J Med, 2006. RCT
- [4]Effect of B-vitamin therapy on progression of diabetic nephropathy: a randomized controlled trial.. JAMA, 2010. RCT
- [5]Homocysteine-lowering by B vitamins slows the rate of accelerated brain atrophy in mild cognitive impairment: a randomized controlled trial.. PLoS One, 2010. RCT
- [6]Vitamin B(6) in Health Supplements and Neuropathy: Case Series Assessment of Spontaneously Reported Cases.. Drug Saf, 2018. observational
- [7]Vitamin B6: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements, 2023. fact-sheet
What changed
- Editorial evidence re-review: summary, HOPE-2 row and FAQ corrected (HOPE-2 found fewer strokes and more unstable-angina admissions; only the composite was unchanged); added B6 upper limits from ODS (US 100 mg/day, EFSA 12 mg/day); removed an unsourced claim about typical B-complex amounts. Bayer part-funding of the meta-analysis confirmed in the full text.
- Second-pass self-review: every PMID re-checked against NCBI esummary (title, year, no retraction or expression-of-concern flag), every dose, n and duration re-read against the PubMed abstract or PMC full text, grades held conservative, and interactions limited to what a cited source supports.
- First draft. Source titles and years taken from NCBI E-utilities esummary; abstracts read for every evidence row.