Taking a daily omega-3 supplement for about five years doesn't seem to lower the chance of getting invasive cancer in healthy people over 50.

We analyzed the available evidence on whether omega-3 supplements prevent cancer in older adults, and what we’ve found so far suggests that taking a daily omega-3 supplement for about five years doesn’t appear to lower the chance of developing invasive cancer in healthy people over 50 [1]. This conclusion is based on one assertion that was supported by 74.0 studies or data points, with no studies contradicting it. The evidence doesn’t show that omega-3s cause cancer or make it worse — it simply doesn’t show a protective effect either. We’re looking at a group of people who were otherwise healthy and didn’t have a history of cancer. The studies tracked cancer outcomes over five years, which is a meaningful timeframe, but cancer can develop over longer periods, and we don’t have data beyond that. We don’t know if omega-3s might help people with certain genetic risks, or if different doses or types of omega-3s could make a difference. The current evidence only covers one scenario: daily supplements in healthy older adults. It’s also worth noting that while 74.0 data points support this finding, we only reviewed one specific assertion. That means we haven’t looked at every possible way omega-3s might interact with cancer risk — just this one question in this one group. If you’re an older adult considering omega-3 supplements for cancer prevention, the evidence we’ve reviewed so far doesn’t support that as a reason to start them. But that doesn’t mean they’re useless — they may still help with other things like heart health or inflammation. What matters most is choosing supplements for reasons the evidence actually supports, not for ones it doesn’t.