Taking omega-3s and B-vitamins can lower a substance in your blood called homocysteine, but how much it goes down depends on how much you take, how long you take it, and how healthy you were to begin with.

We analyzed the available evidence and found that taking omega-3 fatty acids and B-vitamins is associated with lower levels of homocysteine in the blood, but the amount of reduction varies [1]. Homocysteine is a compound that, at high levels, has been linked to increased risk for heart-related issues, though its exact role is still being studied. What we’ve found so far suggests that the effect depends on how much of these nutrients you take, how long you take them, and your starting health status [1]. For example, people with higher initial homocysteine levels or certain health conditions may see a more noticeable drop than those who are already healthy. The evidence we’ve reviewed does not show a one-size-fits-all response — some people see small changes, others see larger ones, and the reasons aren’t fully clear yet. We did not find any studies that contradicted this pattern, but we also don’t have enough detail to say exactly how much of each nutrient is needed for a specific result. The number of studies supporting this is high, but the quality and design of those studies vary, and we can’t yet say whether the drop in homocysteine leads to better health outcomes. Our current analysis shows that combining omega-3s and B-vitamins may help reduce homocysteine, but the effect isn’t guaranteed or uniform. If you’re considering this for your health, it’s worth talking with a provider — especially if you have existing conditions or are taking other supplements or medications.