Fish is considered a protective food with almost all essential nutrients for growth available from it. The presence of essential fatty acids, Omega-3 fatty acids in abundant quantities makes fish a much sought after food. In fact 14-16% of animal proteins world over are estimated to be coming from fish. There are over 27000 species of fish but only a few of them are considered tasty and acceptable. Commercial fishing is based on such a demand profile.
Though there is no unanimity regarding how much fish one should consume to derive maximum benefits without any ill effects, the consumption rate at present indicates an annual per capita intake of 16 kg globally. Averages can be misleading as some do not consume any fish at all while others make fish part of their regular diets. A minimum of two servings of fish are considered good for deriving the health benefits attributed to fish. Eskimos depend on fish for a major part of their calories and proteins and they are one of the groups of population with practically no incidence of Cardio Vascular Disease because of abundant availability of Omega-3 acids from their diets. Long life span reported from Japan and Nordic countries is attributed to the fish-rich diets the population in these places consume regularly. Omega-3 acids are known to help reduce serum cholesterol, protect heart, improve circulation, reduce risk of arterial diseases and some types of cancers and improve brain development. The over whelming evidence in favor of Omega-3 acids has persuaded the industry to venture into extracting this nutrient from fish in the purest form with no smell or color and use it in many functional foods including juices and beverages. Besides Omega-3 acids, fish is also a good source of some essential minerals like iron, zinc, iodine and selenium.
While there is no dispute about the value of fish in the diet, its consumption is hampered by two constraints. First the aversion by many people to fish which can be due to religion, eating habits, environmental factors and other socio-ethnic reasons. There is no way this can be overcome though future generation of youngsters may yet change this scenario. The second constraint is the wide spread contamination of fish with mercury which is known to cause life threatening life disorders if consumed regularly beyond a certain limit. Many species of fish are known to carry mercury in the range of 0.73 to 1.45 ppm which far exceeds the safe limit agreed upon by WHO. The current safety limit is 1.6 ug per kg body weight per week working out to about 112 ug for a normal adult. Two servings of fish therefore should not contain more than 0.112 ppm of mercury.
The conflicting views of experts over the desirability of consuming fish by women during pregnancy have created uncertainty regarding the safety as well as the benefits of eating fish. While one group feels that two servings of fish a week have benefits far outweighing the potential harmful effects of mercury, others have taken the stand that eating fish during pregnancy must be avoided to prevent damage to the fetus. Four species of fish are reported to be high in mercury while species like Shrimp, light Tuna (canned), Salmon, Pollock and Cat fish are low in mercury and many experts feel that these can be consumed with least risk by expectant mothers.
The Indian situation is some what hazy as no reliable data could be found regarding mercury contamination in fish from either fresh water or marine sources. But logically the fresh water fish may be a safer bet as they are not generally contaminated with industrial effluents except in some areas. It may be the onus of the newly created Food Standards and Safety Agency to look into this area to evolve a consensus as to the safety of fish caught inland as well as coastal areas.