Canned Tuna (in Brine)
Food · Protein · Food, Typed Supps
Twenty-six grams of protein, 752 mg of omega-3, and a mercury question worth answering properly.
Stage by stage
- Brine or water (The tin): 400 mg of sodium per 100 g in brine; springwater versions carry far less.
- Protein density (Muscle): 26.1 g on 129 calories — among the best ratios in the library.
- Selenium (Systemic): 72.6 mcg per 100 g, above a full day, and it binds mercury tightly.
- Omega-3 (Brain): 752 mg per 100 g, incorporated into membranes over weeks.
Timing
Nothing to time. Mercury is assessed as a weekly average because its half-life is around 50 days, so a single meal is never the unit of concern.
Time to effect
- 4–12 weeks: Omega-3 membrane status responds to consistent intake.
- ~50 days: Methylmercury half-life, which is why guidance is weekly.
Allergens
Contains: Fish. Derived from what this food is, not from a product label.
Eating patterns
Fits: Pescatarian, Kosher, Low-FODMAP, Gluten-free. Depends on the product: Halal, Keto.
Satiety
201 on the satiety index, where white bread is 100 — very high. Modelled from the Holt et al. (1995) measurements.
Environmental footprint
13.6 kg CO2e and 3691 litres of freshwater per kg, matched to "Fish (farmed)" in Poore & Nemecek (2018), Science 360.
Cost band
Pricey — roughly £20 per kg, as a band midpoint rather than a price.
Key nutrients
Nutrition per 100g
- Calories: 129
- Protein: 26.1g
- Fat: 2.6g
- of which saturated: 1g
- Sodium: 400mg
Food vs. supplement
Fish oil capsules deliver omega-3 and nothing else. A tin of tuna delivers the same omega-3 alongside 26 g of protein, a full day of selenium, iodine and B12 — which is why the fish is recommended in guidelines and the capsule is not.
Kitchen tip
Buy it in springwater rather than brine. The protein and omega-3 are identical and the sodium is a fraction.
Common myth
“Avoid tuna in pregnancy because of the mercury.” In reality: FSANZ advice is species-specific, and canned tuna is not the concern — shark, marlin and swordfish are, at one serve a fortnight. Most fish including canned tuna is fine at two to three serves weekly. Avoiding fish altogether in pregnancy costs the omega-3 a developing brain uses and the iodine requirement that rises during pregnancy, in exchange for nothing.
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