Why measure mercury levels?

Mercury is a common element and at normal temperatures it is a liquid metal. Mercury is commonly used in industry and due to industrial pollution, mercury levels are gradually increasing worldwide in the marine environment.

Algae (seaweed) absorbs a biological form of mercury called methyl mercury. As small fish and shrimp eat algae, they accumulate methyl mercury in their tissues. As larger and larger fish move up the food chain, methyl mercury levels increase substantially. The larger the mouth of a fish, the higher these fish eat on the food chain and usually the higher their tissue level of mercury. Shark, tilefish, blue fin tuna, and swordfish are at the top of the food chain and have very high mercury levels. Grouper, snapper, bass, and albacore tuna have modest methyl mercury levels. Salmon, trout, sole, cod, and shellfish have low methyl mercury levels. People can eliminate some of the mercury they eat. People who eliminate mercury normally can eat seafood such as salmon or shrimp 2-3 times per week and grouper or snapper twice per month without accumulating mercury in their tissues. Higher levels of seafood consumption or eating food high in mercury such as swordfish or blue fin tuna often cause high levels of mercury.

Another source of mercury is dental fillings that contain amalgam. While substantial controversy exists regarding the toxicity and safety of dental amalgam fillings, they have been shown to release some level of mercury into the blood stream.

Methyl mercury is toxic to the human brain. While sudden toxic exposures have caused substantial injury and disability, the biggest concern today is continuous low level consumption from seafood.

Studies have shown that modest intake from canned tuna will increase methyl mercury levels substantially, and that this moderate rise in methyl mercury levels will cause abnormalities in neurobehavioral testing with a reduction in brain speed, reaction time, and other abnormalities in neurological testing. Alzheimer's disease and other neurological disease are strongly associated with elevated mercury levels. Genetic factors impact how well individuals eliminate methyl mercury from their bodies and how their tissue responds to various mercury levels.

A blood sample is a good indicator of methyl mercury levels. Red blood cells are formed in the bone marrow and live about 120 days. Sampling red blood cells for methyl mercury levels provides an excellent means to assess continuous low level mercury consumption and accumulation levels.

Testing mercury levels is not a routine part of usual health care. Yet, if you aim to ensure optimal mental performance into your 90s, assessing your risk for mercury toxicity makes sense. If you consume seafood regularly, retesting yearly would be a wise precaution in the effort to prevent neurodegenerative disease.