B Vitamins And The Risk Of A Stroke

A stroke occurs when the brain is deprived of blood and oxygen, causing brain cells to die. This can be due to a blockage or other interference with the flow of blood from the heart to the brain.

The World Health Organization defines stroke as impairment of cerebral function in either one area of the brain (e.g., weakness in one arm) or in many areas (e.g., affecting consciousness or other cognitive functions)

A stroke can be either ischemic or hemorrhagic. 

• An ischemic stroke is when a blood clot (thrombus or embolus) blocks or restricts an artery supplying blood to the brain, depriving neural tissue of vital oxygen and glucose.
• A hemorrhagic stroke is when a blood vessel ruptures and causes blood to pass into brain tissue (intracerebral hemorrhage) or the area around it (subarachnoid hemorrhage). The blood damages brain cells and increases pressure within the cranium.

When the brain is deprived of oxygen, signs can appear very suddenly. It is critical that these signs are recognized and action is taken as soon as possible.

Typical signs may include:

• Sudden paralysis and being unable to move the arms, legs, or hands. Weakness and tingling in the limbs, as if they have gone to sleep. 
• Drooping on one side of the face. 
• Dizziness
• Swaying, loss of balance, a feeling of ‘spinning’
• Difficulty walking 
• Mumbling, slurred speech, and struggling to put words together
• Confusion
• Impaired field of vision on one side, or unable to see through one eye at all. 
• Severe headache, usually due to bleeding in the brain.
• Nausea and vomiting

The acronym B.E.F.A.S.T. was created to help with recognizing stroke symptoms. This refers to Balance issues, Eyes (impaired vision), Face drooping, Arm weakness, Difficulty with speech, Time to call emergency services. 

The major risk factors for stroke in both men and women include:

• Hypertension (high blood pressure)
• High low-density lipoprotein (LDL) cholesterol
• Elevated homocysteine
• Older age
• Family history
• Diet (especially high salt consumption)
• Low physical activity
• Nutritional deficiencies, especially folate and B12
• Being overweight or obese 
• Diabetes mellitus type 2
• Smoking
• Drug and alcohol use
• Heart disease
• Patent foramen ovale (a small opening between the upper chambers of the heart that remains throughout adulthood) 
• Stress
• Genetic variants, including the MTHFR C667T mutation

• Oral contraceptives (birth control) and hormone replacement therapy have been associated with a higher risk of stroke, as estrogen increases production of clotting factors in the blood, which then increases risk of thromboembolism or clots in cerebral blood vessels¹
• Pregnancy increases blood volume, cardiac output, and viscosity of blood
• Reduced estrogen following menopause can lead to higher LDL cholesterol, weight gain, insulin resistance, and changes in clotting factors

• Men are at greater risk of stroke, especially in older age
• Hypertension, diabetes, and obesity is often higher in men than women²
• Smoking and excessive drinking is a significant risk factor among males
• Obstructive sleep apnoea is more prevalent in men and is associated with higher stroke risk through intermittent hypoxia, high blood pressure, and arrhythmia.
• Low endogenous testosterone is associated with a higher incidence of ischemic stroke³

B12 is required for reducing homocysteine, an amino acid produced naturally in the body that can cause inflammation and blood vessel damage when in excess. Deficiency in B12 can lead to increased levels of homocysteine in the blood, which damages the endothelium, promotes oxidative stress, and increases blood viscosity. All of these factors increase risk of ischemic stroke.⁴
Correcting B12 deficiency with high-dose B12 supplementation is shown to reduce homocysteine, oxidative stress, and other pro‑thrombotic factors associated with stroke. A 2021 meta‑analysis of eight randomized trials (8,513 stroke patients) found that supplementation with vitamins B6, folate, and B12 significantly reduced homocysteine and reduced overall risk of stroke, myocardial infarction, and vascular damage.⁵

B12 may also help to support recovery from stroke. A 2026 study involving ischemic stroke patients found that B12 supplementation improved neurological recovery and fibrotic remodeling, which is essential for overall brain cell repair after stroke.⁶ The researchers concluded that vitamin B12 helps to regulate the expression of RUNX2 (runt-related transcription factor 2), a master transcription factor that plays a critical role in brain repair.

Folate (vitamin B9) works alongside B12 in the conversion of homocysteine to methionine.
Several epidemiological studies have linked folate deficiency with elevated homocysteine, resulting in an increased risk of vascular disease and ischemic stroke.⁷ Folate deficiency may also lead to faulty DNA and chromosomal breakage, which can then cause neuronal damage.⁸
A 2023 study found that almost one in three ischemic stroke survivors has folate deficiency, and that their risk of further cardiovascular events would increase without folate intake.⁹

A 2024 meta-analysis of 24 studies found that high dietary folic acid intake (from fortified foods) was associated with a 17% reduction in stroke incidence. The effect of folic acid was greater in populations with low folate levels.¹⁰ The study authors emphasized the role of folate in reducing risk of stroke and other cardiovascular issues.

A 2024 meta‑analysis of 21 randomized clinical trials worldwide found that supplementation with folic acid reduced overall stroke risk by around 10%.¹¹ Similarly, a 2025 NHANES analysis found that higher intake of dietary folate (at least 250 µg/day) was associated with significantly lower incidence of self‑reported stroke. The researchers suggested that this was due to reduced inflammation and lower homocysteine.¹²

Current research has mostly focused on folic acid as a preventative for stroke. However, a 2022 study found that it may have some restorative effects on the post-stroke brain. Folic acid supplementation was found to significantly improve cognitive performance, reduce neuronal death, increase synapse numbers, and upregulate pre- and post-synaptic proteins. By strengthening synaptic functions, folic acid helped to improve cognitive dysfunctions and ameliorates brain injury.¹³

A 2024 study involving zebrafish found that methylfolate supplementation reduced motor dysfunction, decreased neuroinflammation and neuronal apoptosis, inhibited blood coagulation, and lowered oxidative stress markers while increasing the activity of glutathione peroxidase and superoxide dismutase (SOD), two major antioxidant enzymes. This was the first study to specifically test methylfolate rather than folic acid supplementation in stroke recovery, with the authors suggesting that methylfolate may be a therapeutic option.¹⁴

Vitamin B6 (PLP) is an essential cofactor for cystathionine beta-synthase (CBS) and cystathionine γ-lyase, the two enzymes that convert homocysteine into cysteine via the transsulfuration pathway. Without adequate PLP, homocysteine levels increase, which can then lead to endothelial damage and platelet aggregation.¹⁵ This study also found that PLP levels may predict stroke risk more accurately than CRP, hypertension, or diabetes. B6 suppresses pro-inflammatory cytokines, including IL-6 and TNF-α, which drive the endothelial dysfunction that can lead to both ischemic and hemorrhagic stroke.

A 2024 study found that low serum pyridoxal-5′-phosphate (PLP) was associated with significantly higher odds of stroke, indicating that higher PLP may have a protective effect on cardiovascular health and stroke risk.¹⁶