I often hear about bioaccumulation and biomagnification of certain lipophilic (fat-loving) toxins, typically heavy metals, in the fats of fish, which is why folks are warned against eating too much of the long-living higher-on-the-food-chain fish…like tuna (coincidentally my favourite fish!). As a result, I try not to eat too too much delicious tuna sushi when I’m in a sushi-ridden city (Toronto, Vancouver).
However, I had never really transferred this issue over to animals…until recently,when I heard a blurb on the radio about organic versus conventional meats. They were discussing the concept of bioaccumulation in cows, where conventional cows may be fed animal by-products, resulting in the accumulation of toxins (organic or inorganic) over time. This was compared with organic cows that are grass-fed.
The bottom line was that we should eat as close to the bottom of the food chain as possible. Be a grazer of sorts. Eat things that are grown in soil (good vegetables and fruit) and if you like eating meat, then eat animals that are grown based on things that are grown in soil (grass-fed cattle).