Fish bioaccumulate heavy metals. You may ask what does this mean? Have you heard of a food chain? Simply put, it is that smaller living organisms are eaten by larger organisms. With regards to water bodies it involves bacteria, fungi, archae, and protists at the very bottom, which break up debri - these are the "decomposers" so to speak. Next, phytoplankton (similar to a primitive plants needing sunshine to operate) take up minerals from the water, which they need to survive. Zooplankton eat phytoplankton and small and large fish eat both.
It becomes alarming when a water body does not have a bio-film of oxygen along the bottom, which acts to contain heavy metals. Without it, heavy metals contained in the soil will circulate up into the water column (this is very common in small water bodies, especially if contaminated with fertilizer / sewage). Also alarming is any industrial waste being secreted into water bodies.
Similar to the way plants confuse heavy metals with minerals (both having similar electron configurations) they are readily taken up by algae and work their way up the food chain. Thus, the larger the fish the greater the potential for contamination. Also, the older the fish the more time it has had to bioaccumulate these heavy metals.
Listed here are two great resources, one the Environmental Working Group's Fish guide, where different fish are measured for their mercury content and ranked from most toxic to least (this is particularly important for females trying to get pregnant or who already are or anyone who suspects they may have much heavy metals in their body). The second is an article writen by Oceanus magazine, which shows how a heavy metal such as mercury can accumulate up the water column.
I will be writing about heavy metal toxicity in future articles along with detox so please stay tuned. Until then please eat fish responsibly.
Thank you for reading!
EWG Fish guide:
Oceanus magazine article:
Seafood Calculator based on age, sex, and weight:
A blog dedicated to reviewing and reporting the basics of healthy living from diets, supplements, botanicals, homeopathics, what science says, what tradition says, and everything in between.