Tuna: Nutrition Facts, Health Benefits, and the Complete Mercury Guide

Canned tuna is one of the most nutritionally impressive shelf-stable foods available — at 116 calories per 100g with 26g of complete protein, 115% of daily selenium, 104% of daily B12, 66% of niacin, 23% of B6, and 33% of phosphorus, it combines an extraordinary micronutrient profile with a convenience and affordability that almost no other protein source can match. For athletes, the protein-to-calorie ratio (0.22g per calorie) sits among the very best of any food in our collection.

It also carries a mercury consideration that is the most commonly asked question about tuna in all of nutrition, and which deserves a precise, species-specific, consumption-frequency answer rather than vague warnings — because the answer varies significantly depending on which type of tuna you’re buying.

Tuna Nutrition Facts (per 100g, canned in water, drained)

Tuna Nutrition Facts (per 140g can — one standard can, drained)

A single standard can provides 161% of daily selenium, 146% of B12, and 36g of complete protein at just 162 calories — one of the most nutritionally concentrated affordable foods in existence.

Vitamins in Tuna (per 100g, canned in water)

Standout: Tuna’s vitamin profile is dominated by its extraordinary B vitamin concentration. B12 at 104% DV exceeds the full daily requirement in 100g — a genuinely unusual achievement from a canned food. Niacin at 66% DV is among the highest figures of any fish in our collection, supporting NAD and NADP coenzyme function across hundreds of metabolic reactions. B6 at 23% DV contributes to protein metabolism and neurotransmitter synthesis, fitting given tuna’s exceptional protein content.

Minerals in Tuna (per 100g, canned in water)

Extraordinary standout: Selenium at 115% DV per 100g exceeds the full daily requirement in 100g — making tuna one of the most selenium-dense foods in this entire collection. A single standard can delivers 161% DV of selenium, supporting glutathione peroxidase antioxidant defense and thyroid hormone activation comprehensively from one affordable can. Phosphorus at 33% DV supports both bone mineralization and ATP energy production.

The Mercury Question: A Complete, Species-Specific Guide

This is the single most searched question about tuna in nutrition, and the answer is genuinely important — but it requires species-specific precision rather than a blanket recommendation.

Why Tuna Contains More Mercury Than Smaller Fish

Mercury enters marine ecosystems primarily from industrial pollution. It accumulates through the food chain: plankton absorb it, small fish eat plankton and accumulate it, larger fish eat the small fish and accumulate more, and the largest, longest-lived predatory fish at the top of the marine food chain accumulate the highest concentrations. This process is called biomagnification.

Tuna, as large, long-lived, apex predators, are among the higher-mercury fish in common consumption. However, the different species of tuna vary enormously in their mercury content — and this variation is the critical practical fact for regular tuna eaters.

Species-Specific Mercury Guide

The most important practical distinction: canned light tuna and canned white/albacore tuna are nutritionally similar but meaningfully different in mercury. The data on this page (canned in water) is most representative of canned tuna in general — but if you eat tuna frequently, choosing canned light tuna (skipjack) over albacore for most servings meaningfully reduces mercury exposure at essentially no cost to the nutritional profile.

The Selenium Consideration: A Genuinely Important Nuance

This is one of the more scientifically interesting aspects of tuna mercury toxicology. Selenium and mercury have a strong chemical affinity for each other — mercury binds to selenium, and this binding significantly reduces mercury’s bioavailability and toxicity. Fish that are rich in selenium relative to their mercury content effectively “neutralize” much of the mercury’s potential harm through this binding mechanism.

Tuna’s 115% DV selenium per 100g means that for most commonly eaten tuna species, the selenium vastly exceeds the mercury on a molar basis — suggesting that the actual toxicological risk may be lower than mercury concentration measurements alone would predict. This doesn’t mean mercury concerns should be dismissed, but it is a genuinely important scientific nuance that the mercury discussion alone misses.

