People who take the highest dose of fish oil for six months end up with more oxidized fat in their red blood cells than those taking a low dose — even if they started with the same level of...

After one month of taking high-dose fish oil, your red blood cells temporarily get more of a protective antioxidant called alpha-tocopherol, which helps them resist damage from oxidation.

After six months of high-dose fish oil, the protective antioxidant in red blood cells drops back down, and the cells become more easily damaged by oxidation — and the higher the dose, the worse it gets.

Fish oil can help protect your blood cells from damage at first, but if you take a lot for a long time, it ends up making them more fragile — and how much you take and how long you take it both matter.