Vitamin B12 may not protect the heart, but it could play a role in stroke prevention

Cardiovascular disease remains the world’s leading cause of death, according to the World Health Organization.

Research has long shown that heart-healthy habits, including a balanced diet, can help reduce the risk of cardiovascular disease.

Scientists have also studied whether specific nutrients — including vitamins C, E, D, and B vitamins such as vitamin B12 — may influence heart disease risk.

“Vitamins play essential roles in many processes that help maintain cardiovascular health, including the normal functioning of blood vessels and the regulation of certain metabolic pathways,” Ameer Awashra, MD, a medical doctor in the Department of Medicine at An-Najah National University in Nablus, Palestine, told Medical News Today.

“Studying these relationships is important because nutritional deficiencies are potentially preventable and treatable. However, we also need to understand whether correcting these deficiencies actually reduces the risk of heart attacks, strokes, and other cardiovascular complications,” Awashra noted.

He is the lead author of a new review in Nutrition Journal that found vitamin B12 may affect heart health in some ways, but supplementation does not consistently prevent major cardiovascular events.

Researchers did, however, find the strongest evidence for a possible clinical benefit of vitamin B12 supplementation in stroke prevention.

Why focus on vitamin B12?

For the review, researchers examined previous studies on vitamin B12 and cardiovascular health.

“We focused on vitamin B12 because of its essential role in homocysteine metabolism and other processes involved in maintaining vascular health,” Awashra said.

“Previous observational studies have linked low vitamin B12 levels with an increased risk of cardiovascular disease. However, clinical trials investigating vitamin B12-containing supplementation have not consistently demonstrated that correcting these abnormalities prevents cardiovascular events.”

– Ameer Awashra, MD

“This difference between what we observe in laboratory measurements and what we see in actual patient outcomes caught our attention,” he continued. “We wanted to examine the available evidence more closely, understand why these findings sometimes disagree, and identify which patients might benefit most from vitamin B12 assessment and supplementation.”

Vitamin B12 supplements do not always prevent heart disease

The review concluded that vitamin B12 may influence heart health, but taking it as a supplement did not consistently produce broad clinical benefits or reliably prevent major heart disease events.

“I believe this is one of the most important messages of our review: improving a laboratory measurement does not necessarily translate into better clinical outcomes,” Awashra explained. “For example, vitamin B12-containing supplementation can reduce homocysteine levels, which have been associated with cardiovascular risk.”

“The practical implication is that vitamin B12 supplementation remains important for individuals with a confirmed deficiency, but current evidence does not support routinely taking additional vitamin B12 solely to prevent cardiovascular disease,” Awashra added.

Vitamin B12 may help prevent stroke

Scientists found that the most promising clinical benefit of vitamin B12 supplementation for cardiovascular health may be stroke prevention.

“This finding suggests that the potential cardiovascular benefits of B-vitamin supplementation may depend on a person’s underlying nutritional status and the environment in which they live,” Awashra said.

“Studies have shown a more noticeable reduction in stroke risk in populations where folic acid fortification is not mandatory, possibly because individuals in these regions are more likely to have lower baseline folate levels,” he added.

“Importantly, most of these studies evaluated combinations of B vitamins, particularly folic acid, vitamin B12, and vitamin B6,” Awashra told us.

“Therefore,” he continued, “we cannot conclude that vitamin B12 alone is responsible for the observed reduction in stroke risk. The significance is that nutritional interventions may be more effective when directed toward populations with specific nutritional needs rather than being recommended universally.”

Why might vitamin B12 affect stroke risk?

MNT also spoke with Cheng-Han Chen, MD, a board-certified interventional cardiologist and medical director of the Structural Heart Program at MemorialCare Saddleback Medical Center in Laguna Hills, CA, about the review.

Chen, who was not involved in the study, said it is not entirely clear why vitamin B12 supplementation may be linked to a lower risk of stroke but not a lower risk of heart disease.

One possible explanation, he said, is that these conditions develop through different, though sometimes overlapping, biological pathways.

“Vitamin B12 helps regulate homocysteine, an amino acid that, at elevated levels, has been associated with vascular problems,” Chen explained.

“However, lowering homocysteine does not necessarily reduce the risk of all cardiovascular events equally. More research is needed to determine whether B12 has a meaningful protective effect against stroke in certain populations and why that effect may not extend to other forms of cardiovascular disease,” he pointed out.

A reminder to look beyond associations

MNT also spoke with Monique Richard, MS, RDN, a registered dietitian nutritionist and owner of Nutrition-In-Sight, who also was not involved in the review.

Richard said the findings are a useful reminder that researchers need to look beyond associations and consider what the evidence actually shows.

“Vitamin B12 is essential for neurological function, healthy red blood cell formation, DNA synthesis, and the metabolism of homocysteine, an amino acid associated with cardiovascular risk. It makes biological sense that B12 deficiency could have implications for vascular health, but that does not necessarily mean supplementing everyone will prevent heart disease.”

– Monique Richard, MS, RDN

However, “a supplement is only one part of the equation,” she pointed out. “We need to consider the person, the reason for supplementation, the form and dose, consistency of use, and whether the intervention addresses the underlying issue.”

“Correcting a deficiency is important, but we should not promise cardiovascular protection that clinical trials have not consistently demonstrated,” Richard advised.

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