Practical Guidance Summary

For most healthy adults, canned light tuna (skipjack) 2–3 times per week is safe, affordable, and nutritionally excellent. Canned albacore/white tuna 1–2 times per week is appropriate for the general adult population. Pregnant women, nursing mothers, and young children should follow the more conservative guidance specific to their situation and choose canned light tuna over albacore when eating tuna regularly.

Canned in Water vs Canned in Oil

This is the second most common practical question about tuna and has a straightforward answer:

The key counterintuitive finding: canned tuna in oil may actually deliver fewer omega-3 fatty acids per serving than canned in water, because the omega-3-rich fats from the fish leach into the surrounding oil during canning, and this oil is typically drained away before eating. Canned in water retains more of the fish’s own omega-3 within the flesh.

For protein and calories, both deliver comparable protein at quite different calorie counts — water-packed is the clear choice for anyone managing calorie intake, while oil-packed offers richer texture and more calories for those in a surplus or who find the water-packed version too dry for their taste.

Health Benefits of Tuna

Full Daily Selenium From an Affordable Staple

At 115% DV per 100g — 161% DV in a standard can — tuna provides more than a full day’s selenium from one of the cheapest protein sources available. Selenium supports the glutathione peroxidase enzyme system that provides cellular antioxidant protection throughout the body, and the deiodinase-mediated conversion of thyroid hormone T4 to active T3 that governs metabolic rate.

Complete B12 in a Can

The 104% DV B12 per 100g means a single standard can covers nearly 1.5 days’ B12 requirement — supporting myelin synthesis, red blood cell formation, and the homocysteine methylation cycle that protects arterial health.

Outstanding Niacin for Energy Metabolism

At 66% DV per 100g, tuna is one of the richest niacin sources of any commonly eaten food, supporting NAD and NADP coenzyme function across the hundreds of enzymatic reactions that drive cellular energy production — directly relevant to the energy demands of training.

Exceptional Lean Protein

At 26g of complete protein for 116 calories — 0.22g per calorie — canned tuna sits among the most protein-efficient whole foods available. All 9 essential amino acids are present in strong proportions.

Phosphorus for Bone and Energy

At 33% DV per 100g, phosphorus contributes to bone mineralization alongside calcium and is a structural component of every ATP molecule in the body.

Cardiovascular Profile

At 0.8g of total fat, 0.2g saturated fat, 38mg cholesterol, and 300mg sodium (from the canning process — see below), canned tuna has a clean cardiovascular profile on every dimension except sodium, which is modest by the standards of processed or canned food.

Tuna for Athletes and Active People

The Fitness Community’s Default Canned Protein — Earned Completely

Canned tuna’s dominance in fitness meal prep is entirely justified by the numbers: 36g of protein per can at 162 calories, costing less than almost any other comparable protein source. It requires zero preparation, stores for years, and can be added to virtually any meal.

Selenium for Antioxidant Recovery

At 115% DV per 100g, tuna’s selenium provides comprehensive support for the glutathione peroxidase defenses that manage exercise-induced oxidative stress — ensuring antioxidant capacity is well supported on training days.

Niacin and B6 for Energy and Protein Metabolism

The combination of 66% DV niacin and 23% DV B6 directly supports both the energy metabolism pathways that power training and the protein metabolism enzymes required to utilize tuna’s own exceptional protein content.

B12 for Red Blood Cell Production

Adequate B12 supports erythropoiesis — the red blood cell production that determines oxygen-carrying capacity and aerobic performance — from one of the most practical and affordable B12 sources available.

Practical Daily Meal Prep Cornerstone

A can of tuna with rice or whole grain bread, some olive oil, and vegetables is a complete, calorie-efficient, micronutrient-rich meal that costs under a pound in most markets and takes under three minutes to prepare. For the budget-conscious athlete hitting high daily protein targets, tuna is irreplaceable.

Tuna Species Guide: What’s in Different Products

Understanding what “tuna” means on a label is practically important:

Canned light tuna — primarily skipjack tuna (Katsuwonus pelamis), a smaller, faster-reproducing species with lower mercury. Darker in color, stronger flavor, slightly softer texture. The lower-mercury choice for regular consumption.

