We all have trace amounts of methylmercury in our tissues thanks to the widespread presence of this metal in the environment. Our exposure is largely through consumption of fish and shellfish. The health effects of mercury exposure depend on the dose and duration, your age and health status, and whether you inhaled it, ate food containing mercury, or it entered your body via the skin. Mercury exposure is most dangerous during fetal life because it can adversely affect the growing brain and nervous system with negative impacts on cognitive, thinking, memory, attention, language, and fine motor and visual spatial skills. According to the U.S. Centers for Disease Control and Prevention, later in life most people have blood mercury levels below what we associate with possible adverse health effects.
Physicians can test your blood for mercury, and home tests are available to analyze your hair for mercury (although I can't vouch for their accuracy). The conventional medical method for removing lead, mercury, and other heavy metals from the body is chelation therapy. It involves intravenous injections of EDTA (ethylene diamine tetra-acetic acid), a synthetic amino acid. EDTA binds to (chelates) heavy metals and minerals in the blood, allowing them to be excreted in the urine. Another intravenous agent used by some physicians for mercury detoxification is called DMPS.
An oral chelating agent called Succimer (also known as DMSA) is FDA-approved for treatment of lead poisoning (particularly in children) and is used by some physicians to remove mercury from the body. The drug combines with metals in the bloodstream and then both are removed from the body by the kidneys. The most common side effects include diarrhea, loose stools, loss of appetite, nausea and vomiting and skin rash. If you take this drug, be sure to report any symptoms you develop to your doctor.
Despite insubstantial evidence, some health practitioners offer mercury detoxification supplements such as cilantro tincture, chlorella algae powder, garlic, as well as various amino acids. I've seen two studies suggesting that cilantro can assist in the excretion of mercury, but I understand that the effect is weak. Eating foods rich in vitamin E has also been recommended. This may protect against mercury toxicity, but I know of no evidence showing that it helps the body eliminate mercury.
You can lower your mercury levels over time (months) by avoiding shark, swordfish, king mackerel and tilefish, all of which have unacceptably high levels of mercury. Stick to wild Alaskan salmon, which may be more expensive than other types of fish, but is good for you and low in mercury. I also recommend sardines, herring and black cod (sablefish).
Asparagus is said to be high in glutathione, a peptide (i.e., a small molecule made up of linked amino acids) and an antioxidant naturally produced in the body. Glutathione supplements have been promoted as a means of removing heavy metals from the body, but I've seen no scientific evidence supporting this or the idea that eating asparagus is effective. Chinese asparagus root (from a different species) is a medicinal plant used in cancer treatment, but here, too, I know of no evidence showing that it aids in removing mercury from the body.
Andrew Weil, M.D.