❓How should vegetarians get Omega-3? Is flaxseed oil enough?

Flaxseed, chia seeds, and walnuts contain ALA (a short-chain omega-3), and your body can convert a small amount of it into EPA/DHA (the long-chain forms found in fish), but the conversion rate is low — only about 5-10%. For everyday use: flaxseed needs to be ground to be absorbed well (whole seeds basically pass through undigested — buy ground flaxseed or grind it yourself fresh, and refrigerate after opening). About 1-2 tablespoons of ground flaxseed plus a small handful of walnuts a day is generally enough. If you're specifically concerned about DHA/EPA itself (say, during pregnancy or breastfeeding, or you just want to play it safe), you can go with an algae-oil DHA supplement — algae is actually the original source fish get their DHA from, so it's vegetarian-friendly and there's no concern about heavy metal accumulation.