Why Eating Fish Is So Good for You
The evidence for fish is unusually strong across the heart, the brain, the eyes and the joints — and the practical case for eating more of it is simpler than most diet advice.
Nutritional advice changes with the wind. Fat was the enemy, then sugar, then carbohydrates, then ultra-processing. Through all of it, one recommendation has stayed remarkably stable: eat more fish. It is one of the few dietary claims where the evidence has strengthened rather than wobbled over forty years.
The centre of the case is omega-3 fatty acids, specifically EPA and DHA. These are long-chain fats the human body cannot manufacture in useful quantities. Plant sources such as flax and walnuts provide ALA, a shorter-chain relative, but conversion into EPA and DHA is poor — commonly cited at under ten per cent. Oily fish supply them directly, which is why salmon, mackerel, sardines, herring, anchovies and trout carry most of the benefit.
The heart is the best-established effect. Omega-3s lower triglycerides substantially, modestly reduce blood pressure, and appear to reduce the risk of arrhythmia. Large population studies consistently associate regular fish consumption with lower cardiovascular mortality. The effect is not miraculous, and supplement trials have produced more mixed results than whole-fish studies — which itself suggests the fish matters, not merely the oil extracted from it.
The brain has an unusual dependence. DHA is a structural component of neuronal membranes and is heavily concentrated in the brain and the retina. Observational research links regular fish intake with slower cognitive decline in later life and lower rates of depression, and the requirement during pregnancy and infancy is substantial, because a developing brain is being physically built from these fats.
The eyes benefit for the same reason. DHA is a major constituent of the retina, and higher intake is associated with reduced risk of age-related macular degeneration, one of the principal causes of sight loss in older adults.
Inflammation runs underneath much of this. Omega-3s are precursors to resolvins and protectins, compounds involved in switching off inflammatory responses rather than merely dampening them. This is the likely mechanism behind the reduced joint stiffness reported in rheumatoid arthritis, and possibly behind several of the other effects.
Then there is everything in fish that is not omega-3, which tends to be forgotten. It is an excellent complete protein at a low calorie cost. It is one of the very few meaningful dietary sources of vitamin D, which matters enormously in a country as far north and as grey as Britain. It provides iodine, essential for thyroid function and unusually scarce elsewhere. It supplies selenium, vitamin B12, zinc and, in the small fish eaten whole, a considerable amount of calcium.
The sensible objections deserve answers. Mercury accumulates up the food chain, so the large, long-lived predators — shark, swordfish, marlin and to a lesser extent big tuna — are the ones to limit, particularly in pregnancy. Small oily fish sit low in the chain and carry very little. Farmed fish varies widely in quality; well-managed farms produce excellent, safe fish, and poorly managed ones do not. Sustainability is a genuine concern, though it points towards the smaller species rather than away from fish altogether.
Which leads to the most useful practical point. Sardines, anchovies, herring, mackerel and mussels are simultaneously the cheapest, the most sustainable, the lowest in contaminants and among the highest in omega-3. The nutritional advice and the environmental advice converge exactly, which almost never happens.
Two portions a week is the standard recommendation, at least one of them oily. That is not a difficult target. A tin of sardines on toast takes four minutes. Mackerel under a grill takes eight. Mussels steamed with white wine and garlic take ten and feel like a celebration.
I live on the Kent coast, and I have spent a good deal of my life around the Mediterranean, where fish is not health food but simply lunch. That, I think, is the right framing. The countries with the strongest fish traditions did not adopt them for their arteries. They ate what the sea gave them, cooked it simply, and it happened to be one of the best things a person can eat. The evidence merely caught up.
