A slew of scientific reports have shown that eating fish helps protect against cardiovascular disease and enhances brain development before and after birth. Fish is a rich source of low-fat protein and is full of fatty acids known to lower cholesterol. He adds that FDA's current guideline already helps people avoid excessive mercury exposure, which would be a danger primarily for someone eating frequent meals of fish like swordfish and shark. Fish are the primary source of exposure to mercury around the world. Scientists estimate that about half the mercury in the Earth and its atmosphere originates from natural sources such as volcanoes that belch massive quantities of the substance.
Mercury vapor enters the atmosphere and falls in rainwater to the Earth.
Then, in a poorly understood process in the oceans and other bodies of water, microbes play a key role, transforming the mercury into a substance known as methyl mercury. Methyl mercury subsequently works its way up the food chain and accumulates primarily in large predatory fish, although methyl mercury is found in virtually all fish around the globe. While the study focused on healthy fish from ocean waters, its implications spill over into the freshwater arena, too. Mercury is one of many pollutants that limit consumption of fish from lakes and rivers across the nation. Individual states rely on federal guidelines when developing recommendations on how many fish can be eaten per week or month.