Taking omega-3s and B-vitamins can lower a substance in your blood called homocysteine, but that doesn't mean you're any less likely to have a heart problem or brain disease — the research doesn't show a connection.

We analyzed the available evidence and found that taking omega-3s and B-vitamins does lower homocysteine levels in the blood [1]. Homocysteine is a substance that, at high levels, has been linked in some studies to increased risk of heart and brain conditions. But lowering it doesn’t appear to change your actual risk of those diseases. The evidence we’ve reviewed shows no connection between reducing homocysteine through these supplements and a lower chance of developing heart or brain disease [1]. While 48 studies or assertions support the idea that these nutrients reduce homocysteine, none of them show that this reduction leads to better health outcomes in terms of disease prevention. We haven’t found any research that contradicts this — but we also haven’t found any that say lowering homocysteine helps. So far, the evidence suggests that while the mechanism works — the body responds to these supplements by lowering homocysteine — the expected benefit to your heart or brain doesn’t follow. This doesn’t mean the supplements are useless in other ways, but based on what we’ve seen, they don’t appear to protect against heart or brain disease by lowering homocysteine. If you’re taking them for this reason, the current evidence doesn’t support that goal.