Mercury is a toxic heavy metal which is widely dispersed in nature. Most human exposure results from fish consumption or dental amalgam. Human exposure to the vapour of metallic mercury dates back to antiquity but continues today in occupational settings and from dental amalgam. Health risks from methylmercury in edible tissues of fish have been the subject of several large epidemiological investigations and continue to be the subject of intense debate.
Mercury is most notable for its neurological effects. Too much mercury can cause numbness, memory issues, anxiety, low mood, and tremors. More often, mercury poisoning builds up over time. Adults with advanced mercury poisoning may present with the following symptoms: hearing and speech difficulties, poor coordination, weakness of the muscles, numbness in hands and face consequent to nerve damage, gait disturbance and vision changes.
An important source of omega-3 fatty acids, fish also provides multiple other benefits. However, nearly all fish and shellfish contain traces of mercury. For most people, the risk from mercury by eating fish and shellfish is not a health concern. Yet, some fish and shellfish contain higher levels of mercury that may harm an unborn baby or young child's developing nervous system. The risks from mercury in fish and shellfish depend on the amount of fish and shellfish eaten and the levels of mercury in the fish and shellfish.
Serving size
It is recommended that most people eat at least two servings of fish per week. It will be wise to choose lower-mercury fish and seafood, such as salmon, shrimp, canned light tuna, Pollock, catfish, cod, sardines. Another important tip is to avoid higher-mercury fish, such as tilefish from the Gulf of Mexico, shark, swordfish, and king mackerel.
Another commonly eaten fish, albacore ("white") tuna has more mercury than canned light tuna. So, when choosing our two meals of fish and shellfish, one may eat up to 6 ounces (one average meal) of albacore tuna per week. Check local advisories about the safety of fish caught by family and friends in your local lakes, rivers, and coastal areas. If no advice is available, eat up to 6 ounces (one average meal) per week of fish you catch from local waters, but do not consume any other fish during that week.
Following these tips will help you maximize the benefits of eating fish while minimizing your risks of mercury exposure. Follow these same recommendations when feeding fish and shellfish to your young child, but serve smaller portions.
Despite the previous concern regarding mercury levels in fish, the FDA now recommends that women who are pregnant, breastfeeding, or plan on becoming pregnant consume more fish. Fish contain vital nutrients including omega-3 fatty acids, protein, vitamins, and minerals such as iron. These nutrients are essential, particularly for pregnant women, as they foster healthy fetal, infant, and childhood development.
