What's inside tuna, and where does it go in your body?
Lean protein with selenium, B12 and niacin. Larger tuna species contain more mercury.
Mercury
Canned light (skipjack) is a 'best choice'; albacore is a 'good choice' — the FDA suggests fewer servings of it for pregnant people and children.
Evidence & sources
FDA lists canned light tuna as a 'best choice' and albacore tuna as a 'good choice' for people who are pregnant or breastfeeding and young children. Evidence: regulatory. Known: Based on mercury levels. Unknown: — Source: US FDA / EPA, Advice about Eating Fish (Current revision).