Journal

Introduction — Canned fish: an underestimated food

Canned fish occupies a paradoxical place in modern diets. It is often viewed as a fallback option, when in fact it is among the most nutritionally dense, accessible, shelf-stable foods and one of the easiest to integrate into everyday eating.

Canned sardines, mackerel and tuna share a common foundation: high-quality protein, long-chain omega-3 fatty acids (EPA and DHA), B-group vitamins and essential minerals [1–3].
Behind this apparent similarity, however, lie major biological differences related to species, fish size and position within the food chain.

1) Protein: quantity, quality and food matrix

All three fish provide complete, highly bioavailable proteins with an excellent essential amino acid profile [1].

Canned tuna stands out for its high protein density, often exceeding 23–25 g per 100 g, combined with a low fat content [2]. It is therefore particularly relevant in contexts where targeted protein intake is required.

Sardines and mackerel deliver comparable amounts of protein, but within a richer lipid matrix. This alters the metabolic response: slower digestion, improved satiety and a lower postprandial glycaemic impact [3].

2) Omega-3 fatty acids: a decisive difference

EPA and DHA omega-3 fatty acids are one of the key criteria differentiating these canned fish.

Sardines and mackerel rank among the richest fish sources of EPA and DHA, with intakes often exceeding 1.5–2 g per 100 g [4,5]. These fatty acids are involved in:

• modulation of inflammation,
• cardiovascular health,
• brain and cognitive function,
• regulation of gene expression related to lipid metabolism [4–6].

Canned tuna, although it does contain omega-3s, generally provides lower amounts—particularly in “in brine” or “natural” versions [2,5]. Its primary nutritional interest therefore remains protein rather than lipids.

3) Vitamins and minerals: the advantage of small fish

Canned oily fish are natural sources of vitamin D, vitamin B12, selenium, iodine and phosphorus—key micronutrients for energy metabolism and immune function [1,3].

Canned sardines consumed with their bones offer a specific advantage:
they provide a meaningful source of dietary calcium, with bioavailability comparable to that of dairy products [7].

Mackerel also supplies notable amounts of B vitamins and vitamin D.
Tuna, being leaner, remains rich in B vitamins but is overall less dense in fat-soluble micronutrients [1].

4) Contaminants: why fish size matters

Mercury contamination is strongly influenced by a fish’s trophic position.

The larger, longer-lived and more predatory the species, the greater the accumulation of heavy metals through bioaccumulation [8].

Accordingly:

• sardines and mackerel, which are small- to medium-sized fish, show low mercury levels compatible with regular consumption [8,9];
• tuna, particularly certain species (albacore, yellowfin), may present higher concentrations, justifying more spaced consumption for pregnant women and children [9,10].

5) Lipids: biological quality over quantity

The higher fat content of sardines and mackerel is not a nutritional drawback. These fats are predominantly polyunsaturated and embedded in a naturally protective food matrix [4].

The preservation medium also matters:

• in brine / natural: neutral from an energy standpoint;
• in olive oil: lipid-coherent, with superior oxidative stability;
• refined vegetable oils: lower nutritional interest.

6) Digestive tolerance and practical use

Tuna, being leaner, is often better tolerated by individuals sensitive to fats, but may be less satiating. Sardines and mackerel, richer in lipids, promote prolonged satiety and a more stable metabolic response [3].

7) Which to choose, when and why?

• Inflammation, cardiovascular health, cognition → sardines and mackerel [4–6]
• Targeted protein intake → tuna [2]
• Dietary calcium and micronutrient density → sardines with bones [7]
• Minimal contaminant exposure → sardines and mackerel [8–10]

The most coherent strategy remains species rotation, a core principle of practical, terrain-based nutrition.

Conclusion — Canned fish as a smart nutritional ally

Canned sardines, mackerel and tuna are neither equivalent nor interchangeable. They are powerful nutritional tools whose value depends on biological context and the intended goal.

Dr. Espinasse’s favourite sardines

In clinical practice, Dr. Espinasse regularly mentions La Belle-Iloise.

This choice is based on the quality of raw materials, mastery of preservation processes, respect for species, and simple recipes that preserve the true nutritional value of the fish. And it must be said: they are delicious—an essential condition for any healthy food to become a lasting part of daily life.

Official website: www.labelleiloise.fr

Bibliography

[1] USDA. FoodData Central – Fish, canned.
https://fdc.nal.usda.gov/

[2] Mozaffarian D, Rimm EB. Fish intake, contaminants, and human health. JAMA, 2006.
https://jamanetwork.com/journals/jama/fullarticle/203640
https://pubmed.ncbi.nlm.nih.gov/16772639/

[3] Boirie Y et al. Protein digestion and satiety. Proceedings of the Nutrition Society, 2014.
https://pubmed.ncbi.nlm.nih.gov/25005018/

[4] Calder PC. Omega-3 fatty acids and inflammatory processes. Biochimica et Biophysica Acta, 2015.
https://pubmed.ncbi.nlm.nih.gov/25620439/

[5] EFSA. Scientific opinion on dietary reference values for EPA and DHA.
https://www.efsa.europa.eu/en/efsajournal/pub/1796

[6] Swanson D et al. Omega-3 fatty acids EPA and DHA. Advances in Nutrition, 2012.
https://pubmed.ncbi.nlm.nih.gov/22332096/

[7] Weaver CM et al. Calcium bioavailability of sardines. American Journal of Clinical Nutrition, 1999.
https://pubmed.ncbi.nlm.nih.gov/10500018/

[8] Karimi R et al. Mercury levels in seafood. Environmental Health Perspectives, 2012.
https://pubmed.ncbi.nlm.nih.gov/22633066/

[9] EFSA. Mercury in food.
https://www.efsa.europa.eu/en/topics/topic/mercury

[10] FDA / EPA. Advice about eating fish.
https://www.fda.gov/food/consumers/advice-about-eating-fish