While high levels of mercury are often found in large species of fish, a more important factor to consider is the relative amount of selenium the fish contains. Selenium, also abundant in seafood, actually helps remove mercury from the body. Thus, consuming certain types of seafood (and other foods) that have a high selenium to mercury ratio can purify the body of heavy metals even when the fish contains them.
What is Selenium?
Selenium is an essential trace mineral that functions as an antioxidant and promotes a healthy immune system. Selenium is required in remarkably small amounts, with recommended daily amounts measured in the millionths of a gram (micrograms). Selenium has strong anti-cancer effects and is known to help detoxify the body and remove heavy metals, including mercury.
In the early 1970’s it was discovered that selenium is incorporated into proteins to produce selenoproteins, important enzymes that are antioxidants (they destroy free radicals and prevent cellular damage). Selenoproteins boost the immune system and help regulate thyroid function.
How Much Selenium is Required?
The average person gets about 65 micrograms of selenium per day. 200 micrograms is considered the optimal amount while 400 micrograms is the maximum allowable daily dose. Note that too much selenium is highly toxic to the body.
*Symptoms of too little Selenium:
Cancer, heart disease, fatigue, stunted growth, high cholesterol, compromised immune system function, liver impairment, pancreatic insufficiency and sterility.
*Symptoms of too much Selenium:
Arthritis, brittle nails, bad breath, hair loss, irritability, liver and kidney problems, tooth loss, jaundice. Note that in most places, including South America, most of North America, Africa, Russia and China there is little or no selenium in the soil. Northern Nebraska and the Dakotas have very high levels of selenium, however.
Seafood: Selenium Benefits
According to a recent study by the Western Pacific Regional Fishery Management Council, a new standard (called the Selenium-Health Benefit Value or Se-HBV) is being proposed by leading researchers to measure seafood safety.
The following types of fish have very high Se-HBV, containing between 10 and 25 times more selenium than mercury. High quality servings of the following fish can be expected to lower blood levels of mercury along with providing a healthy amount of selenium.
* Yellowfin Tuna
* Albacore Tuna
* Skipjack Tuna
* Mahi Mahi
Only one fish in the Western Pacific study (Mako shark) showed higher levels of mercury than selenium, while one other (Swordfish) had an even, 50/50 ratio of mercury and selenium.
Another study by Dr. Nicholas Ralston at the National Oceanic and Atmospheric Administration shows that (southern) Flounder and (wild Pacific) Salmon (including Chinook, Sockeye and Coho) have much more selenium than mercury. It also shows that Pilot Whale, Tarpon and most types of Shark should be avoided, with Grouper being about even.
Foods high in selenium
* Brazil Nuts
(dried, unblanched) – Brazil nuts are the only truly concentrated, natural source of selenium, and may contain so much selenium that one shouldn’t consume too many! However, different sources can vary based on the soil in which they are grown. Brazil nuts can contain as much as 550 micrograms per ounce.
(light, canned in oil) – a 3 ounce serving of Tuna contains nearly 100% of the RDA of selenium (about 63 while 65 micrograms is the RDA). Higher quality tuna has as little as .08 ppm of mercury per serving versus .38 ppm in lower quality sources.
Other foods that may contain selenium in lesser amounts include kelp, molasses, whole wheat, turkey, chicken and beef.