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

Three to four portions of fish per week, alternating between white and oily varieties, is recommended by nutrition researchers for good health. Fish provides high-quality protein, omega-3 fatty acids, vitamins A and D, selenium, iodine and calcium. A large review of 106 studies from Europe, Asia, North America and Africa concludes that varied fish consumption delivers more health benefits than risks for the general population. More than thirty percent of Spaniards do not meet this recommendation, and consumption fell by more than thirty percent over the past fifteen years. High price, bones and a lack of cooking skills all play a role in this.

The cardiovascular benefits of oily fish are the most concretely demonstrated. In an analysis of fourteen intervention studies with a total of 1,378 participants, triglycerides fell on average by 0.11 mmol/L and 'good' HDL cholesterol rose by 0.06 mmol/L after eating oily fish such as herring, mackerel and salmon. No effect was found on total cholesterol or LDL ('bad' cholesterol). These are modest but meaningful improvements in well-known risk factors for cardiovascular disease.

Eating fish before and during pregnancy is particularly valuable for the child's brain development. Strong epidemiological evidence points to better neurological outcomes in children of mothers who ate fish; this effect is attributed to the omega-3 fatty acids EPA and DHA. At the same time, a clear warning applies to pregnant women, breastfeeding women and young children: swordfish, bluefin tuna, shark and pike/pikeperch contain so much methylmercury that these groups must avoid these species entirely. Methylmercury is highly toxic to the developing nervous system.

Methylmercury is also the primary risk of fish consumption for the rest of the population. It accumulates in fish high up in the food chain, and fish is the main source of methylmercury for the general population. People who eat a varied diet and avoid the species mentioned remain well below dangerous levels. That said, in the Great Lakes region of the United States an estimated five million fish consumers exceeded the safe consumption limit, with ethnic minorities being overrepresented and less well informed about the guidelines.

On the difference between farmed and wild fish, the available source material states the following: wild fish is not automatically safer than farmed fish. Wild fish from polluted rivers can contain elevated levels of persistent contaminants such as PCBs, dioxins and PFAS. Research into wild fish from the Penobscot River in the United States revealed levels that pose a possible health risk to people who regularly eat large quantities of it. Whether farmed or wild fish has the better nutritional profile cannot be answered on the basis of the available studies; the source provides no direct comparative data on this point.