If you're a healthy young adult, taking a high-purity fish oil supplement might improve your blood fat levels faster than a lower-purity one — and you could see changes in just four weeks.

If you're a healthy young adult, taking a high-purity fish oil supplement might help your body absorb more of the good omega-3s (like EPA and DHA) into your red blood cells compared to a lower-purity version—even if the difference in dose is pretty small.

When healthy young men take a specific form of omega-3 fatty acids bound to medium-chain triglycerides for eight weeks, their blood shows a higher ratio of EPA to arachidonic acid than when they take the same fatty acids in a simple mixed form.

Taking high-quality fish oil pills with more of a certain form (called re-esterified triglycerides) leads to higher levels of a healthy fat called DPA in your blood cells after four months, compared to lower-quality ones.

Fish oil supplements with over 95% re-esterified triglycerides (a type of fat form) seem to get more omega-3s into your blood cells after 16 weeks than those with less than 70%, so this might be a good sign of a better-quality supplement.