Canned white tuna / albacore — albacore tuna (Thunnus alalunga), larger and longer-lived than skipjack, with higher mercury but also a lighter color and milder, firmer flesh that many prefer for sandwiches and salads.

Canned yellowfin (ahi) — increasingly available, particularly in premium canned products. Mercury intermediate between skipjack and bigeye.

Fresh or frozen tuna steaks — typically yellowfin or bigeye; nutritionally the same protein and mineral profile but with higher fat content (particularly in bluefin) and no added sodium from canning. The nutritional data on this page reflects canned; fresh steaks will have different fat and sodium figures.

Tuna sashimi / sushi grade — typically bluefin or yellowfin; highest omega-3 content in the fattier species but also highest mercury. The luxury end of the spectrum nutritionally.

Sodium in Canned Tuna: Context and Management

At 300mg per 100g, canned tuna’s sodium is meaningful — one can contains approximately 420mg from the salt added during canning. This is moderate rather than alarming (a 140g can is about 18% of the 2,300mg daily recommended limit) but worth noting for anyone on a strict sodium-reduction diet.

Practical sodium reduction:

Rinsing — briefly rinsing drained canned tuna under cold water reduces sodium content by approximately 20–30% without significantly affecting flavor or nutritional value for a can destined for a salad or sandwich.

No-salt-added varieties — widely available, these typically contain under 50mg sodium per can while maintaining the full nutritional profile described on this page.

Sodium context — for most healthy people, the 300mg sodium per 100g from tuna is one component of total daily sodium that is easily accommodated within a balanced diet; it does not make tuna a high-sodium food by the standards of processed or restaurant food.

Canned Tuna vs Fresh Tuna

The data on this page reflects canned tuna in water. Fresh tuna differs in several ways:

Fresh tuna is modestly higher in omega-3, naturally lower in sodium, and slightly higher in protein — but the canned version’s nutritional profile is remarkably close to fresh for most practical purposes, while being dramatically cheaper, shelf-stable, and requiring zero preparation.

Practical Ways to Include Tuna in Your Diet

Classic tuna sandwich or wrap — drained tuna mixed with a small amount of Greek yogurt or light mayonnaise, lemon, and herbs in whole grain bread; one of the fastest, most practical high-protein lunches available.

Tuna salad over leaves — tuna with chopped vegetables, capers, lemon dressing, and any seeds or nuts; a complete, nutrient-dense meal in under 5 minutes.

Tuna and rice meal prep — a can of tuna with cooked rice, soy sauce, sesame oil, and vegetables is a complete macro-balanced meal that scales easily for bulk preparation.

Tuna pasta — drained tuna with pasta, olive oil, cherry tomatoes, capers, and chilli; a 15-minute meal with excellent protein and carbohydrate balance.

Japanese-style rice bowls — high-quality canned or fresh tuna over rice with avocado, cucumber, edamame, and soy sauce creates a genuinely excellent bowl with outstanding nutritional credentials.

Niçoise salad — the classic French preparation of tuna with hard-boiled eggs, green beans, olives, potatoes, and a light dressing; one of the most nutritionally complete single-plate meals in any cuisine.

Potential Considerations

Mercury — species matters — as detailed extensively above; choose canned light (skipjack) for regular high-frequency consumption, and follow specific guidance if pregnant, nursing, or feeding children.

Sodium in regular canned tuna — approximately 300mg per 100g from processing; choose no-salt-added varieties or rinse briefly if managing sodium carefully.

Canned in oil vs water omega-3 — as discussed, canned in water retains more of the fish’s own omega-3; canned in oil is higher in calories from the absorbed oil.

Sustainability — tuna fisheries vary enormously in sustainability. Skipjack caught by pole-and-line or FAD-free purse seine methods is generally considered the most sustainable; look for MSC certification or specific sustainability labeling.

Fish allergy — tuna allergy can cause severe reactions in fish-allergic individuals.

Histamine sensitivity — improperly stored tuna (temperature abuse between catch and canning) can develop histamine, causing scombroid fish poisoning symptoms. Commercially canned tuna from reputable producers is safe; improper storage of fresh tuna is the practical risk.