One kilogram (1,000 g) of tuna is about ten 100‑g portions. Nutritionally, 1 kg of tuna packed in water provides roughly 1,000–1,200 kcal and about 220–260 g of protein. Tuna packed in oil is higher in energy (≈1,800–2,000 kcal per kg). Cooking reduces moisture, so cooked yield and nutrient density per gram will be greater than raw or canned weights.

Yes—tuna is a healthy, lean protein rich in omega‑3s, vitamin D, B12 and selenium, supporting heart, brain and muscle health. However, some tuna contain mercury; prefer canned light and limit higher‑mercury types (albacore/large steaks). Aim for about 2–3 servings (roughly 8–12 oz / 200–340 g) of low‑mercury fish weekly; pregnant women and young children should follow stricter limits.

Tuna is expensive because many prized species (especially bluefin) are scarce and tightly regulated to prevent overfishing, reducing supply. Fishing involves long-range vessels, high fuel and labor costs, specialized gear, and costly cold-chain processing and international shipping. Strong demand for sushi-grade fish and premiums for sustainability certifications further push prices up.

Tuna is the flesh of a large, oily bony fish composed mainly of water (about 70–75%) and high-quality protein (≈20–25%). Fat content varies by species and cut — from lean to fatty — and provides omega‑3s (EPA, DHA). Tuna also supplies B vitamins (notably B12 and niacin), vitamin D, and minerals such as selenium, phosphorus, and potassium. Canned tuna may include added salt or oil.

Whether tuna is costly depends on type and form. Canned tuna is generally inexpensive and budget-friendly. Fresh or sushi‑grade tuna—especially premium species like bluefin or high‑quality yellowfin—can be quite expensive. Prices also vary by cut, sustainability certification, season, and region; imported or responsibly caught tuna often costs more than mass‑produced canned varieties.

Tuna is a healthy, lean source of high-quality protein rich in omega-3 fatty acids, vitamin B12, selenium and vitamin D, supporting heart and brain health. However, some tuna species contain mercury; pregnant women, young children and frequent consumers should limit intake—choose light (skipjack) tuna and vary fish choices. Canned tuna is a convenient, nutritious option when consumed in moderation.