Dr. Grey AI

B Vitamins

B vitamins (thiamine B1, riboflavin B2, niacin B3, pantothenic acid B5, pyridoxine B6, biotin B7, folate B9, cobalamin B12) are essential water-soluble vitamins involved in one-carbon metabolism—the transfer of methyl groups for DNA synthesis, neurotransmitter production, and homocysteine regulation. Folate, B12, and B6 reduce homocysteine 25-50%, but large RCTs (HOPE-2, NORVIT; n>10,000) found no cardiovascular benefit despite lowering homocysteine. Meta-analyses show modest stroke reduction (RR 0.93) with ≥3 years supplementation. For cognition, benefits limited to those with elevated homocysteine or MCI—general population shows no effect. Meta-analysis of 16 RCTs found B vitamins reduce stress (SMD 0.23) but not anxiety or depression in healthy populations. Essential for energy metabolism; deficiency causes fatigue, neurological symptoms.

Quick Answer

What it is

B vitamins (thiamine B1, riboflavin B2, niacin B3, pantothenic acid B5, pyridoxine B6, biotin B7, folate B9, cobalamin B12) are essential water-soluble vitamins involved in one-carbon metabolism—the transfer of methyl groups for DNA synthesis, neurotransmitter production, and homocysteine regulation. Folate, B12, and B6 reduce homocysteine 25-50%, but large RCTs (HOPE-2, NORVIT; n>10,000) found no cardiovascular benefit despite lowering homocysteine.

Key findings

  • Grade A: Plasma Homocysteine
  • Grade C: Stroke Risk (Stroke)
  • Grade C: Perceived Stress (Stress)

Safety

  • B12 + SSRI improved outcomes in depressed patients with low-normal B12; stroke survivors showed lower depression risk
ℹ️ Quick Facts: B Vitamins

Quick Facts: B Vitamins

  • Best Evidence:Grade C
  • Conditions Studied:5
  • Research Outcomes:8
  • Grade A Findings:1
  • Key Effect:Stroke
Outcomes by grade:
A1
B0
C4
D3
5 conditions · 8 outcomes

Detailed Outcomes

Grade:
Effect:
Size:
Sort:
|
A
Plasma Homocysteine
Folic acid 0.65-10mg/d ± B12/B6 reduces homocysteine 25-50%
20 studies
large↓Improves
C
Stroke Risk
Meta-analysis: RR 0.93 (0.86-1.00, p=0.04); benefit with ≥3 years follow-up, no folate fortification
19 studies
small↓Improves
C
Perceived Stress
Meta-analysis: SMD 0.23 (0.02-0.45, p=0.03) benefit for stress
12 studies
small↓Improves
C
Cognitive Decline
Benefits in MCI patients with high homocysteine: improved MMSE, episodic memory, slowed atrophy
5 studies
moderate↓Improves
C
Treatment Response
B12 + SSRI improved outcomes in depressed patients with low-normal B12; stroke survivors showed lower depression risk
3 studies
moderate↑Improves
D
CVD Events/Mortality
Meta-analysis: RR 0.98 (0.94-1.03) for CVD; no effect on CHD, MI, or mortality despite homocysteine lowering
19 studies
none
D
Depressive Symptoms
Meta-analysis: SMD 0.15 (-0.01-0.32, p=0.07) - trend but not significant
12 studies
none
D
Cognitive Function
Meta-analysis: no benefit in general population despite up to 7 years of supplementation
11 studies
none

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Folic Acid (Vitamin B9)

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Fish Oil

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Zinc

2 shared conditions · 148 outcomes

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