How much fish is healthy, and is farmed fish just as good as wild fish?

Three to four portions of fish per week is what nutrition researchers recommend, alternating between white and oily varieties. Fish provides protein, omega-3 fatty acids, vitamins A and D, selenium, iodine and calcium. A review of 106 studies from Europe, Asia, North America and Africa shows that varied fish consumption offers more benefits than risks for most people¹. Yet more than 30% of Spaniards do not meet that recommendation, and consumption has fallen by more than 30% over the past fifteen years. High prices, bones and limited cooking knowledge all play a role^2,3.

The benefits of oily fish for your heart are the clearest. In an analysis of fourteen studies involving 1378 participants, blood fats fell by an average of 0.11 mmol/L and 'good' cholesterol rose by 0.06 mmol/L after eating herring, mackerel or salmon. No effect was found on 'bad' cholesterol. Modest improvements, but in well-established risk factors for cardiovascular disease⁴.

Eating fish during pregnancy is particularly valuable for your child's brain development. Strong evidence from population studies points to better neurological outcomes in children of mothers who ate fish; this is attributed to the omega-3 fatty acids EPA and DHA⁵. However, a word of caution: pregnant women, breastfeeding women and young children should completely avoid swordfish, bluefin tuna, shark and pike. These species contain so much methylmercury that they are harmful to the developing nervous system.

Methylmercury is also the greatest risk of eating fish for everyone else. It accumulates in fish high up in the food chain, and fish is its main source in our diet. People who eat a varied diet and avoid the high-risk species stay well below dangerous levels. Nevertheless, an estimated five million fish consumers around the Great Lakes in the US exceeded the safe consumption limit, with ethnic minorities being overrepresented and less well informed about the guidelines^6,7.

Is farmed fish just as good as wild fish? The available studies do not compare them directly. What is known is that wild fish is not automatically safer. Fish from polluted rivers can contain elevated levels of substances such as PCBs, dioxins and PFAS. Research into wild fish in the Penobscot River in the US found levels that pose a potential health risk for people who regularly eat large quantities of it. Which variety has the better nutritional profile remains unanswered based on the current sources.