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

Canned tuna is one of the most nutritionally impressive shelf-stable foods available — at 90 calories per 100g with 19g of complete protein, 123% of daily selenium, 107% of daily B12, 62% of niacin, and 19% of B6, 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 (0.21g 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 answer rather than vague warnings — because the answer varies significantly depending on which type of tuna you’re buying.

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

USDA’s newest (Foundation Foods) analysis of light tuna canned in water. Full sources are at the end of the page.

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

A single standard can provides 173% of daily selenium, 150% of B12, and nearly 27g of complete protein at just 126 calories — one of the most nutritionally concentrated affordable foods in existence.

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

* From USDA’s older SR Legacy data for the same food, used where the newer Foundation Foods data has no value.

Standout: Tuna’s vitamin profile is dominated by its B vitamin concentration. B12 at 107% DV exceeds the full daily requirement in 100g — a genuinely unusual achievement from a canned food. Niacin at 62% DV is among the higher figures of any fish in our collection, supporting NAD and NADP coenzyme function across hundreds of metabolic reactions. B6 at 19% DV contributes to protein metabolism and neurotransmitter synthesis, fitting given tuna’s protein content.

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

Extraordinary standout: Selenium at 123% 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 173% DV of selenium, supporting glutathione peroxidase antioxidant defense and thyroid hormone activation from one affordable can. Phosphorus at 11% DV and iron at 9% DV make smaller contributions.

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 from both natural sources and 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 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 FDA’s advice focuses on pregnant and breastfeeding women and young children because mercury affects the developing brain most. For other adults, the same categories are a sensible guide to how often to eat each type.

The most important practical distinction: canned light tuna and canned white/albacore tuna differ meaningfully in mercury — albacore has nearly three times as much on average. The data on this page is for canned light tuna. If you eat tuna frequently, choosing light tuna for most servings meaningfully reduces mercury exposure. The trade-off is omega-3: in USDA’s data, albacore canned in water has about 1.0g of omega-3 per 100g, roughly four times as much as light tuna.

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 may reduce mercury’s toxicity. Some researchers argue that fish rich in selenium relative to their mercury content pose less risk than their mercury levels alone suggest.

Commonly eaten tuna species contain more selenium than mercury on a molar basis, which may mean the actual risk is lower than mercury measurements alone would predict. This doesn’t mean mercury concerns should be dismissed — official advice is still based on mercury levels — but it is a genuinely important scientific nuance that the mercury discussion alone misses.

Practical Guidance Summary

Canned light tuna is the FDA’s “best choice” — two to three servings a week is appropriate even for pregnant women and children, and is a sensible regular amount for most adults. Albacore and yellowfin are “good choices”, best kept to about one serving a week for pregnant or breastfeeding women and children, and eaten in moderation by everyone else. Bigeye is best avoided by those groups.

Canned in Water vs Canned in Oil

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

Water-packed figures are from USDA’s newer Foundation Foods analysis and oil-packed from its older SR Legacy data, so part of the protein difference reflects the two analyses rather than the packing.

The key counterintuitive finding: despite carrying about eight times the fat, drained oil-packed tuna has slightly less omega-3 than water-packed in USDA’s data. Some of the fish’s own omega-3 fat ends up in the packing oil, which is usually drained away, while the oil itself (often soybean or olive oil) adds fat and calories but little omega-3.

Water-packed is the clear choice for anyone managing calorie intake, while oil-packed offers a 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 123% DV per 100g — 173% 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 107% DV B12 per 100g means a single standard can covers about one and a half days’ B12 requirement — supporting myelin synthesis, red blood cell formation, and homocysteine regulation.

Outstanding Niacin for Energy Metabolism

At 62% 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 19g of complete protein for 90 calories — 0.21g per calorie — canned tuna sits among the most protein-efficient whole foods available. All 9 essential amino acids are present in strong proportions.

Cardiovascular Profile

At 0.9g of total fat, 0.2g saturated fat, 36mg cholesterol, and 219mg sodium (mostly from the canning process — see below) per 100g, canned tuna has a clean cardiovascular profile on every dimension except sodium, which is moderate by the standards of 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: nearly 27g of protein per can at 126 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 123% DV per 100g, tuna’s selenium provides comprehensive support for the glutathione peroxidase defenses that manage exercise-induced oxidative stress.

Niacin and B6 for Energy and Protein Metabolism

The combination of 62% DV niacin and 19% DV B6 directly supports both the energy metabolism pathways that power training and the protein metabolism enzymes required to use tuna’s own 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 very little in most markets and takes under three minutes to prepare. For the budget-conscious athlete hitting high daily protein targets, tuna is hard to beat — with light tuna the better choice for frequent eating.

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, sometimes mixed with yellowfin or tongol. 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 more omega-3, 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 between skipjack and bigeye.

Fresh or frozen tuna steaks — typically yellowfin or bigeye; a similar protein and mineral profile with no added sodium from canning. Yellowfin is very lean; bluefin is much fattier.

Tuna sashimi / sushi grade — typically bluefin or yellowfin; the fattier bluefin is by far the richest tuna in omega-3 but also among the highest in mercury. The luxury end of the spectrum nutritionally.

Sodium in Canned Tuna: Context and Management

At 219mg per 100g, canned tuna’s sodium is meaningful — one can contains around 307mg, mostly from salt added during canning. This is moderate rather than alarming (about 13% of the 2,300mg daily limit) but worth noting for anyone on a strict sodium-reduction diet.

Practical sodium reduction:

Rinsing — briefly rinsing drained canned tuna under cold water removes some of the sodium without significantly affecting flavor or nutritional value for a can destined for a salad or sandwich.

No-salt-added varieties — widely available, with around 50mg of sodium per 100g in USDA’s data, while keeping the same protein and micronutrient profile.

Sodium context — for most healthy people, the sodium in canned tuna 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 light tuna canned in water. Fresh tuna differs in several ways:

Fresh yellowfin is very lean, naturally low in sodium, higher in protein per 100g (canned tuna holds more water), and richer in selenium — but it actually has less omega-3 than canned light tuna. Bluefin is the fatty exception, with several times the omega-3 and B12 of the others, alongside its higher mercury. For most practical purposes, canned light tuna’s profile is close to fresh 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 above; choose canned light tuna for regular high-frequency consumption, and follow the FDA guidance if pregnant, breastfeeding, or feeding children.

Sodium in regular canned tuna — around 219mg per 100g, mostly from processing; choose no-salt-added varieties or rinse briefly if managing sodium carefully.

Canned in oil vs water — as discussed, water-packed has slightly more omega-3 in USDA’s data; oil-packed is much 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 (scombroid) poisoning — tuna that has been stored too warm between catch and processing can develop histamine, causing scombroid fish poisoning, with flushing, headache, and rash soon after eating. Commercially canned tuna from reputable producers is very low risk; improper storage of fresh tuna is the practical risk, and cooking doesn’t destroy histamine once it has formed.

Nutrient data: USDA FoodData Central, Foundation Foods — tuna, light, canned in water, drained solids (FDC ID 334194); values marked * from SR Legacy (FDC ID 173709). Comparison values from SR Legacy (light tuna in oil, FDC ID 173708; albacore in water, FDC ID 175158; yellowfin, cooked, FDC ID 172006; bluefin, cooked, FDC ID 173707). Mercury averages from the US FDA. % Daily Values use the FDA’s current Daily Values.