Do B vitamins (folic acid, B6) help your heart and brain?
Studies show that B vitamins can slightly slow cognitive decline in older adults and probably reduce the risk of stroke. In people with a varied diet and no existing conditions, a clear benefit has not been demonstrated.
B vitamins lower homocysteine, a substance in the blood that, at high levels, is strongly linked to a greater risk of dementia and stroke. Low folic acid levels are linked to an almost twice as high chance of developing dementia. That is a striking association, but it has not been proven to be a cause.
For the brain, the picture is nuanced. Supplements containing B6, B9 (folic acid) and B12 give older adults a small but reliable benefit for cognitive function. The effect is modest: on average just under a quarter of a point on a scale of thirty. People who already have dementia notice no benefit at all. In cognitively healthy people, well-designed studies have found no effect on preventing decline. Getting folic acid through ordinary food is linked to less dementia, but that is not proof that a supplement does the same.
For the heart, the balance is less favourable than you might hope. Folic acid probably reduces the risk of stroke, but the effect varies depending on diet. In people who already eat a well-varied diet with plenty of folic acid, the benefit has not been demonstrated. In people with a narrowed coronary artery, a combination of B vitamins measurably lowers homocysteine and reduces the chance of re-narrowing after a procedure, but it does not prevent heart attacks or death from heart disease. For heart and blood vessel health in general, there is no convincing evidence of benefit. Niacin (vitamin B3) combined with a statin actually increased deaths from all causes, which is a serious safety signal.
The advice therefore depends strongly on your situation. If you are healthy and eat a varied diet, there is little reason to take extra B vitamins for your heart or brain. If you have raised homocysteine or an increased risk of stroke, folic acid supplements are worth discussing with your doctor. People with coronary artery disease were given a combination of folic acid, B6 and B12 in studies; discuss this with your doctor before starting on your own. Niacin in combination with a statin is best not taken on your own initiative.
This answer draws on several large analyses combining dozens of studies. The level of certainty varies by outcome. For cognition in older adults, the authors of the most recent combined analysis concluded that, after accounting for weaker studies, there is high certainty that a small benefit exists. An earlier analysis, however, found low to very low certainty for the large majority of cognitive outcomes. For heart and blood vessel health, researchers rated the evidence as moderate to low. For blood clots, the evidence is too contradictory to draw a conclusion. In short: findings frequently align, but certainty is limited for most questions, and for healthy people with a good diet the practical gain has not been demonstrated.
Are calcium supplements bad for your heart?
Calcium supplements may be associated with an increased heart risk, but not all studies confirm this. It is best to get calcium from your diet, and discuss with your doctor whether a supplement is truly necessary for you.
Is the Mediterranean diet really good for your heart, and why?
For people at increased heart risk, the Mediterranean diet is the best-supported dietary choice currently available. Both large studies in people and dozens of population studies confirm a lower risk of heart attack and stroke.
Do omega-3 (fish oil) supplements benefit my heart?
Fish oil reliably lowers triglycerides and can slightly reduce the risk of a heart attack in people with existing heart disease or high risk, but it does not demonstrably lower the overall risk of death. Always discuss its use with your doctor if you have a condition or are on medication.
Does CoQ10 help your heart or your energy levels?
CoQ10 may be worthwhile in heart failure: several studies show fewer deaths and fewer hospital admissions. Discuss its use with your doctor if you have heart failure or take statins.
Is coffee good or bad for your heart?
For most healthy adults, three to four filtered cups per day is associated with a beneficial effect on the heart and blood vessels. Pregnant women are an important exception: for them, the maximum is around two cups per day.
Is a high homocysteine level bad for my heart?
High homocysteine is clearly associated with a greater risk of heart disease. Whether you lower the level with B vitamins makes no difference to your heart risk, at least for now.