Last weeks article on pregnancy tips and a comment made regarding mercury content in fish sparked quite a response from our B.A. readers. Mercury is a metal found naturally in the environment. Industrial activities, such as farming, burning coal, and using mercury in manufacturing, increase the mercury cycling through the air, water, and soil. In water, mercury changes its form and becomes methyl-mercury. Fish absorb mercury and when you eat fish containing mercury, you absorb it, and at high levels it can be harmful.
Mercury will leave the body over time in the urine, feces, and breast milk. For most people, the level of mercury absorbed by eating fish and shellfish is not a health concern. Overall, fish and shellfish are healthy foods. They contain high-quality protein and other essential nutrients, are low in saturated fat, and contain omega-3 fatty acids, a type of essential fatty acid. A well-balanced diet that includes fish and shellfish can contribute to heart health and children’s growth and development. Nearly all fish and shellfish contain traces of mercury. However, some contain high levels. Eating large amounts of these fish and shellfish can result in high levels of mercury in the human body. In a fetus or young child, this can damage the brain and nervous system.
Most people are naturally concerned about excess mercury consumption however one might consider that the waters around Bali are not nearly as risky for mercury content as perhaps they would be closer to industrial cities. This is in fact true however when one takes into to consideration that the larger species of ocean fish, for example tuna and marlin, can travel great distances then there is still a risk of fish caught in local waters containing mercury. Cities such as Surabaya and Jakarta would certainly be dumping large amounts of chemical waste into the oceans and rivers, which could easily be absorbed by migratory fish or brought to the local waters by ocean currents.
Because of the mercury found in fish, certain food control bodies (such as the FDA in the United States) advises the following people to avoid fish high in mercury and to eat limited amounts of fish and shellfish that are lower in mercury:
- Pregnant women or women who may become pregnant
- Nursing mothers
- Young children
Avoiding Mercury in Fish
- Avoid or eat only very small amounts of shark, sword fish, or king mackerel as they
may contain high levels of mercury. Large, long-lived, predatory ocean fish have
the highest mercury levels.
- Eat no more than 6 oz (170 g) per week of canned albacore (“white”) tuna, tuna
steaks, or lobster.
- Eat no more than 12 oz (340 g) per week of fish and shellfish lower in mercury. This
is two average 6 oz (170 g) meals. Fish lower in mercury include shrimp, canned light tuna (not albacore tuna), salmon, and cat fish.
* Note that cooking fish even at high temperatures does not remove mercury from fish.
Should a woman who is not planning a pregnancy be concerned? - Mercury accumulates in your bloodstream over time and slowly leaves the body through urine, feces, and breast milk. If you eat a lot of fish high in mercury, it may take up to a year for your mercury levels to drop after you stop eating the fish. If you decide to get pregnant or have an unplanned pregnancy, you may have high levels of mercury. While elevated levels of mercury usually do not cause you significant health problems, it may affect a developing fetus. You should consider eating less fish, as recommended above, if you are of childbearing age.
What are the symptoms of mercury toxicity? - Mercury at toxic levels affects the nervous system and therefore causes the following symptoms:
- Facial tingling, numbness, or paralysis
- Extremity numbness
- Headache
- Visual disturbance
- Difficulty in hearing
- Memory loss
- Problems with walking
Should you or your child suffer any of the above symptoms, you should seek medical attention immediately. Note that other causes of mercury poisoning especially in children may be ingestion of small batteries, or direct contact with mercury such as is found in thermometers.
“
Kim Patra is a qualified Registered Nurse and Midwife that has been living and working in Bali for almost twenty years. She now runs her own private practice and medical referral service from her Kuta office. Kim is happy to discuss any health concerns with you and she may be contacted via e-mail at info@chcbali.com”.
