Older mice have less of a healthy fat called DHA in their blood and brain than younger mice, but giving them fish oil helps bring those levels back up.

We analyzed the available evidence and found that giving fish oil to older mice appears to increase DHA levels in their blood and brain. All nine studies or assertions we reviewed support this observation, with none contradicting it [1]. Older mice naturally have lower levels of DHA — a type of omega-3 fat important for brain and cell function — compared to younger mice. When these older mice were given fish oil, which contains DHA, their levels rose closer to those seen in younger animals. This suggests fish oil may help restore DHA that declines with age in mice. We did not find any evidence showing that fish oil had no effect or made DHA levels worse. The pattern across all reviewed reports consistently showed an increase in DHA after fish oil was given. However, we only reviewed assertions based on mouse studies, and we don’t know how this translates to humans or whether the changes lead to noticeable health improvements. What we’ve found so far points to fish oil as something that raises DHA in older mice, but we can’t say why or how much it matters for their overall health. More research would be needed to understand the long-term effects or whether similar results happen in other animals or people. If you’re considering fish oil for an aging pet or for your own health, this mouse data suggests it may help raise DHA — but it’s not proof it will change how you or your pet feel or function.